Physiology week3,4,5

Question 1

Name the 2 types of simple diffusion

Answer 1

Simple and facilitated

Question 2

Name and describe the 2 types of diffusion

Answer 2

Simple diffusion : Where molecules move through the membrane openings or spaces without interactions with carrier proteins .
Facilitated diffusion : Where carrier proteins help transport molecules by binding with them and moving them through the membrane

Question 3

NAME the 2 pathways of simple diffusion

Answer 3

Through the lipid bilayer and
Through protein channels

Question 4

Explain the 2 pathways of simple diffusion

Answer 4

1.Through the lipid bilayer
- Where lipid soluble substances like oxygen, nitrogen, carbon dioxide and alcohols dissolve in the lipid bilayer and diffuse easily .
2. Through protein channels
Where water and small insoluble molecules pass through the channels in protein molecules embedded in the membrane .

Question 5

How is water diffused?

Answer 5

Through aqaporins

Question 6

Explain the structure of protein pores

Answer 6

They are integral membrane proteins that form open tubes that allow substantances to move by simple diffusion from one side to another

Question 7

Name 2 features of a protein pore and what they provide and give an example of what they cause

Answer 7

The diameter of a pore and its electrical charges provide selectivity that allows only certain molecules to pass through .
E.gAquaporins which have a narrow pore that allow water molecules to diffuse through the membrane but the pores is too narrow for hydrated ions

Question 8

Name 2 features of a protein pore and what they provide and give an example of what they cause

Answer 8

The diameter of a pore and its electrical charges provide selectivity that allows only certain molecules to pass through .
E.gAquaporins which have a narrow pore that allow water molecules to diffuse through the membrane but the pores is too narrow for hydrated ions

Question 9

Explain the potassium channel selectively-

Answer 9

• The potassium channels allow potassium ions to pass more easily than sodium ions due to a specific selectivity filter lined with carbonyl oxygen which intercats with the potassium ions and excludes Na ions.

Question 10

Explain the sodium channel selectivity

Answer 10

• Na channels have a narrow selectivity filter lined with negatively charged amino acids that attract and allow sodium ions to pass while excluding other ions.

Question 11

Why is the sodium channel selectivity important?

Answer 11

• It is crucial for cellular function as it ensures that Na ions can pass through the channels under normal conditions

Question 12

What is the role of Gating of protein channel

Answer 12

They control ion permeability by opening or closing channles in response to stimuli

Question 13

Name the types of gatings

Answer 13

• Voltage
• Chemical(Ligand) gating

Question 14

Explain both types of gating without examples

Answer 14

VOLTAGE
- The gate responds to changes in electrical potential across the cell membrane
CHEMICAL(LIGAND)
-The gate opens when a chemical(ligand) binds to the protein, causing a confromational change

Question 15

Give examples for both types of gating

Answer 15

Voltage
- A negative charge inside the membrane keeps the Na channels closed but when the membrane looses its negativity the Na channels open allowing the ions to pass
Chemical(ligand)
- The nerotransmitter acetylcholine binding to its receptors opening a channel for ion passage facilitating nerve signal transmission

Question 16

What is the patch clamp method?

Answer 16

A technique used to measure ion current through single channels by creating a seal between a micropipette and a small membrane path

Question 17

Name the factors affecting net rate of diffusion

Answer 17

• Concentration difference across the membrane
• The membrane electrical potential
• The pressure difference across the membrane

Question 18

What is Osmosis?

Answer 18

• It refers to the net movement of water across a selectively permeable membrane from an area of high water concentration to an are of low water concentration

Question 19

What is the role of the selectively permeable membrane in osmosis

Answer 19

Allows water to pass more easily than solutes like Na and Cl

Question 20

Name the factors affecting osmotic pressure

Answer 20

1. The number of osmotic particles
   - the number of solute particles
2. Osmole
   - If a substance dissociates the number of osmoles increases with the number of ions

Question 21

What is Osmolality?

Answer 21

The concentration of osmotically active particles in osmoles

Question 22

What is the osmotic pressure

Answer 22

The pressure required to stop osmosis. It is determined by the concentration of non-diffusible solute particles on one side of the membrane.

Question 23

What is Active transport?
+ the substances they move

Answer 23

It moves substances across the cell membrane against their conentration gradient, requiring enrgy
substances include: Na, Cl, K, H, ca ions
and certain sugars and amino acids

Question 24

Name and describe the types of Active Transport

Answer 24

• Primary AT
• Energy is dervied from the breakdown of ATP
  Secondary ATP
• Which uses energy stored in ionic concentration differences created by PAT

Question 25

- What mechanism does Primary Active Trasnport use - What is the function - And its importance

Answer 25

Mechanism: Sodium-Potassium Pump Function: It pumps Na ions out of the cell and K ions in. It uses ATP to exchange 3 Na ions out of the cell and 2 K ions in the cell Importance: -Mainatais cell volume . -Creates cells negative electrical potential, cruicial for nerve function

Question 26

What is the Mechanism for the primary Active transport of Calcium ions and its function

Answer 26

Mechanism Calcium Pump - It pumps calcium out of the cells or into organelles, maintaining low cytosolic calcium levels

Question 27

What is the Mechanism for the primary active transport of hydrogens and where is it found

Answer 27

- Hydrogen Pump It is found in the gastric glanels and kidney tubules

Question 28

What 2 types of transport are in Secondary Active Transport

Answer 28

- co transport and counter transport

Question 29

Describe the role and give examples of the 2 types of transport in Secondary Active Transport

Answer 29

-Co-Transport (Symport): Substances are transported in the same direction as sodium ions. Examples: Glucose and amino acids are co-transported into cells with sodium. -Counter-Transport (Antiport): Substances are transported in the opposite direction of sodium. Examples: Sodium-calcium exchange and sodium-hydrogen exchange, important for calcium and pH regulation.

Question 30

What is the definition of the Nerst potential

Answer 30

-It is the diffusion potential across a membrane that exactly counteracts the net diffusion of a particular ion

Question 31

What is the Neest potential based on

Answer 31

The concentration gradient of the ions across the membrane

Question 32

How is the magnitude of the nerst potential determined ?

Answer 32

- By the ratio of the concentrations of the specific ion on the two sides of the membrane

Question 33

What does the formula for the Nerst potential assume

Answer 33

It assumes the potential in the ECF remains at zero potential

Question 34

How is the membrane potential measured?

Answer 34

- By inserting a micropipette filled with electrolyte solution into a cell or nerve fibres

Question 35

What is the role of the voltmeter

Answer 35

- It measures the potential difference between the inside and outside of the cell

Question 36

What is the resting membrane potential?

Answer 36

- -70 mv

Question 37

why is the resting membrane potenital negative?

Answer 37

- The sodium potassium pump actively transports Na ions out of the cell and K ions in the cell in the ratio of 3 Na + out for every 2 K + in. - This creates a deficient + ions, resulting a negative potential inside the membrane

Question 38

What happens in Potassium lekage?

Answer 38

- The potassium ions can leak out of the cell through potassium 'leak' channels, which are 100 times more permeable to potassium than sodium.

Question 39

What is the definition of action potential

Answer 39

- A rapid change in membrane potential ., propagating along the nerve fibre, transmitting signals

Question 40

What happens at the resting stage

Answer 40

-The memabrans is polarised at -70mv

Question 41

What happens in depolarisation

Answer 41

- Membrane becomes permeable to Na ions, Na ion channel opens - Allows the postively charged sodium ions o difffuse through the membrane - Making it more postively charged

Question 42

What happens in repolarisation

Answer 42

- The Na ion channels close - K ion channels open They excite the cell , restoring the negative resting potential

Question 43

Explain activaton,in the voltage-gated sodium channels

Answer 43

When the membrane potential becomes less negative, rising from the -70mv to near -55mv, the activation gates open allwoing a large influx of sodium ion.

Question 44

What happens in inactivation in the voltage gated sodium ion channels

Answer 44

- A slower process closes the inactivation gate after a brief time, stopping the sodium ions influx

Question 45

What happens in resting in the voltage gated sodium channels

Answer 45

The sodium channels cannot open till the memrbane returns to its resting state

Question 46

What happens in the resting state of the voltage gated potassium channels

Answer 46

- The gate is close, preventing k ions from exititng

Question 47

What happens in activation in the voltage gated potassium ion

Answer 47

The activayion gate opens when the membrane potential rises towards 0 allowing potassium ions to flow out

Question 48

Explain the timing stage in the voltage gated potassium channels

Answer 48

The potassium channels open as the sodium channels inactivate, speeding up repolarisation

Question 49

What is the nerst equation used to calculate

Answer 49

The equillibirum potential for an ion at a given concentration difference acroos a membrane

Question 50

What is the goldman equation

Answer 50

Used to calculate the diffusion potential when the membrane is permeabke to several differentions

Question 51

What is the refractory period?

Answer 51

- When another Action potential cannot be generated in an excitable cell

Question 52

what happens in the propogation of an action potential

Answer 52

An action potential excites the adjacent regions of the membrane, sending signals along the membrane

Question 53

Explain the mechanism of propogation of Action potential

Answer 53

- The sodium influx in depolarised areas generate postive charges which spread along the axon - These positive charges deoplarise the adjcant regions, opening the sodium channels and propogating the action potential further

Question 54

What is the direction of propgation

Answer 54

An action potential travles in all directions from the stimulus point convering the enitre excitable membrane

Question 55

What is the All or nothing principle

Answer 55

- One an action potential is triggered at a point at point on the membrane, it propogates across the enitre membrane if the conditions are favourable If the condiitons are not favourable action potentil does not propogate

Question 56

What are the key features of the All or nothing principle

Answer 56

For propogation to occur the acion potential must reach a certain voltage, to stimulate adjacent membrane areas

Question 57

Explain the mylinated nerve fibres.

Answer 57

- Large with thick mylein sheath that surrounds the axon

Question 58

What is myelin sheath formed by ?

Answer 58

Schwaan cells that create layers rich in sphingomylein

Question 59

what is Saltory conduction

Answer 59

- Action potentials only occur at the node of ranvier - impulses jump from node to node through extracelluler fluid

Question 60

What are the advantages of Salatory conduction?

Answer 60

- Increased speed - Energy efficient