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AP Biology U2: Cell Structure and Functions Cheat Sheet by

Cell Structure and Functions. Good Luck :)

Cell theory

1. All living things are made up of cells
unicel­lular or multic­ellular
2. Cells are the smallest and most basic unit of life
prokar­yotic or eukaryotic
3. All cells come from pre-ex­isting cells.

Prokar­yotic or Eukaryotic

no nucleus
has nucleus
no membrane bound organelles
membrane bound organelles
division process is binary fission
division process is mitosis
unicel­lular or multic­ellular
cell wall made of peptid­oglycan
in fungi or plants with cell walls made of chitin or cellulose
smaller cells
larger cells
bacterial cells
animal or plant cells
all cells have cell membrane, cytoplasm, ribosomes, genetic material (DNA or RNA)


Cell (Plasma) Membrane
Phosph­olipid bilayer that surrounds the cell to control what goes in and out of the cell
Network of threadlike fibers made of proteins to give the cell shape, move organelles around, provide structural support for animal cells
jelly-like substance mainly made up of H2O that holds everything in place and provides solution for chemical reactions to take place in
genetic material that's surrounded by a nuclear membrane with nuclear pores that control what goes in and out that protects the DNA that controls the activities of the cell
inside the cell that makes mRNA which makes ribosomes
located on the Rough ER and floating in cytoplasm that make proteins in a process called transl­ation
Rough Endopl­asmic Reticulum
Hugs the nuclues and has ribosomes on it that makes proteins
Smooth Endopl­asmic Reticulum
has no ribosomes and is attached to the Rough ER that makes lipids (membr­anes), destroy toxins (liver), and regulates calcium (muscles)
Golgi Apparatus
folded membrane that gets vesicles of protein from ER to process, sort, and ship proteins where needed
"­min­i-c­art­" that transports proteins around the cell
Contains enzymes that break down the dead stuff and apoptosis
small and numerous in animal cells but one large one in plants cells that act as a storage
made of microt­ubules that happen in cell division helping cells divide by pulling chromo­somes apart
shorter, more numerous, like tiny oars (hairs) that move fluid across cell surface
longer, fewer (tail) that move entire cell
inner membrane and matrix (fluid) where cellular respir­ation happens (breaks down food to release energy as ATP)
grana (stacks) and stroma (fluid) where photos­ynt­hesis happens (converts energy from sun to energy in sugar)
Cell Wall
Provides structural support and protection for bacteria, plant and fungi cells. Bacteria's made with peptid­ogl­ycan. Plant's made with cellulose. Fungi's made with chitin.
membra­ne-­bound organelles primarily involved in lipid metabolism and the conversion of reactive oxygen species

Animal, Plant, Prokar­yotic cells

Plant Cell:
central vacuole
cell wall

Animal Cells:
cilia and flagella

Bacterial Cells

Cell membrane

Phosph­­olipid Bilayer: amphip­­athic
- hydrop­­hilic heads
- hydrop­­hobic tails

Fluid Mosaic Model

membrane is a fluid structure with "­mos­aic­" of various proteins embedd­ed/­att­ached to bilayer
phosph­­ol­i­pids provides fluidity and elasticity
proteins and other molecules embedded in membrane

Structure of Cellular Membrane

main compon­­ents
phosph­­ol­ipids and proteins
other important molecules
choles­­terol and carboh­­yd­rates


transport, enzymatic activity, signal transd­uction, cell to cell recogn­ition, interc­ellular joining, attachment to cytosk­eleton and extrac­ellular matrix
Integral Proteins
embedded in
Peripheral Proteins
attached to surface


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


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

Selective Permea­bility

Allows some materials, but not all to go through
can easily pass: small, non polar, nonionic hydrop­hobic, neutral molecules and H2O
cannot easily pass: large (must use vesicles), polar (must go through proteins), ionic, hydrop­hillic

Cellular Transport

# of molecules of a substance in a given volume
Concen­tration Gradient
differnce in concen­tration (mass) of a substance from one location to another
Passive or Active Transport


the need for an organism to maintain and regulate constant or stable internal conditions
Growth and homeos­tasis are maintained by the constant movement of molecules across membranes.

Passive Transport

Molecules moving DOWN their concen­tration gradient from HIGH to LOW with NO ENERGY until EQUILI­BRIUM is reached
Simple Diffusion
The spreading out of molecules
ion channels
transport proteins allow ion to flow from a high to low concen­­tr­ation
Facili­tated Diffusion
transport protein (channel or carrier) helps to facilitate the diffusion of molecules
aquapo­­rins: tunnel that allows water to go through the membrane
Simple diffusion of water across a semipe­rmeable membrane
Hypertonic solutions = more solutes, less water; water moves out of cell to SHRIVEL
Hypotonic solutions = less solutes, more water; water moves into the cell to SWELL/­BURST
Isotonic Solution = equal solutes and water; cell STAYS THE SAME

Active Transport

molecules moving AGAINST the concen­tration gradient from LOW to HIGH concen­tration
Molecular Pumps
Cell uses energy to pump molecules across a membrane through a protein channel (sodium potassium pump and proton pump)
single ATP-po­wered pump that transports solute indirectly
cell uses energy to export materials out of the cell with a vesicle
cell uses energy to import materials into the cell with a vesicle
Phagoc­ytosis = cell "­eat­ing­" (cell engulfs solids into vesicle and digests them)
Pinocy­tosis = cell "­dri­nki­ng" (cell engulfs liquids into vesicle and digests them)

SA:V Ratio

Surface Area: 6 (lw)
Volume: lwh
Steps to find SA:V
1. calculate SA
2. calculate V
3. Divide SA by V
As cell size increases, the SA:V ratio decreases and the cell becomes less efficient at moving things in and out of the cell
= cell must stop growing or dividing

Cell size

Why are cells small?
To maintain a larger surface area to volume ratio. The smaller the cells are, the faster and more efficient things can go in and out of the cell.

Water Potential

Ψ = ΨS + ΨP
ΨS: solute potential
ΨP: pressure potential
ΨS = -iCRT
i: ionization constant
C: concen­tration (M)
R: pressure constant (0.0821 liters bars/mole K)
T: temper­ature in Kelvin ( oC +273)
Osmotic Potential
the potential of H2O moving from hypotonic solutions to hypertonic solutions (High water potential to low water potential)
Turgor Pressure: When a plant cell is placed in a hypotonic solution and gains a lot of water, the cell wall presses back on the cell membrane to prevent the cell from bursting.


the control of water balance
organisms without cell walls that live in hypertonic or hypotonic enviro­­nment
Osmore­gul­ation maintains water balance and allows organisms to control their internal solute compos­iti­on/­water potential.


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