B2.1 Membranes and membrane transport

Question 1

lipid bilayers structure

Answer 1

phospholipids - 2 layers
hydrophobic tail
hydrophobic head

Question 2

what are phospholipids known as

Answer 2

having both hydrophilic and hydrophobic parts - amphipathic

Question 3

phosphate head of phospholipid

Answer 3

polar and therefore soluble in water (hydrophilic)

Question 4

fatty acid tail of a phospholipid

Answer 4

nonpolar and therefore insoluble in water (hydrophobic)

Question 5

phospholipid monolayer formation

Answer 5

phospholipids are placed in water

hydrophilic phosphate heads go towards the water

hydrophobic hydrocarbon tails go away from the water

Question 6

monolayer

Answer 6

1 layer

Question 7

bilayer

Answer 7

2 layers of phospholipids

Question 8

lipid bilayer barriers - large molecules

Answer 8

Large molecules cannot pass through the barrier as the hydrophobic region is tightly packed and has low permeability to larger molecules

Question 9

lipid bilayer barriers - polar molecules and ions

Answer 9

Polar molecules and ions cannot pass through the hydrophobic tails of the phospholipid structure
The hydrophilic nature of these molecules and ions means that they will not interact with the hydrophobic fatty acid tails of the phospholipids

Question 10

lipid bilayer barriers - in general

Answer 10

The bilayer forms an effective barrier so that it is able to control which molecules pass through and out of the cell

Question 11

Integral protiens

Answer 11

• partially hydrophobic
• embedded in the phospholipid bilayer
• can be embedded across both layers or just one layer

Question 12

peripheral proteins

Answer 12

• attached to the surface of the bilayer
• hydrophilic
• inside or outside

Question 13

increasing of diffusion rate

Answer 13

• increase in temp
• increase in surface area
• increase in distance

Question 14

simple diffusion

Answer 14

• random continuous net movement of a molecule from a region of higher concentration to a region of lower concentration

Question 15

Membrane protein function

Answer 15

transport, receptors, cell adhesion, cell-to-cell recognition and immobilized enzymes

Question 16

transport protein
function

Answer 16

Transport proteins allow ions and polar molecules to travel across the membrane

Question 17

Channel proteins

Answer 17

form holes, or pores, through which molecules can travel

Question 18

Carrier proteins

Answer 18

change shape to transport a substance across the membrane, e.g. protein pumps and electron carriers

Question 19

Receptors

Answer 19

• binding of peptide hormones, e.g. insulin
• The binding generates a signal that triggers a series of reactions inside the cell

Question 20

Immobilised enzymes

Answer 20

integral proteins with the active site exposed on the surface of the membrane

Question 21

Cell adhesion

Answer 21

Cell adhesion allows cells to attach to neighbouring cells within a tissue

Question 22

Cell-to-cell recognition

Answer 22

cell’s ability to distinguish one type of neighboring cell from another.

occurs when complementary molecules on opposing cell surfaces meet.

Glycocalyz (protein + lipid) act as cell markers, or antigens, for cell-to-cell recognition

Question 23

molecules that move by simple diffusion

Answer 23

oxygen
co2

Question 24

Osmosis

Answer 24

net movement of water molecules from a region of higher water potential to a region of lower water potential, through a partially permeable membrane

Question 25

Facilitated Diffusion

Answer 25

movement of water down concentration gradient - movement assisted by protiens and is passive

Question 26

examples of substances that use Facilitated Diffusion

Answer 26

Large molecules
Polar molecules
Ions

Question 27

Active Transport

Answer 27

The movement of molecules and ions across a cell membrane, from a region of lower concentration to a region of higher concentration, using energy from respiration

requires carrier proteins

Question 28

active transport helps to

Answer 28

• take up essential nutrients
• remove waste materials from the cell
• maintain right concentration of ions in cells

Question 29

2 types of active transport

Answer 29

direct and indirect

Question 30

direct active transport

Answer 30

energy released by an exergonic reaction like the breakdown of atp

Question 31

indirect active transport

Answer 31

movement of one solute down its concentration gradient drives the movement of the second solute against its concentration gradient

Question 32

ATP

Answer 32

adenosine triphosphate

Question 33

ADP

Answer 33

adenosine diphosphate

Question 34

Selective Permeability

Answer 34

ability of the membrane to differentiate between different types of molecules, only allowing some molecules through while blocking others

achieved through diffusion and active transport

Question 35

Glycoproteins

Answer 35

are cell membrane proteins that have a carbohydrate chain attached on the extracellular side
Extracellular = outside cells

Question 36

Glycolipids

Answer 36

lipids with carbohydrate chains attached, also located on the outer surface of cell membranes

Question 37

The function of glycoproteins and glycolipids

Answer 37

The carbohydrate chain enables them to act as receptor molecules
This allows them to bind with substances at the cell surface

Question 38

Membranes

Answer 38

Membranes form partially permeable barriers between the cell and its environment, between cytoplasm and organelles and also within organelles

Membranes play a role in cell signalling by acting as an interface for communication between cells

Question 39

Fluid mosaic model components

Answer 39

Phospholipids
Cholesterol
Glycoproteins and glycolipids
Integral and peripheral proteins

Question 40

fluid mosaic model explains

Answer 40

• how biological molecules are arranged to form cell membranes
• Passive and active movement between cells and their surroundings
• Cell-to-cell interactions
• Cell signalling

Question 41

Why is the mosaic model fluid

Answer 41

No bonds
Attraction to eachother but not strictly tied in place

Question 42

what do carbohydrates do in membranes

Answer 42

help with cell recognition and cell adhesion
highly hydrophilic and attracts large amounts of water

Question 43

what are aquaporins

Answer 43

a water channel pore in a membrane that allow water to diffuse through the plasma membrane
is a protein

Question 44

what is facilitated diffusion detailed

Answer 44

particles of a substance that cannot diffuse across the plasma membrane are helped across the membrane by integral proteins that span the membrane

Question 45

functions of peripheral proteins

Answer 45

shuttles between integral proteins
scaffold proteins that hold shape
receptors for extra cellular signals