Biological Membranes Flashcards by millie west

describe a method using a colorimeter to investigate effect of ethanol conc on permeability of cell membrane

-cut 5 small equal beetroot pieces
-prepare 5 solutions of ethanol with conc of 0%, 0.13%, 0.25%, 0.5%, 1%
-place 1 piece of beetroot in each test tube at the same time, start timer
-once timer done, remove beetroot, shake each TT 3 times and take sample from each
-measure absorbance with colorimeter and blue filter
-repeat experiment each time with fresh beetroot pieces and calculate mean absorbance for each conc

How well did you know this?

Not at all

Perfectly

describe a method using a colorimeter to investigate effect of temperature on permeability of cell membrane

-cut 5 equal beetroot samples
-wash with 100ml DW in WB
-increase T of WB by 10 degrees
-take samples of water 5 mins after reached T
-measure absorbance on colorimeter using blue filter
-repeat experiment 3 times, each with fresh beetroot and calc mean

How well did you know this?

Not at all

Perfectly

explain effect of changing solvent conc on permeability of cell membranes

effect of water
-water required for bilayer to be maintained
-non polar tails of PL are orientated away from water, forming bilayer with hydrophobic core
-charged phosphate heads interact with water keeping bilayer intact
-when PL can’t interact with water the bilayer can no longer exist (polar heads aren’t attracted to NP)
Effect of organic solvent
-as conc increases around bilayer, its ability to interact with water decreases and bilayer starts to disperse

How well did you know this?

Not at all

Perfectly

describe effect of solvent conc on membrane permeability

water= polar solvent required to maintain PLB
organic solvents= increase permeability as you increase conc

How well did you know this?

Not at all

Perfectly

explain effect of increase T on permeability of cell membranes

-Ke increases
-PL vibrate more
-increases average PL separation
-increased permeability as more gaps

-PLB may melt completely
-proteins may denature, leaving gaps in membrane
-therefore permeability will increase

How well did you know this?

Not at all

Perfectly

describe effect of increasing T on mebrane permeability

increasing T increases membrane permeability

How well did you know this?

Not at all

Perfectly

explain how binding of a molecule to a glycoprotein can cause effects within a cell

cell signalling
-chemical messenger molecule moves around body, if able to fit the protein receptor binding site, it will bind
-chem reaction is caused- signal transduction which causes a chem reaction within a cell, altering activity

How well did you know this?

Not at all

Perfectly

explain importance of membrane bound proteins in chem reactions

-enzymes can be held in correct location by attachment to membrane
-kept in place where optimum conditions are
-positioned so they can access substrates

How well did you know this?

Not at all

Perfectly

explain effect of cholesterol on fluidity and stability of membranes

-chol positioned between PL in bilayer, preventing aligning too closely & solidifying
-hydrophillic end interacts with heads and hydrophobic end interacts with tails, pulling them together & stabilising bilayer

How well did you know this?

Not at all

Perfectly

cell adhesion definition

cells join together to form tight junctions in certain tissues

How well did you know this?

Not at all

Perfectly

state roles of different proteins in membrane

-receptors in cell signalling (glycoproteins)
-cell adhesion (glycoproteins)
-enzymes being kept in place attached to membrane
-transport proteins (carrier/channel)

How well did you know this?

Not at all

Perfectly

state role of glycolipids in membrane

cell recognition- act as antigens, often related to immune system

How well did you know this?

Not at all

Perfectly

state role of glycoproteins in membrane

cell adhesion
cell signalling (receptors)

How well did you know this?

Not at all

Perfectly

state role of cholesterol in membrane

maintain membrane fluidity
stabilising bilayer

How well did you know this?

Not at all

Perfectly

role of phospholipids in membrane

-main component of cell surface membranes (membrane formation)
-act as a barrier between contents of cell and exterior (hydrophobic barrier)

How well did you know this?

Not at all

Perfectly

receptor protein/glycoprotein definition

proteins that bind to a specific molecule, triggering a chemical reaction

How well did you know this?

Not at all

Perfectly

extrinsic protein definition

peripheral proteins that are present in one side of the bilayer

-amino acids with hydrophilic R groups on outer surfaces and interact with polar heads of the membrane or with intrinsic proteins

How well did you know this?

Not at all

Perfectly

intrinsic protein definition

transmembrane proteins that are embedded through both layers of a membrane
-amino acids with hydrophobic R groups on external surfaces which interact with hydrophobic core of membrane

How well did you know this?

Not at all

Perfectly

carrier protein definition

specific and reversible protein that acts as an enzyme with a region that binds to a molecule to aid transport by facilitated diffusion

How well did you know this?

Not at all

Perfectly

channel protein definition

hydrophilic channel that allows passive movement of polar molecules and ions down a conc gradient through membranes

How well did you know this?

Not at all

Perfectly

glycolipid definition

cell surface membrane lipids with attached carb molecules of varying lengths and shapes

How well did you know this?

Not at all

Perfectly

cholesterol definition

lipid consisting of 4 carbon rings (hydrophobic) with a hydroxyl group (hydrophilic end)

How well did you know this?

Not at all

Perfectly

phospholipid definition

lipids consisting of 2 fatty acids, a glycerol unit, and phosphate group

How well did you know this?

Not at all

Perfectly

glycoprotein definition

membrane proteins with attached carbohydrate molecules of varying lengths and shapes

How well did you know this?

Not at all

Perfectly

fluid meaning in FMM

membranes aren't solid (molecules=weakly held in place) -because PL are weakly attracted and can change places

mosaic meaning in FMM

phosphates and embedded proteins form a tile pattern when viewed from above

phospholipid bilayer definition

arrangement of PL found in cell membranes -hydrophilic phosphate heads from both inner & outer surface of a membrane sandwich the fatty acid tails to form a hydrophobic core

cell signalling definition

complex system of intercellular communication

partially permeable definition

membrane that allows some substances to cross but not others

partially permeable definition

membrane that allows some substances to cross but not others

define compartmentalisation and explain useful

formation of separate membrane-bound areas in a cell -metabolism inc many different & often incompatible reactions -containing reactions in separate parts of cell allows the specific optimum conditions to be met and maintained for each compartment allowing for different reactions to occur.

state 5/6 roles of membranes

-partially permeable barrier, only allows select substances through (compartmentalisation) -cell signalling -anchoring the cytoskeletal framework -cell to cell recognition -endocytosis and exocytosis

equation for straight line

y=mx+c

define relative uncertainty

ratio of absolute uncertainty to reported value

define absolute uncertainty

number which when combined with the reported value gives the range of true values

haemolysis definition

rupture and destruction of red blood cells

cytolysis definition

when a cell bursts and releases contents due to the great influx of water into cell in hypotonic sol

define turgid

plant cell swollen from water uptake, cell wall prevents bursting

define crenation

contraction of a cell after exposure to a hypertonic sol

define protoplast

contents of a cell within the cell membrane

define plasmolysis

when the plant cell membrane is pulled away from cell wall occurs when cell is in a too hypertonic sol

state water potential of pure water

0 kPa (at standard T P)

why can't water potential have a pos value

presents of solute in water lowers water potential below 0 -more solute=more negative

define water potential

pressure exerted by water molecules as they collide with a membrane or container Pa or kPa

define solution

liquid mixture in which the solute is distributed evenly within the solvent

define solution

liquid mixture in which the solute is distributed evenly within the solvent

results expected in an investigation rate of diffusion affected by T

RoD increase as T increases greater Ke higher average speed of particles diffuse faster

results expected in an investigation rate of diffusion affected by SA

RoD increase as you increase SA greater surface for particles to collide and enter/exit

results expected in an investigation rate of diffusion affected by SA

RoD increase as you increase SA greater surface for particles to collide and enter/exit

why can steroid hormones easily cross membrane by simple diffusion

lipid soluble=hydrophobic not repelled by hydrophobic interior therefore don't need carrier proteins

why is it easier for oxygen molecule to diffuse across membrane rather than water

D across membranes involves particles passing through PLB oxygen is small and NP, won't be repelled by hydrophobic interior and pass through easily

which transport mechanisms require an input of energy from ATP

AT (by carrier proteins) Cytosis (bulk transport, exocytosis, endocytosis)

which transport mechanisms require an input of energy from ATP

AT (by carrier proteins) Cytosis (bulk transport, exocytosis, endocytosis)

list factors affecting rate of diffusion of a molecule

SA Conc difference Distance T Permeability

which types of molecues can move across membrane by facilitated diffusion

carrier proteins= large molecules e.g glucose channel proteins= charged/polar particles (hydrophilic/water soluble)e.g sodium ions

which types of molecules can move across membrane by simple diffusion

small, NP and uncharged molecules lipid soluble

phagocytosis definition

endocytosis of solids

pinocytosis definition

endocytosis of liquids

define exocytosis

bulk transport of materials out of cells where vesicles containing the material fuse with the cell surface membrane and contents released outside of cell

define endocytosis

bulk transport of materials into cells via invagination of the cell surface membrane forming a vesicle

define endocytosis

bulk transport of materials into cells via invagination of the cell surface membrane forming a vesicle

define active transport

movement of particles across a plasma membrane against a conc gradient. ATP required

define active transport

movement of particles across a plasma membrane against a conc gradient. ATP required

define passive transport

not require ATP

osmosis definition

net movement of water from a sol of higher to lower water potential through a PPM example of passive transport (no ATP)

define facilitated diffusion

diffusion across a PPM with the assistance of membrane proteins (carrier/channel) passive process (no ATP)

define simple diffusion

diffusion across a PPM without assistance of membrane proteins passive process (no ATP)

define simple diffusion

diffusion across a PPM without assistance of membrane proteins passive process (no ATP)

define diffusion

net movement of particles from region of high conc to lower conc (down conc gradient) without ATP