CELLS

Cell Theory All organisms are composed of one or more cells. Cells are the smallest living units of all living organisms. Cells arise only by division of a previously existing cell.

ALL CELLS HAVE Genetic material Cytoplasm fills cell interior – single circular molecule of DNA in prokaryotes double helix located in nucleus in eukaryotes – nuclear envelope (double membrane Cytoplasm fills cell interior – sugars, amino acids, salts proteins organelles Plasma membrane encloses the cell

Visualizing Cells

Prokaryotic Cells Simplest organisms E.g. bacteria Cytoplasm is surrounded by plasma membrane and encased in a rigid cell wall. no distinct interior compartments no membrane-bound organelles

Prokaryotic Cells Some use flagellum for locomotion (movement) threadlike structures protruding from cell surface Bacterial cell wall Rotary motor Sheath Flagellum

Eukaryotic Cells Characterized by compartmentalisation of areas within the cell, and the presence of membrane-bound organelles. Central vacuole – plants, storage Vesicles (smaller) Chromosomes - DNA and protein Cytoskeleton (internal skeleton) Cell walls – plants and fungi

Generalised Eukaryotic Cell

Nucleus Repository for genetic material Directs activities of the cell Usually only one present in a cell Nucleolus Surface of nucleus bound by nuclear membrane Nuclear pores –gatekeepers

Nucleus

Endoplasmic Reticulum Rough ER - studded with ribosomes Smooth ER - few ribosomes

Endoplasmic reticulum Largest internal membrane Functions in storage and secretion Rough ER Smooth ER

Endomembrane System Golgi apparatus collect, package, and distribute molecules synthesised at one location in the cell and utilised at another location

Endomembrane System Vesicles - storage and transport Lysosomes - contain digestive enzymes

Cytoplasm Extracellular fluid Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cytoplasm Endoplasmic reticulum Phagocytosis Food vesicle Golgi apparatus Lysosomes Transport vesicle Old or damaged organelle Plasma membrane Digestion of phagocytized food particles or cells Breakdown of old organelle Extracellular fluid

Mitochondria A. "Powerhouse of the cell" – create energy usable for the cell

Chloroplasts Contain chlorophyll: a photosynthetic pigment. Convert sunlight, carbon dioxide and water into glucose: chemical energy

Cytoplasm Cytoplasm is the substance that fills the cell (excluding the nucleus). It is a jelly-like material that contains the cytosol (water, dissolved salts and organic molecules) and organelles. It is eighty percent water and usually clear in colour.

Plant Cells Large central vacuole Cell wall Chloroplast often found in the centre of a plant, and serves as a storage facility for water and other materials Cell wall The cell wall is made up of cellulose, a complex carbohydrate Chloroplast Converts light energy to chemical energy