Biochemistry Chapter on Glycoproteins

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Questions and Answers

What is the primary function of glycoproteins in the cell?

Energy storage

Protein degradation

Water binding

Cell-surface recognition (correct)

Proteoglycans are primarily composed of proteins.

False

What are the two types of carbohydrates mentioned in the content?

Starch and Glycogen

Glycoproteins are proteins with __________ covalently attached.

oligosaccharides Signup and view all the answers

Match the following structures with their descriptions:

Proteoglycan = Negatively charged heteropolysaccharides associated with proteins Glycosaminoglycan = Water-binding gel-like matrix components Glycoprotein = Proteins with short carbohydrate chains attached Extracellular Matrix = Structural framework for cells Signup and view all the answers

Which type of glycan is associated with blood group A?

GalNAc Signup and view all the answers

The primary function of glycosaminoglycans is to provide lubricating properties to mucous secretions.

True Signup and view all the answers

What is the most common posttranslational modification of proteins?

Glycosylation Signup and view all the answers

Which blood group is associated with the absence of both GalNAc and galactose?

Blood group O Signup and view all the answers

Humans can digest cellulose efficiently due to specific enzymes.

False Signup and view all the answers

What are the two main types of glycosidic bonds found in plant carbohydrates?

Alpha and Beta glycosidic bonds Signup and view all the answers

The enzyme that disrupts α(1->4) bonds in digestion is called ___(a), and it breaks down oligosaccharides and disaccharides into monosaccharides.

α-amilase Signup and view all the answers

Match the following transporters with their functions:

SGLT-1 = Transport of glucose and galactose with sodium GLUT-5 = Transport of fructose GLUT-2 = Transport of monosaccharides from intestine to blood Signup and view all the answers

Which of the following is not a classification of carbohydrates?

Polypeptide Signup and view all the answers

A glycosidic bond occurs between two polysaccharides to form a disaccharide.

False Signup and view all the answers

What is the general formula for carbohydrates?

C(H2O)n Signup and view all the answers

The simplest form of carbohydrates is called a ______.

monosaccharide Signup and view all the answers

Match the following types of carbohydrates with their characteristics:

Monosaccharides = Simplest form of carbohydrates Disaccharides = Formed by two monosaccharides Polysaccharides = Long chains of monosaccharides Glycogen = Storage form of glucose in animals Signup and view all the answers

Which of the following is an example of a structural polysaccharide?

Cellulose Signup and view all the answers

Fructose and glucose have the same chemical formula but different structures.

True Signup and view all the answers

What type of carbonyl group do aldoses contain?

Aldehyde group Signup and view all the answers

A ______ is formed when two monosaccharides are joined together.

disaccharide Signup and view all the answers

Which carbohydrate serves as a storage form in plants?

Starch Signup and view all the answers

Study Notes

Carbohydrates Overview

Carbohydrates are a group of carbonyl compounds (aldehydes or ketones) that also contain several hydroxyl groups.
Carbohydrates have the general formula (CH₂O)ₙ.
Isomers have the same formula, but different structure.
Fructose and glucose have the formula C₆H₁₂O₆.

Carbohydrate Objectives

Recognize the general structure of carbohydrates
Classify carbohydrates
Recognize disaccharides
Recognize polysaccharides
Explain carbohydrate-modified protein structures and functions
Explain carbohydrate digestion

Carbohydrate Classification

Classification by number of units: monosaccharide, disaccharide, oligosaccharide, polysaccharide
"-ose" suffix is added to name monosaccharides.
Type of carbonyl group: aldose, ketose
Number of carbons: triose, tetrose, pentose, hexose, heptose, nonose

Important Monosaccharides Examples

Aldoses
- 5 carbons: Aldopentose sugars (e.g., ribose, xylose)
- 6 carbons: Aldohexose sugars (e.g., glucose, mannose)
Ketoses
- 5 carbons: Ketopentose sugars (e.g., ribulose)
- 6 carbons: Ketohexose sugars (e.g., fructose)

More Carbohydrate Information

Deoxyaldoses: A hydroxyl group (-OH) is missing in these sugars
Acetylated amino sugars: N-acetyl groups are added to the structure; examples include N-Acetyl-D-glucosamine (GlcNAc) and N-Acetyl-D-galactosamine (GalNAc)
Acidic monosaccharides: Contain carboxyl groups (-COOH); examples include D-glucuronic acid (GIcUA) and L-iduronic acid (IduUA).
Sugar alcohols (alditols): When an aldehyde group is oxidized, it becomes an alcohol; examples include D-sorbitol and D-mannitol.

Disaccharides

Two monosaccharides joined by a glycosidic bond.
Examples: maltose (glucose + glucose), lactose (galactose + glucose), sucrose (glucose + fructose).

Polysaccharides

Polymers of monosaccharides.
Examples:
- Cellulose: Structural component in plants
- Starch: Energy storage in plants
- Glycogen: Energy storage in animals
- Chitin: Structural component in fungi and exoskeletons of insects

Protein-Carbohydrate Structures

Carbohydrates can combine with proteins.
Proteoglycan: Negatively charged heteropolysaccharide (GAG) chains linked to a core protein.
Glycoproteins: Proteins with oligosaccharides attached.

Glycoprotein Functions

Cell-cell communication
Cell-surface recognition
Antigen display associated with blood types
Important for immune system reactions
Components of extracellular matrix (ECM)

Carbohydrate Digestion

Enzymes cleave glycosidic bonds.
Alpha-amylase in the mouth and intestines breaks down alpha glycosidic bonds in starch.
Humans lack enzymes that degrade beta glycosidic bonds in cellulose.

Carbohydrate Absorption

Monosaccharides (glucose, fructose, galactose) are absorbed from the small intestine into the bloodstream.
Different transport proteins (e.g., SGLT-1, GLUT-2, GLUT-5) are used for different monosaccharides.

Carbohydrate Metabolism

Blood glucose concentration is maintained around 5 mM (90 mg/dL).
Important for normal brain function.
Lower levels can lead to confusion, coma, and higher levels can lead to vascular damage.

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Description

Test your knowledge on glycoproteins and carbohydrates in this biochemistry quiz. Questions cover their functions, structures, and involvement in blood groups. Explore glycosaminoglycans and bond types to deepen your understanding.