ap bio unit 2 cell structure and function/membrane structure and function

surface area to volume ratio

cells must maintain a good _______, the volume of a cell determines its metabolic activity and surface area determines the amount of substances that can enter a cell

as cells increase in volume, the relative surface area decreases and the demand for internal resources increases- i.e., you want large SA to volume ratio

characteristics of a prokaryote

• no membrane-bound organelles

• cell wall made of peptidoglycan

• circular DNA

• typically small

characteristics of a Eukaryote

• compartmentalization (membrane-bound organelles)

• cell wall (in plant cells) made out of cellulose

• generally larger than prokaryotic cells

• DNA in the nucleus (diff shape too)

characteristics of both prokaryotes and eukaryotes

• has DNA

• cytoplasm

• ribosomes

relationship between diffusion and small bacteria

takes in required molecules/takes out waste, the smaller the cell the quicker and more efficient it is

how do large cells circumvent the limitations of diffusion

limited due to the cell’s large size and SA:V ratio

• pores (sponges)

• certain cells that do not require much O2 (sea jellies)

why are cells small

to increase surface area, which allows for materials to be transported efficiently

what does compartmentalization do

allow for specialization and more surface area - only displayed in eukaryotes

endomembrane system

interconnected membrane-bound organelles that work to synthesize, package, modify, and transport proteins and lipids throughout the cell

includes nucleus/nuclear membrane, rough ER, golgi, lysosomes, vesicles

Chloroplast and mitochondria origination by endosymbiosis

idea that these two organelles are ancestors of free-living prokaryotes because they both have double membranes, their own ribosomes, and circular DNA (similarities exist between prokaryotes and these organelles)

what makes up a cell membrane?

phospholipids, cholesterol, peripheral and integral proteins, carbohydrates

phospholipid components

hydrophilic (water loving) and polar (charged) head, hydrophobic (water fearing) and nonpolar (noncharged) tail

fluid mosaic model

the membrane is a fluid and the phospholipids are constantly moving and switching

also made of an array of different things

function of cholesterol in cell membrane

stops the membrane from being too far apart/too close together

• holds membrane together when it is hot

• prevents from packing too close when cold

function of proteins in cell membrane

1. transport

2. enzymes

3. receive signals

4. recognition of other cells

5. intercellular joining

6. attachment to the cytoskeleton and extracellular matrix (ECM)

peripheral proteins

proteins not embedded in the bilayer

integral proteins

proteins embedded throughout the entire bilayer

function of carbohydrates sticking off of the cell membrane

how cells recognize one another

what can pass easily through the bilayer

lipids, small/noncharged solutes, glucose through transport proteins, non polar, H20 (unless aquaporins r present)

what cannot pass easily through the bilayer

anything polar and larger than H20, ions/charged things, complex carbs, proteins

active transport requires…

ATP/energy

passive transport…

doesn’t require ATP and includes diffusion

types of passive transport:

1. diffusion

2. osmosis

3. facilitated diffusion

diffusion

high concentration to low concentration

tendency of molecules to spread out evenly until they reach equilibrium

osmosis

diffusion, specifically of water

high water concentration to low water concentration

aquaporin

channel protein in bilayer that facilitates and makes faster the passage of water

facilitated diffusion

transport proteins speed movement of molecules across plasma membrane

high concentration to low concentration

hypertonic solution

high amount of solute

solute concentration that the cell is exposed to (the hypertonic solution) is greater than the concentration inside the cell, therefore the cell loses water

net movement of water is OUT of the cell

hypotonic solution

low amount of solute

solute concentration in the cell is higher than that outside the cell (the hypotonic solution)

net movement of water is INTO the cell

isotonic solution

solute concentration and outside concentration is at equilibrium, not net movement of H20

osmoregulation

form of homeostasis, process by which an organism regulates the water balance in its body

osmoconformers

organisms with the same amount of solute as its enviroment, ex: seastar

osmoregulators

organisms that use a lot of energy to maintain a constant volume of H20/constant molarity, ex: fish

forms of active transport

1. primary active transport

2. secondary active trasport

active transport is…

moving things against the concentration gradient (low to high)

passive transport is…

moving things with the concentration gradient (high to low)

primary active transport

the energy of ATP is directly used to move molecules across the cell membrane against the gradient

ex: sodium potassium pump

secondary active transport

movement of molecules against the concentration gradient driven by the energy stored in an electrochemical gradient (the energy which does the actual moving)

included exocytosis and endocytosis (bulk transport)

exocytosis

a form of bulk transport in secondary active transport

transport vesicles migrate to the membrane, fuse with it, and release their contents

endocytosis

a form of bulk transport in secondary active transport

the cell takes in macromolecules by forming vesicles from the plasma membrane

selective permeability

the ability of a membrane to regulate the passage of molecules and ions through it

water potential

pressure potential + solute potential

free energy per mole of water

the higher the water potential, the greater the concentration of free water molecules (water that hasn’t been bonded with anything) and water has a higher tendency to move OUT of it

the lower the water potential, the lower concentration of free water molecules and water will move TOWARDS it

how does water potential move

from high water potential to low water potential

because it wants to establish equilibrium of water potential