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Metabolism: You are a product of what you ate! 4/21-23 CH26. How do we defecate? How much energy does carbohydrate, protein and fat contain? Why do we prefer to metabolize glucose in the cytosol? How does glycolysis work in the cytosol?
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Like the micturition reflex, the defecation reflex also uses local connections in the sacral roots (weak control). However, primary control of defecation is from higher CNS centers in the brain.
Energy Content: ability to heat water or do work (chemical or physical)
Chemical Calorie (cal)= 1 cal raises temp of 1 ml 1o C
Dietary Calorie (Cal)= 1 Cal raises 1,000 ml by 1o C
Typical Person needs about 1,800 to 2,000 Cal/day
This energy comes from diet (food) or stored reserves (fat/glycogen)
Total = Basal Metabolic Rate + Energy for the “extras”
Sedentary Lifestyle: Caloric needs go DOWN
Active Lifestyle: Caloric needs go UP
Aging: after the age of 40 your Basal Metabolic Rate decreases a few percent per year! This is why we gain weight after 40.
There are 3 nutrient types:
1) Carbohydrates (sugars): 4 Cal/gram-water soluble
2) Lipids (fat): 9 Cal/gram- not water soluble
3) Protein (nitrogen): 45-60 grams/day 4 Cal/gram-variable water solubility
Alcohol is not a nutrient: 7 Cal/gram and must become ATP or FAT
Alcohol cannot be converted to sugars!
Glucose is metabolized by tightly controlled chemical reactions. The Goal is to produce energy (ATP) and CO2!Pathway: GlucoseGlycolysisCitricAcidCycleElectronTranpsort
Occurs Only in Cytosol!
1 GLUCOSEIF O2-PRESENT
YIELDS: 2 PYRUVATE, 2ATP,
and 2 NADH
Hypoxia Causes Fermentation:
2 LACTIC ACID
This allows NAD+ regeneration….So Glycolysis continues at very low efficiency and ATP yield.
When pyruvate is produced by glycolysis, it may be oxidized to acetate, CO2 and NADH. Acetate then enters the mitochondrial “Citric Acid Cycle” where it is fully oxidized to carbon dioxide (CO2) that we exhale!The NADH and FADH2 let oxidative phosphorylation make ATP.
Please don’t try to memorize this…ok?
Just look at the NADH (3) and FADH (1)produced!
Remember: oxygen must be available in mitochondria at the end of the chain to accept the electrons brought to it on NADH and FADH2. This reaction makes “metabolic water” when ATP is produced. Otherwise (no oxygen) THINGS back up and lactic acid fermentation must occur to make ATP!
THIS IS OXIDATIVE PHOSPHORYLATION because you make ATP by phosphorylating ADP (ADP+ Pi + energy ATP)
Summary of energy producing catabolic reactions that use glucose as the primary energy input:#1Glycolysis, #2Citric Acid Cycle, #3Electron Transport!
Electron-transport chain is also called oxidative phosphorylation, it occurs inside a mitochondria IF the cell HAS mitochondria and oxygen.
HOW DO WE GENEREATE ATP FROM FATS?FATTY ACIDS THEN UNDERGO “BETA-OXIDATION” TO YIELD Acetate, NADH, FADH2, CO2 , tremendous amounts of ATP and a few toxins like ketones and acetone.
First Step: The enzyme LIPASE converts storage triglycerides into free fatty acids
Second Step: Mitochondria converts FA into acetyl-CoA and NADH/ FADH2 (16 carbon Fatty acid>>>8 Acetyl-CoA) (1 glucoseonly 2 acetyl-CoA)
Third Step: Send Acetyl-CoA to the Citric Acid CycleNADH and FADH2
Fourth Step: NADH and FADH2 drive oxidative phosphorylation (ATP produced)
Fats and carbohydrates share the citric acid cycle for acetyl-CoA oxidation Do you see why triglycerides can store so much energy? (4 Cal/g glucose verses 9 Cal/g fat).
Fat has a Problem: we must have oxygen and mitochondria present in the cell to use NADH, otherwise no ATP produced.
Problem: sometimes we oxidize fatty acids and accidentally make acetone and ketones that are toxic! This occurs in uncontrolled diabetes.
Plasma Albumen: free fatty acid solubility in blood very limited!
Chylomicrons of gut> carry digested TG
Lymphatics carry chylomicrons through lymphatic vessels that dump into blood at the subclavian vein
Very Low Density Lipoproteins (VLDL)
Deliver fatty acids to body and carry cholesterol
VLDL made by liver and becomes LDL when Triglycerides are removed
LDL(BAD) deliver remaining cholesterol of particle to body
HDL(GOOD) produced by liver and pick up cholesterol in body and recycle it back to the liver.
The problem with using amino acids for energy in the body is that they invariably produce toxins like ammonia and/or ketones.However, if you are starving you may have no choice!
You try to convert toxic ammonia molecules into the less harmful urea for excretion in the urine! However, if ammonia production is greater than urea production and removal we can poison our body. This is why amino acids from protein are poor choices for energy production.
1) Where do the glycolytic reactions occur and what happens to glucose as a result of these reactions?
2) What are the products of glycolysis in the presence of oxygen and in conditions of hypoxia?
3) What does the citric acid cycle do and where in a cell does it occur?
4) What is the name of the chemical reactions in the mitochondria that use the high-energy electrons of NADH and FADH2 to produce ATP?
5) Name two places in the body where one could find cells that cannot use the citric acid cycle or electron transport and are dependent upon glucose and fermentation?
6) Lipase breaks a triglyceride into free fatty acids. Fatty acids are broken down into acetyl-CoA. What enzyme system helps fat oxidizing cells use acetyl-CoA from either glucose or fat?
7) What are two potential toxins created in a cell by beta-oxidation?
8) Where is cholesterol synthesized? How is it carried to the body? How is cholesterol in the body returned to the liver?
9) What nitrogen-containing toxin is produced when we have to burn amino acids from protein as the primary energy source during starvation?
10) Glucose is oxidized without making toxins, and both fats and amino acids can create toxins, this is why our bodies prefer carbohydrates (glucose) for energy.