Chapter 4: Cell structure

Eukaryotic cell: Main components: Cell wall/ or membrane Cytoplasm (cytosol) Nucleus Name the functions of each?

Cell walls Plants, bacteria and fungi have cell walls Plants: cell walls made of cellulose bacterial cell walls made of peptidoglycan Fungi: cell walls made of chitin

Cell membranes Made of: lipids, proteins Primary lipids: phospholipids Make excellent barriers; inside of cell is aqueous (watery) and they form an “oily” layer between inside and outside in the cell Cell membrane: selectively permeable (allows only certain things to pass and restricts others)

Phospholipid: Have polar and non-polar regions Form lipid bilayers Phosphate is polar (hydrophilic) Fatty acid is non polar (hydrophobic) Form lipid bilayers

4 ways substances cross cell membrane 1. Simple diffusion 2. Facilitated diffusion 3. Active transport 4. Bulk transport

1. Simple diffusion Diffusion: movement of substance from area of high concentration to area of low concentration until dynamic equilibrium is reached “moving down concentration gradient” concentration gradient: when there is a change in the concentration of something over a distance equilibrium: equal on both sides (balanced) Only works if substance is lipid soluble (hydrophobic) and can interact with the oily layer ex: oxygen, carbon dioxide, cholesterol

2. Facilitated diffusion Similar to simple diffusion except molecules that cross are not hydrophobic They cannot interact with bilayer and cannot simply cross the membrane Require the help of proteins to facilitate the movement of these substances

3. Active transport Cell must use energy to move something across the membrane Active transport: (differs from simple and facilitated diffusion in that it can move things against a concentration gradient) requires energy Relies on membrane proteins

4. Bulk transport Movement of large, bulky items across the cell membrane Endocytosis (take into the cell) Exocytosis (release from the cell)

Endo/exocytosis Endocytosis: Cell takes up some particle from surroundings by engulfing it within a pocket called a vesicle Phagocytosis: eating Pinocytosis: drinking Exocytosis: the exact opposite of endocytosis Release of particle to outside through vesicle

Osmosis: Movement of water across cell membrane down its concentration gradient Water’s concentration gradient is opposite to the solute (dissolved particles) concentration gradient Water is hydrophilic must cross membrane by facilitated diffusion Hypertonic (cell in concentrated solution) Cell shrivels Isotonic (same concentration) Hypotonic (cell in dilute solution) Cell swells (lyses)

The cytoplasm: Cytoplasm: semiliquid goo that contains eukaryotic cell’s organelles Prokaryotic cells: have no organelles (bacteria) Know: organelles and functions!

Chemical reactions and enzymes (in cytoplasm): Enzymes Enzymes are proteins; large biological molecules that are responsible for thousands of metabolic processes (catalysts that serve to accelerate rate/ specificity of metabolic reactions) Specific 3D shapes give them specificity for particular reactions Denaturation of proteins results in loss of function

Catalysts: Speed up a chemical reaction Are not used up in the chemical reaction (re-usable) Enzymes are specific for particular reactions