B2.1 Membrane Proteins & their functions Flashcards

1
Q

What are the definitions of hydrophobic and hydrophilic?

A

Hydrophobic = does not mix with water. Hydrophilic = does mix with water.

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2
Q

How does insulin affect specific cell types?

A

Insulin will only interact with cells which have a surface receptor for insulin.

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3
Q

What is the structure of a lipid bilayer?

A

Sheet-like bilayers formed by amphipathic lipids in water.

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4
Q

What is selective permeability in the context of lipid bilayers?

A

The ability of the lipid bilayer to regulate the movement of substances.

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5
Q

What is the role of aquaporins?

A

Transporting water across cell membranes.

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6
Q

What are the two main types of membrane proteins?

A
  • Integral proteins
  • Peripheral proteins
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7
Q

What is the fluid mosaic model?

A

A model describing the structure of membranes with integral and perpheral proteins embedded in a fluid lipid bilayer.

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8
Q

Describe the permeability of membranes.

A

Dependent on the size and hydrophobic nature of molecules.

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9
Q

What is simple diffusion?

A

The movement of small molecules like oxygen and carbon dioxide directly through the lipid bilayer.

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10
Q

What are integral proteins?

A

Transmembrane proteins that are embedded through both layers of the membrane.

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11
Q

What are peripheral proteins?

A

Proteins that do not span the membrane and are located on its surface.

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12
Q

What is osmosis?

A

The movement of water from a region of higher water potential to lower potential

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13
Q

What is facilitated diffusion?

A

The process allowing polar or large molecules to pass through membranes via channel or carrier proteins.

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14
Q

What is the difference between active transport and passive transport?

A

Active transport requires energy to move substances against their concentration gradient.
* ATP
* against concentration gradient
* transport proteins

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15
Q

What is endocytosis?

A

The process where the cell membrane engulfs material to form a vesicle.

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16
Q

What is exocytosis?

A

The process where vesicles fuse with the cell membrane to release contents outside the cell.

17
Q

What are gated ion channels?

A

Channels that open or close in response to stimuli, allowing specific ions to pass.

18
Q

What are cell-adhesion molecules (CAMs)?

A

Glycoproteins that mediate the binding of cells to each other.

19
Q

Fill in the blank: Phospholipids are considered _______ molecules.

A

[amphipathic]

20
Q

What are the two types of active transport?

A
  • Direct active transport
  • Indirect active transport (cotransport)
21
Q

What factors affect membrane fluidity?

A
  • Fatty acid composition
  • Presence of cholesterol
22
Q

What is the role of cell junctions?

A

Connect cells to each other, allowing intracellular transport and communication

They play important roles in cell proliferation, cell migration, and prevent unregulated movement of materials between cells.

23
Q

What are the three types of cell junctions found in animals?

A
  • Adhesive junctions
  • Tight junctions
  • Gap junctions
24
Q

What are adhesive junctions?

A

Junctions present in epithelial and cardiac cells that facilitate cell–cell adhesion and ensure structural stability

Also called anchoring junctions.

25
What do tight junctions do?
Form a tight seal between two neighboring cells, preventing unregulated movement of molecules ## Footnote They act as occluding junctions.
26
What are gap junctions?
Intracellular channels that connect neighboring cells for the movement of molecules ## Footnote Often called communicating junctions.
27
What are the main components of biological membranes?
* Lipids * Proteins * Small amounts of cholesterol
28
What is an example of direct active transport?
Sodium–potassium pumps
29
What is an example of indirect active transport?
Sodium-dependent glucose cotransporters
30
Voltage gated ion channels
**Nerve signalling** 1. stimulus causes temporary reversal in pot. diff. = action potential 2. voltage-gated sodium channel opens = defuse = depolarisation (less -) 3. VGSC opens = diffuse = repolarisation (more -) 4. Treshold value = gate closes 5. channel inactivation = particle blcosk opening = prveents reopening
31
Role of cholesterol in membrane
* stuffens & reduces lateral movement = less fluidity * at high temp = stabilises * at low temp = prevents fatty acid chains form coming close (cant become solid)
32
Use of active transport
* uptake of glucose & AA in small intestine * excretion of H+ & urea * absorption of mineral ions by plant roots
33
Ligand gates channels - Nicotonic Acetyl choline receptor
* binding creates conformational change => channel opens * sodium diffuses down conc grad. = depolarisation = enzyme cholinestrase breaks down acetylcholine => channel close Nictoine can activate this
34
Difference between direct vs indirect sodium potassium pump
Direct = in cell membrane & generates energy + 3Na & 2K bidnign sites Indirect = two way solute transport
35
Indirect sodium potassium pump
1. Na+ bind to bidning site on oiter surface 2. simultaneously glucose molecule binds on cotransporter 3. conformational change => transports both inside
36
Direct sodium potassium pump
1. Pump opens to inside = Na+ binds 2. Bond triggers ATP hydrolysis =>attaches => conformational change to outside facing 3. pump releases Na+ to exterior 4. 2 x K+ bind & phosphate latter detaches 5. conformational change back to original form
37
cholesterol function (2)
* membrane fluidity * membrane permeability
38
factors affecting diffusion
* temperature * concentration gradient * composition of molecule * surface area * distance of diffusion pathway
39
function of membrane proteins
* cell recgnition = glycoproteins * transport = carrier/transport proteins * receptors / binding site for neurotransmitter * immobilise enzymes * cell adhesion