Biology Chapter 4: Protein and Carbohydrate Structures

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Questions and Answers

What primarily determines the tertiary structure of a protein?

The primary sequence alone

Hydrophobic and hydrophilic interactions among amino acids (correct)

Interaction of multiple polypeptide chains

Only covalent bonding of disulfide linkages

Which of the following correctly describes quaternary structure?

It involves the bonding of amino acids into a chain.

It relies solely on primary sequences of amino acids.

It is the overall three-dimensional shape of a single polypeptide.

It involves interactions between multiple subunits of a protein. (correct)

Which step occurs first in the process of protein synthesis?

Post-translational modifications

Translation

Amino acid synthesis

Transcription (correct)

How are amino acids obtained by the body?

Synthesized by the body from precursors and also obtained through diet. Signup and view all the answers

What role does mRNA play during translation?

It determines the order of amino acids in a polypeptide chain. Signup and view all the answers

Which carbohydrate contains only one sugar molecule?

Galactose Signup and view all the answers

What is the primary characteristic of polysaccharides?

They contain more than ten sugar molecules. Signup and view all the answers

Which of the following statements is true regarding disaccharides?

They contain two sugar molecules and may have a glycoside bond. Signup and view all the answers

Which of the following is an example of a polysaccharide?

Cellulose Signup and view all the answers

What distinguishes monosaccharides from other types of carbohydrates?

They are always reducing sugars. Signup and view all the answers

What characterizes simple proteins?

They consist only of amino acid residues. Signup and view all the answers

Which type of protein primarily includes fibrous proteins?

Simple proteins Signup and view all the answers

What effect do physical agents like heat have on proteins?

They can denature proteins, leading to coagulation. Signup and view all the answers

How are tertiary structures of proteins predominantly stabilized?

By hydrogen bonds and hydrophobic interactions. Signup and view all the answers

What is the primary structure of a protein?

The sequence of amino acids in the polypeptide chain. Signup and view all the answers

At which point does a protein not move in an electric field?

At the isoelectric point (pI). Signup and view all the answers

What defines conjugated proteins?

They contain non-protein moieties combined with protein components. Signup and view all the answers

Which of the following correctly describes secondary derived proteins?

They are degraded products of simple and conjugated proteins. Signup and view all the answers

What role do carbohydrates play in living organisms?

They are the primary energy source for living beings. Signup and view all the answers

Which carbohydrate is primarily used for energy storage in animals?

Glycogen Signup and view all the answers

What type of carbohydrate cannot be broken down by hydrolysis?

Monosaccharides Signup and view all the answers

Which of the following carbohydrates is classified as an oligosaccharide?

Sucrose Signup and view all the answers

Which carbohydrate serves as a structural component of the cell wall in plants?

Cellulose Signup and view all the answers

During photosynthesis, what compounds are used for the formation of carbohydrates?

Carbon dioxide and water Signup and view all the answers

Which of the following statements about carbohydrates is FALSE?

All carbohydrates are energy sources. Signup and view all the answers

What is the energy yield of carbohydrates per gram?

4 kcal/gram Signup and view all the answers

Which type of carbohydrate is defined by having an aldehyde as the most oxidized functional group?

Aldose Signup and view all the answers

What distinguishes epimers from other isomers?

They differ at only one specific carbon atom. Signup and view all the answers

Which of the following pairs are considered C-2 epimers?

Glucose and mannose Signup and view all the answers

What suffix do ketoses typically have?

-ulose Signup and view all the answers

Which configuration do most sugars found in humans belong to?

D-sugars Signup and view all the answers

How are enantiomers defined in terms of their structural relationship?

Structures that are mirror images of one another. Signup and view all the answers

At which carbon atom is the orientation of the -OH group used to determine D or L configuration?

Carbon 5 Signup and view all the answers

Which statement about isomers is correct?

Isomers can include sugars with the same formula but different structures. Signup and view all the answers

What characterizes a reducing sugar?

It has a free aldose or ketose group at the anomeric carbon. Signup and view all the answers

Which of the following sugars is classified as a non-reducing sugar?

Sucrose Signup and view all the answers

What is the role of the anomeric carbon in a reducing sugar?

It is necessary for the sugar to reduce chromogenic reagents. Signup and view all the answers

Which of the following statements is true about non-reducing sugars?

They do not have a free aldehyde or ketone group. Signup and view all the answers

What happens to the anomeric carbon of a reducing sugar when it acts as a reducing agent?

It gets oxidized. Signup and view all the answers

Which disaccharide is correctly identified as a reducing sugar?

Cellobiose Signup and view all the answers

The reaction of reducing sugars with Benedict's reagent results in what outcome?

Reduction of cupric ions to form a colored cuprous ion. Signup and view all the answers

Which of the following best represents the structure of sucrose?

O-α-D-Glucopyranosyl-(1→2)-β-D-fructofuranoside Signup and view all the answers

What type of glucose monomer is found in cellulose?

β-glucose Signup and view all the answers

What bond type is primarily found in the structure of glycogen?

α(1→4) and α(1→6) glycosidic bonds Signup and view all the answers

Which of the following describes the physical structure of starch?

Coiled unbranched and long branched chains Signup and view all the answers

What type of bond links monosaccharides in glycosidic bonds?

Covalent bonds Signup and view all the answers

Which type of polysaccharide is composed of identical monosaccharide units?

Homopolysaccharide Signup and view all the answers

Which of the following tests can indicate the presence of reducing sugars?

Benedict's test Signup and view all the answers

What are the two forms of starch, and how do they differ in structure?

Amylose and amylopectin; one is linear and the other is branched. Signup and view all the answers

What is the predominant form of glucose in solution?

Pyranose form Signup and view all the answers

Which structure is formed from the reaction between the aldehyde group and an alcohol group in monosaccharides?

Cyclic structure Signup and view all the answers

What represents the anomeric carbon in a cyclic aldose structure?

Carbon 1 Signup and view all the answers

What term describes the ability of α and β anomers to interconvert in solution?

Mutarotation Signup and view all the answers

Which statement correctly describes the OH group on the anomeric carbon of α-D-glucose in a Haworth projection?

It is trans to the CH₂OH group. Signup and view all the answers

Study Notes

Protein Classification

Proteins are classified based on their chemical nature, structure, shape, and solubility.
Simple proteins: Composed of only amino acid residues. On hydrolysis, these proteins yield only constituent amino acids. Further divided into:
- Fibrous protein
  - Examples: Keratin, Elastin, Globulin, Collagen, Histones
- Globular protein
  - Examples: Albumin, Globulin
Conjugated proteins: Combined with non-protein moiety. Example: Nucleoprotein, Phosphoprotein, Lipoprotein, Metalloprotein, etc.
Derived proteins: Derivatives or degraded products of simple and conjugated proteins.
- Primary derived proteins: Proteans, Metaproteins, Coagulated proteins
- Secondary derived proteins: Proteoses, peptones, peptides, albumoses

General Protein Features

Physical agents: Heat, radiation, pH
Chemical agents: Urea solution which forms new hydrogen bonds in the protein, organic solvents, detergents.
Coagulation: When proteins are denatured by heat, they form insoluble aggregates known as coagulation. All proteins are not heat coagulable, only a few like albumins, globulins.
Isoelectric point (pI): The pH at which the number of positive charges equals the number of negative charges, and the overall charge on the amino acid is zero. At this point, when subjected to an electric field, the proteins do not move either towards anode or cathode, hence this property is used to isolate proteins.

Protein Structure

Proteins are divided into four levels of organization:

1. Primary Structure

The primary structure of a protein consists of the amino acid sequence along the polypeptide chain.
Amino acids are joined by peptide bonds.
The sequence is determined by the genetic code.
The primary structure determines the further levels of organization.

2. Secondary Structure

Includes various types of local conformations in which the atoms of the side chains are not involved.
Secondary structures are formed by a regularly repeating pattern of hydrogen bond formation between backbone atoms.
Examples: α-helices, β-sheets, and other types of folding patterns.

3. Tertiary Structure

Refers to the protein's overall three-dimensional conformation.
Types of interactions:
- Hydrophobic interactions
- Electrostatic interactions
- Hydrogen bonds
- Covalent disulfide bonds
Produced by interactions between amino acid residues that may be located at a considerable distance from each other in the primary sequence of the polypeptide chain.
Hydrophobic amino acid residues tend to collect in the interior of globular proteins, where they interact with exclude water, whereas hydrophilic residues are usually found on the surface.

4. Quaternary Structure

Refers to the interaction of one or more subunits to form a functional protein.
The spatial arrangement of subunits in a protein that consists of more than one polypeptide chain.
Stabilized by the same forces that stabilize the tertiary structure.

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Description

Test your knowledge on the structure and synthesis of proteins, as well as the different types of carbohydrates. This quiz covers key concepts including protein tertiary and quaternary structures, amino acid acquisition, and characteristics of sugars. Challenge yourself to see how well you understand these essential biomolecules.