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Biochem Ca1 Cram > Carbs > Flashcards

Carbs Flashcards

1
Q

What are carbohydrates

A

aldehydes or ketone derivatives of polyhydroxy alcohols or compounds which give rise to these on hydrolysis.
Most abundant molecules on earth

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2
Q

3 sources of carbs in plants ?

A

◦ Starch
◦ Cellulose/lignin (Cell wall)
◦ Inulin (sweetener for diabetics)

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3
Q

3 sources of carbs in animals ?

A

In animals
◦ Plant foods
◦ Glycogen
◦ Others (fat, protein)

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4
Q

What are 4 classifications of carbs

A

Monosaccharides – Simple sugars
Disaccharides – 2 monosaccharides
Oligosaccharides – 3 – 10 monosaccharides
Polysaccharides – More than 10 joined together by glycosidic bond

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5
Q

What are Glycocongugates

A

Sugar chain attached to other biomolecules,
◦Proteins – Glycoproteins
◦Lipids – Glycolipids

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6
Q

Explain isomer formation

A

Asymmetric carbon atom – (C*) carbon atom with four different groups attached.
Presence of asymmetric carbon atoms lead to formation of isomers. Isomers - 2n (n- no. of chiral centres)

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7
Q

What are stereoisomers

A

Compounds which are identical in composition but differ in their spatial configuration

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8
Q

5 classifications of stereoisomers

A
  1. Aldose and ketose
  2. D and L isomers
  3. α and β anomers
  4. Epimers
    5- Pyranose and furanose
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9
Q

What are aldoses and ketoses

A

Aldose - monosaccharide containing one aldehyde group per molecule [chemical formula - Cn(H2O)n].
Ketose - sugar containing one ketone group per molecule.

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10
Q

D and L isomers

A

Called enantiomers (mirror images)
Naturally occurring monosaccharides belong to D series

When the OH group around the carbon atom adjacent to the terminal primary alcohol carbon (C- 5) is on the
Right – D series left – L series

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11
Q

A and B anomers

A

Carbon 1 - anomeric carbon atom
α – “OH” is below the plane of the ring
β - “OH” is above the plane of the ring
Anomeric carbon is the type of carbon that changes from acyclic form to cyclic form to become a stereocenter

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12
Q

Epimers

A

Two sugars which differ from one another by only one carbon atom except the anomeric carbon atom
Ex: glu/Man (2)

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13
Q

What is epimerization

A

Epimerization – the conversion of one epimer to another Ex; Galactose to Glucose in the liver

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14
Q

Pyranose vs furanose

A

Pyranose is 6 member ring (hemiacetal Haworth structure)
Furanose is 5 member ring (hemiketal, Haworth structure )

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15
Q

3 monosaccharide hexoses

A

D - glucose (dextrose)
D-fructose
D-galactose

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16
Q

What is D-glucose ?

A

◦ Hydrolysis of starch (polysaccharides), maltose, lactose (disaccharides) yield glucose.
◦ All tissues utilize glucose for energy
◦ Stored as glycogen in liver

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17
Q

12 Consequence of too much sugar

A

Dizziness
Allergies
Cholesterol
Hypertension
Colon and and pancreatic cancer
Type 2 diabetes
ADD/ADHD
Obesity.
Metabolic syndrome
Cardiovascular disease

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18
Q

What is fructose

A

◦ Found in fruits
◦ Canned, dried or preserved (jams) more than fresh
◦ Common sweeteners (honey, maple syrup) more than fresh (tbs)
◦ High consumption leads to Non communicable Diseases (NCD) (not natural sources)

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19
Q

What is galactose ?

A

◦ Constituent of milk sugar (lactose) and glycolipids and glycoproteins
◦ Synthesized in the mammary gland

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20
Q

What are derivatives of monosaccharides and 4 examples .

A

OH groups of sugars can be replaced by some other groups.
1. Deoxy sugars
2. Amino sugars
3. Sugar alcohols
4. Sugar acids

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21
Q

How are deoxy sugars formed and function

A

◦ Hydrogen atom replaces -OH group on C-2
◦ Constituent of nucleic acids

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22
Q

How are amino sugars formed and 2 examples

A

◦ Sugars containing an amino group are called amino sugars [Amino group (NH-) substituted for OH group]
1. Glucosamines
2.galactosamines

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23
Q

Biomedical importance of amino sugars ( glucosamines, galactosamines, antibiotics )

A
  1. Glucosamines
    ◦ Constituents of certain mucopolysaccharides /glycosaminoglycans
    ◦ Constituents of cell walls of fungi and lobster
  2. Galactosamines
    ◦ Constituents of sulphated mucopolysaccharides
  3. Antibiotics (erythromycin, carbomycin) contain amino sugars
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24
Q

What are sugar alcohols and 3 examples

A

Sugars reduced to their corresponding alcohols
1. Glucose to sorbitol
2. Mannose to mannitol
3. Galactose to galactitol

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25
Q

What is cataract and what causes it ?

A

cataract is a cloudy area in the lens of the eye that leads to a decrease in vision.
Dietary sorbitol is rapidly converted to fructose by sorbitol dehydrogenase and other carbohydrates in the liver.
Diabetes – sorbitol is produced rapidly
Intracellular accumulation of sorbitol leads to osmotic changes resulting in hydropic lens fibers that degenerate and form sugar cataracts

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26
Q

What are sugar acids ?

A

Aldoses are oxidized in a way that the aldehyde group remains unaltered but the primary alcohol group is converted to COOH group.
The sugar acid formed in this case is known as an “Uronic acid”.
Ex; D-Glucose to D-Glucuronic acid
D-Galactose to D-Galactouronic acid

27
Q

What are glycosides and 2 examples

A

Compounds containing a carbohydrate and a non- carbohydrate residue
Glucose is glucoside
Galactose is galactoside

28
Q

4 importances of glycoside

A

Cardiac glycosides –used to increase the cardiac output and important in cardiac insufficiency
Oubain – Inhibits Na+-K+ ATPase in cardiac muscle (Inhibitor of Na pump)
Found in certain drugs, spices etc.
Antibiotics (streptomycin)

29
Q

What is glycosidic bond

A

Two monosaccharides joined by a covalent bond is called a glycosidic linkage.

30
Q

What is disaccharide ? 3 examples

A

Bond is created between the C-1 of one sugar and the OH of another carbon
1. Maltose
2. Lactose
3. Sucrose

Intermediate product formed during the breakdown of starch by amylase enzyme

31
Q

What is lactose ?

A

Present in milk (milk sugar) and produced in the lactating mammary gland
Breast milk – main source of energy for the new born
Lactose is Glucose + galactose

32
Q

What is sucrose

A

Present in cane sugar, fruits and some vegetables
Sucrose is Glucose + Fructose

33
Q

What are 2 types of polysaccharides and their examples

A
  1. Homoploysaccharides – Starch, Cellulose, Glycogen
  2. Heteropolysaccharides – Glycosaminoglycans
34
Q

What is starch and where found

A

Storage form of carbohydrate in plants.
Present in cereals (rice, wheat, rye), potatoes, legumes
Mixture of amylose and amylopectin

35
Q

What is amylose

A

15-20% of starch
Glucose joined by α-1,4 glycosidic linkages
Unbranched chain
Forms a helical structure
There are 6 glucopyranose units per turn

36
Q

What is amylopectin

A

80-85% of starch
Highly branched structure
Main chain has α-1,4 glycosidic linkages
Each branch point has a α-1,6 glycosidic linkages

37
Q

What is cellulose?

A

Straight chain homoglycan of glucose with β-1,4 linkages with alternating glucose molecules.
Humans cannot hydrolyze cellulose.

Dietary fibre (Insoluble dietary fibre)
Dietary fiber is the edible parts of plants that are resistant to digestion and absorption in the human small intestine, with complete or partial fermentation in the large intesti

38
Q

5 benefits of fibre

A

1, acheivment of healthy weight
2l lower blood troll levels
3. Cancer prevention
4. Lpwer risk of heart disease
5.Regulate blood sugar

39
Q

What is glycogen and structure

A

Carbohydrate storage form in animals
After a meal glucose will be converted to glycogen (Glycogenesis)
During starvation/fasting glycogen will be broken down to glucose to provide energy (Glycogenolysis)
Main chain has α-1,4 glycosidic linkages and each branch point has a α-1,6 glycosidic linkages.

40
Q

What is reducing sugar and 3 example

A

Some monosaccharides and disaccharides have
◦ A reactive carbonyl group or
◦ Anomeric carbon that can be oxidized.
Ex. Glucose, maltose, lactose / Benedicts test

41
Q

What is non reducing sugar and 1 example

A

Non reducing sugars have both anomeric carbons in a glycosidic bond ( ex . Sucrose)

42
Q

What is heteroglycan

A

Different types of sugars are joined by glycosidic linkages

43
Q

What are GAG

A

Repeating disaccharide units.
Disaccharide units contain either of two amino sugars,
N-acetylgalactosamine (GalNAc) or N- acetylglucosamine (GlcNAc), and a
sugar acid (uronic acid)

44
Q

Name 7 GAG

A
  1. Chondroitin sulphate
  2. Dermatan sulphate
  3. Keratan sulphate (type I)
  4. Keratan sulphate (type II)
  5. Hyaluronate
  6. Heparin
  7. Heparan sulphate
45
Q

What is Chondroitin sulphate (structure and location)

A

Most abundant GAG
Mainly present in adult bone, cartilages and cornea.
It consists of N-acetylgalactosamine, D-glucuronic acid and is sulphated.

46
Q

What is heparin (function and formation )

A

Anticoagulant present in liver produced mainly by the mast cells of liver.
Prevents blood clotting by inhibiting the conversion of fibrinogen to fibrin

47
Q

What’s a glycoprotein

A

Proteins with short oligosaccharide chains which are highly branched and generally do not have a repeating sequence.

48
Q

What is carb content of glycoprotein

A

1% - 85% by weight.

49
Q

3 functions of carbohydrate chain in glycoprotein

A

◦ May stabilize against denaturation (modifying the structure of proteins)
◦ Protect from proteolytic degradation
◦ Enhance solubility

50
Q

5 functions of glycoproteins and examples where possible

A

Integral components of cell membrane
Function as receptors for hormones/molecules in the circulation
Transport molecules of vitamins, minerals – Transferrin, Caeruloplasmin
Immunogenic molecules – Immunoglobulins
Facilitate cell- cell recognition sites – Interaction of sperm with ovulated eggs.

51
Q

What are proteoglycans

A

Proteoglycans are proteins with long, linear, unbranched oligosaccharides with a repeating disaccharide unit.
Disaccharide unit is a glycosaminoglycan

52
Q

What is mucopolysaccharidoses

A

Genetic disorder
Some lysososmal enzymes that degrade GAGs are inactive Unable to break down proteoglycans
Leads to the accumulation of proteoglycans within cells.
Leads to a variety of disease symptoms, depending on the type of proteoglycan not degraded.

53
Q

Significance of type AB

A

Universal recipient

54
Q

Significance of type O

A

Universal donor

55
Q

What are 4 blood group antigens

A

Type A
Type B
Type AB (Universal recipient) or
Type O (Universal donor)

56
Q

What are blood group antigens

A

ABO substances are complex oligosaccharides
Carbohydrate antigens are present on RBC
Oligosaccharide portion gives the antigenic property

57
Q

What are H substance

A

◦ Blood group substance in type O individuals.
◦ Precursor of both A and B substances

formed by addition of the terminal fucose in α,1- 2 linkage onto the terminal Galactose residue.

58
Q

Structure and function of H substance

A

Encodes a fucosyltransferase that produces the H antigen on RBCs.
Consists of a chain of 2 β-D-galactose, β-D-N- acetylglucosamine, and α-L-fucose,
Chain is attached to a protein or ceramide (Type of a lipid molecule).

59
Q

Order of structure of H antigen R to L?

A

Ceramide chain, glucose , galactose , N-acetylglucosamine , galactose

60
Q

How vis A substance formed

A

A allele encodes a glycosyltransferase; GalNAc transferase.
Enzyme bonds N-acetylgalactosamine to D- galactose end of H antigen

61
Q

How is B substance formed

A

B allele encodes a glycosyltransferase; Gal transferase
Above enzyme joins α-D-galactose to D-galactose end of H antigen.

62
Q

How us AB type formed

A

Individuals of AB type possess both enzymes (GalNAc transferase, Gal transferase).
Have both oligosaccharide chains.

63
Q

Regarding carbohydrates
(A) Starch is storage form
(B) RNA contain a derivative of a monosaccharide
(C) Cellulose is digested in the gastrointestinal tract
(D) Heparin is a mucopolysaccharide
(E) Individuals with O blood group type have Gal transferase enzyme

A

Regarding carbohydrates
(A) Starch is storage form in plants (T)
(B) RNA contain a derivative of a monosaccharide (F)
(C) Cellulose is digested in the gastrointestinal tract (F)
(D) Heparin is a mucopolysaccharide (T)
(E) Individuals with O blood group type have Gal transferase enzyme (F)

Biochem Ca1 Cram (13 decks)

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