PHA115 Protein Synthesis and Cell Division Student Handout 2024-25 PDF

MPharm Programme Protein Synthesis and Cell Division Dr Praveen Bhugra PHA115 Slide 1 of 39 PHA115 Protein Synthesis and Cell Division  Learning Objectives From this lecture you should be able to:...

MPharm Programme Protein Synthesis and Cell Division Dr Praveen Bhugra PHA115 Slide 1 of 39 PHA115 Protein Synthesis and Cell Division  Learning Objectives From this lecture you should be able to:  Understand and explain in detail the sequences of events in protein synthesis with knowledge of gene expression , transcription and translation  Understand and explain the different stages , events and significance of somatic and reproductive cell division  Understand, explain and describe in detail the signal that induce somatic cell division. Slide 2 of 39 PHA115 Protein Synthesis and Cell Division  Introduction To Protein Synthesis Cells synthesize many chemicals to maintain homeostasis Cellular machinery is devoted to synthesizing large numbers of diverse proteins. Proteins determine the physical and chemical characteristics of cells Proteins – help assemble cellular structures such as the plasma membrane, the cytoskeleton, and other organelles. – Others serve as hormones, antibodies, and contractile elements in muscular tissue. – Still others act as enzymes, regulating the rates of the numerous chemical reactions that occur in cells, or transporters, carrying various materials in the blood. Slide 3 of 39 PHA115 Protein Synthesis and Cell Division  Introduction To Protein Synthesis DNA is used as a template for synthesis of a specific protein. Transcription Information encoded in a specific region of DNA is transcribed (copied) to produce a specific molecule of RNA (ribonucleic acid). Translation The RNA attaches to a ribosome, where the information contained in RNA is translated into a corresponding sequence of amino acids to form a new protein molecule Slide 4 of 39 PHA115 Protein Synthesis and Cell Division  Protein Synthesis Transcription During transcription three types of RNA are made from the DNA template: 1) Messenger RNA (mRNA) directs the synthesis of a protein 2) Ribosomal RNA (rRNA) joins with ribosomal proteins to make ribosomes. 3) Transfer RNA (tRNA) binds to an amino acid and holds it in place on a ribosome until it is incorporated into a protein during translation. Slide 5 of 39 PHA115 Protein Synthesis and Cell Division  Protein Synthesis Transcription Slide 6 of 39 PHA115 Protein Synthesis and Cell Division  Protein Synthesis Transcription Enzyme RNA polymerase catalyzes transcription of DNA. Only one of two DNA strands serves as a template for RNA synthesis. Segment of DNA where transcription begins, a special nucleotide sequence called a promoter Transcription, bases pair in a complementary manner. Transcription of the DNA strand ends at another special end sequence called the terminator Slide 7 of 39 PHA115 Protein Synthesis and Cell Division  Protein Synthesis Transcription Slide 8 of 39 PHA115 Protein Synthesis and Cell Division  Protein Synthesis Transcription A U T A G C C G A U T A Template DNA Complementary RNA base sequence base sequence Detailed View of Transcription Slide 9 of 39 PHA115 Protein Synthesis and Cell Division  Protein Synthesis Translation The nucleotide sequence in an mRNA molecule specifies the amino acid sequence of a protein. Ribosomes in the cytoplasm carry out translation. Small sub-unit of a ribosome has a binding site for mRNA Large subunit has two binding sites for tRNA molecules, a P site and an A site. First tRNA molecule bearing specific amino acid attaches to mRNA at the P site and the A site the next. Slide 10 of 39 PHA115 Protein Synthesis and Cell Division  Protein Synthesis Translation Slide 11 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Introduction to Cell Division Human body undergo cell division Two types of cell division somatic cell division and reproductive cell Somatic cell :any cell of the body other than a germ cell. – In somatic cell division, a cell undergoes a nuclear division called mitosis and a cytoplasmic division called cytokinesis – Somatic cell division replaces dead or injured cells and adds new ones during tissue growth. Slide 12 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Introduction to Cell Division Reproductive cell division is the mechanism that produces gametes Cells needed to form the next generation of sexually reproducing organisms. Process consists of a special two-step division called meiosis, in which the number of chromosomes in the nucleus is reduced by half. Slide 13 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Somatic Cell Division Cell cycle is an orderly sequence of events in which a somatic cell duplicates its contents and divides in two. Human cells, such as those in the brain, stomach, and kidneys, contain 23 pairs of chromosomes, for a total of 46. One member of each pair is inherited from each parent. The two chromosomes that make up each pair are called homologous chromosomes they contain similar genes arranged in the same (or almost the same) order. Slide 14 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Somatic Cell Division Exception to this rule is one pair of chromosomes called the sex chromosomes (designated X and Y) In females the homologous pair of sex chromosomes consists of two large X chromosomes In males the pair consists of an X and a much smaller Y chromosome. Somatic cells contain two sets of chromosomes, they are called diploid cells , symbolized 2n Cell cycle consists of two major periods: interphase, when a cell is not dividing, and the mitotic (M) phase, when a cell is dividing Slide 15 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division The Cell Cycle Slide 16 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Interphase The G1 phase is the interval between the mitotic phase and the S phase. The cell is metabolically active; it replicates most of its organelles and cytosolic components but not its DNA. Replication of centrosomes also begins in the G1 phase. For a cell with a total cell cycle time of 24 hours, G1 lasts 8 - 10 hours. Cells that remain in G1 for a very long time, perhaps destined never to divide again, are said to be in the Go phase. Slide 17 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Interphase The S phase, the interval between G1 and G2, lasts about 8 hours. During S phase, DNA replication occurs. result into two identical cells formed during cell division later in the cell cycle will have the same genetic material The G2 phase is the interval between the S phase and the mitotic phase, lasts 4 to 6 hours. During G2, cell growth continues, enzymes and other proteins are synthesized in preparation for division, and replication of centrosomes is completed. Slide 18 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Interphase When DNA replicates during the S phase, its helical structure partially uncoils, and the two strands separate at the points where hydrogen bonds connect base pairs Original DNA molecule become two identical DNA molecules Slide 19 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Interphase (a) (b) Slide 20 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Mitotic Phase (Prophase) Slide 21 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Mitotic Phase (Metaphase) Slide 22 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Mitotic Phase (Anaphase) Slide 23 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Mitotic Phase (Telophase) Slide 24 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Mitotic Phase Slide 25 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Checkpoint control system Cell cycle controlled by STOP & GO chemical signals at critical points Signals indicate if key cellular processes have been completed correctly Slide 26 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Checkpoint control system Slide 27 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Checkpoints control system (Go –ahead signal) Signals that promote cell growth & division – proteins – internal signals “promoting factors” external signals – “growth factors” Primary mechanism of control – phosphorylation kinase enzymes Slide 28 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Cyclin & Cyclin dependent kinases CDKs & cyclin drive cell from one phase to next in cell cycle Proper regulation of cell cycle is so key to life that the genes for these regulatory proteins have been highly conserved through evolution The genes are basically the same in yeast, insects, plants & animals (including humans) Slide 29 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Cyclin & Cyclin dependent kinases MPF = Mitosis Promoting Factor; APC = Anaphase Promoting Complex Slide 30 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Reproductive Cell Division Sexual reproduction, each new organism is the result of the union of two different gametes (fertilization), one produced by each parent. Meiosis , the reproductive cell division that occurs in the gonads (ovaries and testes), produces gametes in which the number of chromosomes is reduced by half. Gametes contain a single set of 23 chromosomes and thus are haploid (n) cells. Fertilization restores the diploid number of chromosomes. Meiosis occurs in two successive stages: meiosis I and meiosis II Slide 31 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Meiosis I A B Slide 32 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Meiosis I Slide 33 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Meiosis I to Meiosis II Slide 34 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Meiosis II Slide 35 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Comparison between Mitosis and Meiosis Slide 36 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Comparison between Mitosis and Meiosis Mitosis Meiosis Number of 2 1 divisions Number of 2 4 daughter cells Genetically Yes No identical? Chromosome Same as parent Half of parent Number Where Somatic cells Germ cells When Throughout life At sexual maturity Role Growth and repair Sexual reproduction Slide 37 of 39 PHA115 Protein Synthesis and Cell Division  Cell Division Comparison between Mitosis and Meiosis Slide 38 of 39 PHA115 Protein Synthesis and Cell Division  Further Reading Refer to the Following Textbooks Walter F. Boron and Emile L. Boulpaep Concise Medical Physiology 1st Edition Gerard J. Tortora and Byran H. Derrickson Principles of Anatomy and Physiology 13th Edition Frederic H. Martini Fundamentals of Anatomy & Physiology 7th Edition Elaine N. Marieb and Katja Hoehn Human Anatomy & Physiology 8th Edition VanPutte, Regan and Russo Seeley’s Anatomy and Physiology 12th Edition Slide 39 of 39 PHA115 Protein Synthesis and Cell Division