1 LECTURE DR ZAHOOR ALI SHAIKH

CELL PHYSIOLOGY  Cell is basic building block of the body.  Cell has THREE major parts: 1. Cell Membrane or Plasma Membrane 2. Nucleus : It has Genetic Material 3. Cytoplasm: It has organelles, dispersed in the GELATIN like liquid, the CYTOSOL  Cell performs basic essential functions for its own survival and a specialized task for Homeostasis 2

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CELL MEMBRANE OR PLASMA MEMBRANE  It covers the cell and separates the cell from its surroundings.  It controls the movements of molecules between Intracellular fluid(ICF) and Extracellular fluid(ECF). 4

NUCLEUS  Spherical or Oval in shape, located near the center of the cell.  It is surrounded by double layered membrane which separates it from the rest of the cell.  Within the Nucleus is cell Genetic Material DNA( Deoxyribonucleic acid). 5

Functions of DNA TWO Main Function  Two Main Function of DNA are: 1– Directs protein synthesis 2– Serving as genetic blue print during cell replication therefore produces cell like itself (same cell) 6

OTHER FUNCTIONS OF DNA  DNA controls the cell activity(control center).  DNA provides instruction or CODES for synthesis of protein in the cell (enzymes).  HOW DNA controls cell activity ?  DNA sends coded message via messenger RNA to the cytoplasm RNA (Ribosome). 7

OTHER FUNCTIONS OF DNA (CONT)  Ribosomal RNA (in cytoplasm) translates this message and makes appropriate amino acid sequence for protein synthesis.  Transfer RNA --- it transfers appropriate amino acid to their proper site in the protein under construction in ribosome's (cytoplasm). 8

TYPES OF RNA  There are THREE types of RNA: 1. Messenger RNA [mRNA] - (from DNA to cytoplasm) 2. Ribosomal RNA [rRNA] - in cytoplasm 3. Transfer RNA [tRNA] - in cytoplasm 9

CYTOPLASM  It surrounds the Nucleus. It has membrane enclosed structures called ORGANELLES, which are dispersed in CYTOSOL (gel like mass of cytoplasm). 10

ORGANELLES- present in cytoplasm Membranous Organelle FIVE main types are there: 1-Endoplasmic Reticulum( ER) i. Rough ER- has RIBOSOMES (Granules) ii. Smooth ER - has NO RIBOSOMES 2-Golgi Apparatus 3-Mitochondria 11

ORGANELLES (CONT) 4-Lysosomes 5-Peroxisomes Non-membranous Organelle [three] : 1- Ribosome 2-Vaults 3- Centrioles  Each organelle does specific job.  We will discuss the organelles one by one. 12

1. ENDOPLASMIC RETICULUM (ER)  ER - TWO Types : 1. Rough ER (Flattened sacs) 2. Smooth ER (Inter connected Tubules) 13

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ROUGH ENDOPLASMIC RETICULUM  Why we call it Rough ER ?  Because it has particles which give it rough or granular appearance – these particles are RIBOSOMES, RNA protein complexes which synthesize protein under the direction of Nuclear DNA.  Some Ribosome are free and present in cytosol. 15

ROUGH ER (CONT)  It is protein making factory.  It synthesizes new protein in ER lumen. Some proteins are secretary products e.g. hormones or enzymes (all enzymes are proteins).  Other protein are synthesized for new plasma membrane or organelle membrane. 16

SMOOTH ENDOPLASMIC RETICULUM  It has no ribosome, therefore, no protein synthesis in smooth ER.  It serves other purpose. - Newly synthesized protein and lipids in rough ER pass into smooth ER. - It gives rise to transport vesicles which contain new protein. - Transport vesicle move to Golgi apparatus. 17

SMOOTH ER (CONT) - Membranous wall of smooth ER has enzymes for synthesis of lipids. - In liver cells smooth ER has enzyme which do Detoxification of drugs. - In muscle cells, smooth ER is called Sarcoplasmic Reticulum which contain calcium and plays important role in muscle contractions. 18

2. GOLGI APPARATUS  It directs molecular traffic.  Newly synthesized molecules in rough ER which just came from smooth ER enter Golgi sack or layer.  Golgi complex directs the product for its final destination e.g. that becomes part of plasma membrane or incorporated in Lysosomes. 19

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3. MITOCHONDRIA  They are called ‘Power Plants’ of the cell.  They are rod or oval shaped.  Number of Mitochondria present in the cell depend on cell activity.  Number of Mitochondria vary from hundred to thousands. 21

MITOCHONDRIA (CONT)  They take energy from the food and use for cellular activities.  Energy derived from food is stored in ATP.  When ATP (Adenosine Triphosphate) is split, energy is released.  Energy released from ATP is used by the cell for -synthesis of protein in ER -membrane transport -mechanical work e.g. contraction of heart muscle, skeletal muscle 22

MITOCHONDRIA (CONT)  Mitochondria have their own DNA (it is different from cell nucleus DNA).  Mitochondrial diseases are recognized which cause nervous system and muscle diseases. 23

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4. LYSOSOMES  They work as intra-cellular Digestive System.  Lysosomes are membrane enclosed sacks containing powerful enzymes, capable of removing bacteria and cellular debris.  There are about 300 Lysosomes in a cell.  Lysosomes appear granular-these granules are protein aggregates of powerful digestive enzymes. 25

LYSOSOMES (CONT)  How Lysosomes work ?  When extra-cellular material to be attacked by Lysosomes is brought into the cell by process of Endocytosis (endo=within).  Endocytosis is done by 2 ways: 1. Pinocytosis 2. Phagocytosis  Lysosomes destroy bacteria by hydrolytic enzymes. 26

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5. PEROXISOMES  They have oxidative enzymes.  They destroy various waste produced in the cell and toxic compounds that have entered the cell e.g. Ethanol. 28

NON-MEMBRANOUS ORGANELLES  1. RIBOSOMES  Ribosomes carry out protein synthesis.  They are present free in cytosol.  NOTE – [ Ribosomes are attached to the rough endoplasmic reticulum also] 29

NON-MEMBRANOUS ORGANELLES  2. VAULTS  They are newly discovered organelle.  Cell may contain thousands of vaults.  Octagonal shape organelle transports messenger RNA or Ribosomal units from the nucleus to cytoplasmic ribosome. 30

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NON-MEMBRANOUS ORGANELLES  3. Centrosome, Centrioles  Centrosome is located in the cytoplasm, near the nucleus.  Two centrioles surrounded by protein lie at the center of centrosome.  Centrosome is cell’s microtubule.  Microtubule are part of cytoskeleton.  Centrioles form mitotic spindle to direct movements of chromosomes.  In some cells centriole form cilia, flagella. 32

What You Should Know From This Lecture  What are cell’s three major subdivisions ?  Control Center in the Cell – DNA  Types of RNA - mRNA - rRNA - tRNA  Organelles present in the Cytoplasm - Membranous - Non-membranous  Important Functions  Ribosomes - Protein Synthesis  Mitochondria - Power House  Lysosomes - Bacterial Digestion 33

THANK YOU 34