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MGC > Membranes > Flashcards

Membranes Flashcards

1
Q

What are membranes

A

Thin films composed of mixtures of lipids and proteins

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2
Q

What do lipids do

A

Act as barrier to the movement of H2O and h20 soluble molecules

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3
Q

What is the function of proteins

A

Includes the transportation of molecules across the membrane

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4
Q

What is the purpose of the plasma membrane

A

Maintains movement between intracellular and extracellular environments

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5
Q

What are amphipathic molecules

A

Molecules that have hydrophobic (non-polar) end and hydrophilic (polar) end and form spontaneously from bilayers

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6
Q

What is a common fatty acid

A

Palmitate (palmitic acid) with 2 distinct chemical regions

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7
Q

What are phospholipids composed of

A

Have polar head group and two hydrophobic hydrocarbon tails (tails usually fatty acids)

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8
Q

What impact does the length and saturation of the tail have on membrane fluidity

A

Affects ability of phospholipid molecules to pack together and effects membrane fluidity

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9
Q

How to identify a kink in lipid structure

A

Cis double bond means unsaturated fatty acid which forms kink

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10
Q

Characteristics of saturated fatty acids

A

-Common in dairy and meat products
-solid at room temp

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11
Q

Characteristics of unsaturated fatty acids

A

-common in plants
-liquid at room temp

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12
Q

How do phospholipids aggregate to form bilayers

A

In aqueous environment hydrophobic tails pack together to exclude H2O => forms lipid bilayer

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13
Q

Are the fatty acid tails soluble or insoluble to H2O and why

A

Insoluble in H2O as all atoms are uncharged, non-polar and the tails are hydrophobic

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14
Q

Are the heads of the phospholipid bilayer insoluble or soluble in H2O and why

A

Soluble in water due to charger polar groups and forms favourable electrostatic interactions or H bonds with H2O molecules
-heads hydrophilic (polar)

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15
Q

How is membrane fluidity controlled

A

By fatty acid composition and cholesterol content

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16
Q

What are the two states lipid bilayers can exist in

A

-ordered rigid state
-relatively disordered, fluid state

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17
Q

What is a key regulator of membrane fluidity in eukaryotes

A

Cholesterol

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18
Q

What are transmembranes formed by

A

Multiple alpha helices and a cylinder forming a beta barrel

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19
Q

What is the function of transporters

A

Transports metabolites e.g ions across lipid bilayer

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20
Q

What is the function of anchors

A

Anchor membrane to macromolecules on either side

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21
Q

What is the function of receptors

A

Detect chemical signals in the cells environment and relay them into the cell interior

22
Q

What is the function of enzymes

A

To catalyse specific reactions at membrane

23
Q

What are the membrane-bound intracellular organelles in eukaryotic cells

A

-endoplasmic reticulum
-Golgi apparatus
-mitochondria

24
Q

What functional group is at one end of the hydrophobic tails on fatty acid

A

-COOH (Carboxylic acid)

25
Q

When does phase transition between two states occur

A

Tm (melting temperature)

26
Q

How can fluidity of lipid bilayers be studied

A

Using synthetic lipid bilayers

27
Q

How are synthetic lipid bilayers produced

A

By spontaneous aggregation of amphipathic lipid molecules in water

28
Q

What is the permeability of gasses and small, uncharged polar molecules

A

Freely permeable through the synthetic lipid bilayer

29
Q

What is the permeability of larger uncharged polar molecules

A

Cannot permeate through synthetic lipid bilayer

30
Q

What is the permeability of charged ions through synthetic lipid bilayer

A

Impermeable due to charged ions

31
Q

What are the two main classes of transport proteins

A

Carrier protein and channel protein

32
Q

Function of carrier proteins

A

Bind to molecule to be transported and move through the membrane by a series of conformational changes

33
Q

What is the function of channel proteins

A

Form hydrophilic pores through membrane to allow charged ion solutes to pass through
-faster than carrier proteins

34
Q

What do protein channels discriminate on

A

On basis of size and charge

35
Q

what is passive transport

A

Aka as facilitated diffusion where molecules move down conc. gradient
(For all channels and most carriers)

36
Q

What is active transport

A

Movement of molecules against electrochemical gradient “uphill” - requires energy

37
Q

What is the apical glucose transporter in intestinal epithelial cells

A

Glucose/Na+ symport allows the uptake of glucose even when concentration in cell is already high

38
Q

What is the basal glucose transporter in the intestinal epithelial cells

A

passive glucose transporters and glucose is released as required

39
Q

What is the uniport in carrier mediated transport

A

transport of soluble molecules from one side of membrane to the other e.g glucose transporters

40
Q

What is the symport in carrier mediated transport

A

Coupled transport of two types of solute

41
Q

What is the antiport of carrier mediated transport

A

Transport of one solute in one direction coupled to transport another in the opposite direction

42
Q

What is phagocytosis

A

Process of large particles (e.g bacteria) are internalised (engulfed) by eukaryotic cells

43
Q

Characteristics of cholesterol

A

Very insoluble in lipids and is carried in blood in low density lipoprotein (LDL) particles

44
Q

What is the result of defective LDL receptors

A

LDL (low density lipoprotein) uptake decrease => high circulating cholesterol levels causing hypercholesterolaemia and leads to atherosclerotic plaque formation

45
Q

How do cell surface receptors work

A

Large hydrophilic signalling molecules unable to bind directly to plasma membrane => bind to cell surface receptors => generate 1 or more intracellular signalling molecules in target cell

46
Q

How do intracellular receptors work

A

Small hydrophobic signalling molecules pass through cell plasma membrane => activate intracellular enzymes in cytosol or nuclease => regulates gene transcriptions

47
Q

Are steroid hormones e.g cortisol, oestrogen and testosterone hydrophobic or hydrophilic

A

Hydrophobic => can pass through plasma membrane

48
Q

What is the function of lysosomes

A

Small sacs of digestive enzymes

49
Q

What is the mitochondria

A

Site of ATP synthesis

50
Q

What are the functions of the Golgi apparatus

A

Site of post translational modification of proteins and modification of oligosaccharides added in the ER

51
Q

What climate is to have more unsaturated fatty acids

A

Colder climates

52
Q

What climate is to have more saturated fatty acids

A

Hotter climates

MGC (7 decks)

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