Topic 4 Cell membrane and signalling

Question 1

fluid mosaic model

Answer 1

membranes are not rigid with molecules locked into place but rather consist of proteins that move around within a mixture of lipid molecules that has the consistency of olive oil

Question 2

the lipid molecules of the bilayer they are not stationary and…

Answer 2

vibrate, flex back and forth spin around their long axis, move sideways and exchange places within the same bilayer half.

Question 3

What doesn’t move in cell membrane?

Answer 3

Membrane proteins that anchor cytoskeleton filaments to the membrane

Question 4

An important of membranes is that proteins and other components of one half of the phospholipids are _____ from those that make up the other half. For ex____

Answer 4

different

a range of glycolipids and carbohydrates groups are attached to proteins on the external side of the plasma membrane while components of the cytoskeleton bind to proteins on the internal side of the plasma membrane.

Question 5

freeze fracture technique: (3)

Answer 5

1. block of cell is rapidly frozen by dipping it into liquid nitrogen
2. Block is fractured by hitting it with a microscopically sharp knife edge. This splits the bilayers into inner and outer halfves exposing the membrane interior
3. using electron microscopy, the split membrane appear as smooth layers in which the rise of proteins are embedded

Question 6

lipid (3)

Answer 6

a group of water insoluble molecules that includes fats, phospholipids. and steroids

Question 7

phospholipid long tail is composed of

Answer 7

carbon and hydrogen

Question 8

phospholipid head is composed of

Answer 8

glycerol linked to one of several types of alcohol or amino acids by a phosphate group

Question 9

a property that all phospholipids posses is that they are (word+definition)

Answer 9

amphipathic

molecule contains a region that is hydrophobic and a region that is hydrophilic.

Question 10

Fully saturated

Answer 10

all the carbon are bound to the maximum number of hydrogen atoms

Question 11

unsaturated

Answer 11

contain a carbon-carbon double bound

Question 12

c-c double bond causes a ____ or ____ ion the fatty acid tail

Answer 12

kink/bend

Question 13

when added to water, phospholipds self assemble into one of the three structure:

Answer 13

a micelle

a liposome

a bilayer

Question 14

which structure forms depends on

Answer 14

the phospholipid concentration

Question 15

The fluidity of a phospholipid bilayer is influenced by:

Answer 15

1. type of fatty acids that make up the lipid molecules
2. temperature

Question 16

Which is more fluid and why? Unsat or sat

Answer 16

lipid molecules with unsaturated fatty acids are prevented from packing closely together because the c-c double bond forms a kink in the structure. As a result. the more unsaturated the fatty acids of the lipid molecules the more fluid (less viscous) the membrane

Question 17

as temperature drops and the random molecular motion of lipid molecules slows down,

Answer 17

a point is reached where fluidity is lost and the phospholipid molecules form a semisolid gel.

Question 18

the temperature at which the gelling occurs depends upon (2)

Answer 18

the fatty acid composition

the more unsaturated the lower the temperature at which gelling occurs

Question 19

for most membrane system. the normal fluid state is achieved by

Answer 19

a mixed population of saturated and unsaturated fatty acids

Question 20

at high temps the membrane may become too ____and as a result…

Answer 20

fluid

increased molecular motion associated with higher temp may cause membrane to be too “leaky.” The concentration of K, na and ca ions on either side of a membrane is strictly controlled. If membrane is too fluid these ions can start to freely diffuse across membrane. (distruption of cellular ion balance)

Question 21

exposure of membrane at low temp is bad because

Answer 21

the resulting membrane gelling can decrease cell permeability and inhibit the function of protein complexes attached to or localized within the bilayer. For ex, the protein receptors need to change shape which can be inhibited if the membranes they are associated with is too rigid

Question 22

Sterols +ex+influence of membrane

Answer 22

ex: chlosterol

found in the membranes of animal cells but not in those of plants or prokaryotes

membrane buffers

high temp=restrain movement the movement of lipid molecules thus reducing fluidity
lower temp= distrupt fatty acids from associating by occupying space between lipid molecules thus slowing the transition to the non fluid gel state.

Question 23

what are the two major types of proteins that are associated with the membrane?

Answer 23

integral and peripheral membrane proteins

Question 24

membrane proteins can be separated into four major functional categories______, all these functions may exist in a single membrane and one protein or protein complex may serve more than one of these functions

Answer 24

1. transport (many proteins cannot diffuse freely through the membrane. instead a protein may provide a channel that allows movement of a specific molecule. Alternatively a membrane protein may change its shape and in so doing, shuttle specific molecules from one side of the membrane to the other.
2. Enzyme activities (a number of enzymes are membrane proteins, the best examples are the enzymes associated with the respiratory and photosynthetic electron transport chain)
3. signal transduction (Membranes often contain receptor proteins on their outer surface that bind to specific chemicals such as hormones. On binding, these receptors trigger changes on the inside surface of the membrane that lead to transduction of the signal through the cell.)
4. Attachment/recognition (proteins exposed to both internal and external membrane surfaces act as attachment points for a range of cytoskeleton elements as well as components involved in cell-cell recognition)

Question 25

integral membrane proteins (2)

Answer 25

proteins that are embedded in the phospholipid bilayer
- interact with both aqueous environment on either side of the membrane and the hydrophobic core, there have 2 distinct parts that differ markedly in polarity

Question 26

domain of integral proteins that interact within the lipid bilayer/ outside

Answer 26

• consist predominantly of non polar amino acids and domains that are exposed on either side of the membrane are composed to primarily polar amino acids

Question 27

peripheral membrane proteins+what made up of?

Answer 27

positioned on the surface of a membrane and do not interact with the hydrophobic core

mixture of polar and non polar amino acids

Question 28

how are peripheral protein held to the membrane?

Answer 28

non covalent bond- ionic or hydrogen

Question 29

diffusion of o2 and co2

Answer 29

diffuse rapidly due to vital role in cellular respiration and photosynthesis

Question 30

passive transport+ex

Answer 30

movement of molecules across a membrane without the need to expend chemical energy

-diffusion

Question 31

diffusion (2)

Answer 31

net movement from high concentration to low concentration
-primarily mechanism of solute movement within any particular cell

Question 32

driving force of diffusion is:

Answer 32

increase in entropy

Question 33

the rate of passive transport depends on

Answer 33

the concentration gradient that exist across membranes

Question 34

the diffusion of molecules across a membrane releases

Answer 34

free energy which can be used to do work

Question 35

there are ____ types of passive transport:__________

Answer 35

two

simple diffusion
facilitated diffusion

Question 36

simple diffusion

Answer 36

the movement of molecules directly across a membrane without the involvement of a transporter

Question 37

the rate of simple diffusion depends on (2)

Answer 37

1. molecular size
2. lipid solubility

Question 38

Small non polar molecules/uncharged molecules and steroid hormones

Answer 38

move easy thru the membrane

Question 39

membrane impermeable to

Answer 39

charged molecules

Question 40

facilitated diffusion

Answer 40

the diffusion of molecules across a membrane through the aid of a transporter

Question 41

the diffusion of charged and polar molecules such as (4) relies o specific transport complexes

Answer 41

water

amino acid

sugars

ions

Question 42

facilitated diffusion is carried put by two types of transport proteins

Answer 42

channel proteins and carrier proteins

Question 43

Channel proteins (2)

Answer 43

form hydrophilic pathways in the membrane

-transport of ions and water

Question 44

aquaporins (3)

Answer 44

water specific transport proteins

has a positive charge in the centre of the change; that repel the transport of protons.

single file of water

Question 45

gated channels (5)

Answer 45

found in all eukaryotes

type of channel protein

can switch between open closed and intermediate to allow the movement of ions (na, K and Ca, CL)

the opening and closing is influenced by changes in voltage across the membrane or by binding signal molecules

the opening and closing involves changes in the proteins three dimensional shape.

Question 46

carrier proteins

Answer 46

the second type of transport protein under facilitated diffusion

binds a single specific solute such as a sugar molecule or amino acid and transport it across the lipid bilayer

single solute is transported (uniport transport)

Question 47

osmosis

Answer 47

the passive transport of Peter

Question 48

osmosis can occur by

Answer 48

simple diffusion through the lipid or facilitated by aquaphors

Question 49

facilitated diffusion is much
– then simple diffusion

Answer 49

faster