Cell Structure and Composition Prepared by: Ms. Bernabeth Jo T. Tendero

Major Parts of the Cell Nucleus Cytoplasm Cell Surface

Nucleus Region of the cell where the genetic material is located Generally oval-shaped or spherical shaped Most conspicuous part of the cell Regulates and coordinates all the activities of the cell Denser than surrounding cytoplasm

Parts of the Nucleus

Chromosomes - in form of chromatin - contains genetic information - Composed of DNA - Thicken for cellular division - Set number per species (i.e. 23 pairs for human)

Chromosomes

Chromatin

Nuclear Membrane Surrounds the nucleus Double membrane Has numerous opening called nuclear pores which serves as pathways for exchange of materials between the nucleus and the cytoplasm

Nuclear Membrane

Nucleolus Spherical shape Visible when cell is not dividing Contains RNA for protein manufacture

Nucleolus

Cytoplasm Protoplasm found outside the nucleus Collective term for cytosol and organelles Colloidal suspension Cytosol composed mainly of water with free floating molecules Viscosity constantly changes

Organelles Discrete structures of a cell having specialized functions

Centrioles: Helper in Cell Division Paired cylindrical organelles near nucleus Composed of nine tubes, each with three tubules Involved in cellular division Lie at right angles to each other

Centrioles

Cytoskeleton: Framework of the Cell Composed of microtubules Supports and provides shape Aids movement of materials in and out of cells Microtubules provide pathways for certain cellular molecules to move about

Cytoskeleton

Endoplasmic Reticulum: Manufacturers and Builders of the Cell Tubular network fused to nuclear membrane Goes through cytoplasm onto cell membrane Stores, separates and serves as cell’s transport system

Endoplasmic Reticulum

Endoplasmic Reticulum: Manufacturers and Builders of the Cell 2 types Rough Endoplasmic Reticulum (RER) - occurs as flattened sheets studded on its outer surface with small spherical bodies called ribosomes - aids in protein synthesis - prevalent in cells that specializes in secreting proteins

Rough Endoplasmic Reticulum

Endoplasmic Reticulum: Manufacturers and Builders of the Cell 2 types Smooth Endoplasmic Reticulum (SER) - occurs as tubes of membranes without ribosomes attached - site for fat metabolism and forms vesicles for transporting large molecules to other cell parts

Smooth Endoplasmic Reticulum

Golgi Apparatus: Packaging Counters of the Cell Discovered and named after Camillo Golgi in 1898 by observing nerve cells of an owl A system of membrane-bound sacs that look like a stack of pancakes Believe to be part of ER and where new membranes for the ER are manufactured Believe to prepare proteins for secretion after they are released from the ER

Golgi Apparatus

Lysosomes: Suicide Bags of the Cell “Lyso” – dissolving power and “some” – body Discovered in 1952 Contains hydrolytic/digestive enzymes for proteins, lipids and carbohydrates Transports undigested material to the cell membrane for removal Destroys cells when lysosomes burst

Lysosomes

Mitochondria: Powerhouses of the Cell 2 nd largest organelle with its own DNA (mtDNA) Double layered outer membrane with inner folds called cristae Energy-producing chemical reactions (produces ATP) takes place on cristae Controls level of water and other materials in cell Recycles and decomposes proteins, fats and carbohydrates, and forms urea

Mitochondria

Mitochondria

Ribosomes: Protein Factories of the Cell Composed of nucleic acids (RNA) and proteins Numerous in cells Manufacture proteins

Ribosomes

Ribosomes

Vacuoles: Storage Tanks of the Cell Membrane-bound sacs for storage, digestion and waste removal Contains water solution Contractile vacuoles for water removal

Vacoules

Peroxisome Contain enzymes that transfer hydrogen to various substrate of oxygen to produce hydrogen peroxide Use oxygen to break fats to use as fuel for cellular respiration Detoxify alcohol and other harmful compounds

Peroxisomes

Chloroplast: Site of Photosynthesis Plastid found in plant cells Contains green chlorophyll where photosynthesis takes place Has its own DNA and ribosomes Double membrane bound organelle Mobile and move around the cell through cytosleleton

Chloroplast

Cell Surface Protectively surrounds the cell Plasma membrane Cell wall Plasmodesmata

Plasma Membrane Double layer of phospholipid molecules Each phospholipid is composed of fats, phosphate and carbohydrates (oligosaccharide) Protein molecules are embedded in phospholipids Because of its structure the membrane has a semi-permeable property that allows only chosen substances to enter and leave the cell

Plasma Membrane

Cell Wall Lies outside the plasma membrane Compose of cellulose Protects the cells and provide rigid structure for cells Remains intact even after the rest of the cell has died

Cell Wall

Plasmodesmata small channels that directly connect the cytoplasm of neighboring plant cells to each other, establishing living bridges between cells allow certain molecules to pass directly from one cell to another and are important in cellular communication

Plasmodesmata

Plasmodesmata