Unit 1.3

Question 1

Describe Phospholipids in a membrane in terms of structure

Answer 1

Hydrophillic head + Hydrophobic 3 fatty acid tails

Question 2

what is the arrangement of Phospholipids?

Answer 2

They form a bilayer with the molecule opposite each other
The hydrophillic heads point outwards + the fatty acids point inwards
The phospholipid component allows lipid soluble molecules to cross but not water soluble

Question 3

Examples of water soluble?

Answer 3

Na+
K+
Cl-
Po4 3-

Question 4

Examples of lipid soluble?

Answer 4

O2
Vitamin A
Vitamin K
CO2

Question 5

Describe proteins in the membrane?

Answer 5

vary in shape size and patern

Question 6

Extrinsic?

Answer 6

on either surface of the bilayer but does not penetrate through the layer

Question 7

what is the function of an extrinsic protein?

Answer 7

structural support collectively

Question 8

Individually?

Answer 8

recongnition site for hormone attatchment

Question 9

Intrinsic?

Answer 9

extend across both layers of the bilayer

Question 10

Function?

Answer 10

to transport water soluble substances
if channel, allows the active transport of ions

Question 11

When was the Fluid Mosaic Model invented and by who?

Answer 11

Singer and Nicolson
1972

Question 12

What do we say about it?

Answer 12

fats move with respect to each other
vary in shape size and pattern

Question 13

What is the glycocalyx?

Answer 13

a layer of carbohydrate around the membrane which contains hormone receptors or allows cell - cell recognition

Question 14

What is diffusion?

Answer 14

the passive movement of molecules or ions down a concentration gradient from a region of high concentration to a region of low concentration

Question 15

Factors affecting diffusion rate?

Answer 15

surface area of the membrane
nature of the diffusion molecule
(fat soluble = faster than water soluble)
non polar = faster than polar
thickness of exchange surface
(thinner the membrane, faster the rate)
Temperature - higher the temp, more kinetic energy, faster the rate
concentration gradient
(higher the diffusion, the faster the rate)
size of the molecule - smaller but faster

Question 16

Equation for diffusion?

Answer 16

surface area x conc difference / distance of diffusion path

Question 17

shape of graph?

Answer 17

straight line
proportional

Question 18

Def of facilitated diffusion?

Answer 18

passive transfer of molecules or ions down a concentration gradient across a membrane, using a proton carrier in the membrane
limited by the number of ions present + the availability of channles

Question 19

what does it do?

Answer 19

allows the diffusion of large polar molecules such as glucose or amino acids
carrier protein changes the shape to release the molecules to the other side of the membrane

Question 20

shape of graph?

Answer 20

goes up in straight line then plateaus

Question 21

Def of active transport?

Answer 21

the movement of molecules or ions across a membrane against the concentration gradient
using energy from the hydrolysis of ATP synthesised by the cell during respiratio

Question 22

Features of Active transport?

Answer 22

Ions or molecules move from low to high concentration
If process requires energy, any factor affecting respiration will affect active transport
e.g cyanide
Active transport occurs in an intrinsic carrier protein
Limited by the number + availability of the carrier proteins

Question 23

What are the processes using Active transport?

Answer 23

Muscle contraction
Nerve transmission
Reabsorption of Glucose in the nephron
Reabsorption of minerals by Plant root hairs

Question 24

What does the graph look like?

Answer 24

Goes up then plateaus then goes straight down

Question 25

Co transport?

Answer 25

a type of facilitated diffusion that allows molecules and ions into the cell together within the same transport protein molecule for co - transport in the ileum, kidney + nephron

Question 26

what are the 3 steps?

Answer 26

a glucose molecule + 2 sodium ions attatched to a carrier protein in the cell membrane
the carrier protein changes shape + deposits the glucose + sodium into the cell
the glucose + sodium diffuse seperately through the cell
Glucose passes into the blood by FD + sodium = actively transported into the blood

Question 27

Def of Osmosis?

Answer 27

the diffusion of water molecules from a region of high water potential to a region of low water potential through a selectively permeable membrane

Question 28

Water potential?

Answer 28

the tendency of water molecules to move out of a system - measured in kPa

Question 29

Pressure potential?

Answer 29

the pressure extended by the cell wall on the contents of the cell

Question 30

Solute potential?

Answer 30

a measure of the Osmotic strength of a solution

Question 31

Turgid?

Answer 31

when the entry of water = prevented as the cell wall no longer expands

Question 32

Haemolysis of Red Blood cells?

Answer 32

Animal calls have no cell wall so as water enters the cell, the membrane can only withstand a certain pressure before it bursts
the water potential will be the same as the solute potential
if the red blood cell = placed in salt solution, the water leaves the cell + shrinks becoming crenated

Question 33

What is the definition of Endocytosis?

Answer 33

when material is engulfed by extensions of the plasma membrane

Question 34

Phagocytosis?

Answer 34

the uptake of solid material that is too large to be taken in by diffusion or active transport e.g Granulocytes engulf bacteria and a lysosome fuses with the vesicle which contains hydrolytic enzymes which digest the bacteria
products are absorbed into the cytoplasm

Question 35

What is the def of Pinocytosis?

Answer 35

The uptake of liquid into vesicles which are smaller

Question 36

Exocytosis?

Answer 36

process by which the substances leave the cell after they have been transported through the cytoplasm in a vesicle
the vesicle attaches to the plasma membrane , causing the membrane to change shape which require energy
exocytosis uses ATP, generated by respiration