Cell membranes and cell transport

Question 1

Fluid mosaic model

Answer 1

Used to describe membrane structure

Question 2

Phospholipid structure

Answer 2

Saturated & unsaturated fatty acid

Double bond leads to bend in structure

Phosphate

Glycerol

Hydrophilic head
Hydrophobic tail

Question 3

Phospholipid properties w

Answer 3

When compact: too rigid

When straight & bent: fluid & flexible, phospholipids spaced out due to unsaturated tails

Question 4

Phospholipid bilayer contains

Answer 4

Carbohydrate 
Glycolipid
Glycoproteins
Cholesterol 
Integral protein
Protein channel
Phosphate

Question 5

Glycoproteins & glycolipids function

Answer 5

Important in cell recognition and the immune systems ability to differentiate between self and non self in cell adhesion

Cell attachment

Receptors

Question 6

Integral protein function

Answer 6

Transport/reactions

Question 7

Protein channel function

Answer 7

Transport of proteins

Question 8

Hydrophilic core makes

Answer 8

membrane impermeable to most substances, acting as a barrier

Question 9

Diffusion

Answer 9

Movement of particles from an area of high to low concentration

The process is passive (energy is still required but it’s not from ATP or respiration)

Question 10

Explain how oxygen enters the cell

Answer 10

Oxygen particles diffuse down the concentration gradient

O2 particles move directly through the phospholipid bilayer due to them being small and non-polar (simple diffusion)

Question 11

What happens to particles after final picture

Answer 11

Once equilibrium is reached, the particles continue to move although diffusion stops

No net change in concentration

Question 12

Facilitated diffusion

Answer 12

If particles are large/non-polar, they need the help of protein channels & protein carriers

Passive process

E.g. glucose, amino acids

Question 13

Describe what will happen to the water in the diagram

Answer 13

Osmosis is the movement of water from an area of high water potential to an area of low water potential

This occurs through a semi permeable membrane

Passive process

Question 14

Water & simple diffusion

Answer 14

Can move through PLBL through simple diffusion but it’s very slow

So uses protein channel (aquaporin)

Question 15

Particles in diagram

Answer 15

If particles aren’t made clear, they’re solute

Question 16

Types of solution

Answer 16

Hypotonic
Isotonic
Hypertonic

Question 17

Hypotonic

Answer 17

LWP inside cell

Solution has less solute than cell

Question 18

Isotonic

Answer 18

Solution has the same solute as the cell

WP same on inside and outside

Question 19

Hypertonic

Answer 19

HWP inside cell

Solution has more solute than cell

Question 20

Active transport

Answer 20

Movement of particles against the concentration gradient

Requires the help of a protein and energy from the hydrolysis of atp

Often K+, Na+, Ca2+

Energy driven process

Question 21

Endocytosis

Answer 21

2 types

Phagocytosis - taking in large substances (e.g. pathogens) and enclosing them in a vesicle

Pinnocytosis - taking in liquids and enclosing them in a vesicle

Question 22

Exocytosis

Answer 22

Giving out (secreting) substances out of the cell by fusing a vesicle with the cell membrane

Question 23

Co-transport

Answer 23

Process in which two substances are taken into a cell simultaneously by one protein

Question 24

Co-transport lumen of ileum

Answer 24

Sodium is pumped out into the blood, creating a high Na+ conc in ileum

Sodium ions move down conc gradient from lumen to cells by facilitated diffusion

At same time as sodium, glucose is brought in by sodium-glucose transporter proteins

As conc of glucose inside cell increases, glucose moves down conc gradient through a protein channel from cell to blood

Question 25

Cell transport adaptations

Answer 25

Increase in surface area of the internal membranes or of the cell surface membrane e.g. microvilli

Increase in the number of protein channels and carrier molecules in their membranes

By mechanisms to set up concentration, water potential or electrochemical gradients across membranes