Catalyst (12/3) 1. Write 3 things you already know about cells. 1. Blood cells (red and white)* 2. Eukaryotes prokaryotes 3. Plants have cell wall 4. Cells.

Catalyst (12/3)

1. Write 3 things you already know about cells.1. Blood cells (red and white)*2. Eukaryotes prokaryotes3. Plants have cell wall4. Cells make up every living things5. Prokaryotes split6. Mitosis/meiosis*7. Organelles

2. Write 2 things you want to know about cells1. What’s the function of different cells?2. How are cells affected when damaged?3. What a good way to remember difference between meiosis and

mitosis?*

A TOUR OF THE CELL(CELL STRUCTURE &

FUNCTION)

AP Biology-Chapter 6

Cell Function

All known living things are made of cells

Structural and functional unit Produced by division of

existing cells Contain hereditary information

that is passed from cell to cell—DNA

Smallest units that perform vital physiological functions

Each cell maintains homeostasis at the cellular level

Homeostasis at higher levels reflects combined coordinated action of many cells.

Regulates itself!

Common Features of All Cells

Plasma membraneCytoplasmDNANucleoid region/NucleusRibosomes

=prokaryotes

=eukaryotes

Prokaryotes

No membrane bound nucleus“naked” circular DNANo internal membrane-bound organelles

“naked” circular DNASmall; <1.0-3.0 μm in diameterSimple structureComprised of Domain Bacteria and Archaea

Kary=seed

NO membrane bound

organelles!

Prokaryotes older than eukaryotes

Eukaryotes

Have a membrane bound nucleus—linear DNA

Internal membrane-bound organellesLarge; 10-100 μm in diameterComplex structureComprised of Algae, Protozoa, Fungi,

Animals, and Plants (Domain Eukarya)

Prokaryotic Structures and Functions

External Structures Glycocalyces—capsule or slime layer Flagella Pili Fimbriae

Glycocalyces

Gelatinous, sticky substance surrounding outside of cell Composed mainly of polysaccharides

Some species make polypeptides Two types:

Capsule Slime layer

Capsule Composed of organized repeating units of organic

molecules Firmly attached to cell surface Protects cells from drying out May prevent bacteria from being recognized and

destroyed by host

Like “skin”

Flagella

Responsible for movement Long and whiplike Composed of filament, hook, and basal body Flagellin protein forms filament Base of filament inserts into hook Basal body anchors filament and hook to cell wall Capable of rotating 360°.

(cell wall)Basal Body

Eukaryotic flagella just move back and

forth

Pili

Long hollow tubules Typically only 1 or 2 per cell Join two bacterial cells to transfer DNA from one

to the other (conjugation) Also called:

Sex pili Conjugation pili

“reproduction”

Fimbriae

Nonmotile extensions Sticky and proteinaceous Used to adhere to other bacteria, hosts, and other

surfaces May be hundreds per cell Shorter than flagella

“not moving”

“stick”

“made from proteins”

Cell Wall

Provides structure and shape Protects cell from osmotic pressure Assists in attaching cells to other cells and

surfaces Made of peptidoglycan Target bacterial cell wall with antibiotics because

animal cells do not have them

Penicillan inhibits bacteria’s ability to repair and make

cell walls.

Catalyst (12/4)

1. What does the word “prokaryote” mean?Pro=before kary=seed (before the nucleus)

2. Who evolved first, eukaryotes or prokaryotes?Prokaryotes (less complex—endosymbiotic theory)

3. How does not having membrane bound organelles affect prokaryotes?

Naked DNA—more exposed to damage?Don’t go through mitosis/meiosisCan’t have sex—pili (conjunction)Make ATP not in mitochondria instead on plasma membrane(the two not crossed out are better answers)

Glycocalyces

Formed from glycolipids and glycoproteins

Never as organized as prokaryotic capsules

Helps anchor animal cells to each otherStrengthens cell surfaceProtects against drying outFunction in cell-to-cell recognition and

communication

Glycolipid=lipid & carbGlycoprotein=protein & carb

pro

tei

n

Carbohydrate side chain

Flagella

Shaft composed of tubulin“9+2” arrangement of microtubulesanchored to cell by basal body; no hookbasal body has “9+0” arrangement of microtubules

single or multiple; generally found at one pole of cell

do not rotate, but undulate rhythmically

CilliaCan see 9+2 arrangement

Can see 9+0 arrangement

Cilia

Shorter and more numerous than flagella

Composed of tubulin in “9+2” arrangement

Coordinated beating propels cells through their environmentAlso used to move substances past

the surface of the cell

Cilia found in….Nasal cavityTrachea (throat)EarsFallopian Tubes

Microvilli

Small (0.08 um in diameter, 1 um long) Plasma membrane covered extensions with microfilaments

Actin cross links that allow limited motion Increase the surface area by approx. 600 fold (humans)

Several thousand microvilli present on apical surface of a single cell in human small intestinal cells

Found in absorptive and secretory epithelial cells Kidney cells Intestinal cells

Also occur in sensory cells Inner ear Taste buds Olfactory receptor cells

Also occur on sperm and egg. Clustering of microvilli around the sperm holds it close and tight, enhancing

fusion.

(small intestine)More microvilli in….KidneyIntestineEarTongue (taste buds)Nose (olfactory)

FUNCTION: absorption, secretion, cellular adhesion, and mechanotransduction (mechanical stimulus to chemical—sense touch, balance, hearing)

Cell Walls

Fungi, algae, and plants have cell walls but no glycocalyx

Composed of various polysaccharidesPlants—celluloseFungi—cellulose and chitinAlgae—cellulose and other

polysaccharides

(not in animals!)Rigid

!

*chitin makes fungi more closely related to animals than plants

Plasma Membrane

Fluid mosaic of phospholipids and proteins

Contains cholesterolControls movement into and out of cell

(picture on back)

Nonmembranous Organelles

Ribosomes Cytoskeleton Centrioles and centrosome

Ribosomes

Ribosomes Larger than prokaryotic ribosomes Site of protein synthesis Assembled in the nucleolus Made of RNA and protein Exported into the cytoplasm Free—unbound in the fluid cytoplasm

Produce proteins for use in the cell Bound—attached to the endoplasmic reticulum

(ER) Produce proteins for export, or for plasma membraneRough

ER

Cytoskeleton

Extensive Functions

Anchor organelles Cytoplasmic streaming and movement of organelles Critical in mitosis and meiosis Cell contraction Movement during endocytosis and amoeboid action Provides basic shape

Composed of Tubulin microtubules

Cylindrical tubes• In cilia and flagella• “superhighway” for organelles

Actin microfilaments Fine, thread-like protein fibers Work with myosin in muscle contraction

Intermediate filaments Provide tensile strength

“cell”

STRUCTURE & MOTION

Cytosol=liquidCytoskeleton-proteins that make structural part

thinnest

thickest

Centrioles

Barrel shaped microtubule structure Found in animal cells and algae; rarely in plants Organize the mitotic spindle

During mitosis

Nucleus

Largest organelle in the cell Consists of

Nucleolus—site of ribosomal RNA synthesis Chromatin—uncoiled DNA Nuclear Envelope—separates nucleus from cytoplasm

Two main functions Stores hereditary material Coordinates cell’s activity

CONTINUOUS!

Chromatin

Fibrous material consisting of DNA and proteins DNA is never found “naked” Always associated with histones—proteins Also associated with RNA and other molecules (hormones

and vitamins) During mitosis chromatin condenses to become

chromosomes

Chromatinchromosomes (condensed)

Catalyst (12/5)

What do you already know about the endomembrane system (Endoplasmic Reticulum, Golgi apparatus, microbodies, lysosomes)?

TEST CORRECTIONS DUE TODAY!! TURN IN IN UPPER LEFT HAND CORNER OF DESK!

Nuclear Envelope

Double membrane with a space in between called the perinuclear space

Outer membrane is continuous with rough ER

Nuclear pores regulate passage of material

Selectively permeable

Endomembrane System

Series of continuous membrane enclosed vesicles, or Discontinuous vesicles that communicate with one

another through vesicles that are formed at one surface and move to another where they are incorporated

Endoplasmic reticulum Rough ER Smooth ER

Golgi apparatus Vesicle—transport and storage Microbody

Peroxisome in animal cells Glyoxyomes in plant cells

Lysosomes

Flow of materials

“inside” “things that work together”

Type of vessicle

Rough Endoplasmic Reticulum

Netlike arrangement of hollow tubules Continuous with nuclear envelope Transport network

Molecules that are targeted for certain modifications and/or Specific final destinations

Produces and processes proteins for export or secretion Produces transmembrane proteins—embedded in the

membrane Adds carbohydrates to some Transports proteins to the golgi apparatus via vesicles Transports proteins directly to nucleus due to close

association of the ER lumen and the nucleus

(RER)—ribosomes attached

(glycoproteins)

Insulin, nonsteroid hormones

Na+/K+ pump, proteins in membrane

More RER in….ThyroidPancreasLiverAdrenal

Medulla

Smooth ER

Lipid production (fats)Detoxification of drugs and poisonsStores calcium

(SER)—no ribosomes

(Skin, ovaries, testes)(liver)

(bones, sarcoplasmic

reticulum) Specialized SER in

muscle cells

Golgi Apparatus

Series of cup-shaped, membrane-covered sacs called cisternae

Animal cells—10 to 20 stacks per cell Usually located near the nucleus Modifies proteins and lipids build in the ER

Molecules are added or removed off the ends Identification and destination tags are added

Produces some polysaccharides (e.g. pectin) Product is extruded from the GA vesicle

Secreted outside the cell Incorporated into plasma membrane Returned to rough ER Vesicle may mature into a lysosome

(GA)

“post office” of the cell—packages and sends proteins

Closer to ER

Secretory Vesicle

Transport cell secretions from the GA to the plasma membrane for release Hormones Neurotransmitters Vesicle=small,

membrane bound, holds something

Catalyst (12/6)

If you were absent yesterdayWhat do you already know about the endomembrane system (Endoplasmic Reticulum, Golgi apparatus, microbodies, lysosomes)?

If you were here yesterdaywhere in the body is there more RER? Why?

TEST CORRECTIONS WERE DUE YESTERDAY (BUT SOME OF YOU WERE’NT HERE)!! TURN IN IN UPPER LEFT HAND CORNER OF DESK!

Peroxisome

Roughly spherical and bound by a single membrane

Contain variety of enzymes Primary function to destroy toxic substances

In particular, hydrogen peroxide (by product of cellular metabolism)

In liver cells—detoxify alcohol and other harmful compounds

Self-replicate No DNA Import the proteins they need to perform fission

Lots of peroxisomes in liver cells—detox!

Break in 2

Lysosomes

Roughly circular membranous sacs Contain approx. 40 hydrolytic enzymes Digest cellular materials that have exceeded their lifetime

Cellular waste products Fats Carbohydrates Proteins Worn out organelles (e.g. mitochondria)

Safety net Internal environment has pH 4.8 If lysosome ruptures the hydrolytic enzymes would denature in the

neutral cytosol environment Maintains low internal pH with the help of H+ ion pumps located in

the membrane Avoids self-digestion by glycosylation of membrane proteins.

Many lysosomal disorders!

Perform hydrolysis

(breakdown)

Enzymes won’t break down the

cell!!

acidic

(the enzymes optimal pH is 4.8 but the cell’s pH is

7 denature)

Mitochondria

Relatively large, oblong, double membrane bound organelles

Occur in numbers directly correlated to the cell’s level of metabolic activity

Convert oxygen and nutrients into ATP Aerobic respiration

Elaborate structure very important to function Aerobic respiration is a complex

multi-step process Reproduce independently—

contain circular DNA

CELLULAR RESPIRATION

(exergonic/catabolic) Lots of mitochondria in muscles!!

Mitochondria DNA is maternally inherited(you got it from your

momma!)

Chloroplast

Relatively large, oblong, double membrane bound organelles

Occur in all green parts of plants Majority in leaves—one-half million

per square millimeter Convert solar energy and

carbon dioxide into glucose photosynthesis

Elaborate structure very important to function Photosynthesis is a multi-step

complex process Reproduce independently—

contain circular DNA

PHOTOSYNTHESIS (endergonic/anabolic)

Central Vacuole

Large, single membrane bound vacuole (can take up to 80% of cell)

Structural supportStorageWaste disposalProtectionGrowth

Vacuoles (in animals) small and used for temporary storage or material transport

(Plants only!)

(aka vesicle)

(turgor pressure) (salts,

nutrients, pigments) (can release molecules that are poisonous, odiferous, or unpalatable

to predators)

(endocytosis, exocytosis)

Groups of cells are organized into…

TissuesOrgansOrgan systems

More organized

These neighboring cells must be able to

AdhereInteractCommunicate

“stick to each other”

Cell to Cell Junctions

Plasmodesmata—plants only Cytosol passes through interacting with neighboring

cells Water and small solutes pass through

Sugars Amino acids Proteins and RNA

Larger molecules pass with aid of actin filaments

There are three types for animal cells

Occluding Junctions—Tight JunctionsAdhesive Junctions—Adherens Junctions and

DesmosomesCommunicating Junctions—Gap JunctionsAll three common in epithelial tissue

“stop or obstruct”

Tight Junctions

Hold cells togetherSeparate apical membranes and

basolateral membranesPrevents the movement of solute and water

between cells

Adherens Junctions

Proteins called cadherins and cateninsActin filaments connected to cateninsPerform signaling functions

Desmosomes

Fasten cells in strong sheets Still permit materials to move in intercellular space

Reinforced with intermediate filaments and connecting fibers

Also called anchoring junctions

Gap Junctions

Also called communicating junctions Cytoplasmic channels between neighboring cells

Special membrane proteins layer each channel Connected by hexagonal tubes called connexons Connexons can open and close

Pore wide enough for passage of: Salt ions Sugars Amino acids Other small molecules Electric current

Catalyst (12/7)

Explain how the different types of cell junctions help organize cells into tissues.

--Cell junctions are tight, adherens, gap.--tight help cells hold together, prevent movement of

fluids--communicate with the signaling of adherens jxns

and electric current passing allowed by gap jxns--gap junctions and plasmodesmata exchange cytosol,

sugars, amino acids, salts/ions allows them to interact or work together

“What is Health?”journal response due by MIDNIGHT TONIGHT!!

Evolution of Eukaryotic Cells

Endosymbiotic Theory Theory of the process of organelle incorporation

into a cell Larger anaerobic eukaryotes engulfed aerobic

prokaryotes Became endosymbionts that enables host cell to become

aerobic Symbiotic relationship became crucial over time

Developed by Lynn Margulis in 1966

“requiring air”

Close relationship between the individuals of 2 or more species

Endosymbiotic Theory

What would later become

plants

What would later become

animals

Evidence supporting Endosymbiotic Theory

Physical similarities exist between mitochondria, chloroplasts, and prokaryotes Similar size

Molecular data indicates mitochondria and chloroplasts are prokaryotic in origin Mitochondria and chloroplasts carry their own DNA, RNA, and unique

70S ribosome Some mitochondrial DNA sequences similar to Rickettsia, bacterial

obligate intracellular parasite Lateral gene transfer occurred between mitochondria and the

host cell nucleus Mitochondria and chloroplast have double membrane

Possibly retaining their original membrane inside the membrane produced by the host cell

Mitochondria evolved from proteobacteria Chloroplasts evolved from cyanobacteria.

* this…evidence is always important

Process of swapping genetic material between neighboring bacteria (not necessarily of the same species)

Lateral (or Horizontal) Gene transfer

Catalyst (12/10)

Why are cells small but not infinitely small? compartmentalization, bigger to store

machinery (organelles), smaller= higher surface are to volume ratio (can more materials in and out and more rxns on cell membrane)

How does having smaller cells affect metabolic rate (rate at which the cell can perform all of its reactions)? Metabolic rate increases

Catalyst 12/11

Prokaryotes are much smaller than eukaryotic cells, what does this mean about their surface area to volume ratio? Explain how this affects their metabolic rate, growth rate, and generation time as compared to eukaryotes? Prokaryotes have a larger surface area to volume ratio Higher metabolic rate Grow faster Shorter generation time