Cell Biology PDF

# Cell Biology ## Cytology - The study of cells as fundamental units of living organisms. - **Cyto**=Cell - **Ology**=Science ## Cells ### Cytology - Cells - Tissue - Organ - System - Whole body ### Cells - Basic building unit of human body. - Animal - Has millions of differentiated cells. - Gro...

# Cell Biology ## Cytology - The study of cells as fundamental units of living organisms. - **Cyto**=Cell - **Ology**=Science ## Cells ### Cytology - Cells - Tissue - Organ - System - Whole body ### Cells - Basic building unit of human body. - Animal - Has millions of differentiated cells. - Grouped into tissues, organs and systems to make specific functions. ### Cell Size and Shape - Wide ranges (large, medium, small) - Rounded, flattened, spindle, cuboidal, columnar, rod ## How to Observe an Object? - Naked eye - Light microscope - Electron microscope ## Relative Sizes on a Logarithmic Scale - Atom - Protein - Lipids - Flu virus - Animal cell - Mitochondria - Bacterium - Plant cell - Human egg - Frog egg - Chicken egg - Ostrich egg - Adult female ## Cell Structure ### 1- Cell Membrane - **Cell Membrane= Plasma Membrane= Plasma Lemma= Tri-lamellar Membrane** - Bound all cells - Interface between internal and external of cell environment - **Structure** - Appears as 3 layers (Tri-lamellar membrane) - Middle Light Layer (Electron Lucent) - Outer + Inner Dark Layers (Electron Dense) ### Cell Membrane Compositions: - Lipids - Proteins - Carbohydrates ### 1- Lipids= Phospholipid Molecule: - Double membrane. - Arranged perpendicular to surface membrane. - Each molecule has 2 ends: - Hydrophilic end (HEAD)= Water soluble (Polar) - Hydrophopic end (TAIL)=Fat soluble (Non-Polar) ### 2- Proteins (2 Types): - **Intrinsic=Integral:** - Embedded totally in lipid bilayers. - Extended from one side of membrane to the other. - **Extrinsic-Peripheral:** - Partially embedded only to outside lipid layer. - Found on surface only. ### 3- Carbohydrates: - In the form of Glycolipids & Glycoproteins - They are projected from external surface of the membrane to form cell coat (Glycocalyx) - **Physical Protection** ## Cell Membrane “Fluid-Mosaic membrane” - **Fluid:** - Normally Lipids: in fluid phase at body temperature. - **Mosaic:** - Proteins: are globular in shape Floating and moving on lipid surface. ## Differences between inner and outer halves of cell membrane? - Halves are *NOT SYMMETRICAL* due to: - Cell coat(Carbohydrates): on outer surface only. - Cell Receptors (peripheral proteins): on outer surface only. ## Functions: - **1- Exchange of materials between cell and its surrounding by:** - **Simple Diffusion** - Depend on conc. gradient on either sides of membrane. - (From high conc. to..... Low conc.) - No need of Energy (ATP) - e.x: water (OSMOSIS) and small molecules - **Active Transport** - Against conc. Gradient. - (From Low to... high conc.) - Need of Energy (ATP) - e.x: Large molecules - (Sugars, Amino acids, fatty acids) - **Selective Transport** - Depend on Cell Receptors on outer cell membrane. - Receptors: select which substances to pass and which to be stopped. - e.x: Hormone - **2- Sodium-Potassium Pump (Na-K Pump):** - Has enzymatic activity (ATPase enzyme and Energy). - Move 2 ions against conc. gradient in the same time (mutually). - Carry Na+ ions to outside cell. Transport K+ ions to inside cell. - Importance:---Balancing of Osmotic pressure. - **3- Cytosis :** - **1* - *Endocytosis** - **Phagocytosis = (eat)** - Membrane can engulf any solid which found outside cell (surroundings) into... cytoplasm. - **Pinocytosis = (drink)** - Membrane can pick up fluid’s droplets. - **2- Exocytosis** - Membrane can extrude (unwanted materials) from cytoplasm to..... extracellular fluid (outside) ## 2-(Nucleus) - **Number:** - Generally, a cell contains a single nucleus - **Structure:** - **Nuclear membrane:** - *Double membrane structure the called nuclear. Envelope.* - **Nuclear pores:** - *Pores in the nuclear envelope the pathway for the exchange of micro molecules & DNA.* - **Nucleoplasm:** - *Transparent matrix contains (Nuclear chromatin Nucleolus).* - **Nucleolus:** - *Not bound by a membrane. - They are rich in RNA and proteins. It is known as factory of ribosomes.* ## Function: - **Control center:** It controls all the metabolic activities of the cell. If it is removed the cell dies. - **Genetic information :** It is responsible for the transmission of hereditary traits. - **Ilt regulates cell cycle.** - **Ribosomes are formed by nucleolar part of nucleus.** - **Nucleus plays a central role in cellular reproduction:** (process by which single cell divides to form two new cells). ## Nuclear chromatin & Chromosomes: - The nucleoplasm contains many thread like, coiled threads known as :chromatin. - During cell division chromatin condense and distinguishes into rodlike structures known as chromosomes. - Each chromosome consists of two parts known as Hetero-chromatin and Euchromatin. - Each chromosome contains small button shaped particles known as genes. - They are made up of DNA and help in the transfer of heredity characters from one generation to another. ## Hetero-chromatin and Euchromatin. | Hetero-chromatin | Euchromatin | |---|---| | Highly condensed | Less condensed | | Gene-poor | Gene-rich | | Transcriptionally silent | More easily transcribed |