There are 4 Concepts of Cell Theory (Definition) The Living Units There are 4 Concepts of Cell Theory (Definition) Basic Structure and functional units of life All activities for life occur in cells Human body contains 3 trillions of cells Biochemical activities of a cell are dictated by their organelles

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Structure of the Basic Cell

Characteristics of a Cell Plasma membrane Is a double layer of phospholipids, cholesterol and proteins and encloses the cell as outer layer : Selective permeability Cytoplasm: is a clear substance that consists of all of the contents outside of the nucleus of a cell The cytosol or intracellular fluid (ICF) or cytoplasmic matrix is the liquid found inside cells. Organelles or a cell organs. Specialized part of a cell having some specific function; Different in Size shape and function All Cells are composed primarily of Carbon, Hydrogen and Nitrogen and Oxygen All Cells have the same basic parts and some common functions Typical cell has: plasma membrane , cytoplasm , cytosol, organelles and nucleus Nucleus: contains the majority of the cell's genetic material in the form of multiple linear DNA molecules organized into structures called chromosomes.

The Structure of The Cell

CELLS VARY GREATLY IN SIZE , SHAPE AND FUNCTIONS ALL CELLS ARE COMPOSED OF PRIMARILY CARBON , HYDROGEN, NITROGEN AND OXYGEN All cells have same basic parts and some common functions A generalized human cell contains the plasma membrane , the cytoplasm, and the nucleus

The Structure of The Cell The Plasma Membrane : The Cytoplasm Nucleus Organnes

The Structure of The Cell The Plasma Membrane: Is made up of double layer of phospholipids, cholesterol and proteins Inwards facing and outward facing – have different amount of lipids they contain Glycolipids, lipid rafts in outer layer cell signal Plasma membrane is selectively permeable barriers Passive process Diffusion Osmosis filtration Active process Use energy to transport (ATP) Use solute pumps

The Cytoplasm The cellular membrane between the cell membrane and the nucleus . Most cell activities occur here The major elements of the cytoplasm Cystosol: located in the cytoplasm inside the plasma membrane and contains water fluid Cytoplasmic Organelles: small organs found in the Cystosol: E.g. Nucleus , Mitochondria, ribosomes, Endoplasmic Reticulum, Golgi Apparatus , lysosomes, and cytoskeleton

Nucleus Almost all Cells have Nucleus : These are spherical bodies found inside the cytoplasm Most cells have only one nucleus, but some like the skeletal muscles have more than one Cells without nucleus : matured erythrocytes RBCs A Nucleus is the largest organelle in the cell the controlling center of the cell Nucleus contains the body’s genetic material which directs all metabolic activities of the body (46 Chromosomes) made up of Deoxyribonucleic acid DNA a fine network of thread called chromatins

Mitochondria ( Power house ) Shaped like sausage they are found in the cytoplasm They are responsible for the energy of the cell: They are responsible for aerobic respiration which produces chemical energy i.e. ATP

The Structure of The Cell Endoplastic Reticulum ER Golgi Apparatus ER: series of canals in the cytoplasm- 2 types Smooth Rough Smooth -ER synthesizes Fatty acids & Steroids and detoxify some drugs Rough ER –synthesizes enzymes and hormones outside the cell Are flat membranous sacs Package proteins from ER to form secretory granules Packages Digestive Enzymes into lysosomes

The Structure of The Cell Lysosomes Cytoskeleton Spherical organelles contain Digestive Enzymes and other enzymes for breaking down RNA & DNA to be recycled to excluded as waste Some lysosomes are in White Blood Cells WBCs where they breakdown foreign materials (Microbes) These are tiny strands of protein include: Microfilaments small fibers fro structural support Microtubules helps in cell divisions and cell extensions & chromosomes to divide

The Structure of The Cell Centrosome Made up of small centrioles For organization of microtubules within the cell For cell division Cell Extensions These are projections from plasma membranes help in cell movement, Example: CILIA: small hair like projections ( found in respiratory track) FLAGELLA: long whip like projections

CELL CYCLE Cell cycle is the process that makes the life of each cell. The life of a cell therefore is a series of changes a cell goes through from the time it is formed to the time it reproduces: There are two Processes : Interphase Cell Division

CELL GRPWTH & REPRODUCTION INTERPHASE Is the first three steps where the cell: Grows Matures Carries out its life function The stage just before cell division

INTERPHASE INTERPHASE Interphase occurs when the cell is not undergoing mitosis. It engages in metabolic activity. DNA duplicates during this phase the cell prepares for mitosis. Chromosomes are not visible in the nucleus yet and only chromatin is present. Cells spend the majority of their cycle in interphase.

CELL GROWTH

CELL DIVISION Most body complete body Cell division by mitosis Mitosis involves a process that results in two new genetically identical cells. Other cell division are: MEIOSIS CYTOKINESIS Meiosis: Involves formation of gametes ( sex cells) ova and spermatozoa