These are simplified slides from the second lecture in a three-lecture series by Dr. Sidra Arshad, diving into the significance of genetic control which stands as one of the most intricate, yet complex, physiological control mechanisms intimately interlinked with homeostasis and cellular functioning. Learning objectives: 1. Briefly describe the process of translation 2. Discuss the mechanisms of genetic control of cell functions 3. Describe the cell cycle 4. Briefly describe the process of DNA replication Study Resources: 1. Chapter 3, Guyton and Hall Textbook of Medical Physiology, 14th edition 2. Chapter 1, Ganong’s Review of Medical Physiology, 26th edition 3. DNA replication, https://www.genome.gov/genetics-glossary/DNA-Replication

1. Cell Physiology
The Genetic
Control of Cellular
Functions II
Dr. Sidra Arshad
Assistant Professor
MBBS, FCPS (Physiology)

2. Learning Objectives:
1. Briefly describe the process of translation
2. Discuss the mechanisms of genetic control of cell functions
3. Describe the cell cycle
4. Briefly describe the process of DNA replication

3. Translation
• translating the messenger RNA code into a protein
• initiated at an appropriate sequence of RNA bases called the chain
initiating codon
• the ribosome reads the codons of the mRNA  complementary tRNA
bring the amino acid to be added to the growing chain

4. • clusters of ribosomes frequently occur, with 3 to 10 ribosomes being
attached to a single mRNA at the same time
• these clusters are called polyribosomes

5. Chemical steps in the formation of a peptide chain

6. activation of amino acid
(ATP gives up two
phosphates worth of energy)
activated amino acid + tRNA
= amino acid–tRNA complex
attaches temporarily to its
specific codon of the mRNA
peptidyl transferase in the
ribosomes helps form the
peptide bond
Biochemical
steps of
Translation

7. Peptide-Linkage
peptidyl transferase

8. Post-translational
Modifications

9. • Achieved by:
1. Genetic regulation – the genes can be activated or inhibited
2. Enzyme regulation – the enzyme systems can be activated or
inhibited
Control of Different Cellular Constituents

10. • The ultimate measure of gene expression is whether (and
how much) of the gene products (proteins) are produced
• Because proteins carry out cell functions specified by the
genes
• Regulation of gene expression occurs at the levels of:
transcription
RNA processing
translation
Genetic
Control

11. • Transcription factors are the regulators of transcription which can either promote or
inhibit the transcription
• These factors act on these regions of DNA:
Basal promoter regions
Upstream promoter regions
Enhancers
Insulators

13. • Enzymatic regulation involves positive and negative feedback
regulatory processes
• Some cell-produced substances inhibit the specific enzymes,
particularly on the first enzyme in a sequence, that synthesize
them
• Preventing the accumulation of unused intermediary products
• Intracellular concentrations of amino acids, purines,
pyrimidines, vitamins, and other substances regulated
Enzymatic
Control

14. • Enzymes that are normally inactive can be activated as needed
• Such as glycogen phosphorylase in response to ATP depletion
• Facilitated by cyclic adenosine monophosphate (cAMP) as an enzyme
activator

15. Cell Cycle
• The period from cell reproduction to
the next cell reproduction
• Terminated by a series of distinct
physical events called mitosis -
division of the cell into two new
daughter cells
• Mitosis, itself, lasts for only about 30
minutes
• More than 95% called interphase

16. DNA Replication
• DNA begins to be duplicated 5 to 10 hours before mitosis
• The duplication is completed in 4 to 8 hours
• The net result is two exact replicas of all DNA
• One for each of the two daughter cells
• Semi-conservative – one new and one old strands

17. • Almost similar to DNA transcription, except:
Both of the DNA in each chromosome are replicated, not just one of them
Both entire strands of the DNA helix are replicated from end to end, rather
than small portions
DNA polymerase attaches to and moves along the DNA template strand,
adding nucleotides in the 5′ to 3′ direction

18. 1
2
5’ to 3’ direction 4. exonucleases
remove primers
3

19. DNA proofreading
process
Between DNA replication and mitosis, active repair occurs
through proofreading mechanisms
Enzymatic
correction
Special enzymes identify and remove inappropriate
nucleotides, replacing them with correct complementary
ones
Low error rate Due to repair and proofreading, DNA replication is highly
accurate, minimizing mistakes
Mutation
consequences
Mistakes, when they occur, result in mutations that can lead
to abnormal protein formation and disrupt cellular function
Genomic protection Despite potential mutations, the presence of two sets of
chromosomes ensures functional genes, minimizing the
impact of mutations on offspring

20. Mitosis

21. Study Resources
1. Chapter 3, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 1, Ganong’s Review of Medical Physiology, 26th edition
3. DNA replication, https://www.genome.gov/genetics-glossary/DNA-
Replication