CYTOLOGY: Cell structure and function

Robert Hooke The first person to identify and see cells. 1665. Coined the term “cell”

The cell theory Cells are the basic units of life. All living things are made up of cells. All cells are produced by existing cells.

Cell types. They are either PROKARYOTIC or EUKARYOTIC cells. Karyon means ‘kernal’ Eu means ‘true’ Pro means “before”

Prokaryotic Cells Kingdoms: 1. Eubacteria 2. Archaebacteria Characteristics: 1. lack a nuclear membrane. 2. have no membrane-bound organelles. 3. “naked” genetic material.

Prokaryotic Cell - Bacteria

Eukaryotic Cells Kingdoms: 1. Protista 2. Fungi 3. Plantae 4. Animalia Characteristics: 1. have a nuclear membrane around genetic material “nucleus” 2. have specialized membrane-bound organelles

Eukaryotes Prokaryotes DNA linear strands within membrane-bound nucleus single circle in “nucleoid region Size 5-100 µm 0.2-10 µm Organization often multicellular, some have cell walls (no peptidoglycan) usually single-celled, some have peptidoglycan cell walls Metabolism usually need oxygen to exist may not need oxygen to exist Organelles membrane bound organelles like mitochondria no organelles, different ribosomes Examples plants, animals, protists, fungi bacteria, archaea 8 8

Eukaryotic - Animal Cell

Eukaryotic - Plant Cell

Cellular Evolution Current evidence indicates that eukaryotes evolved from prokaryotes between 1 and 1.5 billion years ago. Two theories: 1. Infolding theory 2. Endosymbiotic theory

1. Infolding Theory The infolding of the prokaryotic plasma membrane gave rise to eukaryotic organelles.

2. Endosymbiotic theory Endosymbiosis refers to one species living within another - the host. Theory - the movement of smaller photosynthetic (chloroplast) and heterotrophic (mitochondria) prokaryotes into larger prokaryotic host cells.

Cytoplasm Entire region between the nuclear membrane and the cell (plasma) membrane. This includes all organelles! Buildings, factory layout, matrix cytoplasm

Cytosol The semi-fluid medium found in the cytoplasm. This does not include the organelles. School grounds, city area.

Nucleus A double membrane organelle which contains the coded instructions for making proteins. Found only in eukaryotes. Contains DNA, also called chromatin. (Blueprints) principal, mayor, control center

Nucleolus Spherical region in nucleus. Produces the ribosomes. Sometimes more than one nucleolus present. Training center, machine shop nucleolus

Ribosomes Nuclear and cytoplasmic organelle. Composed of 60% protein and 40% ribosomal-RNA (rRNA). Site of protein synthesis. Either free or attached. Machines, teachers, law enforcers

Endoplasmic Reticulum (ER) Extensive membranous network of tubules and sacs. Two distinct regions: A. Rough endoplasmic reticulum (RER). B. Smooth endoplasmic reticulum (SER).

Endoplasmic Reticulum A. Rough endoplasmic reticulum (RER). 1. Studded with ribosomes. 2. Site of protein modification. Classrooms, assembly line, roadway B. Smooth endoplasmic reticulum (SER). 1. Synthesizes lipids, phosolipids and steroids. 2. Detoxifies drugs, alcohol and poisons. Detox center, water treatment plant, detention hall.

Golgi Apparatus, Body or Complex A stacked, flattened membranous organelle of sacs. Modifies, stores and routes products from the ER to the plasma membrane. Shipping department, post office

Lysosomes Membrane-enclosed bag of hydrolytic enzymes (digestive enzymes). Functions: Phagocytosis - intracellular digestion Autophagy - engulfs other cellular organelles Apoptosis – Programmed cell death Janitors, recycling bins

Vacuoles Large membrane-enclosed sacs for cellular storage. Three types: 1. Food vacuole (lysosomes attach) 2. Contractile vacuole (Protozoans) 3. Central Water Vacuole (mature plant cells) Water pump, storage sheds, refrigerator.

Cell Membrane The boundary of every cell, also called the plasma membrane. Semi-permeable, acts as a selective barrier. Fence with gates, moat with bridges, security system

Cell Wall Strong fibers surrounding plant, fungi, some protista and most bacteria cells. Composed of polysaccharides and proteins, gives the cell shape. Boundary lines, open fences, structural supports.

Mitochondria A doubled membrane cellular organelle with its own circular DNA found in both plants and animals. It is the site of cellular respiration, an oxygen requiring process that uses energy extracted from organic macromolecules (like glucose) to produce energy for the cell in the form of ATP. Power plant, generator, battery.

Mitochondria

Chloroplast A doubled membrane cellular organelle with its own circular DNA found only in plants. The site of photosynthesis, a carbon dioxide requiring process the uses light energy (sun) and water to produce glucose, which the cell will use for energy. Cafeteria, restaurants, solar panels.

Chloroplast

There is always an exception…… Elysia chlorotica

Cytoskeleton Network of fibers through out the cytoplasm. Aids in cellular support and movement. Framework, scaffolding, roadways

Cilia and Flagella Extensions of the plasma membrane. Used for movement or to move food to an oral groove.

Plastids (I) Primary function of plastids is to store molecules. One molecule that they store is pigment; pigments give fruits and vegetables an orange or red color. Plastids also store photosynthetic products like starch. Chloroplasts are plastids. Potatoes, for example, have many plastids in their cells. Warehouses, study halls, storage drums.