Topic 1

Question 1

Fluid Mosaic Model

Answer 1

fluid- fatty chins of the phospholipids are like thick oily liquid
mosaic-external surface (viewed from above) has mosaic appearance, various embedded proteins in uniform background

Question 2

Function of plasma membrane

Answer 2

• Selectively controls molecules entering and leaving the cell- diffusion, osmosis, facilitated diffusion, active transport, bulk transport
• establishes compartments in cell, separates cell components
• restricts movement of substances between one part of cell from another
• have receptors involved in intercellular communication via nerves/hormones
• involved in cell recognition and adhesion-can recognise and respond to self/non-self molecules
• produce electrical activity

Question 3

Phospholipid structure

Answer 3

• hydrophilic head made of phosphate groups

- two hydrophobic tails consisting of fatty acid chains

Question 4

what does phospholipid structure allow

Answer 4

flexible, soft. and self repairing-allows shape change

• e.g RBC can squeeze through capillaries
• nucleus can be pierced and then repair itself

Question 5

why are phospholipids amphipathic

Answer 5

they contain a hydrophilic and hydrophobic portion

Question 6

Transport proteins passive transport) function

Answer 6

allows some substances to move through membrane via facilitated diffusion

• two different types carrier and channel proteins
• these become saturated- has maximum rate of transportation

Question 7

transport proteins

Answer 7

a gated protein channel, opens to transport a specific molecule, in response to contact with another molecule

Question 8

transport proteins (active transport)

Answer 8

protein pump involved in active transport- requires ATP input
also referred to as carrier proteins

Question 9

catalytic proteins

Answer 9

enzymes speed up rate of chemical reactions across the membrane

Question 10

receptor proteins

Answer 10

hormones and other substances bind to them- affects cell activities
-different cell types have different receptor proteins e.g glycoproteins

Question 11

recognition proteins

Answer 11

act as markers-antigens

• enable immune system to recognise self from non self
  e. g glycoproteins

Question 12

adhesion proteins

Answer 12

join cells together-multi-cellular organisms

occluding, communication and anchoring junctions

Question 13

cytoskeleton proteins

Answer 13

anchor cytoskeleton to membrane

Question 14

cholesterol function

Answer 14

regulates membrane consistency, firmness and stability
also maintains fluidity by separating fatty acid tails-to avoid crystallisation
-reduces some solutes permeability

Question 15

glycolipids functions

Answer 15

play role in tissue recognition

glyco- meaning carbohydrate

Question 16

glycoproteins functions

Answer 16

cell surface markers-antigens

Question 17

Simple diffusion

Answer 17

net movement of a substance across the phospholipid bilayer from a region of high solute concentration to region of low solute concentration of that substance

• passive process-energy not required
• occurs along concentration gradient- must be concentration difference between two regions
• gases, small uncharged/ hydrophobic molecules can diffuse

Question 18

osmosis

Answer 18

net movement of water from a region of low solute concentration to high solute concentration across a selectively permeable membrane

• occurs down concentration gradient- energy not required
• occurs between phospholipid molecules- occurs more slowly than specific protein channel movement

Question 19

dilute solution pressure

Answer 19

low osmotic pressure, more solvent, less solute

Question 20

concentrated solution pressure

Answer 20

high osmotic pressure, more solute, less solvent

Question 21

hypotonic solution movement

Answer 21

net movement of water into cell- due to higher solute concentration in cell compared to surrounding solution

Question 22

hypertonic solution movement

Answer 22

net movement of water out of cell- due to lower solute concentration in cell compared to surrounding solution

Question 23

isotonic solution movement

Answer 23

no net movement of water- equal solute concentrations in both cell and surrounding solution

Question 24

facilitated diffusion

Answer 24

transport proteins in plasma membrane assist diffusion of charged particles and larger molecules and hydrophilic molecules to diffuse across lipid bilayer

• form water-filled connections across bilayer- allow specific water soluble molecules and ions through
• occurs along concentration gradient, doesn’t require energy

Question 25

channel proteins

Answer 25

channels, which open and close to allow specific water soluble molecules and ions through - selective- only allow specific molecules through - open and close in response to certain signals e.g change in voltage or binding of another molecule

Question 26

carrier proteins

Answer 26

combine with molecule or ion and carry it across plasma membrane - once molecule has bound to protein- changes shape and releases its content - -selective- only allow specific molecules through - -open and close in response to certain signals e.g change in voltage or binding of another molecule

Question 27

active transport

Answer 27

movement of molecules or ions from a region of low concentration to region of high concentration - occurs against concentration gradient- requires energy in the form of ATP - involves carrier proteins for each substance - extremely important process- allows plants to uptake nutrients in low concentrations and excrete waste

Question 28

exocytosis

Answer 28

actively transported out of cell by moving in small vesicles - membrane of vesicles are filled with non permeable secretions - vesicles fuses with plasma membrane, releasing content outside cell - requires ATP

Question 29

Endocytosis

Answer 29

three types - pinocytosis - phagocytosis - receptor mediated cytosis - all require ATP( energy)

Question 30

phagocytosis

Answer 30

transports solids from outside to inside e.g bacteria, food particles - part of plasma membrane engulfs the solid-forms vesicles- moves into cytosol - vesicle fuses with another vesicle-containing digestive enzymes that digest contents

Question 31

pinocytosis

Answer 31

transport of liquid containing dissolved material into cell - -part of plasma membrane engulfs the solid-forms vesicles- moves into cytosol - vesicle fuses with another vesicle-containing digestive enzymes that digest contents

Question 32

receptor mediated endocytosis

Answer 32

- process of internalizing molecules/viruses | - depends on interaction of molecule with specific receptor in cell membrane

Question 33

factors affecting diffusion rate

Answer 33

``` size of particle temperature concentration difference diffusion distance surface area permeability ```

Question 34

factors affecting active transport rate

Answer 34

``` number/type of proteins(carrier)/pumps per unit area surface area ATP availability temperature pH ```

Question 35

factors affecting membrane

Answer 35

pH molecules that disrupt lipid bilayer temperature

Question 36

what determines selectivity of membrane

Answer 36

phospholipid bilayer, number and type of protein channels, carrier proteins and protein pumps

Question 37

Ribosomes

Answer 37

smallest organelle - composed of rRNA and protein - not membrane bound - site of protein synthesis - stationary type: embedded on rough ER - mobile: inject proteins directly into cytoplasm

Question 38

Endoplasmic Reticulum (ER)

Answer 38

- tubular network, fused to plasma membrane, forming channels of membrane - stores, separates and serves as cells transport system - smooth ER- lack ribosomes, make lipids-abundant in steroid hormone producing cells - rough ER- ribosomes embedded in surface-makes proteins and some proteins are modified here.

Question 39

golgi apparatus

Answer 39

proteins are modified - packaging of molecules in vesicles - composed of numerous layers to form sac - abundant in product exportation cells

Question 40

excretory vesicles

Answer 40

- packaged into excretory vesicles - vesicles break free from Golgi - move to/merge with plasma membrane - proteins removed from cell by exocytosis

Question 41

protein synthesis steps

Answer 41

rRNA stored in nucleoli - passes out into cytoplasm- becomes part of ribosomes - mRNA is produced in nucleus-passes out into cytoplasm and binds to ribosomes - protein synthesis is initiated by binding of mRNA to ribosome - proteins are synthesised by either free ribosomes with tRNA carrying specific amino acids which usually function as enzymes within cytoplasm or are synthesised by ribosomes with TRNA carrying specific amino acids into position. - (no.2)proteins pass into cavity of ER then to golgi apparatus - protein is further modified and packaged for export in vesicle via exocytosis.