Metabolism

If Ken ask: what do you think my metabolism is?…

people don’t really know what it is, just like to have a feeling about it

Ken: Information in food found on campus…

-Hickory Nuts

-Cornelian Cherry

-Hickory Nuts: $, eat=eat CO2 someone breathed out or stored in tree

-Cornelian Cherry: Natural iridoids

*PPAR: enzyme pathway making mito; what people who go running try to activate for adaptations

*** we don’t have to know all these details; need some knowledge though

“Most Astounding fact” video

-astrophysicist Neil Tyson

-H and He from stars smashed and make heavier elements

-”universe is us; our atoms came from stars”

-people want to feel like they mean something in this world

-all connected, and want to feel connected

Review of Metabolism from EXPH

-can’t store ATP, so constantly modulating to meet energy needs at given moment

-can’t directly burn carbs and fats, need to convert to ATP first (store lots kcals)

-”Metabolism”: rate burn carbs and fats to make ATP

-1 kcal/min @ rest

-RER 0.7 - 1.0 (fat → carb; what burn aerobically)

-can’t see metabolism

-no perfect human diet; animals often find balance

***The phrase “You are what you eat” does not stand up to the reality of the digestive system. To be more accurate, the phrase should be “You are what you absorb in conference with whom you host.” So what exactly becomes of what you absorb?

how many kcal do you burn to run a mile?

~100 kcal/mile

Metabolism definition

is the sum total of all of the chemical reactions in living cells. More specifically, energy metabolism includes all of the reactions by which the body obtains and expends the energy from food.

Major metabolic destinations for macronutrients

-Energy for active processes

*most of what’s happening

-Synthesis into structural or functional molecules

-Storage as fat or glycogen for later use as energy

*burn storage between means; same weight= burnt all kcals (unless lose weight or gain weight=store fat and protein on body)

Without net change in storage or synthesis, macronutrients are essentially for __

energy

Enzyme regulation

is the primary means by which all metabolic reactions are controlled

metabolism: anabolic or catabolic

-Organic metabolic reactions can be classified into either catabolism or anabolism.

-The coupling of energy-requiring (anabolic) and energy-releasing (catabolic) reactions is achieved through ATP (adenosine triphosphate). It provides the energy for the energyrequiring reaction. However, ATP cannot be stored, so it must constantly be resynthesized. Therefore the rate of this resynthesis is your rate of metabolism.

*overall goal: make ATP

3 energy systems in ATP resynthesis (list + overview)

*resynthesis: ADP + Pi → ATP)

1. Immediate energy system: reactions catalyzed by creatine kinase

*1 step so quick

*creatine kinase: takes P off PCr and puts on ATP

2. Glycolysis

*10 steps; invest 2 prod 4= 2 ATP

*1 & 2= anaerobic

3. Aerobic metabolism

*products from glycolysis (or fat and protein breakdown) → Krebs → ETC where get 28-30 ATP

Advantages and Disadvantages of 3 energy systems

-PCR: + make ATP fast; - run out fast

-Glycolysis: + make ATP next fastest; - lactate decrease pH and leads to fatigue

-Aerobic: + unlimited supply (could walk to Boston!); - ATP slow (even at max)

timing for when each energy system is dominant

-10 sec: majority PCR (not glycolysis though)

-1 min: ana dominant but aerobic bigger

->2/5 min: aerobic dominant

*increase time= increase dominance aerobic

*not just about how fast; are they going max for certain time?

*athletes: make ATP aerobically faster than us anaerobically

true or false: All nutrient molecules have energy stored in their structure

true!

Oxidation (+ in context of metabolism)

-Oxidation is the removal of electrons from a molecule and results in a decrease in the energy content of the molecule, and because most biological oxidations involve the loss of hydrogen atoms (that includes an electron), they are called dehydrogenation reactions (take H off).

(e- + H+ = H)

*H has energy!

-When a substance is oxidized, the liberated hydrogen atoms do not remain free in the cell but are transferred immediately by coenzymes to another compound.

*grab on to H; B-vitamins

-Two coenzymes are commonly used by living cells to carry hydrogen atoms:

1. Nicotinamide adenine dinucleotide (NAD+ ) (from niacin)

2. Flavin adenine dinucleotide (FAD) (from riboflavin)

*get H=reduced

Reduction

Reduction is the opposite of oxidation, that is, the addition of electrons to a molecule, usually accompanied by a proton.

Oxidation and Reduction reactions are always ___

coupled

• Whenever a substance is oxidized, another is almost simultaneously reduced.

• This coupling of reactions is simply referred to as oxidation-reduction (redox) reactions

Carb Metabolism: what gets the first crack at it?

-During digestion, polysaccharides and disaccharides (bc amylase) are converted to monosaccharides (primarily glucose; bc BBE), which are absorbed into capillaries in intestinal villi and transported to the liver via the hepatic portal vein.

-Liver cells convert much of the remaining fructose and practically all of the galactose to glucose, so carbohydrate metabolism is primarily concerned with glucose metabolism.

Fate of Carbs

-Glucose is the body's preferred source for synthesizing ATP when it makes up the bulk of nutrient intake and also during high intensity exercise because it yields more energy per liter of VO2. Yet, the fate of absorbed glucose depends on the energy needs of body cells.

1. Catabolism including oxidation to reform ATP (ADP + Pi = ATP) (*breakdown 100% over time; for energy)

2. Glycogenesis (*store as glycogen; ex: if eat)

3. Amino acid synthesis

4. Lipogenesis

^3 & 4: certain circumstances/if excess calories so convert to AA and fat; more likely convert to fat but that takes energy; so stop fat burn, burn carbs, and store fat normally burn

Glucose Catabolism

-Complete oxidation of glucose to reform ATP occurs in every cell of the body, beginning in the cytoplasm w/ glycolysis and finishing in the mitochondria (except red blood cells, which lack mitochondria).

*glycolysis in cytoplasm bc where actin and myosin are

*ATP in mito has to get out

-Complete oxidation of glucose (or other food monomers) to CO2 and H2O (in the presence of O2) produces large amounts of energy and is called cellular respiration.

-Complete glucose oxidation occurs in four successive stages (Fig 4.9)

1. Glycolysis (occurs in the cytoplasm)

2. Formation of acetyl coenzyme A (acetyl CoA)

3. Krebs cycle

4. Oxidative phosphorylation (the electron transport chain)

*2-4: in mito

Glycolysis

-Anaerobic breakdown of glucose (6-C molecule) into two pyruvate molecules (3-C)

-Under “anaerobic” conditions (when ATP demand is high), pyruvate is reduced to lactate. (if rate fast)

-Under aerobic conditions, pyruvate is converted to acetyl CoA and enters the Krebs cycle. (if rate slow)

-After glycolysis, there is a net production of 2 molecules of ATP.

*No CO2 produced so no C lost; no O2 used

*22222222302222222222230 (but if only 1 glucose molecule would want to do aerobic)

Formation of acetyl CoA

-Each pyruvate is transported into the mitochondria and prepared for entrance into the Krebs cycle by conversion to a two-carbon compound (acetyl group) followed by the addition of coenzyme A (CoA) to form acetyl CoA (2C). Thus, our first CO2 molecule is released.

-Coenzyme A is derived from pantothenic acid, a B vitamin (*no known UL; ushers molecule to next step/Krebs)

-The decarboxylation (remove C) of pyruvate requires thiamin (B vit) and magnesium.

Krebs Cycle (/citric acid cycle/TCA clyce)

*yield H

-This process involves a series of biochemical reactions that occur in the matrix of mitochondria and acts to harness chemical energy primarily in the form of H atoms (protons and electrons).

-Thus, the formation of acetyl CoA and the subsequent Krebs cycle produce:

•CO2; NADH+; H+; FADH2; GTP (guanosine triphosphate, the equivalent of ATP)

-The energy originally in glucose and then each pyruvate is primarily in the reduced coenzymes NADH + H+ and FADH2, because they have the H atoms

ETC