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Lectures 1-4? Flashcards

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1
Q

What are two forms of carrier mediated transport?

A

1) Facilitated diffusion( not requiring energy)

2) Active transport ( requiring energy)

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2
Q

What is Km?

A

Substarte concentration at which half-maximal rate of transport occurs

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3
Q

What is the comparison of caries mediated transport and simple diffusion down a concentration gradient? ( graph)

A

Facilitated is a hyperbolic relationship and simple diffusion is a linear relationship.

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4
Q

Describe the saturation characteristic of carrier mediated transport?

A

Unlike simple diffusion, rate of transport is not linearly related to the concentration of substrate. The rate of transport has a maximum (Tm) which is reached when all carriers are occupied by substrate

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5
Q

Describe the selectively characteristic of carrier mediated transport?

A

Each carrier is specialised to transport or specific substance or a few structurally related compounds

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6
Q

What 3 important characteristics determine the kind and amount of material transferred across the membrane?

A

1) selectively
2) Saturation
3) Competition

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7
Q

What Netflux?

A

The difference in the change of molecules when molecules move to an area of least concentration

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8
Q

What 2 properties influences entry into the selectively permeable membrane?

A
  • Solubility of particle in lipid

- Mass of particle

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9
Q

What occurs when there is no net movement of K+ and what equation can you use?

A

The equilibrium potential for K+ is reached (Ek) and the Nernst equation

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10
Q

What is secondary active transport?

A

The transfer of a solute across the membrane is always coupled wit the transfer of the ion that supplies the driving force (typically Na+)

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11
Q

Describe the mechanism of Na+/K+ ATPase?

A

1) 3Na+ bind from ICF
2) Pump is phosphorylated (ATP hydrolysis)
3) 3Na+ unbind (dissociate) and are released into ECF
4) 2K+ bind from ECF
5) Pump is dephosp

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12
Q

What is the resting membrane potential?

A

The diffusion of ions down their concentration gradients gradients generates an electrical potential

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13
Q

What is a membrane potential?

A

Is the separation of opposite charges across the membrane

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14
Q

What is antiport ( exchange)?

A

Type 2 of secondary active transport. The solute and Na+ move in opposite directions (Na+ into cell, solute out the cell)

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15
Q

What is the difference between primary and secondary active transport?

A

Primary transport uses energy directly derived from the pump, hydrolysing ATP to ADP + Pi by acting as ATPase. Secondary transport does not use energy directly , it uses second-hand energy stored in the form of an electrochemical gradient (usually Na+)

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16
Q

What are the exofacial state and endofacial state?

A

Exofacial - carrier protein open, facing the extracellular fluid
Endofacial- carrier protein open, facing the intracellular fluid

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17
Q

What is facilatated diffusion?

A

Uses a carrier to facilitate (assist) the transfer of a substance across a membrane from high to low concentration (never against the concentration gradient)

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18
Q

What is depolarisation?

A

When the membrane potential becomes less negative ( sometimes even positive)

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19
Q

How is Na+/K+ ATPase electrogenic?

A

The net transfer of the equivalent of 1 negative charge into the cell for each cycle of the pump

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20
Q

What is the role of Na+/K+ ATPase?

A

Maintains the concentration gradients by pumping back K+ that has leaked from the cell and pumping out Na+ that has entered the cell in the ratio 3Na+(out):2K+(in)

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21
Q

How do you calculate the driving force?

A

Membrane potential (Vm) - equilibrium potential (Elon)

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22
Q

When is there no net movement of K+?

A

When the energy in the concentration gradient is equal and opposite to that In the electrical gradient

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23
Q

What is hyperpolarization?

A

When the membrane potential becomes more negative

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24
Q

What is the membrane potential determined by?

A
  • the selective permeability of the membrane to certain ionic species
  • the concentration gradients of the permeant ions across the membrane
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25
Describe the competition characteristic of carrier mediated transport?
When a carrier can fit 2 substrates, the presence of both diminishes the rate of the transfer for either since they compete with each other
26
What are the important roles for the Na+-K+ ATPase?
1) maintains Na+ and K+ concentration gradients across the plasma membrane 2) Helps regulate cell volume b y controlling concentration of solutes to the cell 3) Energy stored in the EC gradient established by the pump can be harasses to drive secondary transport by coupling movement of a solute to Na+
27
What is the rate of diffusion governed by?
It is governed by the permeability coefficient and concentration gradient
28
What do occlusion junctions do?
- inhibit diffusion - Appear as a focal region of close opposition between adjacent cell membranes - Known as tight junctions
29
What are the 3 types of intercellular junctions?
1) Occluding junctions:link cells to form barrier 2) Anchoring junctions:provide mechanical strength 3) Communicating junctions: allow movement of molecules between cells
30
Why for Na+/K+ ATPase, is the hydrolysis of ATP necessary?
Provides energy energy to pump against the energy in relevant electrochemical gradients
31
What is vesicular transport and name the 2 types?
- Requires energy for vesicle formation and movement within the cell - Endocytosis - Exocytosis
32
What is symport (co-transport)?
- Type 1 of secondary active transport | - The solute and Na+ move in the same direction
33
When is there no potential across the membrane?
When there is no movement of ions due to equal charges on both sides of the membrane
34
Describe vesicular transport Phagocytosis?
Bacteria/ larger particulate material from the extracellular space can be incorporated into the cell.Bacteria binds to the cell surface receptors triggering extensions of the cell to engulf it forming a phagosome
35
What generates an electrical gradient (potential)?
The difference in charge between 2 adjacent areas
36
What is Exocytosis?
- vesicle fuses with the plasma membrane, released contents to the ECF - the vesicle incorporates into the plasma membrane - secretion of enzymes, protein hormones, neurotransmitters
37
What is a junctional complex?
Close association of several types of junctions found in certain epithelia tissues
38
What do anchoring junctions do?
- Adherent junctions:link submemnrane actin bundles of adjacent cells - Transmembrane adherin molecules bind to each other in ECS, and so through link molecules , to the actin of the cytoskeleton - appear far apart
39
What do communicating junctions do?
- Allow selective diffusion of molecules between adjacent cells - "gap junctions" - circular patch studded with several hundreds pores - Pores are produced by connexion proteins - also found in smooth muscle and cardiac muscle
40
Describe vesicular transport : Exocytosis
Works in a reverse way to endocytosis. It discharges material and many secretory products are released this way into ECS
41
What is Endocytosis?
- "pinching off" of membrane to engulf substance - materials from the cell interior are enclosed in a segment of the plasma of the plasma membrane that pockets inward and pinches off as an endocytotic vesicle
42
What is osmolarity?
The concentration of osmotically active particles (solutes) present in a solution (NOT THE MASS)
43
What is osmotic pressure and how can it be calculated ? | What does it depend on?
- The pressure that arises from an equal solute concentrations across a semi-permeable membrane - Depends on the number of particles, not their chemical form
44
What is osmosis 1?
Osmosis is the net diffusion of water down its own concentration gradient across a semi-permeable membrane
45
What is osmosis 2?
Movement of water when a selectively permeable membrane separates pure water from a solution of a non- permeant solute
46
What is Osmosis 3?
Movement of water when a selectively permeable solute i.e at equilibrium, no net movement of water occurs
47
What is osmosis 4?
Movement when a selectively permeable membrane separates unequal solutions of impermeable solute - flexible membrane prevents high hydrostatic pressure
48
What is Osmosis 5? | What is an aquaporin?
- Movement of water molecules through aquaporins in single file - Channels that conduct water selectively and greater increase permeability to water
49
what are effects of cholestral on the membrane?
high temp- prevents movement of lipids and maintain structure low temp- prevents crystallisation
50
what is tonicity?
effect a solution has on a cell
51
what movements can phospholipids do?
- rotate - vibrate - move around their own leaflet of the membrane millions of times per second
52
What diffusion is likely and what diffusion is unlikely with phospholipids?
likely- lateral diffusion | unlikely-transversal diffusion
53
What effects does cholesterol have on the membrane in cold temperatures?
Maintains fluidity of membrane by preventing dense packing of phospholipids (crystallisation)
54
What effects does cholesterol have on the membrane in warm temperatures?
Decreases fluidity of membranes by restraining phospholipids movement
55
What effect does cholesterol have on membrane permeability?
reduces membrane permeability to hydrophilic molecules
56
what is it called when short carbohydrate chains bound to membrane proteins and lipids?
Glycosylated - glycoproteins - glycolipids
57
What layer does glycoproteins and glycolipids form?
the glycocalyx
58
What are the functions of the lipid bilayer?
-it forms the basic structure of the membrane -its hydrophobic interior serves as a barrier to polar and charged substances -the cell can maintain differences in solute composition and concentrations inside/outside the membrane -it is responsible for the fluidity of the membrane enables the cell to change shape
59
What are docking-marker acceptors?
a membrane protein located on the inner membrane surface which interact with secretory vesicles leading to exocytosis of the vesicle contents (neurotransmitter )
60
What are the 2 cell adhesion molecules (CAMs)?
- cadherins - help hold cells within tissues together | - integrins- span the plasma membrane acting as a link between extra and intra cellular environments
61
what acts asself-identity markers that enable cells to identify and interact with one another?
short carbohydrate chains on the outer membrane
62
what role does carbohydrate have on tissue growth?
- cells do not overgrow their own territory | - except cancer cell growth(abnormal surface markers)
63
What are tight junctions?
join the lateral edges of epithelial cells near their lumenal (apical) membranes (tight, or leaky)
64
what are desmosomes?
adhering junctions that anchor cells together, especially in tissues subject to stretching (e.g. skin, heart, uterus)
65
What are gap junctions?
‘communicating’ junctions that allow the movement of ions and small molecules between two adjacent cells (e.g. heart)

Physiology (4 decks)

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