BIOLOGY MIDTERM STUDY GUIDE 2015
*Look over textbook, notes, labs, tests and quizzes to enhance
your studying*
I. Scientific Method
a. Steps of scientific method
b. Hypothesis
c. Theory
d. Inference vs. Observation
e. Variables
f. Control
II. Tools of a Biologist
a. Microscope
i. Labeling
ii. Function of each part
b. Identifying Lab equipment
III. Characteristics of Life
a. All of the different characteristics and examples of each
b. Asexual vs. sexual reproduction
IV. Ecology
a. Biodiversity
b. Abiotic vs Biotic Factors
c. Levels of ogranization
i. Organims, population, community, ecosystem, biome,
biosphere
d. Autotroph (producers)
e. Heterotrophs (consumers)
i. Omnivores
ii. Carnivores
iii. Herbivores
f. Competition
i. Intraspecific vs Interspecific
g. Predation
h. Symbotic Relationships
i. Mutualism
ii. Commensalism
iii. Parasitism
I. Food Chain vs. Food Web
V. Cells
a. Microscopes
i. Compound light microscope
ii. Scanning electron microscope
iii. Transmission electron microscope
b. Endosymbiosis
c. Scientists
i. Redi
ii. Pasteur
iii. Hooke
iv. Leeuwenhoek
d. Cell Theory
e. Organization- celltissueorganorgan systemorganism
f. Prokaryotes vs. Eukaryotes
g. Plants vs. Animals
h. Domains
i. Organelles
i. Labeling
ii. Functions
VI. Biochemistry
a. Elements
i. Definition
ii. Examples
b. Atoms
i. Definition
ii. Structure
1. Protons
2. Neutrons
3. Electrons
c. Macromolecules
i. Carbs
ii. Lipids
iii. Proteins
iv. Nucleic Acids
VII. Cellular Transport
a. Membranes
i. Labeling
ii. Phospholipids, proteins, cholesterol
b. Passive transport
i. Diffusion
ii. Osmosis
1. hypertonic
2. hypotonic
3. isotonic
iii. Facilitated Diffusion
c. Active Transport
d. Vesicular Transport
i. Endocytosis
1. Pinocytosis
2. Phagocytosis
ii. Exocytosis
e. Diffusion Lab!
i. Indicators
1. Iodine- starch
2. Benedicts solution- glucose
ii. What crossed the membrane?
VIII. Cellular Energy
a. Types of energy
i. Chemical
ii. Solar
iii. Autotrophs
iv. Heterotrophs
b. Photosynthesis
i. Reaction
ii. Starting materials
iii. Process
iv. Products
v. 2 Types of reactions
1. Label Diagram
2. Light reactions
a. Where do they occur?
b. What goes in, what comes out?
3. Dark Reactions/ Calvin Cycle
a. Where does it occur?
b. What goes in, what comes out?
4. Diagram of a chloroplast
a. Stroma
b. Thylakoid
c. Grana
I. What is the Scientific Method?The scientific method is a
process that uses questioning, analysis, and evidence to solve a
problem or answer a question.
Step 1.Make an Observation.After making an observation of the
natural world, define the problem/questionBe specific and
investigate one problem/question at a time.ALLscientific
experimentation starts with observation!
EXAMPLE: An OBSERVATION is any perceived characteristic of the
natural world that is OBJECTIVE (the same for everyone), this
includes anything that can be QUANTIFIED (can be measured) or
QUALIFIED (has a describable quality like color or smell)
Step 2.Research the problem (question). Use all available
resources to collect data on the problem/question being
investigated in order to form the most logical and informed
hypothesis you can. Libraries, Internet, books, magazines, personal
interviews, etc.
EXAMPLE: Any time an observation is made, the observer makes one
or many conscious or subconscious INFERENCE(S). An INFERENCE is any
SUBJECTIVE (may differ between people) conclusion that is drawn
from an observation. Inferences take into account logic, prior
experience, prior knowledge, and other factors.
Step 3.Develop a hypothesis (educated guess/proposed
explanation). Make it a short definitive statement that can be
proven to be true or false. Hypotheses are often presented as an
IfThen statement. The if part will establish a condition of the
hypothesis and the then part will make a prediction that will be
proven or disproven at the end of the controlled experiment.
Hypotheses are often modified, or changed, over many rounds of
experimentation.
A PREDICTION is an outcome that is expected based on an
OBSERVATION and a given INFERENCE. Predictions may be correct or
incorrect. A hypothesis is basically a testable prediction with
controlled conditions. Through experimentation we can test the
prediction to be correct or incorrect.
EXAMPLE: I walk into a room and OBSERVE a pot of water bubbling
and steaming; I make an INFERENCE that the water is boiling; I
PREDICT that if the water is boiling, then I will get burned if I
touch it. I can then create a hypothesis, If I touch the water,
then I will get burned
Step 4.Develop a controlled experiment.A controlled experiment
is an experiment that contains only one experimental variable.An
experimental or independent variableis the thing being tested (what
the scientist changes). Everything else in the experiment or all
other variables must be the same. These variables are also called
thecontrolled variables. Keeping these variables the same allows
the experimenter to show that it was the experimental variable
alone that caused the results.Thedependent variableis what changes
when the independent variable changes - the dependent
variabledependson the outcome of the independent
variable.Datashould beorganized into charts, tables, or graphs.
EXAMPLE: If I am investigating the relationship between how much
fertilizer I give a plant and how much it grows, the amount of
fertilizer would be my independent variable and the amount of plant
growth would be my dependent variable. Everything else must be
controlled variables (amount of sunlight, water, temperature, etc.)
in order to accurately measure the effect of the fertilizer on
plant growth.
Step 5.Analyze the data and come up with a conclusion. Data may
bequantitative(numbers) orqualitative(appearance, properties,
etc.). The conclusion may or may not support the hypothesis.
Additional experimentation must then take place to build
documentation concerning the problem/question. If the hypothesis is
proven wrong, change the hypothesis, not the data.Scientists must
be unbiased (do not take sides or make data fit their ideas).
WHAT FOLLOWS:Scientific research must bepublished, but first it
must bereviewed by peers(other scientists) and verified for
accuracy/reproducibility. Research may result in a scientific
theory or law (accepted as fact or the best explanation by the
scientific community).
II. Tools of a Biologist
Microscopes
1. Compound Light microscope: Uses visible light to look at a
thin sample; can observe cells but not detailed organelles
Eyepiece/Ocular Lens is always 10X magnification
Can have objective lenses of 4X, 10X, and 40X OR 10X, 40X, and
100X
To find total magnification we multiply the 10X magnification of
the eyepiece and the magnification of whatever objective lens we
are using
EXAMPLE: 10X (eyepiece) and 40X (objective lens):10 * 40 =
400X
The weakest magnification would be 4X objective: 10 * 4 =
40X
The strongest magnification would be 100X objective: 10 * 100 =
1000X
2. Scanning Electron Microscope (SEM): Uses an electron beam to
produce 3D, surface images of a specimen at up to 100,000X Total
Magnification (think SCANNING=SURFACE)
3. Transmission Electron Microscope (TEM): Uses and electron
beam to penetrate a thin sample and produce images of a specimen at
up to 300,000X Total Magnification (think TRANSMISSION=THROUGH)
Compound Light Microscope
Identifying Laboratory Equipment Names and Functions
1. Hand lens: magnifies small objects
2. Dissecting Tray: hold specimens for dissection
3. Dissecting Pins: hold specimen on the dissecting tray
4. Forceps: grasps small objects
5. Dissecting Scissors: cut specimens to be studied
6. Dissecting Probe: pointed object used to examine
specimens
7. Scalpel: cuts specimens to be dissected
8. Safety Goggles: protects eyes from fire and chemicals
9. Hot Plate: heats objects
10. Graduated Cylinder: measures liquids
11. Test Tube: holds liquids
12. Beaker: holds and measures liquids
13. Test-Tube Rack: holds test tubes
14. Electronic Balance: measures mass
15. Dropper Pipette: measures out drops of liquid
16. Pipette: transfers measured amounts of liquid
17. Compound Microscope: magnifies very small objects
18. Microscope Slide: holds object for examination with the
compound microscope
19. Coverslip: covers material on a glass slide
20. Petri Dish: shallow dish used for bacterial cultures
21. Thermometer: measures temperature
22. Funnel: transfers liquid from one container to another;
filters materials with filter paper
23. Metric Ruler: measures length
24. Hot Hands: protective gear to hold extreme hot or cold
objects
25. Weigh-Boat: used to hold materials when they are being
weighed
26. Spatula: used for transferring small amounts of dry/solid
material
27. Test-Tube Holder: grabs test tube for safe
handling/holding
28. Mortar and Pestle: grinds/crushes material
29. Test-Tube Brush: used to clean glassware (test tubes,
beakers, etc.)
III. Characteristics of Life
Living things are/display:
A. Composed of ONE or MORE Cells
a. Unicellular: Organisms composed of only one cell
i. Directly exchange nutrients and waste with their
environment
ii. Example: Bacteria, Algae, Amoebae, Paramecia
b. Multicellular: Organisms composed of multiple/many cells
i. Specialized cells that have specific forms and perform
specific functions working together to maintain the life functions
of an organism
ii. Living things can organism simple substances into complex
ones (i.e. macromolecules)
iii. Example: Animals, Plants, most Fungi
B. Organized
a. Living things display organization and forms that fit the
functions necessary to maintain life functions
b. Living things exhibit body plans that allow them to survive
in their environment
C. Growth and Development
a. Cells can growth in size
b. Cells can divide/reproduce
D. Respond to Stimuli
a. Living things display responses to environmental stimuli
b. A stimulus (plural: stimuli) is a thing or event that elicits
a response from an organism
c. Example: Shivering (response) because it is cold (stimulus:
drop in internal temperature); Pulling away hand (response) from a
fire (stimulus: tissue-damaging heat)
E. Require Energy
a. While some life processes occur spontaneously (require no
input of energy), the vast majority require an input of energy
b. Cells utilize energy in the form of ATP (Adenosine
Triphosphate) in order to drive the biochemical processes necessary
to maintain life functions
c. The SUN is the ultimate source of all energy used by
organisms on Earth
d. Cells obtain energy from their environment and produce
waste
F. Reproduction
a. Organisms produce offspring (new members of the parent(s)
species)
i. Asexual Reproduction: offspring are produced by a single
parent, offspring are genetically identical to the parent
1. Example: Bacteria
ii. Sexual Reproduction: offspring are produced by two parents,
offspring are a mix of each parents genetic material
G. Heredity
a. The passing of traits/characteristics from one generation to
the next (all qualities: physical, mental, behavioral, etc.)
genetically
b. Genetic information is carried by molecules of DNA
(Deoxyribonucleic Acid) and acts as the blueprint or body plan for
an organism
c. Offspring receive DNA from one (asexual reproduction) or two
(sexual reproduction) parents that dictates all aspects of their
biology
H. Evolve and Adapt
a. Adaptation: the ability of an organism to change with its
environment in order to increase its chances of survival and
reproduction
b. Evolution: the modification of a species (on the genetic
level) over many generations in order to maximize survival and
reproduction in a dynamic (changing) environment
i. Example: camouflage, thick fur, large brains, sharp teeth,
etc.
c. A series of adaptations over many generations produces
evolution and the diversification of life we see on Earth. It is
the ability of life to adapt that allows it to endure catastrophes
(like the meteor that wiped out the dinosaurs) and drastic climate
changes (think ice age)
I. Homeostasis
a. The state of stability that organisms maintain in order to
continue life functions (pH, solute concentration, temperature,
etc.)
b. Although the ideal stable state varies from organism to
organism, all organisms must maintain a stable internal environment
despite the state of the external environment to survive
i. Example: Humans maintain an internal temperature of about
98.6 F despite living in a wide range of external temperatures
IV. Ecology
Ecology: The study of interactions betweenorganismsand
theirenvironments. Ecology includes the study of individuals,
populations, communities, ecosystems, biomes, and the
biosphere.
Biodiversity: The degree of diversity present amongst living
things on Earth. Diversity is indicated by the genetic variation
(number of different species) present in the various ecosystems on
Earth (biosphere).
Biotic: Anything that is, or has ever been, ALIVE. Biotic
factors also include organic products of life such as waste.
Examples of biotic factors in an environment include organisms,
organic molecules, and cells. Biotic is the opposite of
abiotic.
Abiotic: Anything that is not, nor has ever been, alive. Some
examples of abiotic factors in an environment include
precipitation, sunlight, and minerals. Abiotic is the opposite of
biotic.
Niche: An organism's role/place in an environment, including how
it uses its resources, relates to other organisms, and times its
reproduction. Each individual organism has a niche in its
population, community, and ecosystem, but niches are flexible and
change depending on circumstances.
Habitat: The physical environment where a population of a single
species lives, orinhabits. A habitat consists of all theabiotic, or
nonliving, resources influencing the population. A habitat is only
understood in terms of the population it describes. For instance,
we say "the black bear habitat" or "the whale habitat." It doesnt
describe the entire ecosystem, or a community of organisms, or even
the home of a single individual. Habitats of different species
dooverlap (Ex. The habitat of a lion overlaps with the habitat of a
gazelle).
Autotroph: Any living organism that makes its own food by
converting simple inorganic molecules into complex organic
compounds like carbohydrates, fats, and proteins. Autotrophs are
the "producers" in a food chain or web. Autotrophs are able to
capture sunlight and convert/store it as chemical energy that is
accessible to the cell (creating its own food in the form of
glucose).
Heterotroph: An organism that cannot convert sunlight into
"food" (carbohydrates). Heterotrophs must obtain their nutrients by
consuming other organisms. All animals, all fungi, and some kinds
of bacteria are heterotrophs. This means that all carnivores,
herbivores, and omnivores are also heterotrophs.
Food Chain: A simple, direct, andtrophic (eating) relationship
among a group of organisms, where one organism, like a plant, is
the food source for the next organism, like a cow, which in turn is
the food source for the next organism, like a human, and so on and
so forth. A food chain traces the flow of energy from one type of
producer to one type of primary consumer (and perhaps one type of
secondary consumer, etc.)
Food Web: A complex trophic relationship among a group of
organisms, consisting of interactions among multiplefood chains(see
definition above). A food web describes how
multipleproducersandconsumersdirectly or indirectly interact in a
community.
Herbivore: An organism that only eats autotrophic organisms,
like plants and algae. Some examples of herbivores include members
of the bovine family, like cows, bison, antelope, and sheep;
members of the deer family, like moose, reindeer, and elk; and many
insects, like leaf beetles, lady bugs, and aphids.
Carnivore: An organism that only eats animals. Most predators
and scavengers are exclusively carnivorous. Some examples of
carnivores include members of the feline familylike lions, tigers,
and house cats, and birds of preylike eagles, hawks, and owls.
Omnivore: An organism that eats both plants and animals. Some
examples of omnivores include members of the hominid familylike
humans, chimpanzees, and orangutans, and many bird specieslike
chickens, ducks, and woodpeckers.
Decomposer: An organism that feeds on and breaks down dead or
decaying matter in the process ofecological decomposition. Examples
of decomposers include fungilike mushrooms and molds; wormslike
earthworms and some nematodes; and some bacteria. Decomposers are
essential for recycling nutrients in an ecosystem.
Detritivore: An organism that consumes detritus, aka decomposing
organic matter, to obtain nutrients. All decomposers are
detritivores, including fungi, worms, and some bacteria.
Decomposers are usually associated with eating things like dead
animals (think vulture eating a carcass) while detritivores are
usually associated with breaking down biotic materials (think
fungus breaking down a rotting log).
Competition: An interaction where individuals of different
species (interspecific competition) or the same species
(intraspecific competition) fight for limited resources.
Examples of interspecific competitioninclude trees of different
species fighting for limited sunlight in a rainforest, birds of
different species fighting for limited prey in a prairie, and even
bacteria of different species vying for limited oxygen in your
large intestine.
Examples ofintraspecific competitioninclude lions fighting for
mates on the Savannah, piglets vying for limited milk from their
mother, and even humans vying for limited space to build a
home.
Predation: A type of species interaction where one organism, aka
thepredator, consumes, in part or in whole, another organism, aka
theprey. Examples of predators include snakes and members of the
big cat family, such as lynx. The difference between parasitism and
predation is that predators kill their prey almost immediately
while parasites live in or on their hosts for an extended period of
time and do not necessarily kill them.
Symbiosis: An ecological interaction between individuals of
different species. Symbiotic relationships
includemutualism,parasitism, andcommensalism. They DO NOTinclude
predator-prey interactions or competition.
Mutualism: Two organisms interact in a way that is BENEFICIAL to
both
Ex. Bees and Flowers
Commensalism: Two organisms interact in a way that is BENEFICIAL
to one organism and has no impact (either beneficial or harmful) on
the other.
Ex. Clownfish and Sea Anemone
Parasitism: Two organisms interact in a way that is BENEFICIAL
to one organism and HARMFUL to the other
Ex. Ticks and Mosquitoes
Levels of Biological Organization:
Organism: A single living member of a species. Ex. Humans, wolf,
cucumber plant, etc.
Population: A group of organisms of the same species living in
the same geographic area at the same time. For example, all of the
coyotes in a desert ecosystem, or all of the oak trees in a forest
ecosystem.
Community: A group of two or morepopulationsof organisms from
different species inhabiting the same location at the same time.
Communities are composed only of biotic factors. Abiotic factors
like sunlight, temperature, and terrain are not considered part of
a community; these factors are part of the ecosystem, which can
contain one or more communities of organisms.
Ecosystem: A term describing all the living and nonliving things
in a certain location. Ecosystem studies in ecology explore the
interactions between organisms, like individuals, populations, or
communities, and the abiotic components in the environment, like
chemical composition, landscapes, and weather patterns.
Biome: A large grouping of area that contains a number of
different ecosystems. The defining characteristics of a biome are
the dominant plant life and the climate. Examples include Deserts,
Rainforests, Deciduous Forests, Savannahs, etc.
Biosphere: The entire area of the earth that supports life. The
biosphere is made up of all of the individuals, populations,
communities, ecosystems, and biomes found on Earth.
V. Cells
Endosymbiotic Theory: MITOCHONDRIA and CHLOROPLASTS were once
distinct organisms that were absorbed into larger, pre-eukaryotic
cells. Over billions of years, the symbiosis between
MITOCHONDRIA/CHLOROPLASTS and the EUKARYOTIC HOST CELLS has evolved
to the point that they are inseparable. MITOCHONDRIA are found in
ALL eukaryotic cells, while CHLOROPLASTS are found only in
eukaryotes that perform PHOTOSYNTHESIS. This implies that
MITOCHONDRIA were acquired before the split of animals and plants
and CHLOROPLASTS were acquired after.
Scientists (make sure you know what they discovered and what
their experiment was)
1. Robert Hooke:
Observed dead cork cells under a microscope
Called what he saw cells after the cells that monks occupied in
monasteries
2. Anton von Leeuwenhoek
First person to observe living cells
Observed living cells in a sample of pond water
3. Francesco Redi
Spontaneous Generation: In Redis timethe 1600sit was commonly
believed that living organisms would randomly come in to being from
non-living materials.
Fly/Meat Experiment: A commonly-held assumption by Redis
contemporaries was that maggots (fly larvae) were generated in
decaying meat and dead flesh. In order to test this hypothesis,
Redi placed rotten meat in both an OPEN CONTAINER and in a CLOSED
CONTAINER. Although adult flies tried to get into BOTH containers,
they could only gain access to the meat in the OPEN CONTAINER.
After some time, maggots appeared ONLY on the meat in the open
container, suggesting that THE ADULT FLIES WERE THE SOURCE OF THE
MAGGOTS and SPONTANEOUS GENERATION DID NOT OCCUR!!
4. Louis Pasteur
Pasteurization: Process developed by Louis Pasteur after
discovering that bacteria in the air could contaminate food. By
superheating and then rapidly cooling food items, bacterial
concentrations can be greatly reducedprolonging shelf-life and
reducing spoilage/infection.
Bacteria/Broth Experiment: Preparing two flasks containing a
broth (proteins, carbohydrates, etc. to support bacterial growth),
Pasteur then sterilized them using high heat to kill any bacteria
potentially present in the broth. Now, with both flasks bacteria
free, Pasteur left one flask OPEN and left one flask CLOSED
AIR-TIGHT. After some time, the OPEN FLASK HAD BACTERIAL GROWTH,
while the CLOSED FLASK HAD NO BACTERIAL GROWTH. After opening the
closed flask and exposing it to air, it went on to DEVELOP
BACTERIAL GROWTH. This was strong evidence that bacteria is present
in the air around us and led Pasteur to develop the technique for
sanitizing foods called Pasteurization (see above). The results of
this experiment also demonstrated that CELLS MUST COME FROM OTHER
CELLS!!!!
CELL THEORY: 3 Parts
1. ALL LIVING THINGS ARE COMPOSED OF ONE OR MORE CELLS
2. THE CELL IS THE MOST BASIC STRUCTURAL AND FUNCTIONAL UNIT OF
LIFE
3. ALL CELLS ARISE FROM EXISTING, LIVING CELLS
Levels of Organization within an Organism:
SimplestMost Complex
CellTissueOrganOrgan SystemOrganism
Prokaryotes vs. Eukaryotes
Prokaryote: Means before nucleus and includes the domains
Bacteria and Archaea
Eukaryote: Means true nucleus and includes the domain
Eukarya
Biological Domain: The highest and most inclusive classification
for life on Earth.
Bacteria: this domain includes all bacteria, which are
PROKARYOTIC
Archaea: similar to bacteria but unique in a number of ways,
also PROKARYOTIC
Eukarya: this domain includes all plants, animals, and fungi,
which are EUKARYOTIC
ORGANELLE STRUCTURE, FUNCTION, and LOCATION:
Centriole
organelles made of microtubules involved in cell division
Golgi Apparatus
process materials manufactured by the cell
Smooth Endoplasmic Reticulum
Site of lipid synthesis
Rough Endoplasmic Reticulum
Site of protein synthesis
Ribosome
produces proteins
Cilia and Flagella
Used for movement/moving substances around outside of the
cell
Central Vacuole
Maintains shape of cell, stores water, nutrients and waste
Chloroplast
Captures light energy and converts to sugar
Cell Wall
Maintains cell shape, works with central vacuole to maintain
turgor pressure
Cell Membrane
support, protection, controls movement of materials in/out of
cell
Nucleus
controls cell activities
Mitochondrion
breaks down sugar molecules into energy
Cytoplasm
fluid substance that fills the interior of the cell
Lysosome
breaks down cellular waste products and debris (contains
enzymes)
VI. Biochemistry
HINT: ATOMIC MASS will always be larger than ATOMIC NUMBER, this
will help with deciding which one is which!!!!
ELEMENT: A substance that cannot be broken down into simpler
substances by chemical means. An element is composed of atoms that
have the same atomic number, that is, each atom has the same number
of protons in its nucleus as all other atoms of that element.
MATTER: Anything that has mass and takes up space.
COMPOUND: A compound is a substance formed when two or more
chemical elements are chemically bonded together.
Acids and Bases:
Acid: Solution containing a higher concentration of H+ ions than
OH- ions
Base: Solution containing a higher concentration of OH- ions
than H+ ions
Neutral: Solution containing an equal concentration of H+ and
OH- ions
pH SCALE:
*****Alkali is another word for BASIC*****
NEUTRALIZATION REACTION: The reaction of an acid and base to
form a neutral solutionHydrogen Ions (H+) and Hydroxide Ions (OH-)
are balanced to produce a pH 7 solution.
MACROMOLECULES: Large, organic molecules essential for life
Proteins: Responsible for Growth, repair, enzymes, and
transport.
Carbohydrates: Gives us energy. Examples include glucose and
fructose.
Lipids: Can be saturated or unsaturated. Used forstoring energy,
signaling, and acting as structural components of cell
membranes.
Nucleic Acids: Encode, transmit, and express genetic
information. Found in the form of DNA and RNA.
VII. Cellular Transport
Fluid Mosaic Model: This is a model that describes the plasma
(cell) membrane of animal cells (including humans). The membrane is
composed of two layers of phospholipids (PHOSPHOLIPID BILAYER)
which are fluid (flexible and capable of movement) at animal body
temperature. The membrane functions to give the cell a definite
volume (separate the components of the cell from the surrounding
environment) and to moderate what goes in and out of the cell
(keep/let beneficial things in and keep/send harmful things out).
Because the membrane is selective in what it permits in and out of
the cell, it is described as SELECTIVELY-PERMEABLE. Within the
bilayer are proteins, cholesterol, and carbohydrate chains that
give it the look of a mosaic (a type of art that uses many colored
pieces). Because the components of the membrane can move freely
through the membrane (like things floating on water), the plasma
membrane is described/modeled as FLUID-MOSAIC. REMEMBER THAT
PHOSPHOLIPIDS ARE A TYPE OF LIPID!!
Phospholipids: Each layer in the bilayer is composed of many
units called PHOSPHOLIPIDS, and each phospholipid is composed of a
hydrophilic (water-loving) HEAD and a hydrophobic (water-fearing)
TAIL. The head of each phospholipid always faces towards either the
watery fluid outside of the cell (extracellular fluid; extra:
beyond, cellular: having to do with cellbeyond-cell fluid) or the
watery fluid within the cell (intracellular fluid; intra:
withinwithin-cell fluid). The tail of each phospholipid always
faces away from the extra and intracellular fluids, so a bilayer
forms with the heads on the outside and the tails facing each other
on the inside. Think of a sandwich, with the heads representing the
bread on the top and the bottomand the middle representing the
tails!
Proteins: Provide structure, enables transport of materials
through the membrane, and anchor carbohydrate chains
Carbohydrate Chains: Acts a receptorsending and receiving
chemical messages for the cell
Cellular Transport: The movement of materials across the plasma
membrane. Transport can be either PASSIVE or ACTIVE.
Passive Transport: The movement of particles (atoms or
molecules) from a higher concentration to a lower concentration
(down the concentration gradient). Passive transport DOES NOT
REQUIRE ENERGY and will happen spontaneously until dynamic
equilibrium is reached.
DYNAMIC EQUILIBRIUM: A condition where constantly moving
particles are balanced.
Equilibrium: a state in which opposing forces (motion, charges,
etc.) are balanced
Dynamic: constantly changing
**In the natural world, at the molecular level, things never
stop moving; because of this constant motion they tend to spread
out and become balanced through random motion. Although
atoms/molecules never stop moving, if the same amount are coming as
are going, there is no change in concentration.**
SIMPLE DIFFUSION: The movement of particles from a higher
concentration to a lower concentration. For the cell membrane,
diffusion takes place across the membrane between the outside and
inside of the cell. There are a number of factors which affect the
rate of diffusion (how long it takes to reach dynamic
equilibrium).
1. Temperature: higher temperatures= faster particles= faster
diffusion
2. State of matter: gasses diffuse faster than liquids, liquids
diffuse faster than solids
3. Concentration: The greater the difference in concentration,
the faster diffusion occurs (steeper concentration gradient). For
example, diffusion would occur faster if the concentration of
glucose outside of the cell is 10x that of the inside of the cell
vs. 3x.
4. Size of particles: Smaller particles diffuse faster than
larger particles. This makes sense because for the same amount of
energy, something smaller can move faster than something bigger
(What can you move faster if you give it all you got: a shopping
cart or a truck?) **With a membrane, size can determine whether a
substance will even be capable of diffusion. For example, O2
(oxygen gas) can readily diffuse through the cell membrane while
large sugars cannot. Think of the permeability of a membrane as a
net, with bigger holes letting more through than smaller
holes**
OSMOSIS: The diffusion of liquid water across a semi-permeable
membrane. Osmosis can only take place with liquid water and is used
mostly when talking about the cell
FACILITATED DIFFUSION: To facilitate something is to help it
occur. Remember how some particles where too large to cross the
cell membrane by SIMPLE DIFFUSION, or move too slowly? This is
where membrane protein channels help out by FACILITATING the
diffusion of these particles.
Active Transport: The movement of particles AGAINST the
concentration gradient. This REQUIRES CELLULAR ENERGY to perform.
This is commonly seen in nerve cells, where ions must be pumped
against their concentration gradient (byyou guessed itmembrane
proteins!) in order to create an electric potential (like a
battery) for signal transmission.
ENDOCYTOSIS: **into cell ENDO think IN** A cell envelopes an
object of interest until it forms a bubble around the object. The
cell membrane then changes shape so that the cell membrane is
reestablished and a vesicle (containing the object) is on the
inside of the cell. When the object is solid (Ex. White blood cell
eating a bacterial cell) it is called PHAGOCYTOSIS (cell eating).
When the object is some amount of liquid it is called PINOCYTOSIS
(cell drinking).
EXOCYTOSIS: **out of cell EXO think EXIT** A cell moves a
vesicle (typically containing wastes) towards the border of the
cell membrane. The vesicle and the cell membrane merge expelling
the vesicles contents outside of the cell and reestablishing the
cell membrane. It looks a lot like endocytosis in reverse.
***When comparing the fluid within a cell and a fluid outside of
a cell, we can characterize the solution a cell is in by describing
it as HYPOTONIC, ISOTONIC, or HYPERTONIC**
Hypotonic solution- the concentration of solute particles is
greater within the cell than outside of the cell; this will cause
to water to enter the cell through osmosis, and the cell will swell
(possibly bursting in the process depending on a number of
factors).
Isotonic solution- the concentration of solute particles in both
the inside fluid and outside fluid of the cell is in equilibrium
(balanced); water content of the cell is stable and thus ideal.
Although there is no observable change, water is moving in and out
of the cell at the same rate. The cell and solution are in DYNAMIC
EQUILIBRIUM.
Hypertonic solution- the concentration of solute particles is
greater outside the cell than within the cell; this will cause
water to leave the cell through osmosis, and the cell will
shrivel.
DIFFUSION LAB
This lab made use of two indicatorsIodine Solution and Benedicts
Solution
What is an indicator? An indicator is a chemical/substance that
produces a visible color change in the presence of another
chemical/substance at certain concentrations. For instance,
Phenolphthalein will turn bright pink in solution with a high OH-
concentration (base indicator). Remember, indicators enable
QUALITATIVE observation, not quantitative as there is nothing that
can be accurately and practically measured.
Iodine Solution: Tests for the presence of STARCH. Iodine
solution is an amber/yellow by itself, but in the presence of
starch it turns a dark black/purple/blue. The color change can very
quickly be observed at room temperature.
Benedicts Solution: Tests for the presence of simple sugars, in
the case of the lab we tested for GLUCOSE. Benedicts Solution is a
light, bright blue by itself, but in the presence of glucose sugars
turns orange. BENEDICTS SOLUTION MUST BE HEATED IN ORDER TO SEE A
COLOR CHANGE!!!
EXPERIMENTAL SETUP:
Recall that we placed a solution of GLUCOSE and STARCH into
dialysis tubing and tied it off to create an environment that was
isolated from the outside. Dialysis tubing forms a SEMIPERMEABLE
(allows some substances to diffuse, while preventing others from
diffusing) membrane meant to simulate a cell. We then placed the
water-tight dialysis tubing cell in a solution of water and iodine.
After some time, it was observed that the contents of the dialysis
bag turned a dark blue/black/purple. Additionally, the water in the
beaker was found to test positive for glucose, and the mass of the
dialysis bag increased in mass (after drying and weighing). So what
happened? What was able to diffuse into and out of the bag?
ABLE TO diffuse:
A. Water: the mass of the bag increased, suggesting that water
was small enough to diffuse into the bag
B. Iodine: the contents of the bag turned dark
black/blue/purple, suggesting that iodine was small enough to
diffuse into the bag and contact the starch
C. Glucose: the sample from the solution surrounding the bag
tested positive for glucose, suggesting that glucose was small
enough to diffuse out of the bag
UNABLE TO Diffuse
A. Starch: the solution surrounding the bag did not change color
to dark black/blue/purple, suggesting that the starch molecules
were too large to diffuse out of the bag. This was later supported
when the bag was cut open, and the entire beaker solution
immediately turned dark black/blue/purple.
VIII. CELLULAR ENERGY
Types of Energy: Although energy may be classified in a number
of different ways and as a number of different types, two forms of
energy are of particular interest to biologists: SOLAR and
CHEMICAL
I. Solar Energy: Energy emitted from the Sun (essentially a
nuclear fusion reactor) in the form of LIGHT and HEAT. Light can be
described by its WAVELENGTH.
Wavelength is the distance between two identical points on a
repeating wave, in this case peak (crest) to peak, however any
repeating points could be used (for example, trough [bottom] to
trough)
Wavelength directly relates to the energy carried by light, with
shorter wavelengths carrying more energy than longer wavelengths.
Below is the Electromagnetic Spectrum of lighta useful tool in
visualizing the different forms light can take. REMEMBER SHORTER
WAVELENGTH=MORE ENERGY!!
Reds---------Oranges----YellowsGreens-----Blues--------Violets
***Note: the units of length are in nanometers which are one
billionth of a meter!!
II. Chemical Energy: Type of potential energy where the energy
is stored in the chemical bonds that form molecules. When certain
chemical reactions takes place, bonds are broken and energy is
released. Chemical reactions can be represented using a chemical
equation in the form: ReactantsProducts. The Law of Conservation of
Mass dictates that all matter that enters a chemical reaction must
leave (although in different forms), so this helps in that we can
see and track everything going in and everything going out.
SOMETIMES YOU WILL SEE SOMETHING WRITTEN ABOVE THE ARROW (an
enzyme, light, ATP, etc.) THIS MEANS THAT IT PLAYED A ROLE IN THE
REACTION BUT DID NOT DIRECTLY PARTICIPATE. (EX. An enzyme helps a
reaction take place but is not chemically altered in the process;
light is essential for photosynthesis but is not matter and cannot,
therefore, be accounted for in the reaction; the energy to produce
ATP is provided by a chemical reaction, but the reaction itself
does not involve ATP)
What we think of as food is chemical energy! Where does it come
from?
Photosynthesis: photo means light and synthesis means putting
together, so photosynthesis means putting together with light. What
is being put together? MoleculesFOOD. Photosynthesis is a process
used by plants and other organisms to convert light energy,
normally from the Sun, into chemical energy (in the form of
molecular bonds) that can be later released to fuel the organisms'
activities.
Photosynthesis takes place in a very specialized organelle found
in plant cells called the CHLOROPLAST which contains specialized
pigments that absorb visible light.
Pigment: A chemical/substance that absorbs certain wavelengths
of light and reflects others.
Absorbance: A wavelength, or series of wavelengths, of light
is/are trapped by a pigment along with energy it/they contain(s)
the visible light wavelengths absorbed never reach your eye and,
thus, are not seen.
Reflection: A wavelength, or series of wavelengths, of light
is/are scattered by a substance the visible light wavelengths
reflected are the ones that enter your eye and are seen.
Example: A leaf that appears green absorbs all wavelengths
except for green, and reflects it in all directions (some of this
light enters your eye and causes you to perceive the leaf as
green); something that appears black absorbs all wavelengths of
visible light and appears to have no color (because no visible
light is reflected into your eye); something that appears white
reflects ALL wavelengths and appears to have every color (light of
all visible wavelengths is reflected into the eye and the brain
perceives this as white)
**Now you know why light colors keep you cooler in the summer
and dark colors get hot fasterdark colors ABSORB more light and
ENERGY (which dissipates as heat)!!**
Important Pigments used in Photosynthesis:
I. Chlorophyll- pigment with strong absorbance in the blue and
violet wavelengths, and moderate absorbance in the orange-red
wavelengths. There are two types Chlorophyll- (A) and Chlorophyll-
(B) CAUSES THE GREEN APPEARANCE OF PHOTOSYNTHESIZING PLANTSREFLECTS
GREEN LIGHT!!
II. Carotenoids- pigment with moderate absorbance in the blue
and green wavelengths. Causes the orange-yellow-red appearance of
photosynthesizing plants. Typically seen in the Fall when plants
stop replenishing their chlorophyll (absorbs orange-red
wavelengths) concentrations in preparation for winter (decreased
sunlight).
The Chloroplastthe Site of Photosynthesis:
Thylakoid: Site of the LIGHT-DEPENDENT REACTIONS
Granum (plural Grana): Stack of thylakoids surrounded by the
stroma
Stroma: Watery fluid (like the cytoplasm, but thicker), site of
the LIGHT-INDEPENDENT REACTIONS
Photosynthesis takes place through two stages:
I. The Light-Dependent Reaction (aka Light Reaction)
II. The Light-Independent Reaction (aka Dark Reaction aka Calvin
Cycle)
The Light-Dependent Reaction:
LOCATION: THYLAKOID
Inputs (what goes in):
Light energy(from the Sun) In photosynthesis equation as
reactant
Water (H2O) In photosynthesis equation as reactant
NADP+
ADP + P
Outputs (what comes out):
Oxygen gas (O2) In photosynthesis equation as product
ATP
NADPH
The Light-Independent Reaction (Calvin Cycle):
LOCATION: STROMA
Inputs (what goes in):
Carbon Dioxide gas (CO2) In photosynthesis equation as
reactant
NADPH
ATP
Outputs (what comes out):
Glucose (C6H12O6) In photosynthesis equation as product