2nd unit ap bio

most basic unit of life

it doesnt necessarily mean its not complex tho

membrane

ribosome

genetic info (mostly in dna)

endoplasmic reticulum, nucleus (dna is in)

simple

no membrane-bound organelles

true

like garbage disposal. must maintain an acidic pH to get rid of cellular waste

basically supervisor

carries out oxidation reactions (chem reactions) and makes hydrogen peroxide

dmgs cell if they arent tucked safely in their own compartment

eukaryotic cells can do complex metabolic reactions that prokayotic cells cant (haha loser)

also y eukaryotic cells can grow much bigger than prokaryotic cells can

membrane bound nucleus (central cavity surrounded by membrane- holding DNA)

membrane bound organelles (compartments w specialized functions that float in cytosol)

linear chromosomes (prokaryotes have circular)

do it rn

cell membrane

nuclear envelope

endoplasmic reticulum

golgi apparatus

vesicle

vacuole

lysosome

these r all made of phospholipid bilayers that work w protein and lipid synthesis for modification, transport, and recycling in cell

dna→mRNA:nucleus, transcription

mRNA→protein: ribosome, translation

makes up basic fabric of plasma membrane. good for the plasma membrane bc phospholipids r AMPHIPATHIC= both hydrophilic et hydrophobic

good barrier keeping water and other polar/charged substances from easily crossing hydrophobic core of membrane

phospholipids form bilayers spontaneously under right conditions *** under right conditions

phosphate grp= negatively charged

“R” might or might not b charged or polar

head of phospholipid contacts both aqueous (watery) fluid inside & outside of cell

• since wota is a polar molecule, it forms electrostatic (charge-based) interactions w phospholipid heads

hydrophobic tails (unsaturated fatty acids) easily can interact w non-polar molecules, interacts poorly w water

• so its more energetically favourable for phospholipids to put fatty acids tails to inside of membrane=fatty acids tails shielded from surrounding water

depending on size of tail phospholipids form

small= micelle: single layered sphere

big et thick= may form liposome: hollow droplet of double layered membrane

water can still travel across the plasma membrane, but it just travels slowly (bc tails is hydrophobic) and if they get away w it they have to be small

types of protein channels that ALLOW water to flow thru are called “aquaporins”

cells open/close when needed. aquaporins r used for rapid transport of water across plasma membrane

2nd largest major component of plasma membrane

2 major categories of membrane proteins: integral membrane proteins and peripheral proteins

integrated into membrane, has at least 1 hydrophobic region that attaches them to inner hydrophobic part of phospholipid bilayer. outside/exposed to cytoplasm/extracellular fluid is hydrophilic (polar and non-polar regions)

some integral membrane proteins stick in bilayer halfway/all the way (all the way across membrane= “transmembrane proteins.

trans=on the other side of/across

some form channels to allow ions/other small molecules to pass

found on outside and inside surfaces of membranes

attached to integral proteins to phospholipids or to integral proteins

unlike integral membrane protein it sticks more loosely to hydrophobic core of membrane

transmembrane proteins might cross membrane just once or have max 12 dif-membrane spanning sections

a typical membrane spanning segment has 20-25 hydrophobic amino acids arranged in an alpha helix. but not ALL transmembrane proteins are in this form

3rd major component of plasma membrane

found on outside surface of cells/bound to …

proteins: —>glycoproteins

lipids: —> glycolipids

these carb chains might consist of 2-60 monosaccharids units

can b straight/branched

forms cellular markers (kinda like molecular ID) for cells to recognize each other. fun fact: v important in immune system, allows cells to differentiate btwn body cells (which they shouldn’t attack) and foreign cells and tissues which they should attack

structure of fatty acid tails of phospholipid is important in determining fluidity

saturated fatty tails:

have no double bonds (saturated w H+)

low temps: straight tails can pack tightly togehter→ makes membrane dense et rigid

unsaturated fatty tails:

havebdouble bonds→ bonds/kinks formed

membranes w unsaturated phospholipids will stay fluid @ low temps bc their bent tails, they can’t pack tightly together

tru

false. they can by changing proportion/ratio of unsaturated fatty acids in their membrane.

they also have cholesterol to help maintain fluidity (another membrane component)

another type of lipid, type of steroid that is embedded among phospholipids of membrane. since has lots of rings its has stable structure

helps minimize effects of temp on fluidity, regulates the exit and enter of molecules

low temp: cholesterol ups fluidity by keeping phospholipids packed tightly together by nudging itself into the spaces btwn phospholipid molecules. makes sure they arent packing too closely together or becoming too spread out. so helps maintain functional and healthy fluidity

temps lower, cholesterol helps increase fluidity

temps higher, cholesterol helps reduces fluidity of cell membrane

phospholipids: main fabric of membrane

cholesterol: tucked btwn hydrophobic tails of membrane phospholipids

integral proteins: embedded within phospholipid bilayers: may/may not extend thru both layers.

peripheral proteins: on INNER or OUTER surface of phospholipid bilayer. not embedded IN its hydrophobic core. attached to proteins/lipids on extracellular sides

carbohydrates: attached to proteins/lipids on extracellular side of membrane (forming glycoproteins/glycolipids)

cell membrane: specialized structure that surrounds the cell et its internal environment; controls movement of substances into/out cell,,, protecc,, semipermeable that’s made of phospholipid bilayer along w various other lipids, proteins, et carbohydrates.

hydrophilic: molecule that is attracted to wo’ah

hydrophobic: molecule that repels wo’ ah

amphipathic: molecule that contains both a hydrophobic et hydrophilic end

phospholipid: amphipathic lipid made of glycerol backbone (it holds phosphate head+tails tgther), 2 fatty acid tails ( that are made of chains of C atoms), et a phosphate grp. in other words

has 2 hydrophobic tails and a hydrophilic head, head that faces outward. hydrophobic tails face inward toward each other (kinda tryina get as far away as water as possible)

phospholipid bilayer: biological membrane involving 2 layers of phospholipids w their tails pointed inward. its unique structure lets preferably nonpolar, small substances (like gasses, 02 and c02) to easily pass thru: “passive diffusion”

semi permeable membrane: membrane that allows certain substances to pass thru

its not cuz cell membrane has phospholipid bilayer, but phospholipid bilayer is not the only thing that makes up the cell membrane. like other things such as membrane proteins.

cell membrane made of phospholipid bilayer + OTHER stuff.

slowly. altho theyre big, theyre nonpolar, so it doesn’t clash with the hydrophobic part of membrane

cant go thru cell membrane. has to be consumed thru other means

can’t go through cell membrane either,

act as receptors (process outside events)

usually in transmembrane proteins that they act as transporters for molecules in and out of cell

bc since proteins have such important functions, compared to middle, its useless

since everything is moving around = fluid

mosaic=lots of stuff

is the top view of cell membrane

1. phospholipids

2. cholesterol

3. proteins

3 main factors that influence cell membrane fluidity:

1. temp: affects density of phospholipids and their movement. cold, come closer together. rigid, fragile.

   hot, move further apart. too fluid, can’t hold shape

2. cholesterol: holds the phospholipids together so that they don’t separate too far, letting unwanted substances in, or compact too tightly, restricting movement across the membrane. without cholesterol, cells get closer together when exposed to cold, which makes it more difficult for smaller molecules (eg. gases) to squeeze in btwn the phospholipids like they normally do.

3. saturated and unsaturated fatty acids: saturated fatty acids easer to stack vs unsaturated fatty acids bc of the kinks in their carbon chains; increase the space between the phospholipids (kinda like when its hot), making the molecules harder to freeze at lower temperatures (when rigid (cold), more prone to freezing). increased space also allows certain small molecules (eg. cO2 and O2) to cross the membrane quickly and easily.

1. Small, nonpolar molecules (e.g. 02 and CO2): pass thru lipid bilayer by squeezing thru phospholipid bilayers. don't need proteins for transport and can diffuse across quickly

2. Small, polar molecules (e.g. H2O): can pass thru lipid bilayer without proteins’ help. but not easy for water molecules to cross so its a slower process.

3. Large, nonpolar molecules (e.g. carbon rings): These rings can pass through but also slow process

4. Large, polar molecules (e.g. simple sugar,glucose): size and polarity makes it too hard to pass through the nonpolar region of the phospholipid membrane without help from transport proteins.

5. Ions (e.g.Na+): the charge of an ion makes it too difficult to pass through the nonpolar region of the phospholipid membrane without help from transport proteins.

tru

the phospholipids make bilayer (2 layers) bc of hydrophobic and hydrophilic

concentration of electrons on molecule

electrons are not evenly distributed,, one side is more pos and the other is more neg

electrons are evenly distributed, molecules has evenly charged across surface

cubic bc cell wall

grow and are upright bc of all the pressure and fluid and the cell walls.

hemicellulose

cellulose (polysaccharide made of glycose units which assemble into microfibrils (fibres)

pectin

mesh like pattern

middle lamella, sticky layer that helps hold cell walls of adjacent plant cells together

plasmodesmata connect plant cells thru tunnels in their cell walls

TRUE BESTIE

collagen proteins

modified w carbohydrates,, w release they assemble into collagen fibrils (long fibres)

btw in ECM collagen fibres interwoven w a class of carbohydrate bearing proteoglycans (which may be attached to long saccharide backbone)

they play a big role in giving tissues strength and structural integrity

human genetic disorders that affect collagen (eg. Ehlers-Danlos syndrome makes tissue fragile that tears and stretches too easily.

ECM: extracellular matrix (complex network of large molecules,,, proteins and carbohydrates)

directly connected to the cells it surrounds

• key connectors: integrins (proteins) that are embedded in the cell membrane. on the inside integrins r linked to the cytoplasm

• integrins anchor cells to ECM. also integrins act as cell receptors→helps cell sense its environment,,, detect chemical and mechanical cues from ECM and which triggers signaling pathways in response

• fibronectin (proteins): can act as bridges btwn integrins and other ECM (eg. collagen)

blood clotting.

when cells lining blood vessels are dmged, they display tissue factor (a protein receptor)

when tissue factor binds to molecule in ECM, triggers a range of response that reduce blood loss (eg. cause platelets to stick to wall of dmged blood vessels and stimulate clotting factors)

active transport: transport requires energy to move substances against a concentration or electrical gradient (usually uses ATP) to maintain the right concentrations of ions and molecules in living cells

needs assistance from carrier proteins

the sodium-potassium pump is a key example of active transport (where it pumps sodium/ k against the electrical/ concentration gradient) bc it directly uses ATP

during active transport, substances move against the concentration gradient, from low concentration area → high concentration. active bc uses energy, usually atp

carrier proteins help by changing shape during ATP hydrolysis.
Membrane proteins involved in active transport include symporters, antiporters, and the sodium-potassium pump (pumps sodium out the cell against concentration gradient energy: hydrolyzed ATP (primary active transport)

passive transport: transport doesn’t require energy. substances move along their gradient

like a canoeist drifting downstream

true

region of space where concentration of a substance changes

substances naturally move down their gradients, from area of higher to area of lower concentration

state where substance is equally distributed throughout a space

true

tru. polar, charged

FALSE!!!

Substances transported through facilitated diffusion still move with the concentration gradient, but the transport proteins protect them from the hydrophobic region as they pass through.

adenosine triphosphate, the main energy source in living organisms

• Active transport is not the same as facilitated diffusion. Both active transport and facilitated diffusion do use proteins to assist in transport. However, active transport works against the concentration gradient, moving substances from areas of low concentration to areas of high concentration. In addition, the types of proteins that they use are different

  • Active transport uses carrier proteins, not channel proteins. These carrier proteins are different than the ones seen in facilitated diffusion, as they need ATP in order to change conformation. Channel proteins are not used in active transport because substances can only move through them along the concentration gradient.

  
  
  ***** help need clarification

general term for types of active transports that move particles into cells by closing them in a vesicle made of cell membrane

endo: internal

cytosis: transport mechanism

phagocytosis: phago= eat

process the cell eats and internalizes a large particle thru extending its membrane around it

pinocytosis: pino=drink

similar to phagocytosis, but instead cell eats droplets of extracellular fluid, also taking in any dissolved substances inside.

occurs in many cell types and takes place constantly, with cells sampling and resampling surrounding fluids for nutrients

particles held in vesicles. vesicles, compared to food vacuole, is much smaller

form of bulk transport that transports large numbers of molecules or large molecules OUT ze cell

vesicle, which r small membrane bound compartments, has these molecules, then merges to cell membrane, then molecules released (eg. signaling molecules or waste)

important for transport of neurotransmitters

because theyre too small and picky to take an entire bacterium

get nutrients from environment

selectively grab certain particles out of extracellular fluid

release signaling molecules for communication

yasss sister

1. cell ate

2. pocket containing particle pinches off from membrane

3. forms food vacuole (membrane-bound compartment)

4. vacuole merges w lysosome (recycling centre of cell)

5. using lysosomes enzymes, lysosomes break engulfed particles down into its basic components (eg. amino acids et sugars)

6. cell can use

form of endocytosis where receptor proteins on cell surface capture specific targeted molecules

receptors made of transmembrane proteins that clump in regions on cell membrane,, the coated pits

allows cells to take in large amnts of molecules that are pretty rare in extracellular fluids

HOWEVER, using this process, unfriendly particles can enter this same pathway

made from coat proteins (layer of protein). found on cytoplasmic side of pit.

btw, clathrin is the best studied coat protein.

coat proteins give vesicles their round shape and assist them in budding off the membrane

type of passive transport that uses specialized proteins (eg. channel proteins and carrier proteins) to help molecules move across a cell membrane

molecules move down their concentration gradient w/out any energy input from the cell by going thru channels/carrier proteins that protects them from phospholipid part of membrane

regulate passing thru of substances and quantity

essential to cells ability to obtain nutrients, get rid of wastes, and maintain homeostasis

passive transport

no energy required

substance goes down its concentration gradient across membrane

substance achieves equilibrium: substance moves from high concentration to area w low concentration until its equal throughout

itself is a form of stored energy thats used up as the concentrations equalize

molecules can move thru the cytosol by diffusion. some molecules can diffuse across the plasma membrane

every individual substance in a solution/space has its own concentration gradient and will diffuse according to that.

in different cells, there can be dif rates and directions of diffusion of different molecules

eg. stronger concentration gradient (larger concentration difference between regions=faster diffusion)

summary of sodium-potassium pump process: the protein going back and forth between two forms: an inward-facing form with high affinity for sodium (and low affinity for potassium) and an outward-facing form with high affinity for potassium (and low affinity for sodium). The protein can be toggled back and forth between these forms by the addition or removal of a phosphate group, which is in turn controlled by the binding of the ions to be transported.

both these types transport materials @ dif rates

channel proteins (eg. aquaporins): span across the membrane and make hydrophilic tunnels. channels r selective and will only accept 1 type of molecule/related molecules for transport. allows polar and very closely related charged compounds

some channels open/close the whole time, some “gated” = close/open in response to signal

carrier proteins: can change shape to move target molecule from one side to the other

usually selective for 1/a few substances

kind of like a bridge for their existing concentration gradients

much quicker bc simple tunnels, may facilitate diffusion at millions of molecules/sec

slower bc need to change shape and “reset” when transporting a molecule

may facilitate 1000 molecules/sec

using the potential energy created by electrochem gradient to actively transport other substances against their own gradients

transports molecule against the electrochem. gradient by other means

when 2 molecules r being transported, theres two types of proteins that transported to send them off in dif directions

symporter: move in same direction

antiporter: opposite directions

concentration gradient+voltage affects the ions movement

bc atoms and molecules can form ions and carry pos or neg charges, there is electrical gradient (dif in charge) across plasma membrane

true !

inside of cell has higher concentration of k+ and a lower concentration of Na+ VS. surrounding extracellular fluid

Na+ ions outside the cell tend to move into cell bc less Na+ in cell (concentration gradient) and voltage across membrane (more neg charge on inside of membrane)

the voltage across membrane encourages K+ to go into cell but concentration gradient opposes. in the end, equilibrium of k+ on both sides of membrane is achieved

primary active transport: (uses chem energy, like ATP): to move molecules across membrane against their concentration gradient

secondary active transport (cotransport): uses electrochemical gradient, which is generated by active transport

types of pumps that maintain concentration of ions that r involved in establishment and maintenance of membrane voltage

ps. in plants, the primary electrogenic pump, pumps h+ ions instead of na+ and k+

contributes to electric potential difference between inside and outside of cell

3 na+ ions exit cell, 2 k+ ions enter

1. pump is open to the inside of the cell. pump rlly like to bind w na+ ions and will take 3

2. na+ ions bind and trigger pump to hydrolyze (breakdown) ATP

   1 phosphate grp from atp attaches to pump (phosphorylated)

   ADP released as a by-product

3. phosphorylation makes pump change shape to open itself towards extracellular space. pump not rlly interested so release 3 na+ ions outside cell.

4. now pump rlly likes k+. binds 2 and triggers removal of the attached phosphate grp

5. since p+ grp is gone, changes back into its shape where it was facing inward to cell. pump loses interest again of the 2 k+ and releases them into cytoplasm

trueee

something you have more of

something you have less of

true bestie

movement of molecules from area of high concentration to area of lower concentration

higher concentration of solute outside

when place cell in a hypertonic solution water leaves cell and cell shrivels

these reactions are bc of cell membrane’s semi permeability and concentration of solutes.

less concentration of solute on outside of cell vs inside

when place cell in hypotonic solution theres a net flow of wo ah into cell, rushes in=cause cell to expand/burst

these reactions are bc of cell membrane’s semi permeability and concentration of solutes.

type of diffusion especially for water molecules moving across semi-permeable membrane

yes!

water molecules move from areas w fewer solutes to areas w MORE solutes bc of diffusion

molecules like wo ah usually move from places of high concentration to lower bc they’re always in random constant motion

more solutes= less likely water to move across membrane,, so net flow of water from low solute areas to more until equilibrium

(concentrations don’t achieve perfect equal bc of hydrostatic pressure coming from the rising water column from the push of water)