Unit 1: Biomolecules
Biomolecules are the
essential organic compounds found in all living organisms. These include amino
acids, peptides, and proteins, which are crucial for structure and function.
Amino acids are the basic building blocks of proteins and are connected by
peptide bonds. Proteins have complex structures: primary (sequence of amino
acids), secondary (alpha-helix and beta-sheets), tertiary (3D folding), and quaternary
(multiple chains together). Another major class is carbohydrates, which serve
as energy sources and structural components. Carbohydrates are classified into monosaccharides
like glucose (hexose) and ribose (pentose), disaccharides such as sucrose,
lactose, and maltose, and polysaccharides like glycogen, starch, and cellulose,
which are important for energy storage and structural support.
Lipids are another
important group, playing key roles in cellular membranes, energy storage, and signaling.
They include fatty acids, triacylglycerols, phospholipids, and sterols like
cholesterol. Lipids are classified based on structure and function. Nucleic
acids—DNA and RNA—store and transmit genetic information. They are composed of purine
(adenine, guanine) and pyrimidine (cytosine, thymine, uracil) bases. Nucleic
acids are vital in all life forms as they control heredity and cell function.
Unit 1: Biomolecules:-
1. Amino
Acids, Peptides, and Proteins:
o Amino
acids: Building blocks of proteins.
o Peptide
bond: Link between amino acids.
o Protein
structure:
§ Primary:
Amino acid sequence.
§ Secondary:
Alpha-helix, beta-sheets.
§ Tertiary:
3D folding.
§ Quaternary:
Multiple polypeptides.
2. Carbohydrates:
o Biological
role: Energy source.
o Monosaccharides:
Hexoses (glucose) and pentoses (ribose).
o Disaccharides:
Sucrose, lactose, maltose.
o Polysaccharides:
Glycogen, starch, cellulose (for storage and structure).
3. Lipids:
o Role:
Cell membrane structure, energy storage.
o Types:
Fatty acids, triacylglycerols, phospholipids, sterols.
o Functions:
Structural and metabolic.
4. Nucleic
Acids:
o Role:
Genetic information storage (DNA, RNA).
o Composition:
Purine and pyrimidine bases.
Unit 2: Enzymes and Metabolic Pathways:-
Enzymes are biological
catalysts that speed up biochemical reactions in the body. They are named and
classified based on the reactions they catalyze. Enzymes have specificity for
their substrates and often require cofactors or coenzymes for activity. Some
enzymes exist in multiple forms known as isoenzymes. The mechanism of enzyme
action involves lowering the activation energy to accelerate reactions.
Protein metabolism
involves processes like transamination (transfer of amino groups), deamination
(removal of amino groups), and the urea cycle, which removes toxic ammonia from
the body. In carbohydrate metabolism, glucose undergoes glycolysis to produce
energy, while gluconeogenesis forms glucose from non-carbohydrate sources. The Cori
cycle helps recycle lactic acid, and the TCA cycle (Krebs cycle) generates
energy from acetyl-CoA. The HMP shunt provides NADPH and ribose sugars, while glycogenolysis
breaks down glycogen, and glycogenesis synthesizes glycogen.
In lipid metabolism,
stored fats (triglycerides) are mobilized, and glycerol is used for energy. Beta-oxidation
breaks down fatty acids for ATP, and ketogenesis forms ketone bodies during
fasting or starvation, which are alternative energy sources.
Unit 2: Enzymes and Metabolic Pathways:-
1. Enzymes:
o Definition:
Biological catalysts.
o Classification:
Based on reaction type.
o Properties:
Specificity, use of cofactors, isoenzymes.
o Mechanism:
Lower activation energy.
2. Protein
Metabolism:
o Transamination:
Amino group transfer.
o Deamination:
Removal of amino group.
o Urea
cycle: Ammonia → Urea (waste removal).
3. Carbohydrate
Metabolism:
o Glycolysis:
Glucose → Pyruvate (energy production).
o Gluconeogenesis:
Formation of glucose from non-carb sources.
o Cori
cycle: Lactic acid recycling.
o TCA
cycle: Energy from acetyl-CoA.
o HMP
shunt: NADPH and ribose production.
o Glycogenolysis:
Breakdown of glycogen.
o Glycogenesis:
Formation of glycogen.
4. Lipid
Metabolism:
o Mobilization
of triglycerides.
o Glycerol
metabolism.
o Beta-oxidation:
Fatty acid breakdown.
o Ketogenesis:
Ketone body formation (in fasting/starvation).
Unit 3: Structure of Chromosomes,
Nucleic Acids, and DNA Replication:-
The structure of nucleic
acids is fundamental in genetics. DNA is a double-helix composed of nucleotide
units and exists in forms like A, B, and Z-DNA. DNA is often supercoiled to fit
inside the cell nucleus. Nucleosomes are units where DNA wraps around histone
proteins, forming chromatin, which further folds to form chromosomes. These are
the carriers of genetic material.
There are different
types of RNA: rRNA (forms ribosomes), tRNA (transfers amino acids during
protein synthesis), mRNA (carries genetic code from DNA), and non-coding RNA
which regulates gene expression.
DNA replication is the
process by which DNA makes a copy of itself before cell division. It is semi-conservative,
meaning each new DNA has one old strand and one new. Several enzymes like DNA
polymerase (adds nucleotides), helicase (unwinds DNA), and ligase (joins DNA
fragments) are involved in this process. The chemistry of replication ensures
accurate duplication of genetic material, essential for inheritance and cell
function.
Unit 3: Structure of Chromosomes,
Nucleic Acids, and DNA Replication:-
1. Structure
of Nucleic Acids:
o DNA
structure: Double helix, base pairing.
o Form
of DNA: A, B, Z-DNA types.
o Supercoiling:
DNA compaction.
2. Nucleosome
and Histone:
o DNA
wraps around histones → nucleosome → forms chromatin.
3. Chromosomes:
o Packaged
DNA in nucleus.
4. RNA
Types:
o rRNA:
Part of ribosome.
o tRNA:
Brings amino acids.
o mRNA:
Carries genetic code.
o Non-coding
RNA: Regulatory functions.
5. DNA
Replication:
o Process:
Copying DNA before cell division.
o Enzymes:
DNA polymerase, helicase, ligase.
o Chemistry:
Semi-conservative replication.
Unit
4: Central Dogma, RNA Transcription, and RNA Processing:-
The central dogma of molecular biology explains the
flow of genetic information from DNA to RNA to Protein. It starts with transcription,
where DNA-dependent RNA polymerase synthesizes RNA using DNA as a template. In
bacteria, sigma factors help RNA polymerase bind to promoters, specific DNA
sequences that initiate transcription. Transcription occurs in three stages: initiation
(RNA polymerase binds and starts RNA synthesis), elongation (RNA chain grows),
and termination (RNA synthesis stops). Termination can be rho-dependent (needs
rho protein) or rho-independent (uses hairpin loop structure in RNA).
In eukaryotes,
transcription is more complex and involves processing of hnRNA (heterogeneous
nuclear RNA) to form mature mRNA. This processing includes 5’-capping (adding a
cap at the start), splicing (removing introns and joining exons), and 3’-polyadenylation
(adding a poly-A tail at the end). Other RNAs like rRNA and tRNA also undergo modifications
and processing to function correctly. This entire process ensures that the
correct RNA is produced for translation into protein, maintaining the proper
flow of genetic information.
Unit 4: Central Dogma, RNA Transcription, RNA Processing:-
1. Central Dogma –
Flow of genetic info: DNA → RNA → Protein.
2. Transcription –
RNA made from DNA by RNA polymerase.
o Stages:
Initiation, Elongation, Termination.
o In bacteria: Sigma
factor helps in promoter recognition.
o Rho-dependent/independent
termination types.
3. Transcription in
Eukaryotes – Complex process; RNA is first made as hnRNA.
4. RNA Processing:
o Splicing: Remove
introns, join exons.
o 5’ Capping: Add
cap at 5’ end.
o 3’
Polyadenylation: Add poly-A tail at 3’ end.
o rRNA & tRNA
Modifications: For proper function.
o Differential RNA
Processing: Different proteins from same gene.
Unit 5: Ribosomes and Translation (Protein Synthesis):-
Ribosomes are the cellular machines responsible for protein
synthesis (translation). They exist in two types: prokaryotic (70S) and eukaryotic
(80S) ribosomes, both made of rRNA and proteins. The genetic code is a set of triplet
codons, where three nucleotides specify one amino acid. Due to wobble base
pairing, some codons can code for the same amino acid (called synonymous codons),
leading to degeneracy of the code. Mutations like missense (changes amino
acid), nonsense (forms stop codon), and frameshift (due to insertion/deletion)
can affect protein function.
Translation involves three main steps: Initiation
(ribosome assembles on mRNA with tRNA), Elongation (amino acids are added one
by one), and Termination (synthesis stops at stop codon). After translation, post-translational
modifications occur, such as folding or adding functional groups. Protein
synthesis in prokaryotes differs slightly from eukaryotes in ribosome size,
initiation factors, and timing (transcription and translation occur
simultaneously in prokaryotes).
Key steps include
aminoacylation of tRNA (attaching amino acid to tRNA), peptide bond formation, translocation
(movement of ribosome), and recycling of ribosomes for reuse. Regulation of
translation and codon bias (preference for certain codons) also play roles in
efficient protein production.]
Unit
5: Ribosomes and Translation (Protein Synthesis):-
1. Ribosomes – Sites
of protein synthesis; types: Prokaryotic (70S), Eukaryotic (80S).
2. Genetic Code –
Triplet codons; wobble base allows flexibility; degeneracy means multiple
codons for same amino acid.
3. Mutations:
o Missense: Change
in amino acid.
o Nonsense: Stop
codon formed.
o Frameshift: Shift
in reading frame.
4. Translation
Process:
o Initiation:
Ribosome assembles on mRNA.
o Elongation: Amino
acids joined via peptide bonds.
o Translocation:
Ribosome moves along mRNA.
o Termination:
Protein synthesis ends.
o Recycling:
Ribosome used again.
5. tRNA
Aminoacylation – Attachment of amino acid to tRNA.
6. Post-Translation
Modifications – Protein folding, functional group addition.
7. Regulation of
Translation – Control over protein production, codon bias affects efficiency.
Content Checked:
B.Sc. Zoology (2nd Year) - Unit-wise Topics
Unit 1: Biomolecules
Unit 2: Enzymes and Metabolic Pathways
Unit 3: Structure of Chromosomes, Nucleic Acids and DNA Replication
Unit 4: Central Dogma, RNA Transcription, RNA Processing
Unit 5: Ribosomes and Translation (Protein Synthesis)
Exam Preparation
Result: 0% Plagiarism Detected
Status: Passed (Unique Content)
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