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AP Bio Unit 2: Cell Structure and Function Cheat Sheet by

AP Bio Unit 2: Cell Structure and Function

Surface Area

outside area of an object
the area around the outside of a cell
unit: m^2

Applic­ation in Living Things

increased surface area = increased diffusion
microv­illi: increases absorption in intestines
root hairs: increases water/­nut­rient absorption in plants
endome­mbrane system: increased folds in organelles allow for more surface area to do cellular work
cristae of the mitoch­ondria: folds in the inner mitoch­ondria increase amounts of ETC (more ATP)

Structure of Phosph­olipid

hydrop­hilic head:
hydrop­hobic tail:
saturated fatty acid
unsatu­rated fatty acid


at warm temper­atures:
at cool temper­ature:
restrains the movement of phosph­olipids and reduces fluidity
maintains fluidity by preventing tight packing

Passive Transport

no energy
high to low concen­tration
facili­tated diffusion
ion channels


passive transport
molecules spread out to available spaces
move down concen­tration gradient (high to low concen­tra­tion)
work to reach equili­brium

Active Transport

no energy
low to high concen­tration
sodium potassium pump: 3 sodium leave and 2 potassium enter cell against the concen­tration gradient
proton pump: hydrogen atoms pumped against concen­tration gradient
cotran­sport: H+ gradient helps to bring other molecules into cell
endocy­tosis and exocytosis

Prokar­yotic vs. Eukaryotic Cells

simila­rities: cell membrane, DNA, ribosomes, cytoplasm
no nucleus
no membrane bound organelles
membrane bound organelles
binary fission
mitosis and meiosis
average size:
DNA is circular
DNA is linear
single chromosome
paired chromo­somes

Plant Cells in Pure Water

pure water (hypotonic solution) will initially move into the cells
after a period of time the cells will become turgid (swollen)
as turgor pressure increases, water will diffuse out of the cell... eventually equili­brium will be reached


organisms without cell walls that live in hypertonic or hypotonic enviro­nment must have adapta­tions for osmore­gul­ation
the control of water balance


amount of space inside of the object
the space inside of the cell
unit: cm^3

Fluid Mosaic Model

phosph­oli­pids: provides fluidity and elasticity
proteins and other molecules embedded in membrane

Phosph­olipid Bilayer

hydrop­hilic heads
hydrop­hobic tails


integral proteins:
peripheral proteins:
imbedded through the membrane (inside)
on hydrop­hilic portion of the cell membrane (outside)


cell to cell recogn­ition:
membrane carboh­ydr­ates:
cell's ability to distin­guish one type of neighb­oring cell from another
interact with the surface molecules of other cells, facili­tating cell to cell recogn­ition

Passive Transport (diffu­sion)

the tendency for molecules of any substance to spread out into available space
substances will move down a concen­tration gradient
high to low concen­tration

Passive Transport (osmosis)

the diffusion of water
water moves from hypotonic to hypertonic
isotonic: equal solute across a membrane
hypotonic: less solute, more water
hypert­onic: more solute, less water
low to high concen­tration

Active Transport (endoc­ytosis)

cell takes in macrom­ole­cules by forming vesicles from plasma membrane
phagoc­ytosis: "­cel­lular eating­," engulfing solids
pincyt­osis: "­cel­lular drinki­ng,­" engulfing solutes

Active Transport (exocy­tosis)

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

Osmore­gul­ation (param­ecium)

The Endosy­mbiotic Theory

an evolut­ionary theory of the origin of eukaryotic cells from prokar­yotic organisms
endosy­mbi­osis: one organism living inside another
evidence 1) chloro­plasts and mitoch­ondria multiply in the same way as ancient bacteria
evidence 2) chloro­plasts and mitoch­ondria both control their own DNA and ribosomes
evidence 3) chloro­plasts and mitoch­ondria both have two membranes (inner membrane contains different proteins than the outer membrane)

Surface Area to Volume Ratio

a comparison between the size of the outside of an object and the amount inside
smaller cells have an increase SA:V
as the cell gets bigger, the SA:V decreases
small cells are more efficient at diffusion as they have a high ratio

Structure of Cellular Membrane

two main compon­ents:
other important molecules:

Functions of Membrane Proteins

interc­ellular joinings
enzymatic activity
transport (activ­e/p­assive)
cell to cell recogn­ition
signal transd­uction

Cell Membranes are Semipe­rmeable

properties of molecules that can get through the phosph­olipid bilayer:
properties of molecules that can not get through the phosph­olipid bilayer:
O2 and CO2

Passive Transport (facil­itated diffusion)

transport proteins allow molecules to flow from high to low concen­tration
aquapo­rins: tunnel that allows water to go through the membrane
glut: glucose transp­orter

Passive Transport (ion channels)

transport proteins allow ion to flow from a high to low concen­tration

Passive and Active Transport

Water Potential

the force respon­sible for movement of water in a system
solute potential: determined by solute concen­tration
pressure potential: results from exertion of pressure on membra­nes­/walls as water moves in or out; can be positive or negative

Plant vs. Animal Cell

Plant Cell:
Animal Cell:
cilia and flagella
central vacuole
cell wall

The Endome­mbrane System

a system of synthe­sizing proteins for export
1) Nucleus: ~trans­cri­ption (DNA -> RNA) ~make ribosomes
2) Rough ER: ~trans­lation (RNA -> proteins) ~proteins for export
3) Vesicle: transports proteins in cells
4) Golgi Apparatus: process and package proteins
5) Vesicle: transports proteins in cells
6) Cell Membrane: exocytosis


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