What is a Living Cell? Discovery of cells – Robert Hooke observed the “ cells ” inside a piece of cork with a very primitive microscope

What is a Living Cell? Cell theory 1.All living things are made up of one or more cells 2.Cells are the basic living units within organisms, and the chemical reactions of life take place within cells 3.All cells arise from pre-existing cells

What is a Living Cell? Eukaryotic cell – DNA is enclosed in a nucleus and associated with proteins – Contains membrane-bound organelles Ex. humans, animals, and plants

Eukaryotic Cell – Animal Cell Membrane proteins Plasma membrane Smooth endoplasmic Reticulum Lysoysome Rough endoplasmic reticulum Ribosome Mitochondrion Golgi apparatus Cytoplasm Nucleolus Centriole Nucleus Cytoskeleton Nuclear envelope Nuclear pore

Eukaryotic Cell – Plant Cell Rough endoplasmic reticulum Golgi apparatus Lysosome Smooth endoplasmic reticulum Cell wall Plasma membrane Plasmodesmata Chloroplast Mitochondrion Vacuole Cytoplasm Ribosome Nucleolus Nuclear envelope Nuclear pore Nucleus

What is a Living Cell? Prokaryotic cells – DNA is loose in the cell – Generally have no internal membranous organelles – Evolved earlier than Eukaryotic cells Ex. eubacteria and archaebacteria

What is a Living Cell? HIV size relative to micrograph of prokaryotic cell at right (a) HIV Genetic material (b) Prokaryotic cell Prokaryotic cell size relative to micrograph of eukaryotic cell at right Cytoplasm Plasma membrane Cell wall (c) Eukaryotic cell Nucleus

What Are the Parts of the Cell? Plasma membrane – for the exchange of materials in and out of the cell (selectively permeable) – Diffusion – when small molecules go across the plasma membrane from a high concentration to a low concentration – Facilitated Diffusion – when a protein helps a substance cross the plasma membrane without the expenditure of energy

A Model of Membrane Structure Carbohydrate Protein OUTSIDE CELL INSIDE CELL Hydrophilic ends Channel protein Cholesterol

What Are the Parts of the Cell? Other terms relating to the passage of substances across the plasma membrane: – Active Transport – energy is required – Phagocytosis – a cell engulfs debris – Endocytosis – the cell membrane invaginates and takes in a substance – Exocytosis – vessicles merge with the plasma membrane to expel substances

What are the Parts of a Cell?

(a) A white blood cell engulfs a yeast cell White blood cell Yeast

A Cell Engulfs and Expels Proteins Endocytosis Receptor proteins Nucleus Exocytosis

What are the Parts of the Cell? Nucleus – Contains genetic material – Controls most of the cell ’ s activities – Information flows as follows: DNA RNA Protein

What are the Parts of the Cell Cytoplasm – Semifluid in which organelles are suspended – 70% water, 20% proteins Ribosomes – Proteins are synthesized here Rough endoplasmic reticulum – Ribosomes attached to a flattened membrane in the cytoplasm

Endoplasmic Reticulum 1.RNA joins ribosome 2.Synthesis of HIV envelope proteins 3.Proteins enter transport vesicles