Bio quiz cell membrane

Explain: the cell membrane is a semipermeable, amphiapthic, mosaic, fluid, phosophlipid bilayer

Semipermeable- lets some substance cross more easily than other; it can discriminate

Amphipathic: phospholipids have a hydrophilic head and the hydrophoobic tails

Mosaic: many different proteins are embedded in it

Fliud: the parts move freely; proteins bob about the phospholipids

Phoso Bilayer: two layers with tails facing each other, heads facing the water

What does selectively permeable mean

the membrane allows some substances to cross more easily than others. It has the ability to discriminate

why is the membrane called fluid

It is made of many ingredients that move in a free-flowing manner. Phosp lipids moving side to side rapidly. proteins moving slower

What does cholestrol (a steroid) do in the membrane

It wedges between phoso lipids to slow down their movement

Integral vs peripheral proteins

Integral- penetrate the hydrophobic bilayer; called transmembrane proteins

Peripheral- not embedded in the bilayer; loosely bound to the inner surface of the membrane

Describe an integral protein

penetrates the hydrophobic bilayer. transport molecules, transmit signals, and provide structural support

What are aquaporins

Channel proteins that allow water to pass. some integral proteins are secondary structure only (they move water)

List every type of membrane protein

By location- intergral and perheral

By use- channel protein, carrier protein, aquaporin, receptor enzyme, glycoprotein (marker), proteins that join cells, protein that attach to the cytoskeleton

Channel protein: what is it and what does it do

An integral protein with an opening in the center (can be a gate). Forms hydrophillic tunnels that let certain molecules, mainly ions (Cl, Ca, Na, K) pass through. *Also called an ion channel

Carrier protein: what is it and what does it do

Integral protein that changes its shape (conformational change) to move molecules, such as glucose, across the membrane. Used for molecules too big to pass on their own

Aquaporin: what is it and what does it do

A channel protein that allows water to pass

Protien function 1: transport

Channel proteins and carrier proteins move substances across the membrane. Some, like the Na-k pump, use atp

Protein function 2: enzymatic activity

membrane proteins can acts as enzymes, speeding up reactions as the membrane

Proteins functions 3: signal transduction

A recepetor protein binds a signal molecule outside the cell and passes the message to the inside of the cell

Protein function 4: cell-cell recognition

Glycoproteins with carbohydrates markers identify the cell to other cell

Protein function 5: intercellular joining

proteins of neighboring cells hook together

Protein functions 6: attachment to the cytoskeleton and ECM

Proteins anchor the membrane to the cytoskeleton (inside) and the extracellular matrix (outside) to hold things in place

What do the cytoskeleton and extraceullar matrix do

cyto- holds the membrane and parts together on the inside

Extra- holds the membrane together on the outside of the cell

What is the function of a carbohydrate marker

it acts a marker that identifies the cell (cell-cell recognition)

What membrane proteins typically hold a marker

integral membrane proteins typically hold a marker to indentify the cell

Glycoprotein vs. glycolipid

Glycoprotein- an integral protein with a carbohyrdate marker

Glycolipid- a phospolipid with a carbohydrate marker

Define passive transport and name its 3 types

No energy from the cell is required for molecules to pass through the membrane

Types: diffusion, osmosis, facilitated diffusion

Diffusion

Movement of particles of any substance from high to low concentration, down the concentration gradient. End result: equilibrum

Osmosis

Diffusion of WATER from an area of high water concentration to low water concentration. End result: equilibrum. The solvent (water) chases the solute.

Facilitated diffision

passive transport using a carrier or channel protein. Still moves high to low (glucose via a carrier, ions via channel)

How are the 3 types of passive transport similar and different

Similar: no energy needed, move down the gradient (high to low), end in equilibrum.

Different: diffusion=any substance directly through the bilayer

Osmsis: water only

Facilitated diffusion: needs a channel or carrier protein

What crosses the membrane by each passive route

Directly through the bilayer: O2, CO2, steroid hormones

Aquaporin: h2o

Carrier protein: glucose

Channel protein: ions (chloride, calcium, sodium, potassium)

Define active transport and name its 3 types

Movement of molecules AGAINST the gradient from low to high concentration. Energy is required

Types: sodium-potassium pump, endocytosis, exocytosis

Name the 3 types of endocytosis

Phag- cell eating

phino- cell drinking

receptro-mediated: receptors on the membrane grab specefic item from the extracellular area

How are the 3 types of active transport similar and different

Similar: all require energy and move against the gradient (low to high)

Different: the Na-K pump moves individual ions using carrier proteins

Endo-brings bulk in

exoc-brings bulk out

Active vs passive transport

Passive: no energy, with the gradient (high to low), end in equilibrum

Active: requires energy (ATP), against the gradient (low to high)

3 osmotic solutions

Hypotonic, isotonic, hypertonic

Hypotonic solution: definition and end result

Low solute concentration outside the cell, high inside. Water travels toward the solute (into the cell)

Animal cells: burst (lyses)

Plant cell: turgid

Hypertonic solution: def and end result

High solution concetration in the solution not the cell. water leaves the cell.

Animal cell: dehydration

plant cell: plasmolysis (membrane seperates from the cell)

Isotonic solution: def and end result

Equal solutes and solvent on both sides of the membrane. End result equillibrum

Animal cell: ideal state

Plant cell: not enough water, wilting (flaccid)

Which is ideal for a plant cell and animal cell

Animal cell: isotonic

Plant cell: hypotonic (turgid)

List the steps of the Na-K pump

1. cytoplasmic Na+ binds the pump

2. Na+ binding stimulates phosphorlyatin by ATP

3. phisphorylation changes the proteins shape, expelling Na outside

4. extracellular K binds, triggering release of the phosphate

5. loss of the phosphate restore the orginal shape

6. k+ release inside, Na sites are receptive again and the cycle repeat