AP Biology Unit 2

prokaryotes

domains bacteria and archaea; no nucleus

characteristic of prokaryotic cells

DNA in the nucleoid region; generally smaller in size

eukaryotes

protists, fungi, animals, and plants

characteristics of eukaryotic cells

membrane-bound organelles, genetic information in nucleus

endomembrane organelles

group of membrane-bound organelles and subcellular components that work together to modify, package, transport substances intercelullarly

nucleus

contains chromosomes; enclosed by the nuclear envelope; pore complex, nucleolusp

pore complex

for communication between nuclear envelope and cytoplasm

nucleolus

contains rRNA which combines with proteins to form ribosomes

ribosomes

translates message on mRNA and synthesizes proteins

sites of ribosomes

floating in the cytosol & bound to the ER/nuclear envelope

endoplasmic reticulum

network of sacs and tubes (cisternae)

RER

synthesizes proteins with ribosomes

SER

synthesis lipids, detoxifies the cell, metabolizes carbohydrates

Golgi apparatus function

1. modifies proteins

2. sorts and adds tags

3. packages materials into a vesicle and releases them (exocytosis)

cis face

receives vesicles

trans face

exports vesicles into the cytosol or outside the cell (trans- for transport)

lysosomes

hydrolyzes macromolecules with hydrolytic enzymes

autophagy

recycling cell material

peroxisomes

catalyzes reactions that produce H2O2, and breaks down H2O2 → H2O

vacuoles

membrane-bound sacs

central vacuole (plants)

maintains turgor pressure through nutrient and water storage

turgor pressure

pressure exerted by fluid against the cell wall; structural purpose

endosymbiotic theory

early eukaryotic cells engulfed prokaryotic cells and become an endosymbiont

endosymbiotic theory evidence

mitochondria and chloroplasts: double membrane, have their own ribosomes, have circular DNA

intermembrane space

between outer and inner membrane of mitochondria

matrix

inside the inner membrane; site of Krebs cycle and contains enzymes that produce ATP and catalyze cellular respiration

chloroplast

contains chlorophyll and thylakoids

granum

stack of thylakoids

stroma

fluid outside the thylakoids; site of Calvin cycle

cytoskeleton

network of fibers

microtubules

rod-like structure made of tubulin

microtubules function

structural support for motor proteins; separation of chromosomes; cell motility

SA:V

ratio between surface area and volume

SA:V and exchange rate

cells need a higher SA:V ratio to optimize exchanges

cell junctions

protein complexes that connect cells to each other

tight junction function

preventing leaks

desmosomes function

anchoring junction & attachment

gap junctions function

for cell-to-cell communication

plasmodesmata

small channels that directly connect the cytoplasm of neighboring plant cells to each other

cell membrane

divide intra- and extracellular space

fluid mosaic model

describes the plasma membrane structure: can move and shift (fluid) and contains a phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates (mosaic)

cell membrane structure

bilayer of phospholipids (amphipathic) with embedded proteins, cholesterol, and carbohydrates; described by the fluid mosaic model

cholesterol function

regulates fluidity of the cell membrane

cholesterol

a steroid that is randomly distributed

membrane proteins (types)

integral proteins and peripheral proteins

membrane carbohydrate function

cell-to-cell recognition

membrane carbohydrate types

glycolipids and glycoproteins (most abundant)

composition of cell walls for different domains

plants: cellulose

fungi: chitin

prokaryote: peptidoglycan (complex carbohydrate w a protein)

cell wall functions

shape and structure, protection, regulate water intake

selective permeability

some substances pass through the membrane easily

What substances pass through the cell membrane easily?

1. small non-polar hydrophobic substances

2. hydrocarbons

3. gases

passive transport

transport without energy; goes with concentration and electrochemical gradient

electrochemical gradient

difference in solute concentration and charge across a membrane

diffusion

process that results from high to low concentration (down the gradient)

facilitated diffusion

uses transport proteins that increase the rate of diffusion

channel proteins

provides a channel for molecules in facilitated diffusion

aquaporins

channel proteins used to transport water

carrier proteins

change shape for substances to pass the membrane

ion carrier proteins

carrier proteins that carry ions through the membrane; NOT the same as an ion pump

osmosis

water moving down the concentration gradient (low to high solute conc.)

active transport

transport that requires energy bc it is against the concentration gradient

What does ATP do in active transport?

It causes a conformational change in the protein to function

active transport types

pumps and cotransport

pumps

it creates an unequal concentration of ions (electrochemical gradient)

sodium-potassium pump

pumps 3 Na+ ions out and 2 K+ ions in

cotransport

energy from an electrochemical gradient to transfer two different ions across the membrane through a protein

symport

cotransport; same direction

antiport

cotransport; different direction

cytosis function

transport of large molecules across the membrane

exocytosis

large substances transported out of the cell via vesicles

endocytosis

uptake of molecules from the plasma membrane

phagocytosis

when a cell engulfs particles to be digested by a lysosome

pinocytosis

uptake of extracellular solutes and fluids

osmoregulation

balances uptake and loss of water and solutes

What facilitates osmosis?

1. aquaporins

2. osmolarity

osmolarity

the total solute concentration per L of a solution

isoosmotic

two solution having the same conc.

hyperosmotic

the solution that has a higher solute conc.

hypoosmotic

the solution that has a lower solute conc.

tonicity

the ability of a solution to make water move in or out of the cell by osmosis

water potential

water flows from high to low water potential, i.e. low to high solute concentration

formula for water potential

ψ = ψ_s + ψ_p

ψ_s = solute potential

ψ_p = pressure potential

ψ_p of pure water in an open container

zero

cell compartmentalization

allows different metabolic processes to occur, prevents interfering reactions from occurring together, increases SA to reactions