Cells

Cells

Chapter 7

Cell Theory

1665- Robert Hooke examines cork Named the little “boxes” cells

150 years later, several other scientists combined ideas to form Cell Theory:Cell Theory: Living things have cells Cells are basic units of structure and function Cells come from reproduction of existing cells

Check yourself!

Can cells appear spontaneously without genetic material from previous cells?

Cell Types

Come up with a list of all the different cells that might be in your body. What shape/size might they be? Do they have anything in common? How are they different?

Cells

All cells haveAll cells have A plasma (cell) membrane Genetic material in some form Break down molecules for energy Can be one of two types:

Prokaryotic- cells with no nucleus, smaller Eukaryotic- cells with a nucleus, larger, have

organelles Fig. 7.4

Eukaryotic Cells

Have: Membrane bound organelles (organelles are

structures that carry out specific functions) Nucleus- contains the cell’s genetic material in

the form of DNA

Multi-cellular organism (plus algae and yeast)

Prokaryotic Cells

Have: Plasma membrane No nucleus No membrane-bound organelles Very simple organisms Could have been the first on Earth Thought that eukaryotes evolved from

prokaryotes Been classified as bacteria, usually

Prokaryote Examples

Cocci Bacteria-Round-Streptococci

Bacilli

Bacilli-Rod Shaped

Spirilli-Spiral shaped

Video Lab

DVDTime: 7.57Identify these four cells

1. 2. 3. 4.

Plasma Membrane- Section 7.2

What does it do? Maintains homeostasis (the balance in an

organism’s internal environment) Controls what goes into and out of the cell

What does it look like? Thin, flexible boundary around a cell

Where is it found? In any organism- it separates the inside of the

organism from the watery outside environment.

Plasma Membrane

Unique- It has selective permeability Membrane allows some substances to pass through cell

without allowing others The cell is surrounded by water on all sides Like a fish net Fig. 7.5, pg. 187 Animation

Plasma Membrane

Structure: Mostly made of lipids

Lipids are usually made of glycerol and three fatty acids However, in this case, a phosphate group replaces a fatty

acid making a phospholipid Therefore, these lipids are called Phospholipids: glycerol

backbone, two fatty acid chains and a phosphate group Has a bilayer of phospholipids- two layers of

phospholipids are arranged tail to tail Fig. 7.6

Phospholipid Bilayer of P.M.

Each phos.lip. is diagramed as a head with two tails. Heads are polar (the phosphate group makes it

that way) and attracted to water- Hydrophilic Fatty acid tails are nonpolar- Hydrophobic

So, the head loves water and the tails hate water. Water will not pass easily through the tails.

How does water get into the cell then?

What else is in the Plasma Membrane?

Cholesterol, proteins, and carbs Proteins help give transport materials (such as

water) & give shape to the membrane Cholesterol helps prevent fatty acid tails from

sticking together Carbs help recognize chemical signals from the

outside environment

Analyze this statement: High levels of cholesterol lead to reduced blood flow, making cholesterol bad for individuals.

Fluid Mosaic Model

This bilayer of phospholipids create a sea that molecules can float in- like apples floating in a crate. Fish Tank Demo

The F.M.M can move around like a blanket on a swimming pool

The collection of the proteins, cholesterol and carbs let some substances in and keep others out

Fig. 7.7 Animation

Reading Check- Why is it beneficial to have a 2 layer system than a 1 layer system?

Structures and Organelles- Section 3

Concepts in Motion Plant Cells and Animal Cells

Eukaryotes contain organelles that allow for specialization within cells

Consider a boot manufacturing company. If every person who worked their made their own pair of boots, the factory wouldn’t be very efficient. So, an assembly line is formed. Cells have assembly lines in them, too. Parts move

from one place in the cell to another, collecting more parts to complete the manufacturing process.

Organelles

Cytoplasm: Area between the membrane and the nucleus Gelatin-like fluid called cytosol Salts, minerals and molecules are found here

Cytoskeleton

Protein fibers in the cytosolHelp the cell maintain it’s shape. Fig. 7.8Made of

MicrofilamentsProtein threadsCell mvmt and shape

MicrotubulesStrands of hollow tubes of proteinHelp move things around in the cell

Nucleus - Fig. 7.10

Surrounded by the nuclear envelope Similar to plasma membrane, except it allows

larger sized substances to move through it

Stores heredity infoChromatin is spread throughout

Complex DNA with proteins attached

Contains a nucleolus Makes ribosomes

Ribosome

Most numerousNo membraneMade of proteins and RNAMade in nucleus and transported to

cytosol- May remain “free” in cytosol, or attach to the ER- “bound”

Protein synthesis (makes proteins) Proteins can turn into ANYTHING, they are the

play-dough of the cell

Endoplasmic Reticulum

Tubes and sacs folded Why folded?

Site of lipid and protein synthesis Amount of ER depends on the cell function Two types:

Rough- found in cells that make lg amts of proteins for other cells

Smooth- no ribosomes, but it still has functions – Fig. 7.11

What types of cells would contain a large amount of rough endoplasmic reticulum?

Golgi Apparatus- Fig. 7.12

Processes, modifies and packages proteins into sacs called vesicles The vesicles can then fuse with the plasma

membrane to release proteins outside the cell

Membranes, like ER, looks like pita bread

Writing Activity

Create a short biography of Camillo Golgi, who discovered the organelle.

Chloroplast

Nucleolus

Nucleus

Vacuoles

Golgi Bodies

Vacuoles- Fig. 7.13

Fluid-filledStores food, enzymes and wasteMost animal cells do not contain vacuoles

Vacuole Size in a Beet Cell

Chloroplast

Nucleolus

Nucleus

Vacuoles

Golgi Bodies

Lysosomes- Fig. 7.14

Small, digest excess or worn-out organelles and food particles

Found only in animal cells Digest bacteria and viruses Has a membrane- keeps the potent enzymes

inside from digesting the rest of the cell Connection: Tay-Sachs disease is caused by a

lack of a cell to clean out wastes Concepts in Motion

Centrioles- Fig. 7.15

Made of groups of microtubulesUsed in cell divisionFound in cytoplasm of animal cells near

the nucleus

Mitochondria- Fig. 7.16

Converts sugars into energy for cell Site of reactions that transfer energy from compounds to

ATP More mitochondria in more energetic cells Made of folded membrane that provides a large surface

area for breaking sugar bonds Energy produced from breaking bonds is stored Kleenex box demo of surface area Do plant cells have mitochondria?

Real-World Connections: Some diseases are due to problems with the energy (metabolism) carried out by the mitochondria

Some scientists believe the key to diseases such as Parkinson's and Alzheimer's is to increase the activity of the mitochondria in patients

Chloroplasts- Fig. 7.17

Capture light and energy and convert to chemical energy through photosynthesis

Contain thalakoids that trap energy from sun in chlorophyll (green pigment)

Belong to a group of plant organelles called plastids which are mostly used for storage

Mostly found in plant cells

Cell Wall- Fig. 7.18Plant cells onlySurrounds the plasma membraneSupport and protects the cellContain cellulose (carbo) help add

rigidnessHow do plants benefit from the cell wall?How is a cell wall different from the

classroom wall?

Cilia and Flagella- Fig. 7.19

Found in both eukaryotic and prokaryotic cells Made of microtubules Assist in mvmt If the cell is stationary, they move substances along the surface Cilia propel eukaryotic organisms through water, line respiratory

organs to help breath Flagella- less numerous and longer Where in the body would you find cillia? Used for transportation

Esophagus Stomach Intestines Female Reproductive organs

Sperm

BrainPop

www.brainpop.comIf time- Cell Structure

Developing Concepts- Review

Concepts in Motion- Visualizing Cells Name the location of protein synthesis Relate DNA to protein synthesis Generalize how DNA in the nucleus can guide

protein synthesis son the ribosome in the cytoplasm

Analyze why it would be an advantage to a protein-secreting cell to have ribosomes on the ER

What would happen to a cell if the number of ribosomes was reduced?

Compare Cells

Complete a Venn Diagram showing which cell structures are found only in plant cells, only in animal cells, only in prokaryotes and found in all three

Table 7.1 will help!Working Together- Read Pg. 200 togetherConcepts In Motion

Cell Organization

Charades!

Students: act out the part of an organelle while other groups try to guess your part