Biomolecules

The antibody (immunoglobulin) is a Y-shaped glycoprotein molecule made up of: Diagram:
\begin{center} \begin{tikzpicture}[scale=1.0, line width=1pt] % Left light chain \draw (0,0) -- (1,2); % Left heavy chain \draw (0,-2) -- (1,2); % Right light chain \draw (4,0) -- (3,2); % Right heavy chain \draw (4,-2) -- (3,2); % Base/stem \draw (1,-2) -- (2,-4) -- (3,-2); % Labels \node at (0.5,1.5) {Light chain}; \node at (3.5,1.5) {Light chain}; \node at (-0.3,-1) {Heavy chain}; \node at (4.3,-1) {Heavy chain}; \node at (2,-3.8) {Fc (constant region)}; \node at (2,2.3) {Fab (antigen-binding site)}; \end{tikzpicture} \end{center}

Step 1: Understanding antibody structure.
An antibody (immunoglobulin) molecule is a Y-shaped protein consisting of two identical heavy chains and two identical light chains. These chains are held together by peptide (disulfide) bonds.

Step 2: Number of bonds.
There are four peptide bonds (disulfide bridges) in each antibody molecule: - Two bonds connect each light chain to a heavy chain.
- Two bonds connect the heavy chains to each other.

Step 3: Conclusion.
The correct answer is (B) Four, as each antibody molecule has four peptide (disulfide) bonds linking its chains.

A nucleotide is the basic building block of nucleic acids (DNA and RNA). It consists of three main components: 1. Phosphate group: A molecule containing one phosphorus atom bonded to four oxygen atoms. This group links adjacent nucleotides together to form a strand of nucleic acid. 2. Sugar molecule: In DNA, the sugar is deoxyribose, while in RNA, it is ribose. Both are pentose sugars (five-carbon sugars) that form the backbone of the nucleotide. 3. Nitrogenous base: There are four types of nitrogenous bases: - Purines: Adenine (A) and Guanine (G). - Pyrimidines: Cytosine (C), Thymine (T) in DNA, and Uracil (U) in RNA. These components combine to form nucleotides, which are the structural units of nucleic acids.
Final Answer: A nucleotide consists of a phosphate group, a sugar molecule, and a nitrogenous base.

Step 1: Understand the structure of a nucleoside.
A nucleoside is made up of two components: 1. A nitrogenous base: This can be a purine (adenine or guanine) or a pyrimidine (cytosine, thymine, or uracil). 2. A sugar: This can either be ribose (in RNA) or deoxyribose (in DNA).
Step 2: Difference between nucleosides and nucleotides.
A nucleoside consists of the nitrogenous base and sugar, while a nucleotide also includes a phosphate group. The phosphate group is what distinguishes a nucleotide from a nucleoside.
Step 3: Examples of nucleosides.
- Adenosine (Adenine + Ribose) - Guanosine (Guanine + Ribose) - Thymidine (Thymine + Deoxyribose)
Final Answer:

Step 1: Function 1. - LAB are involved in the fermentation process, converting sugars into lactic acid. This helps preserve food and increase its shelf life.
Step 2: Function 2. - LAB also promote gut health by enhancing the balance of beneficial bacteria in the digestive system.
Final Answer: Lactic Acid Bacteria are useful in food preservation through fermentation and promoting digestive health by maintaining a healthy gut flora.