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Biochemistry > L10-11: Carbohydrates > Flashcards

L10-11: Carbohydrates Flashcards

1
Q

What is the most abundant main class of biomols?

A

Carbohydrates

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2
Q

What are the major roles carbohydrates play in biological processes?

A

-Storage and transport of energy
-cell-cell communication/adhesion
-Host-pathogen and host-symbiont interactions
-Structural components of animals, plants & fungi
-components of DNA and RNA

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3
Q

What is the main composition of carbs?

A

Contain C,H and O
2 or more hydroxyl groups
An aldehyde or ketone group

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4
Q

What are the 2 simplest carbs?

A

Glyceraldehyde and Dihydroxyacetone

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5
Q

What does it mean when sugars are chirally active?

A

They have 2 stereoisomers

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6
Q

What are the names when carbs contain aldehyde group or ketone group?

A

Aldehyde- Aldoses
Ketones- Ketoses

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7
Q

How do sugars with >4 carbons form rings?

A

Because the alcohol is part of the same molecule as the aldehyde/ketone

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8
Q

What are the names when aldehyde or ketone and alcohol form then when they form rings?

A

Aldehyde- Hemiacetal, ring- pyran
Ketone- Hemiketal, ring- furan

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9
Q

Why do the rings have a chair configuration?

A

Due to the tetrahedral geometry of carbon atoms

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10
Q

What are the 2 orientations on the carb rings?

A

Axial (up or down, opposite directions)
Equatorial (same plane as ring)

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11
Q

How do the alpha and beta forms arise from sugars?

A

The formation generates and additional asymmetric carbon at position 1 (NOT NEW) (for aldoses)

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12
Q

Where does the asymmetric carbon arise in ketoses?

A

C2

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13
Q

How many carbons do most sugars have?

A

5-6

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14
Q

What do L and D stand for?

A

Laevorotatory and Dextrorotatory

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15
Q

What happens when only asymmetric carbon 2,3 or 4 are in a different configuration to glucose?

A

Molecule is a different structure, they are epimers

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16
Q

What can sugars join to become?

A

Disaccharides
Oligosaccharides
Polysaccharides
(linked by glycosidic bonds)

17
Q

What are the different configurations of the glycosidic bond?

A

Alpha or beta (from either 2 alpha or a alpha and a beta)

18
Q

What are 3 disaccharides and what are they used as?

A

Maltose, lactose and sucrose used as an important energy source when hydrolysed

19
Q

What are the main polysaccharide storage molecules?

A

Starch and glycogen

20
Q

What are starch and glycogen polysaccharides of?

A

D-glucose

21
Q

What type of glycosidic bonds to starch and glycogen have?

A

Alpha 1,4-glycosidic bonds

22
Q

What makes a reducing sugar a reducing agent?

A

It has a free aldehyde or ketone group

23
Q

What are most of the reducing sugars?

A

They are all monosaccharides and most disaccharides/oligo/poly

24
Q

Why are alpha glycans good storage molecules?

A

The alpha1,4-linkage causes the polysaccharide to twist into a helical structure which makes it more compact

25
Q

What does branching in starch and glycogen do?

A

Alpha1,6 branching makes it compact and has many non-reducing terminals so easy to digest

26
Q

What are the structural properties of cellulose?

A

Plant polysaccharide
Long beta1,4-linked glucose chains (form highly crystalline microfibrils)
Very strong
Most abundant organic molecule on planet

27
Q

How is biofuel formed?

A

Cellulose hydrolysed to glucose with enzymes then convert glucose to ethanol by microbial fermentation

28
Q

What is the main component of bacterial cell walls?

A

Peptidoglycan

29
Q

What are properties of the bacterial cell wall?

A

Without cell wall bacteria are osmotically sensitive and burst
Good target for antibiotics as not present in animal cells
Lysozyme targets bacterial cell wall

30
Q

What are glycoconjugates?

A

When carbs are often covalently linked to molecules such as proteins or lipids

31
Q

How is N-glycosylation useful?

A

As it plays a role in protein folding, stability and cell recognition

32
Q

What are O-linked glycans?

A

Oxygen linked

33
Q

What are characteristics of O-glycans?

A

Joined to hydroxyl of serine or threonine
Common is GlcNAc (N acetyl glucosamine)
Cytoplasmic

34
Q

What are key components of mucus?

A

Mucins (O-glycoproteins)

35
Q

What are proteins that are attached to mostly O-linked polysaccharides called?

A

Glycosaminoglycans

36
Q

What are the functions of glycosaminoglycans?

A

Joint lubricants
Structural components of Extracellular Matrix
Mediate adhesion of cells the ECM
Bind factors that stimulate cell proliferation

37
Q

What are characteristics or proteoglycans?

A

GAG component determines function
Made of disaccharide repeats of amino sugar & uronic acid
Heavily sulfated
Bind lots of water (hydrated gel withstand high compressive loads)

38
Q

How are complex carbs synthesised?

A

Glycosyltransferases

39
Q

How are blood groups different?

A

A- GTA puts GlcNAc on
B- GTB puts Gal on
O- GTs non-functional
AB- GTA and GTB

Biochemistry (10 decks)

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