(a) Chemical level: a molecule in the membrane that encloses a cell (b) Cellular level: a cell in the stomach lining (c) Tissue level: layers of tissue in the stomach wall (d) Organ level: the stomach (e) Body system level: the digestive system (f) Organism level

Recall basic cell physiology This class I will assume you know the basic functions of these structures: Smooth and rough endoplasmic reticulum Golgi Peroxisomes Lysosomes Mitochondria Basic structure of the plasma membrane

Gazing into a cell…. Golgi Nucleus Rough ER Smooth ER Peroxisome Lysosome Smooth ER Mitochondria Golgi

Cristae Inner membrane Outer membrane

Glycolysis can occur with or without oxygen Yet, aerobic respiration yields more energy from glucose and occurs in the mitochondria

Chemical reactions for energy Citric acid cycle Glycolysis Electron transport chain Cytosol

First, glycolysis – then either: Making ATP First, glycolysis – then either: Aerobic Pathway Citric acid cycle Electron transport chain Anaerobic Pathway Fermentation

Within the mitochondria... Pyruvate enters mitochondria Citric Acid Cycle matrix Electron Transport Inner membrane (cristae)

Pyruvate Acetyl-CoA Citric Acid (or Krebs) Cycle CO2 CO2 ATP

Where does weight ‘go’ when someone loses weight?

Electron Transport Chain High energy electrons taken from hydrogen are transferred through a series of carriers on inner membrane ATP Synthase w/in cristae 32 ATP formed

Free radicals from ETC A by-product of ETC is the production of abnormal versions of O2 (O2-, O2--) These molecules are highly reactive and produce “free radicals”, which contribute to aging and some diseases.

Energy Harvest Glycolysis (from one glucose) 2 ATP 2 NADH (makes 4 ATP in ETC) Citric Acid Cycle 2 ATP plus NADH, FADH2 for ETC Electron Transport Chain 28 ATP by oxidative phosphorylation

Anaerobic conditions Aerobic conditions

Lactic acid myth Lactic acid (really lactate) isn’t the cause of muscle fatigue and soreness Lactate leaves muscle, enters blood and is used elsewhere for ATP production (using O2)

Lactate threshold Interval training uses periods of training above and below the L threshold. High intensity portions stimulate your body to produce enzymes that speed the use of lactate fuel (MCT1 carrier protein)

Plasma membrane of cells

EXTRACELLULAR ENVIRONMENT oligosaccharide groups phospholipid cholesterol EXTRACELLULAR ENVIRONMENT (cytoskeletal proteins beneath the plasma membrane) open channel protein gated (open) (closed) active transport RECEPTOR PROTEIN RECOGNITION PROTEIN ADHESION PROTEIN TRANSPORT PROTEINS CYTOPLASM Receptor sites (ex: endocrine sites) Cell adhesion (CAM) grips neighbor cell Channels for ions, small molecules Carrier proteins Attach to cytoskeleton

Membrane receptors Binding to the receptor will: Open or close channels for ions (Na+, K+, Ca++) Transfer a signal to 2nd messenger to trigger events in the cell

2nd messenger system will activate an enzyme

Other cell adhesions Extracellular matrix - Biological “glue.” 3 protein fibers are interwoven in this matrix: collagen, elastin, fibronectin. Secreted by cells Desmosomes – “Rivets” to anchor adjacent cells that are not touching

Other cell adhesions Tight junctions – Epithelium cells form tight seal at points of contact Gap junctions - Small tunnels connect cells

open channel proteins gated channel proteins transport protein

Passive transport (facilitated diffusion) transport protein with binding site for a specific substance (the solute) Passive transport (facilitated diffusion) protein has 2 different conformations

Active Transport phosphorylation required Concentration gradient high solute concentration Concentration gradient Active Transport phosphorylation required Direction of transport

concentrations now equal Membrane (permeable to water only) Side 1 Side 2 Solute can’t move to side 1 down its gradient but water moves H2O Side 1 Side 2 Water and solute concentrations now equal

Osmosis is balanced by hydrostatic pressure Membrane (permeable to H2O) Side 1 Side 2 Solute can’t move to side 1 down its gradient H2O Pure water Gradients still exist Osmosis is balanced by hydrostatic pressure Side 1 Side 2 Hydrostatic (fluid) pressure difference Osmosis Hydrostatic pressure

Isotonic Hypotonic Hypertonic