Biochemistry-2: Carbohydrate Chemistry

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Questions and Answers

What type of glycosidic linkages are present in cellulose?

α-(l ----> 4) glucosidic bonds

α-(1 ----> 6) glucosidic bonds

β-(l ------> 4) linkages (correct)

α-(l ----> 6) glucosidic bonds

What is the function of proteoglycans in the body?

Component of RNA

Component of ECM (correct)

Component of cell wall

Component of DNA

What is the term for carbohydrates linked to protein?

Glycolipid

Mucopolysaccharide

Glycoprotein (correct)

Proteoglycan

What are the repeating units of glycosaminoglycan (GAG) chains?

Disaccharide units Signup and view all the answers

What is the function of proteoglycans in the cell membrane?

Act as cell surface receptors for hormones Signup and view all the answers

What is the term for the carbohydrate part of proteoglycans?

Glycosaminoglycan (GAG) Signup and view all the answers

What is the function of proteoglycans in the GIT?

Component of mucins in the GIT Signup and view all the answers

What is a primary function of carbohydrates in living organisms?

Primary source of energy Signup and view all the answers

Which classification of carbohydrates includes glucose and fructose?

Monosaccharides Signup and view all the answers

What type of polymer is glycogen?

Homoglycan Signup and view all the answers

Which of the following carbohydrates performs structural functions in plants?

Cellulose Signup and view all the answers

What distinguishes a heteroglycan from a homoglycan?

Type of monosaccharide units Signup and view all the answers

Which type of carbohydrate is sucrose classified under?

Disaccharide Signup and view all the answers

Where is chondroitin sulphate commonly found?

Skin, blood vessels, heart valves & cartilage Signup and view all the answers

What differentiates epimers from other sugar molecules?

They differ in configuration at only one of several chiral centers Signup and view all the answers

Why does dihydroxyacetone not have enantiomers?

It has no chiral center Signup and view all the answers

Which component is part of intracellular granules of mast cells?

Heparin Signup and view all the answers

What is the smallest monosaccharide aldose?

Glyceraldehyde Signup and view all the answers

How many possible stereoisomers exist for a compound with $n$ chiral carbons?

$2^n$ Signup and view all the answers

Which sulfate is typically found in the cornea?

Keratan sulphate Signup and view all the answers

How are D- and L- configurations of sugar molecules determined?

By the position of the -OH group on the bottommost stereo genic center Signup and view all the answers

What is the characteristic feature of an anomeric carbon in ring structures?

It is chiral. Signup and view all the answers

In Haworth projections, groups below the plane of the ring correspond to what in Fischer projections?

Groups on the right-hand side Signup and view all the answers

Which entities are epimers in the context of monosaccharides?

Monosaccharides differing in the configuration around one carbon atom Signup and view all the answers

Which of the following monosaccharides is a reducing sugar?

Glucose Signup and view all the answers

What distinguishes α and β anomers in carbohydrate structures?

The orientation of hydroxyl group on the anomeric carbon Signup and view all the answers

Which of the following sugars is non-reducing?

Sucrose Signup and view all the answers

How do the groups on the two ring carbons bonded to the endocyclic oxygen atom behave in Haworth projections?

They do not apply to the typical rules Signup and view all the answers

What describes D-glucose and L-glucose?

Optical isomers Signup and view all the answers

Why is sucrose considered a non-reducing sugar?

Because both anomeric carbons are involved in bonding Signup and view all the answers

Which carbon is typically the anomeric carbon for aldoses?

C-1 Signup and view all the answers

What defines whether a sugar is a D- or L-sugar in a Fischer projection?

The position of the –OH group at the highest numbered asymmetric carbon Signup and view all the answers

Which carbon is the anomeric carbon in D-gulose?

C-1 Signup and view all the answers

What type of stereoisomers are D-gulose and D-glucose?

Diastereomers Signup and view all the answers

Why are some monosaccharides considered reducing sugars?

Because they contain free anomeric carbons Signup and view all the answers

How can one determine the alpha anomer in a Haworth projection?

By finding the –OH group pointing below the ring Signup and view all the answers

At what position is the OH group that determines the D- or L- configuration in D-gulose?

C-5 Signup and view all the answers

Study Notes

Carbohydrate Chemistry

Carbohydrates are polymers of monosaccharides (CH2O)n, acting as energy-storage molecules and structural components.
They are the main source of energy for living organisms and can be oxidized to yield energy to drive metabolic processes.

Functions of Carbohydrates

Primary source of energy
Energy-storage molecules
Help reserve muscle
Structural functions (e.g., ribose in RNA, deoxyribose in DNA, cellulose in plant cell wall)

Classification of Carbohydrates

Simple:
- Monosaccharides (e.g., glucose, galactose, fructose)
- Disaccharides (e.g., sucrose)
- Oligosaccharides (2-20 units)
- Polysaccharides (>20 units)
Glycoconjugates:
- Linked covalently to a peptide chain, protein, or lipid

Homoglycans and Heteroglycans

Homoglycan: polysaccharide containing only one type of monosaccharide unit (e.g., starch, glycogen)
Heteroglycan: polysaccharide containing more than one type of monosaccharide unit (e.g., lactose)

Polysaccharides

Homoglycans:
- Chondroitin sulfate (skin, blood vessels, heart valves, and cartilage)
- Dermatan sulfate (cartilage, bone, heart valves)
- Heparin and Heparan sulfates (basement membranes, components of cell surfaces)
- Keratan sulfate (cornea, bone, cartilage aggregated with chondroitin sulfates)

Stereoisomers, Epimers, and Enantiomers

Stereoisomers: compounds having the same structural formula but differing in spatial configuration
Epimers: sugar molecules that differ in configuration at only one of several chiral centers
Enantiomers: occur when you have 2 mirror image structures that aren't superimposable, with opposite configurations at each chiral carbon

D- and L- Configurations of Sugars

Look at the –OH on the bottommost stereogenic center that is far away from the carbonyl group
If the OH- is on the right, then it's D-, while if it is on the left, then it's L-

Anomers

The most oxidized carbon of a cyclized monosaccharide, the one attached to two oxygen atoms, is referred to as the anomeric carbon

Conjugated Carbohydrates

Carbohydrates + protein or carbohydrates + lipid
Includes:
- Glycolipid (in lipid part)
- Glycoprotein (mucoproteins) and proteoglycan:
  - Both consist of protein + carbohydrates
  - Differ in sites, sugars, shape, and size

Glycoprotein and Proteoglycan

Glycoprotein: protein part >> CHO part
Proteoglycan: consist of chains of GAGs attached to protein core (CHO >> protein part)
Functions:
- Component of ECM and supporting tissues like cartilage
- Component of mucins in GIT and lung
- Component of cell membrane and acts as blood group antigen and cell surface receptors for hormones

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Description

Learn about the chemistry of carbohydrates, their role as energy-storage molecules, and their structural components in living organisms.