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cells and biomolecules 🧬 > carbohydrates > Flashcards

carbohydrates Flashcards

1
Q

functions of carbohydrates

A

energy store
- starch in plants
- glycogen in animals

structural
- cellulose in plants
- chitin in insects

cell recognition
- cell surfaces carbohydrates

metabolism
- metabolic intermediates
- energy substrates

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2
Q

sizes of carbohydrates

A

monosaccharides
- single sugars
- basic units of carbohydrates

oligosaccharides
- 2-10 residues
- name changes depending on how many eg di or try

polysaccharides
- more than 20 residues
- macromolecules with long chains
- made of one or many monosaccharides

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3
Q

monosaccharides

A

simplist carbohydrates - building blocks
cannot be easily broken down

classifying according to:
- number of carbon atoms in structure
- whether they have an aldehyde (aldose) or ketone (ketose)

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4
Q

structure of a monosaccharide

A
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5
Q

aldoses

A

all have aldehyde group on first carbon -CHO
CH2OH on lowest carbon

in same group have same general formula with different arrangements of OH groups

glucose, mannose and galactose

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6
Q

structure of glucose

A
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7
Q

structure of mannose

A
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8
Q

structure of galactose

A
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9
Q

ketoses

A

all have ketone group on second carbon C=O
CH2OH on first and last carbon

within group have same general formula with different arrangement of OH groups

names end in -ulose

eg fructose

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10
Q

structure of fructose

A
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11
Q

what is an epimer?

A

different compounds with the same molecular formula that differ by configuration at only one carbon

important as biological system can differentiate between them

eg glucose and galactose
have same atoms joined to same atoms
except configuration at carbon 4
= c4 epimer of glucose

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12
Q

hemiactal

A

where intramolecular (within some molecule) monosaccharides react with themselves
hydroxyl OH reacts with a carbonyl C=O

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13
Q

internal hemiactal

A

occurs in monosaccharides with 5 or more carbons
results in a ring structure
forms a new chiral (asymmetric) carbon

carbon atom bound with 4 different groups bonded to it
special as bonded to 2 oxygen atoms
called anomeric carbon

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14
Q

common monosaccharides

A

glucose
fructose
ribose
galactose

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15
Q

glucose

A

aldose (aldahexose)

monomer to create cellulose
central to cell metabolism
found in monosaccharide form in plants, fruit and blood

structure

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16
Q

fructose

A

ketose (ketohexose)

monomer to create sucrose
found in leaves, fruit and honey

anomeric carbon of ketone is c2 not c1

structure

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17
Q

ribose

A

aldapentose

component of ribonucleic acid
reduced form (deoxyribose) used in DNA

structure

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18
Q

galactose

A

component of lactose
makes galactans - structural cell wall polysaccharide in plants
component of antigens on blood cells that create blood groups

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19
Q

how are monosaccharides joined?

A

hydroxyl OH on carbon 1 reacts with the hydroxyl on carbon 4 of another molecule

2 hydrogens and an oxygen released in a condensation reaction = water

covalent bond forms between oxygen on anomeric carbon and carbon 4 of another
= glycosidic bond

20
Q

what is a disaccharide?

A

two monosaccharides joined by a glycosidic bond
alpha or beta depending on arrangement of OH on anomeric carbon

eg maltose, lactose and sucrose

21
Q

maltose

A

2 glucose molecules
formed during breakdown of starch

alpha 1,4 bond

structure

22
Q

lactose

A

galactose and glucose joined by beta 1,4 bond

beta bond harder to degrade than alpha = harder to breakdown

structure

23
Q

sucrose

A

fructose and glucose joined

both anomeric carbon of fructose and glucose involved
glycosidic bond described differently depending on which molecule you start with

if start with glucose = alpha 1,2
if start with fructose = beta 2,1

structure

24
Q

reducing sugars

A

a sugar that can be oxidised and therefore acts as a reducing agent

if only one anomeric carbon involved in bond, free anomeric is not trapped in ring structure

free to reform a straight chain

means carbonyl carbon on straight chain is free to be oxidised

if oxidised then acts as a reducing agent and reduces other molecules

eg maltose

25
Q

what determines whether a sugar is reducing or non-reducing?

A

which carbons are involved in the bond

only one anomeric involved means second glucose isn’t trapped
can reform a straight chain
not in ring structure

26
Q

non-reducing sugars

A

eg sucrose

fructose is a ketose (anomeric carbon is carbon 2)

means anomeric carbon of both glucose and fructose is used in the glycosidic bond
so both locked I bring and no straight chains form

27
Q

sugar derivates

A

as well as monosaccharides, there are derivates

include amino sugars, acidic sugars and deoxy sugars

28
Q

deoxy sugars

A

formed when a hydrogen replaces one of the hydroxyl groups
eg ribose and deoxyribose

29
Q

acidic sugars

A

formed when a carboxylic acid group replaces the CH2OH at carbon 6
creates a uronic acid

eg glucuronic acid for glucose

30
Q

amino sugars

A

formed when hydroxyl group is replaced by an amino group
further modification of amino group by acetic acid forms an amide

eg amino sugar of glucose = glucosamine

amide modification is N-acetyl-glucosamine

31
Q

polysaccharides

A

polymers of monosaccharides

two types based on presence of basic sugar units
can be straight or have side chains

functions include storage and structural

32
Q

homo/hetero polysaccharides

A

homo = one monosaccharide unit repeated

hetero = more than one monosaccharide unit

33
Q

properties of a storage polysaccharide

A

energy stores
- many monosaccharides in one, broken down and used in metabolism

alpha links readily degraded by enzymes
- means they can be broken down easily

highly branched
- rapid release of monosaccharides
- more monosaccharides sotred within
- more ends made for quicker enzyme action

less dense energy store than triacylglycerol
- due to associated water weight whereas triacyglycerol is hydrophobic

34
Q

glycogen

A

storage polysaccharide in animals
stored in liver and muscle cells

structure similar to amylopectin
but more alpha 1,6 branches every 10-12 glucose molecules

more branches = more glucose per molecule
many branches = many non-reducing ends
so more easily broken down by enzymes

35
Q

inulin

A

storage polyacchiade in root and tubers of some plants

polymer of fructose, and usually glucose at one end
joined by an alpha 1,2 bond

non-reducing sugar
both anomeric carbons used in glycosidic bonds, cant open up
not digested in human gut

regulate osmosis and stabilise membranes

36
Q

industrial applications of inulin

A

food industry
- honey
- isolated frucrans = dietary fibre
oligofructans = sweeteners in reduced calories foods

37
Q

properties of structural polysaccharides

A

provide structural integrity in plant, agal and fungal cell walls
form skeleton of arthropods

contain beta links between sugars
not as easily broken down by enzymes

alternate monosaccharide units invert to give long straight chains

hydrogen bonding between chains increases strength

viscous polysaccharides contain substituted monosaccharides which are charged a physiological pH

38
Q

starch

A

energy storage polysaccharide in plants

present in starch granules of chloroplasts

two components - amuse and amylopectin

39
Q

amylose

A

glucose polymer with alpha 1,4 bonds

one long chain with one reducing sugar end (locked in ring) and one non-reducing (straight chain) end

angle of glycosidic bonds cause coils and form a helix
- two helical forms: single or double

not soluble in cold water (only hot)

40
Q

amylopectin

A

glucose polymer with alpha 1,4 linked backbone

branches joined by alpha 1,6 bonds every 15-25 glucose units

branches = more glucose molecules per chain

one reducing end and many non-reducing ends
- useful for quicker enzyme action for metabolism

41
Q

industrial applications of starch

A

food industry
- thickener and stabilisers

pharmaceutical industry
- filler in drug tablets due to large polymeric structure

cosmetics
- foundation and toothpaste

paper
- provide strength and smoothness

glue
- swells and gelatinises

biofuels

42
Q

cellulose

A

structural polysaccharide in plant cell walls
glucose polymer joined by beta 1,4 bonds

alternate monosaccharide unit invert to create long straight chains
- important for structural integrity

several chains align to form microfibrils
- hydrogen bonds between chains
- arrange in random directions to give strength to cell walls, no shear plane

43
Q

chitin

A

structural polysaccharide in insects and crustacean exoskeletons

beta 1,4 linked N-acetyl glucosamine

base unit is a sugar derivative
hydroxyl group at carbon 2 of glucose replaced by amide group

44
Q

peptidoglycan

A

chains of heteropolysaccharide composed of alternating N-acetyl glucosamine and N-acetyl muramic acid

linked by beta 1,4 bonds
used in bacterial cell walls

held by tetra-peptide chains attached to NAM
- cross links to another chain
- forms strong structure for cell wall

peptide chains on N-acetyl muramic acids residues in adjacent molecules are linked by further short peptide chains

45
Q

what determines blood groups?

A

short polysaccharide chains attached to cel membrane protein
terminal 3 or 4 sugars determine the blood group sugars

galactose
N-acetylglucosamine
N-acetylgalactosamine
fructose

46
Q

blood group types

A

type O = no terminal sugar
type A = alpha 1,3 linked GalNac
type B = alpha 1,3 linked galactose

47
Q

why must the correct blood group be given?

A

must not give blood cells with surface antigens that will react with recipients plasma antibodies

A or AB can receive A
B or AB can receive B
O can only receive O
AB can receive any

O = universal donors
AB = universal recipients

cells and biomolecules 🧬 (11 decks)

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