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BDS1 BAMS: Molecules and Cells > Proteins, Polysaccharides and Lipids > Flashcards

Proteins, Polysaccharides and Lipids Flashcards

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1
Q

What are the secondary structures of proteins?

A

Alpha helix and beta pleated sheets

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2
Q

Describe the alpha helix secondary structure of proteins

A
  • Rod-like, right handed orientation
  • Found in strong extensible proteins
  • Stabilised by hydrogen bonds
  • CO of each amino acid is H-bonded to NH of amino acid 4 residues ahead in sequence
  • 3.6 residues per helix turn
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3
Q

Give some examples of proteins with alpha helix secondary structure

A

Haemoglobin, myoglobin, keratins, fibrins, myosin

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4
Q

Describe the beta pleated sheet secondary structure of proteins

A
  • Zigzag chains
  • Place several chains side by side, CO and NH groups align, H bonding occurs -> sheet like structure
  • Parallel: chains run in same direction
  • Anti-parallel: chains run in opposite direction
  • Found in proteins where flexibility is needed e.g. silk fibroin
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5
Q

Which is the only protein that has a triple helix structure?

A

Collagen
Very strong, water-insoluble fibres
3 chains wound round each other -> tropocollagen

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6
Q

How many amino acids are there in each of the 3 chains that wind together in a triple helix structure to make up collagen?

A

~1000 amino acids

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7
Q

What is the repeating structure present in each of the 3 chains that wind together in a triple helix structure to make up collagen?

A

X-Pro-Gly OR X-Hyp-Gly

Hyp = hydroxyproline

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8
Q

Give examples of fibrous proteins

A

Collagen, keratin, fibrin, elastin, myosin

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9
Q

What are fibrous proteins?

A

Insoluble, metabolically unreactive, principally structural proteins

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10
Q

What are globular proteins?

A
  • Spherical
  • Backbone folds in on itself
  • Water-soluble compact structures
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11
Q

What is the role and structure of myoglobin?

A
  • Oxygen storage in muscle
  • Globular protein, associated with tertiary structure
  • Single chain (153aa)
  • Contains 8 helical regions
  • Prosthetic haem group contained within hydrophobic pocket
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12
Q

What is the role of haemoglobin?

A

Oxygen transport

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13
Q

Describe the structure of haemoglobin

A
  • Associated with quaternary structure
  • Has 4 subunits: 2 alpha chains and 2 beta chains
  • Speroidal molecule
  • Contains 4 haem groups
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14
Q

How many amino acids are in each alpha chain of haemoglobin?

A

141 aa

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15
Q

How many amino acids are in each beta chain of haemoglobin?

A

146 aa

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16
Q

What are peripheral membrane proteins?

A

Proteins that lie on the membrane surface

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17
Q

What are integral membrane proteins?

A

Proteins within the lipid bilayer

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18
Q

What are channel proteins?

A
  • Forms a channel in membrane

- Facilitate movement of small molecules across membrane (simple diffusion)

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19
Q

What are carrier proteins?

A

Proteins that bind to transported molecules (facilitated diffusion)

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20
Q

What are hormones?

A

Messenger proteins that allow cells to communicate with each other

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21
Q

What are some of the common modes of action of hormones?

A
  1. Influence the rate of synthesis of enzymes and other proteins
  2. Affect rate of enzymatic catalysis
  3. Alter permeability of cell membrane
22
Q

What is the sequence of events that follows after a hormone binds with its specific membrane receptor?

A

Hormone binds to receptor -> message relayed to inside of cell -> cascade events -> cellular actions

23
Q

Give 3 examples of hormones

A
  1. Insulin: sugar uptake by cells from bloodstream
  2. Glucagon: sugar release by cells into bloodstream
  3. Human growth hormone (HGH)
24
Q

What are enzymes?

A
  • Biological catalysts
  • Globular proteins
  • Increase reaction rates by up to 10^20
  • High specific
25
Q

Which proteins are for immune protection?

A

Antibodies, cytokines, chemokines

26
Q

Which proteins are for muscular contraction?

A

Myosin (fibrous)

Actin (globular)

27
Q

What are the building blocks of polysaccharides?

A

Monosaccharides

28
Q

What are the 2 types of monosaccharide?

A

Aldoses (contain CHO group)

Ketoses (contain CO group)

29
Q

What is a disaccharide?

A

When 2 monosaccharides come together (involves elimination of water)

30
Q

What is maltose composed of?

A

Two glucose molecules joined by alpha-1,4-glycosidic linkage

31
Q

What is sucrose composed of?

A

One glucose molecule and one fructose molecule

32
Q

What is lactose composed of?

A

One glucose molecule and one galactose molecule

33
Q

What type of sugar is glucose?

A

An aldose sugar

34
Q

Describe the structure of glucose

A

6 membered ring
Exists in linear or ring form
Important monosaccharide

35
Q

What are the 2 isomeric forms which glucose can exist in?

A
  • Alpha configuration: hydroxyl group pointing downwards

- Beta configuration: hydroxyl group pointing upwards

36
Q

What type of reaction forms polysaccharides from monosaccharides?

A

Dehydration reactions/hydrolysis reactions form/catabolise complex carbohydrates from monosaccharides

37
Q

What is starch composed of?

A

1,4 linkages of alpha glucose

38
Q

What is cellulose compose of?

A

1,4 linkages of beta glucose

39
Q

Which polysaccharide is a food reserve in humans?

A

Starch

40
Q

Why can’t humans digest cellulose?

A

Don’t have the enzymes to do so (beta-glycosidase enzyme) - breaks down beta 1,4 glycosidic bonds between glucose monosaccharides

41
Q

Describe the structure of glycogen

A
  • Inner region and outer region
  • Inner region comprised of alpha 1,4 linkages
  • At branch point: alpha 1,6 linkages
  • Tree-like structure, lots of branching
42
Q

Describe the structural differences between glycogen and starch

A

Starch = linear structure. Comprised of alpha 1,4 glycosidic linkages

Glycogen = branched structure. Outer region comprised of alpha 1,4 glycosidic linkages. At branch point = alpha 1,6 glycosidic linkages

43
Q

Which polysaccharide are plant cell walls made up of?

A

Cellulose

44
Q

What are the main architectural units of plant cell walls?

A

Microfibrils composed of cellulose

45
Q

What are the monomeric units of lipids?

A

Fatty acids

46
Q

What are lipids?

A
  • Fatty type molecules

- Most lipids are glycerides, based upon glycerol

47
Q

What is a phosphatidylcholine?

A
  • A diaglyceride

- A major phospholipid of membranes

48
Q

what is the major phospholipid of membranes?

A

Phosphatidylcholone

49
Q

What is the function of triaglycerides?

A

Storage compounds

50
Q

What determines whether a fatty acid is solid or liquid at room temperature?

A
  • Degree of saturation
  • Affects van Der Waal’s forces
  • Changes the lipids physical property
  • Saturated fatty acids are solid at room temperature, unsaturated fatty acids are liquid at room temperature
51
Q

Give some examples of sterols

A

Cholesterol, cortisol, oestrogen, testosterone

52
Q

What are the roles of sterols?

A
  • Some have essential biological activity

- Others are important constituents of biological membranes (e.g. cholesterol)

BDS1 BAMS: Molecules and Cells (13 decks)

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