AP Biology Unit 2: Cell Structure & Function

cell structure of an animal cell(eukaryotic)

1. nucleus

2. lysosome

3. mitochondria

4. small vacuole

5. ribosome

6. smooth ER

7. rough ER

8. peroxisome

9. golgi apparatus

10. plasma membrane

plasma membrane

selectively permeable, separates inside and outside of cell

Nucleus

Contains genetic info(DNA cannot leave the cell so it gets copied to RNA)

Lysosome

digestive organelle, has enzymes(hydrolytic/digestive enzymes) that hydrolyze(break down) macromolecules, helps with apoptosis

-lysosomes can fuse with food vacuoles to help digest food

mitochondria

ATP production

small vacuole

stores/transport material/waste

Ribosomes

free ribosomes(in the cytoplasm): make proteins for use inside the cell(intracellular use)

bound ribosomes(to the rough ER): ribosomes that make proteins to be transported outside the cell

Smooth ER

lipid synthesis, carb metabolism, detoxifying, Ca+ storage

Peroxisome

metabolic functions, makes H202 to break down fatty acids

Golgi apparatus

synthesis, modify, sort and transport/secrete cell products

Rough ER

contains bound ribosomes that make proteins to be released outside of the cell

Endomembrane system

-these organelles working together to produce, modify, package, and transport materials out of the cell

nucleus(DNA→mRNA) —> Rough ER(proteins) —> Golgi(modify, sort, transport proteins) —> vesicles go to cell membrane to release material(proteins transported to cell membrane and released)

Structures in plant cells but NOT animal cells

-large central vacuole: storage, water & other molecules

-chloroplast: photosynthesis

-cell wall: made of cellulose, maintains shape, protection

Cell size and surface area to volume ratio

Smaller cells = LARGER surface area to volume ratio(more efficient at getting materials in and out)

Larger cells = SMALLER SA:V ratio (Less efficient at transporting materials in and out)

Mitochondria SA:V

the highly folded inner membrane = more SA to produce ATP(where the ETC is located)

Intestinal cells

highly folded membranes = more surface area for nutrient absorption

The cell membrane(phospholipid bilayer)

• phosphate group(head) = polar, hydrophilic

• fatty acid tails = nonpolar, hydrophobic

• selectively permeable

• fluid mosaic

What can passively go through/diffuse the cell membrane?

• nonpolar, small molecules(N2, CO2, O2)

• steroid hormones(lipids, small, nonpolar)

• H2O(polar but very small) — osmosis

What cannot passively go through/diffuse through the cell membrane?

• ions(charged) - NA+, K+

• polar substances

• very large substances

Fluid mosaic model

The cell membrane is modeled as a “fluid mosaic”. It’s called a mosaic because it contains MANY other components such as proteins, cholesterol, glycolipids, etc. that are peppered throughout. It’s “fluid” as those components are not locked in place but can move around.

Passive transport

• NO energy input(NO ATP)

• High conc. —> Low conc.

• goes down the conc. gradient

  1. osmosis

  2. facilitated diffusion

  3. aquaporins

  4. simple diffusion

Active transport

• energy input(ATP) required

• Low conc. —> High conc.

• goes against the conc. gradient

  1. endocytosis

  2. exocytosis

  3. sodium potassium pump

Osmosis

• passive transport

• H2O moves across membrane from high H2O conc. to low H2O conc.

• H2O moves from low to high solute conc.

Movement of H2O across aquaporins

• passive transport

• pore in the cell membrane that allows large amounts of water through

simple diffusion

molecules move across membrane from high to low conc.

passive transport

facilitated diffusion

involves use of carrier protein or protein channel

passive transport

sodium(Na+) potassium (K+) pump

-transporting ions

requires ATP - active transport

endocytosis

taking materials into the cell

active transport

exocytosis

getting materials out of the cell

active transport

Water potential

H2O flows from where there is high ψ to low ψ

cell compartmentalization

eukaryotic cells are compartmentalized - have many different compartments or “cell parts” that each do a different function to help the cell work as a whole

prokaryotic cell structure

• no nucleus

• free DNA

• cell wall

• ribosomes

• cytoplasm

• flagella(some)

Endosymbiotic theory

explains the evolutionary origin of eukaryotic cells from prokaryotic cells - how they evolved from free-living prokaryotes

-symbiotic relationship in which the smaller “cells”(organelles) have a place to live + they make food or ATP for the larger “cell”(host)

What is the evidence for endosymbiotic theory?

-mitochondria and chloroplasts have their own naked and circular DNA like prokaryotes

-mitochondria and chloroplasts have double membranes

-mito. and chloro. have their own ribosomes similar to prokaryotic cells

-mito. and chloro. do fission-like division