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BDS1 - Human Body > Carbohydrates > Flashcards

Carbohydrates Flashcards

1
Q

what are the functions of carbohydrates?

A

-storage
-energy source
-structural
-inter-cellular communication

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2
Q

what is the general formula of carbohydrates?

A

(CH2O)n

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3
Q

what structure do larger monosaccharides have?

A

form ring structures

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4
Q

what are six and five member rings called?

A

-five: furanoses
-six: pyranoses

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5
Q

how can you differentiate between aldoses and ketoses?

A

-if oxygen is on an aldehyde, it is an aldose
-if oxygen is on an a ketone, it is a ketose

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6
Q

which stereoisomers do carbohydrates form

A

Form D- and L- stereoisomers

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7
Q

which stereoisomer is naturally found?

A

D-stereoisomer

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8
Q

what other shape can sugars be found (apart from rings) and why?

A

can form chair conformation because of the spread of electrons

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9
Q

two different anomers can exist, why and what is the importance of this

A

why = depends on orientation of OH group on anomeric carbon (carbon 1)
important because the orientation of OH group determines the shape of the molecule when sugars bind to each other

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10
Q

which 2 anomers exist?

A

OH group can be across from each other (equatorial)
or
OH group can be down from each other (axial)

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11
Q

how is a glycosidic bond formed?

A

when two monosaccharides join together in a condensation reaction

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12
Q

what does a glycosidic bond being beta or alpha depend on?

A

the orientation of the OH group

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13
Q

which other chemical groups can carbohydrates contain?

A

-phosphate
-amino
-acetyl

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14
Q

how can other chemical groups affect carbohydrates?

A

-changes properties e.g. charge

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15
Q

describe glucosaminoglycans

A

-unbranched polysaccharide made up of repeating disaccharide units that contain a hexosamine and uronic acid
-highly polar and attract water

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16
Q

how do disaccharides differ?

A

-types of monosaccharide
-nature of bond

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17
Q

what is an oligosaccharide?

A

-more than two but less than a lot (maybe 6) monosaccharides

18
Q

describe O-linked glycosylation

A

-attachment of sugar molecule to oxygen atom of certain amino acids
-this is a post-translational modification
-clustered in proteins
-has protective role e.g. mucin

19
Q

describe N-linked glycosylation

A

-attachment of oligosaccharide to nitrogen atom of certain amino acids
-spread through protein
-more variable
-has effect on protein folding, activity and cellular location

20
Q

what is mucin?

A

a glycoprotein constituent of mucus

21
Q

what is the difference between homopolysaccharides and heteropolysaccharides?

A

-homopolysaccharides are made up of the same monosaccharides
-heteropolysaccharides are made up of different monosaccharides

22
Q

what is cellulose?

A

-linear chains of glucose joined by beta 1-4 glycosidic bonds
-main component of plant cell walls
-strong bc lots of H bonds form between the straight chain glucose
-forms more complex structures w other polysaccharides

23
Q

describe chitin

A

-main structural component of exoskeletons of insects, crustaceans, spiders
-present in cell wall of fungi, algae and in capsule of some bacteria
-structurally different from cellulose bc formed from chains of N-acetyl-D-glucosamine
-stronger than cellulose

24
Q

describe starch

A

-stores energy in plants as food reserve
-forms insoluble granules in cytoplasm
-made of a-amylose and amylopectin

25
Q

describe a-amylose

A

-linear homopolysaccharide
-glucose monomers linked by alpha 1-4 linkages
-forms spiral structure (helical conformation) bc bonds are in different places compared to cellulose - this makes it more compact

26
Q

Describe amylopectin

A

-branched bc of occasional 1-6 linkages
-can contain up to million glucose monomers

27
Q

Describe glycogen

A

-present in all tissue but prevalent in liver and muscle
-structurally similar to amylopectin but more branched
-degraded to glucose by glycogen phosphorylase and debranching enzyme

28
Q

Describe glycoproteins

A

short carbohydrate chains covalently linked to serine, threonine or asparagine
-often branched
-circulating proteins

29
Q

how is glycogen degraded to glucose?

A

-glycogen phosphorylase removes glucose molecules at end of chains
-debranching enzymes act as transferase by removing glucose molecules near branch points and also cleave branch points

30
Q

what are examples of glycoproteins?

A

-hormones
-antibodies
-extracellular matrix
-enzymes
-components of bacterial cell wall

31
Q

What 2 ways can carbohydrate groups in glycoproteins be linked

A

N-linked glycosylation tends to be quite variable and has important effects on protein folding, activity and cellular location
O-linked glycosylation often occurs in clusters on proteins with a protective role ie mucin

32
Q

what are the functions of salivary mucins?

A

-Have between 2 and 7 sugar units attached
-formation of mucus
-lubrication
-modulation of oral bacteria

33
Q

what are the two forms of salivary mucins?

A

high or low molecular weight mucins

34
Q

describe glycolipids

A

-Cerebrosides and gangliosides
-present in all eukaryotic cell membranes
-involved in intercellular communications
-contain the same oligosaccharides as glycoproteins
-act as cell recognition factors
-important feature of bacterial cell wall - causes strong immune reaction in humans
-glycolipids determine blood group

35
Q

GlycoRNA?

A

Paper published last year describes existence of glycosylated RNA
Found on plasma membrane
As yet, function unknown

36
Q

describe digestion of carbohydrates

A

-begins in the mouth
-saliva contains a-amylase which hydrolyses alpha 1-4 linkages except outermost bonds
-along w chewing, this reduces polysaccharides to oligosaccharides of eight or less monomers
-further digested by pancreatic a-amylase and other glycosidases
-some bacteria break up complex carbs that body cannot do itself

37
Q

Digestion overview

A
38
Q

describe the relationship bw carbohydrate intake and oral health

A

-high carbohydrate intake is linked to oral health (caries, gum disease (diabetes predisposes)
-bacteria in mouth that can cause gum disease uses glycoproteins and glycolipids as food source

39
Q
A
40
Q

describe Glycocalyx

A

-The glycoproteins and glycolipids on the cell surface form the glycocalyx
-This forms a thick protective barrier
-In bacteria, the glycocalyx can form a layer on which bacteria can adhere to objects such as replacement joints and teeth

BDS1 - Human Body (22 decks)

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