ATP: The energy currency of the cell. The ATP Cycle:

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1 ATP: The energy currency of the cell The ATP Cycle: Changing the rate of catabolic and anabolic reactions- How do you control these chemical reactions? Enzymes and Activation Energy Enzymes as biological catalysts Activation Energy - the probability of a reaction Enzymes effect the rate of reactions by changing the amount of activation energy needed for the reaction Enzymes and Activation Energy A cartoon view of sucrase activity: breaking down sucrose 1

2 Other factors that influence enzyme activity: Cofactors: metal ions and coenzymes Vitamins like niacin and riboflavin Temperature, ph Metabolic Pathways Regulation and Organization Negative feedback Temperature and ph Optima Enzyme regulation Metabolism The sum total of all the chemical reactions happening in a cell (or living thing) Two main types of chemical reactions Anabolic: unfavorable; uses energy to do work, transport, synthesize, move Catabolic: favorable; breakdown of molecules release energy used to fuel other reactions Anabolic and Catabolic Reactions Intro to Cell Structure Cell Theory: All organisms are made of one or more cells Cells are the smallest living thing Cells come from other cells (today) 2

3 Two Main Classes of Cells 3 Domains of Life Prokaryotic (Bacteria and Archaea) Pro = Before ; Karyon = Kernel No nucleus, DNA coiled up inside cell Eukaryotic (Everything else) Eu = True DNA inside membrane bound organelle inside cell, the nucleus Eukaryotic Cell (non bacterial) Prokaryotic Cell (bacteria) Size Differences Prokaryotic Cell Animal Cell 3

4 Plant Cell Why are cells so small? i.e. What are the determinants of cell size? 1- Surface area to volume ratio 2- Diffusion rates Surface Area to Volume Ratios Mechanisms of Cellular Transport Diffusion of oxygen in solution 1 µm m in.5 msec 10 µm m in 50 msec 100µm m in 5 sec 1000 µm m (1mm) in 8.3 min µm m (1cm) in 14 h! Molecular Mechanisms- Solutes and Solvents Passive Diffusion and Osmosis Active Transport Osmoregulation Hypo-, Iso-, and Hypertonic Below, Equal, and Above Bulk transport: Endo- and Exocytosis Diffusion Hypertonic Hypotonic Isotonic Diffusion goes in all directions along the Concentration Gradient Passive Transport- important to all cells O 2 and CO 2 What about molecules that can t get through the Plasma Membrane? 4

5 Still doesn t use any energy! Just High conc. to low Examples: Sugar, A.a., ions, even water!? Transport Proteins- Facilitated Diffusion Osmosis- passive transport of water across a membrane Why? Osmosis and living cells Freshwater Fish Transport Passive- (downhill) Free or gated (chemical or ion) Facilitated- (downhill with a push ) Active-ATP mediated (uphill) Saltwater Fish 5

6 Active Transport 1. Solute attaches to binding site of transport protein 2. ATP causes the protein to change shape 3. so that solute is taken outside membrane 4. Phosphate groups leaves and causes the reverse change. Active Transport Sodium-Potassium Pumps Na-K pumps up to 40% of all our energy is used for this pumping Active Transport of Large Molecules, etc. - Exocytosis moving things outside cell. Active Transport of Large Molecules, etc. - Endocytosis moving things inside cell- 3 ways Crying Insulin others Endocytosis Review: passive and active transport compared Phagocytosis- cell eating Pinocytosis- cell drinking Receptor-mediated- highly specific 6

7 The Plasma Membrane What Controls all this Transport in Living Cells??? General functions of the Plasma Membrane Selective permeability to maintain separation Control exchange of wastes and metabolites Framework for organization of enzymes Anchorage between cells Binding site for hormones Receptors for selective uptake Intercellular identification Membrane Structure: The Fluid Mosaic Membrane Model Lipid bilayer (double layer) Nonpolar tails point inward, polar outside Layers are fluid Many things embedded within membrane Phospohlipids and cholesterol Carbohydrates Proteins Much of the structure and functions of the PM depend on these embedded proteins The Singer Nicholson Fluid Mosaic Model of Membrane Structure: General Properties Phospholipid bilayer: 50% Backbone of most membranes Lateral movement only Oily core forms hydrophobic barrier Proteins: 50% Integral and peripheral cytosolic and exoplasmic faces Free movements of: lipids proteins Healing properties The variable nature of the fluidity of membranes: Sat. vs Unsat. FA s Cholesterol The fluidity of membranes 7

8 Some functions of membrane proteins 8