Organisms and Exchange no

Question 1

E. coli has no cholesterol in its cell-surface membrane. Despite this, the cell maintains a constant shape. Explain why

Answer 1

Cell unable to change shape;
2. (Because) cell has a cell wall;
3. (Wall is) rigid / made of peptidoglycan / murein.

Question 2

Explain why the structure of a membrane is described as fluid-mosaic.

Answer 2

Fluid - the individual phospholipid molecules can move relative to one another - gives the membrane a flexible structure that is constantly changing shape
Mosaic - proteins that are embedded in the phospholipid bilayer vary in shape and size and pattern like a mosaic

Question 3

2 Active transport and facilitated diffusion are two ways by which substances cross cell surface membranes.
State one difference and one similarity between active transport and facilitated diffusion. (2)

Answer 3

difference - FD occurs along a concentration gradient from high concentration to low concentration and does not require energy rather than AT from low concentration to high concentration occurs against the concentration gradient and requires energy

Similarity- both use proteins to assist them :???

Question 4

Cholesterol function

Answer 4

regulates membrane fluidity/ stability
less fluid at higher temps
regulates lateral movement of phospholipids

Question 5

Channel/carrier Protein function

Answer 5

transport of substances across the membrane by facilitated diffusion or Active transport

Question 6

Glycoproteins function

Answer 6

cell signalling, binding cell together

cell recognition for hormones and neurotransmitters

Question 7

Glycolipids function

Answer 7

receptor, antigens, stacking cells together
helps maintain stability of membrane

Question 8

Describe how you would test a piece of food for the presence of lipid.

Answer 8

Dissolve in alcohol, then add water; emulsion test goes cloudy white

Question 9

protein channel explained

Answer 9

protein with specific shape that complements shape of substrate to be transported across membrane
- passing of ion through

Question 10

What is a glucolipid?

Answer 10

Carbohydrate attached to lipid phospholipid

Question 11

protein channel

Answer 11

tertiary structure specific
passing of ions
facilitated diffusion

Question 12

protein carrier def

Answer 12

protein with specific shape that complements shapes of substance to be transported across membrane
AT and facil diffusion

Question 13

other word for protein carrier

Answer 13

integral protein

Question 14

Intrinsic protein

Answer 14

in membrane

Question 15

Extrinsic protein

Answer 15

outside membrane

Question 16

Glycoprotein def

Answer 16

act as antigens allowing cells to recognise one another

Question 17

Phospholipid bilayer structure

Answer 17

Phosphate -> head- hydrophilic - polar
Lipid -> tail -> hydrophobic - form semi- permentant bilayer

Question 18

phospholipid bilayer def

Answer 18

allows lipid soluble substances to enter and leave and prevent water soluble entering and leaving
gives membrane fluidity
hydrophobic region
spinning - energy (kinetic)

Question 19

Facilitated diffusion

Answer 19

passive - relays on input of kinetic energy
charged ions and polar molecules - by carrier and channel proteins - dont diffuse easily - hydrophobic fatty acids in phospholipid bilayer

Question 20

Simple diffusion

Answer 20

non polar molecules
across phospholipid bilayer
passive transport - no ATP
down conc

Question 21

down concentration

Answer 21

Diffuson

Question 22

against concentration

Answer 22

Active transport

Question 23

active tranport defintion

Answer 23

net movement of molecules form low to high conc against conc gradient

Question 24

Endocytosis

Answer 24

a process by which cells absorb external material by engulfing it with the cell membrane.

Question 25

Excocytosis

Answer 25

involves secretion from the cell

a vesicle containing molecules of substances fuses with the inside of the cell membrane and the molecules are secreted from the cell.

Question 26

Diffusion and osmosis compare similarities

Answer 26

high to Low conc
both passive transport

Question 27

How does glucose move through membrane

Answer 27

co transport?

Question 28

contrasport

Answer 28

1- cotransport protein
2- carrier protein used
2- NA + conc kept low
3- Sodium potassium pump
Atp energy
Active transport of NA + into blood
glucose facilitated diffusion into blood