Today Finish up: Nerves: Na/K concentration gradient Fats, Sugars, Food you need to survive. Last Homework due this Wednesday
Nerves How (electrical) signal is transported along a nerve
From Atoms to molecules to macromolecules to you! 3-6 elements make up majority of you. About 3 dozen organic compound -- precursors of almost all biomolecules Body (Cell) uses 4 types of small molecules 1. Amino acids– make up proteins 2. Nucleic acids—DNA, RNA 3. Fatty acids/Lipids-- membranes 4.Sugars/polysaccharides/Carbohydrates— structural, food What does body/cell uses 4 molecules for? 1. Building blocks 2. Energy Source 3. Information
Primarily made of 4 small molecules 1. Sugar: carbohydrate= (poly)saccharide Monosaccharide (CH 2 O): has an -OH or =O Most common form: D-glucose: But many isomers! (Can generate an enormous # of isomers.) 2. Fatty Acid: long (CH 2 ) n with a Fat (Lipids): fatty acids, with Triglycerides: insoluble in H 2 O 3. Nucleotides 4. Amino Acids: H2CHRCOOH: R= 1 or 20 side groups
A complete diet must supply the elements; carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur, and at least 18 other inorganic elements. The major elements are supplied in carbohydrates, lipids, and protein. In addition, at least 17 vitamins and water are necessary. If an essential nutrient is omitted from the diet, certain deficiency symptoms appear. Minimal Requirements of Food
Wood— 50% cellulose: C, H 2 O [C 6 (H 2 O) 5 ] n Polysaccharide of glucose [We can’t break down because of linkage between glucose] PE chem. bonds KE, i.e. heat Fire We “burn” our food. Life is a slow burn Most common form: D-glucose: But many isomers! (Can generate an enormous # of isomers.) 6 CH 2 O + O 2 6 CO 2 + H 2 O + energy Breakdown of Glucose ATP at kT / ATP
Figure 2-69: Schematic representation of the controlled stepwise oxidation of sugar in a cell, compared with ordinary burning (A) In the cell, enzymes catalyze oxidation via a series of small steps in which free energy is transferred in conveniently sized packets to carrier molecules—most often ATP and NADH. At each step, an enzyme controls the reaction by reducing the activation energy barrier that has to be surmounted before the specific reaction can occur. The total free energy released is exacly the same in (A) and (B). But if the sugar was instead oxidized to CO2 and H2) in a single step, as in (B), it would release an amount of energy much larger than could be captured for useful purposes. From: How Cells Obtain Energy from Food Molecular Biology of the Cell. Burning vs. eating of sugars/food Eating done in small steps– each step leads to intermediate carrier
Breakdown of food 3 stages 1. Digestion: (Intestines [outside], lysosomes [inside cells, separated by membranes] polymer monomers 2. glycolysis: (Mitochondria) glucose (& other sugars) pyruvate (+ some ATP, NADH) 3. acetyl CoA CO 2 + H 2 O + 36 ATP’s. Citric acid cycle produces a lot of high energy electrons in NADH which are then transferred through the electron transport chain to produce ATP (from ADP). Roughly 10 9 molecules of ATP are in solution in a typical cell at any instant, and in many cells, all this ATP is turned over (that is, used up and replaced) every 1–2 minutes. NAD
Amino Acids 1. Building blocks 2. Energy Source 3. Information -- Make proteins -- Eat proteins -- Signaling between cells/nerves
Neurons (Nerve cells) and Synapses Neuron: –Building blocks of nervous systems. Soma –Cell body Dendrites –Collect signals Axon –Sends signals Synapse –Dendrite-axon junctions Image from wikipedia Neurons transmit signals via synapses.
The Synapse Synapse –Presynapse (Axon) –Postsynapse (dendrite) –Synaptic cleft (~30 nm) Active zone (PAZ) –Vesicle release Postsynaptic density (PSD) –Receptors –Scaffold proteins PSD size is nm The PSD is small, comparable to the light diffraction limit. Super-resolution techniques are required for imaging the PSD. Ax on Dendrite Presyn apse Postsynapse Informa tion flow nm
Presynaptic cell Postsynaptic cell Axon Presynaptic membrane Synaptic vesicle containing neurotransmitter Postsynaptic membrane Synaptic cleft Voltage-gated Ca 2 channel Ligand-gated ion channels Ca 2 Na KK The action potential travels down the axon to the terminal. Arrival at the terminal causes membrane depolarization, which opens voltage-dependent Ca 2+ channels situated in the active zone where the neurotransmitter vesicles are docked. Ca 2+ binds to proteins, mainly synaptotagmin (a presynaptic protein—see next pg), which cause vesicle fusion mainly through an interaction of synaptotagmin with the SNARE proteins. Figure How does nerve impulse traveling down the axon lead to vesicle fusion and glutamate release? Vesicles & membrane contains SNARE proteins which dimerize w Ca 2+
Sugars = Carbohydrates 1. Building blocks 2. Energy Source 3. Information -- Make complex sugars… glucose, glycogen (polymer of glucose Holds your cells together--Extra- cellular space filled with sugars Cellulose (if a plant) -- Eat Hershey’s chocolate! Glucose makes ATPs -- A lot! Much information. Signaling that you are different than a pig.
Sugar is a carbohydrate (C + H 2 O)
Sucrose & Lactose broken down into Glucose then into Pyruvate and then into ATP as energy.
If no Enzyme can’t digest! With Enzyme can digest!
Interesting Details about Energy Storage
Class evaluation 1.What was the most interesting thing you learned in class today? 2. What are you confused about? 3. Related to today’s subject, what would you like to know more about? 4. Any helpful comments. Answer, and turn in at the end of class.