Membranes

Question 1

Functions of membrane proteins (5)

Answer 1

Receptors, transport, enzymes, maintenance of cell structure, communication

Question 2

What do receptor proteins do

Answer 2

Allow communication of an extracellular signal to the intracellular space to create a cellular response

Question 3

Types of transporters

Answer 3

Channels and carrier mediated transport proteins

Question 4

How does water cross the membrane

Answer 4

Aquaporins

Question 5

Function of carrier mediated transport proteins

Answer 5

Open to ECF or ICF, never both at the same time. Open and close. Move large molecules like glucose

Question 6

Glucose transporters permanently present in cell membranes are what

Answer 6

Insulin independent. These cells have glucose transporters in their membrane all the time. Insulin is only required for glucose uptake in muscle and adipose tissue.

Question 7

Membrane enzymes do what

Answer 7

Catalyse chemical reactions on the cell membrane. Ligand binding to a receptor enzyme activates an intracellular enzyme which catalyses an intracellular response

Question 8

Structural proteins do what

Answer 8

Anchor the cell membrane to the intracellular skeleton, extracellular matrix and or to other cells. Dysfunction or loss can cause serious debility

Question 9

What are G proteins

Answer 9

Peripheral proteins that relay a signal along the membrane from an integral receptor protein to an integral enzyme protein. Moves along the internal layer of the protein, can’t move across.

Question 10

Protein content of myelin

Answer 10

Low content of protein (18%), major component is lipid, very good insulator so ideal for function which is insulating myelinated nerve fibres

Question 11

Plasma membranes protein content

Answer 11

Greater activity so protein content is 50%

Question 12

Membranes involved in energy transduction such as mitochondria protein content

Answer 12

Roughly 75%

Question 13

To pass passively and rapidly through the lipid bilayer, molecules need to be

Answer 13

Small, uncharged and lipophilic (hydrophobic)

Gases pass readily

Question 14

What uses facilitated diffusion

Answer 14

Ions and nutrients like glucose which are large and charged

Question 15

What is used in facilitated diffusion

Answer 15

Protein channels and mediated transport proteins

Question 16

Sodium concentration is higher ____ the cell

Answer 16

Outside the cell

Question 17

Pumps out ___ sodium ions and in ___ potassium ions

Answer 17

3 , 2

Question 18

Electrogenic pump does what

Answer 18

Produces net movement of positive charge out of the cell. Creates a charge difference across the membrane

Question 19

How much of the resting energy if the body is used by Na/K ATPase

Answer 19

40%

Question 20

Endocytosis

Answer 20

Invagination of cell membrane to form a vesicle that eventually disintegrates on the cytoplasmic surface of the membrane which then releases the content into the cell to get to their destination. Common mechanisms for terminating signals from extracellular ligands

Question 21

Exocytosis

Answer 21

The reverse of endocytosis. proteins manufactured in cells are released from the cells by the process of exocytosis. Some hormones are released this way

Question 22

What is required to prevent movement of water across a membrane

Answer 22

Osmotic pressure

Question 23

Osmosis is

Answer 23

Movement of water molecules across a membrane to create equal concentrations at either side. Not equal volume

Question 24

Why is osmosis without diffusion clinically important

Answer 24

This is when there is a change in cell volume. This can be a problem as the cells can shrivel up or they can swell and burst

Question 25

What determines the osmotic effect on water

Answer 25

The number of solute particles, not molecules

Question 26

Osmolarity

Answer 26

Number of particles per litre of solution. Determines concentration of biologocial solutions in terms of osmoles

Question 27

Normal human plasma has osmolarity of

Answer 27

300 mOsmol/l

Question 28

Tonicity

Answer 28

Number of non penetrating particles in solution

Non penetrating (Na and Cl in ECF and K in ICF)

Question 29

Isoosmotic

Answer 29

Same total number of solute particles as the normal ECF

Question 30

Isotonic

Answer 30

Same total number of non penetrating solute particles as the normal ECF

Question 31

Haemolysis

Answer 31

Bursting of red blood cells

Question 32

Urea

Answer 32

CO(NH2)2

Organic compound with chemical formulae

Question 33

What happens if a cell goes into a hyperosmotic urea solution (in vitro)

Answer 33

swell and burst because urea is penetrating and is in aqueous hypotonic solution. Urea equilibrates by diffusion and as the urea goes in the water goes out. The cell is still full of non penetrating species. So the extracellular fluid has lots of water ( more than the intracellular fluid) so the water tries to go inside the cell to find osmotic equilibrium and this causes cell to swell and burst

Question 34

What happens to NaCl when it is put in solution

Answer 34

Na and Cl split up so if there’s a solution of NaCl that is 150mM then u have 150mM of Na and 150mM of cl so altogether u have osmolarity of 300mOsmols

Question 35

What causes changes in cell volume

Answer 35

Tonicity Only

Question 36

1 mol of sodium chloride solution has an osmolarity of

Answer 36

2osmoles/litre