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Nutrition Ch. 7
Metabolism
79
Science
Not Applicable
10/20/2005

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Term
Metabolism
Definition
The sum total of all the chemcial reactions that go on in living cells. Energy metabolism includes all the reactions by which the body obtains and spends energy from food.

Example: Nutrients provide the body with FUEL and follows them through a series of reactions that release energy from their chemical bonds. As the bonds break, they release energy in a controlled version of the process by which wood burns in a fire.
Term
Energy metabolism
Definition
All of the chemical reactions through which the human body acquires and spends energy from food
Term
Anabolism
Definition
Small compounds joined together to make largers ones; energy must be used in order to do this

Ana = up
Term
Catabolism
Definition
Larger compounds BROKEN down into smaller ones; energy is RELEASED

kata = down
Term
Coupled reactions
Definition
Energy released from the breakdown of a large compounds is used to drive other reactions
Term
ATP
Definition
Adenosine triphosphate; energy currency of the body -- produced when large compounds are broken down

ATP is used to make large compounds from smaller ones.
Term
Ribosomes
Definition
Cellular machinery used to make proteins
Term
Mitochondria
Definition
Where energy is derived from fat, CHO, protein via TCA cycle, electron transport chain
Term
Coenzyme
Definition
Complex organic molecules that work with enzymes to facilitate the enzymes' activity. Many coenzymes have B vitamins as part of their structures.

co = with
Term
Cofactor
Definition
The general term for substances that facilitate enzyme action is cofactors; they include both organic coenzymes such as vitamins and inorganic substances such as minerals
Term
Enzymes
Definition
Protein catalysts - proteins that facilitate chemical reactions without being changed in the process
Term
Metalloenzyme
Definition
Enzymes that contain one or more minerals as part of their structure
Term
BREAKING DOWN NUTRIENTS FOR ENERGY

CHO (Carbohydrate)
Definition
CHO - glucose (6 carbons)
Term
BREAKING DOWN NUTRIENTS FOR ENERGY

Fat
Definition
TG's - glycerol (3 carbons) + fatty acid (typically 18 carbons)
Term
BREAKING DOWN NUTRIENTS FOR ENERGY

Protein
Definition
Protein - amino acids

2C-N, 3C-N, or 5C-N
Term
BREAKING DOWN NUTRIENTS FOR ENERGY

New Compounds
Definition
Pyruvate (3 carbons)

Acetyl CoA (2 carbons)
Term
GLUCOSE BREAKDOWN
Definition
CHO - glucose (6 carbons) - pyruvate (3 carbons)
Term
GLUCOSE BREAKDOWN

With oxygen present = aerobic
Definition
Glucose (6C) - pyruvate (3C) - acetyl CoA (2C) - TCA cycle
Term
GLUCOSE BREAKDOWN

With inadequate oxygen present = anaerobid
(during strenous exercise)
Definition
Glucose (6C) - Pyruvate (3C) - Lactic acid
Term
GETTING RID OF LACTIC ACID

Cory Cycle (liver repackages lactic acid as glucose)
Definition
Glucose (6C) - Pyruvate (3C) - Lactic acid - liver - glucose - back to blood - muscles (stored as glycogen)
Term
FAT BREAKDOWN


Trigycerides
Definition
TG's - 3 fatty acids + glycerol
Term
FAT BREAKDOWN
TG's - 3 fatty acids + glycerol

Glycerol may be convered to
Definition
glucose or pyruvate depending on the cells needs; glucose is made if the blood glucose is low; pyruvate is made if energy is needed (will be broken down further in the TCA cycle)
Term
FAT BREAKDOWN
TG's - 3 fatty acids + glycerol

Fatty acids may be converted to
Definition
acetyl CoA and proceeds through TCA cycle; requires oxygen to do this (an aerobic process)
Term
FAT BREAKDOWN
TG's - 3 fatty acids + glycerol

Can you make glucose from fatty acids?
Definition
NO!!!!!
Term
PROTEIN BREAKDOWN

Use of protein depends upon
Definition
cells needs and availablity of glucose

Note: before amino acids maybe used, they must be deaminateed (nitrogen group removed)
Term
PROTEIN BREAKDOWN

If glucose is needed....
Definition
Protein - amino acid (deaminated) - glucose

(Glucose is used by the brain, red blood cells)
Term
PROTEIN BREAKDOWN

If energy is needed and glucose level is adequate....
Definition
Protein - amino acid (deaminated) - glucose - pyruvate - aceytl CoA - TCA cycle

Note: Some amino acids enter pathway and are converted to acetyl CoA, some amino acids enter the TCA cycle directly.
Term
PROTEIN BREAKDOWN

Deamination
Definition
amino acic - keto acid (NH3)

keto acid - non-essential amino acid (NH3)
Term
PROTEIN BREAKDOWN

Transamination
Definition
A method for making non-essential amino acids; B6 needed for this process

amino acid A + keto acid B = keto acid A = amino acid B
Term
GETTING RID OF AMMONIA PRODUCED FROM DEAMINATION

Urea cycle
Definition
Ammonia is toxic; must be converted to nontoxic compound immediately; liver packages ammonia as UREA; kidneys excrete UREA

High protein intake creates more work for kidneys; if eating high protein diet increase water intake to keep urea soluble
Term
ELECTRON TRANSPORT CHAIN (an aerobic process, requires oxygen)

Process?
Definition
1. Once acetyl CoA (2 carbon) enters the TCA cycle it quickly combines with a 4 carbon compound to create a 6 carbon compound
2. 2 carbons are lost during one turn of the cycle -- they are lost as CO2
3. There are also a number of HYDROGENS that are pulled off compounds and transferred to NAD which carries hydrogens
4. These HIGH ENERGY HYDROGEN atoms (high energy since they desperately want to combine with another molecule/atom so there will be 2 shared electrons) are transferred to NAD (niacin) and FAD (riboflavin) to electron transport chain
5.At the electron transport chain, HIGH ENERGY HYDROGENS (electrons) are take down a series of three little (waterfall) reactions to harness this energy -- ATP's are produced in this series of reactions
Term
FEASTING

What happens to excess CHO's?
Definition
1. CHO's used first to replenish glycogen stores

2. Extra is converted to fat

CHO - glucose - pyruvate - acetyl CoA - fatty acids OR CHO - glucose - gylcerol + (see notes)
Term
FEASTING

What happens to excess Fat?
Definition
Triglycerides stored directly into fat tissues, no breakdown required (except for chylomicron formation in GI)
Term
FEASTING

What happens to excess protein?
Definition
1. Dispose of Nitrogen group first via deamination

2. keto acid (amino acid minus nitrogen group) may enter metabolic pathway at pyruvate, acetyl CoA stage - acetyl CoA - fatty acids - TG's

*Some protein will be used to replenish glycogen stores
Term
FASTING

What happens if you fast less than 24 hours?
Definition
Will use up glycogen stores in liver and muscle tissue
Term
FASTING

What happens if you fast LONGER than 24 hours, but less than 3-4 days?
Definition
Will begin gluconeogenesis using muscle tissue protein to generate new glucose (about 90% of glucose supplied by breaking down muscle tissue; fat (via glycerol) contributes only 10%)
Term
FASTING

What happens if you fast LONGER THAN 3-4 DAYS?
Definition
Body shifts to KETOSIS to preserve muscle tissue; ketone bodies are 2 acetyl CoA' stuck together; some brain tissue is able to use ketone bodies for energy instead of glucose, which helps to preserve muscle tissue
Term
FAD DIETS

Fad diets which promote eating only protein and fat will result in...
Definition
KETOSIS after 24 hours of diet
Term
ALCOHOL AND NUTRITION

Historical findings show humans have used alcohol for over...
Definition
5000 years
Term
ALCOHOL AND NUTRITION; Biochemisty

ethanol
Definition
alcohol in fermented beverages
Term
Fuel
Definition
Compounds that cells can use for energy. The major fuels include glucose, fatty acids, and amino acids; other fuels include ketone bodies, lactic acid, glycerol and alcohol.
Term
Photosynthesis
Definition
The process by which green plants use the sun's energy to make carbohydrates from carbon dioxide and water.

photo = light
synthesis = put together (making)
Term
Name one of the body's high-energy molecules, and describe how it is used.
Definition
ATP (adenosine triphosphate) is a common high-energy compound composed of a purine (adenine), a sugar (ribose) and three phosphate groups.

During digestion the energy-yielding nutrients - carbohydrates, lipids, and proteins - are broken down to glucose (and other monosaccharides), glycerol, fatty acids, and amino acids. Aided by enzymes and coenzymes, the cells used these products of digestion to build more complex compounds (anabolism) or break them down further to RELEASE ENERGY (Catabolism). THE ENERGY RELEASED DURING CATABOLISM MAY BE CAPTURED BY HIGH ENERGY COMPOUNDS SUCH AS ATP.
Term
What are the coenzymes, and what service do they provide in metabolism?
Definition
MEtabolic reactions almost always require enzymes to facilitate their action. In many cases, the enzymes need assistants to help them. Enzyme helpers are called coenzymes. Coenzymes are complex organic molecules that associate closely with most enzymes, but are not proteins themselves. Without its coenzyme, an enzyme cannot function.
Term
Name the four basic units, derived from foods, that are used by the body in metabolic transformations.

How many carbons are in the "backbones" of each?
Definition
Glucose - 6 carbons

Glycerol - 3 carbons

Fatty acid - even number of carbons (commonly 16 or 18)

Amino acid - 2, 3 or more carbons with a Nitrogen attached
Term
Define aerobic and nonaerobic metabolism. How does insufficient oxygen influence metabolism?
Definition
aerobic - requiring oxygen

anaerobic - not requiring oxygen

an = not

Anaerobic pathway yield energy quickly, but cannon be sustaned for long - a couple of minutes at most. You would use this type of pathway during a sprint.

Conversely, the aerobic pathways produce energy more slowly, because they can be sustaned for long period of time, their total energy yield is greater. This is the pathway you use most often, even at rest.
Term
How does the body dispose of excess nitrogen?
Definition
The liver continuously produces small amounts of ammonia in deamination reactions (removing nitrogen from amino acids). Some of this ammonia provides the nitrogen needed for the synthesis of nonessential amino acids. The liver quickly combines any remaining ammonia with carbon dioxide to make urea, a much less toxic compound. The liver releases the urea into the bloodstream and it is taken up and excreted by the kidneys.
Term
Summarize the main steps in the metabolism of glucose, glycerol, fatty acids and amino acids.
Definition
The digestion of carbohydrates yields glucose (and other momosaccharides): some is stored as glycogen, and some is broken down to pyruvate and acetal CoA to provide energy. The acetyl CoA can then enter the TCA cycle and electron transport chain to provide more energy.

The digestion of fat yields glycerol and fatty acids; some are reassembled nd stored as fat, and others are broken down to acetyl CoA, which can enter the TCA cycle and electron transport chain to provide energy.

The digestion of protein yields amino acids, most of which are used to build body protein or other nitrogen-containing compounds, but some amino acids may be broken down through the same pathways as glucose to provide energy. Other amino acids enter directly into the TCA cycle, and these, too, can be broken down to yield energy.

In summary, although carbohydrate, fats and protein enter the TCA cycle by different routes, the final pathways are common to all energy-yielding nutrients.
Term
Describe how a surplus of the three energy nutrients contributes to body fat stores.
Definition
ALL EXCESS NUTRIENTS STORED AS FAT!!!

Carbohydrate - broken down to glucose - used for liver and muscle glycogen stores - excess stored as FAT

Fat - broken down to fatty acids - stored directly as FAT

Protein - broken down to amino acids - used for body proteins - some loss of nitrogen in urine (urea) and then excess stored as FAT
Term
What adaptations does the body make during a fast?
Definition
*Increasing the breakdown of fat to provide energy for most of the cells

*Using glycerol and amino acids to make glucose for the red blood cells and central nervous system

*Producing keytones to fuel the brain

*Supressing appetite and slowing metabolism.

All these measures conserve energy and minimize loses.
Term
What are ketone bodies?
Definition
Ketone bodies are compounds produced during the imcomplete breakdown of fat when glucose is not available.

Ketosis is a sign that the body's chemisty is going awry; Ketosis is the body's way to use its fats stores to fuel the brain by using ketones as an alternature fuel source. The brain prefers glucose.
Term
Define ketosis
Definition
An undesirably high concentration of ketone bodies in the blood and urine.

Ketosis is the body's way to use its fats stores to fuel the brain by using ketones as an alternature fuel source, when glucose is limited (during starvation).
Term
Distinguish between a loss of fat and a loss of weight, and describe how each might happen.
Definition
Weight loss can be caused by shrinkage in the mass of organ tissues and wasting of muscles (due to starvation, fasting, etc.) Because of slowed metabolism during these conditions FAT loss may actually be at a minimum, less that it would be on a low-calorie diet, when at least SOME food is eaten.
Term
Hydrolysis is an example of:

a) coupled reaction
b) anabolic reaction
c) catabolic reaction
d) synthesis reaction
Definition
b) catabolic (breaking)
Term
During metabolism, released energy is captured and transferred by:

a) enzymes
b) pyruvate
c) acetal CoA
d) adenosine triphosphate
Definition
d) adenosine triphosphate (ATP)
Term
Glycolysis:

a) requires oxygen
b) generates abundant energy
c) converts glucose to pyruvate
d) produces ammonia as a by-product
Definition
c) converts glucose to pyruvate
Term
The pathway from pyruvate to acetyl CoA:

a) produces lactic acid
b) is known as gluconeogenesis
c) is metabolically irreversible
d) requires more energy that it produces
Definition
c) is metabolically irreversible
Term
For complete oxidation, acetyl CoA enters:

a) glycolysis
b) the TCA cycle
c) the Cori cycle
d) the electron transport chain
Definition
b) the TCA cycle
Term
Deamination of an amino acid produces:

a) vitamin B and energy
b) pyruvate and acetyl CoA
c) ammonia and a keto acid
d) carbon dioxide and water
Definition
c) ammonia and a keto acid
Term
Before entering the TCA cycle, each of the energy-yielding nutrients is broken down to:

a) ammonina
b) pyruvate
c) electrons
d) acetyl CoA
Definition
d) acetyl CoA
Term
The body stores energy for future use in:

a) proteins
b) acetl CoA
c) triglycerides
d) ketone bodies
Definition
c) triglycerides
Term
During a fast, when glycogen stores have been depleted, the body begins to synthesize glucose from:

a) acetyl CoA
b) amino acids
c) fatty acids
d) ketone bodies
Definition
b) amino acids
Term
metabolism **
Definition
all of the chemical reactions which take place in the body
Term
energy metabolism **
Definition
all of the chemical reactions through which the human body acquires and spends energy from food
Term
anabolism **
Definition
small compounds joined together to make larger ones; energy must be USED in order to do this
Term
catabolism **
Definition
larger compounds broken down into smaller ones; energy is RELEASED
Term
coupled reaction **
Definition
energy released from the breakdown of large compounds used to drive other reactions
Term
ATP **
Definition
adenosine triphosphate - the body's energy currency; produced when large compounds are broken down; ATP is USED when smaller compounds are made into larger ones
Term
ribosomes **
Definition
cellular machinery used to make proteins
Term
mitochondria **
Definition
where energy is derived from fat, CHO, protein via TCA cycle, electron transport chain
Term
Breaking down nutrients for energy

CHO's
Fats
Protein

What do they break down to and how many carbons do they each have?
Definition
CHO - glucose (6c)
TG's - glycerol (3c) + fatty acid (typically 18c)
Protein - amino acids (2C-N, 3C-N, or 5C-N)
Term
Breaking down nutrients for energy

New compounds; number of carbons
Definition
Pyruvate (3c)

acetyl CoA (2c)
Term
Glucose Breakdown

CHO (glucose 6c) - pyruvate (3c)

With oxygen present.....
Definition
aerobic

glucose (6c) - pyruvate (2c) - Acetyl CoA (2c) - TCA cycle
Term
Glucose Breakdown

CHO (glucose 6c) - pyruvate (3c)

Without oxygen present.....
Definition
withinadequate oxygen = anaerobic
(during strenuous exercize for 1-3 minutes)

glucose (6c) - pyruvate (3c) - LACTIC ACID
Term
Getting rid of Lactic Acid:

Cori Cycle (liver repackages lactic acid as glucose)
Definition
glucose (6c) - pyruvate (3c) - lactic acid - liver - glucose - back to blood - muscles (stored as glycogen)
Term
Fat breakdown:

TG's 3 fatty acids + glycerol
Definition
A) GLYCEROL may be converted to glucose OR pyruvate depending upon cells needs, glucose is made if blood glucose is low -- pyruvate is made if enertgy is needed (will be broken down further in TCA cycle)

B) FATTY ACIDS may be converted to acetyl CoA and proceeds through TCA cycle -- requires oxygen to do this; and aerobic process
Term
Can you make glucose from fatty acids?
Definition
NOOOOOO!!!!! Only the glycerol portion of TG's can be coverted to glucose.
Term
Protein breakdown: Use of protein depends on cells needs, availability of glucose.

Note: Before amino acids can be used, they must be deaminated - take off Nitrogen group

1) If glucose is needed....
2) If energy is needed and glucose lovel is ade
Definition
1) protein - amino acid (deaminated - glucose; glucose used by brain, red blood cells

2) protein - amino acid (deaminated) - glucose - pyruvate -acetal CoA - TCA cycle
Note: some amino acids enter pathway and are converted to acetyl CoA, soem amino acids enter the TCA cycle directly

3) amino acid - keto acid (NH3)

keto acid - non-essential amino acid (NH3)

4) a method for making non-essential amino acids; B6 needed for this process

amino acid A + keto acid B - keto acid A + amino acid B
Term
Getting rid of ammonia produced from deamination
Definition
A) urea cycle (ammonia is toxic; must be converted to nontoxic compound immediately; liver packages ammonia as UREA; kidneys excrete urea

B) high protein intake creates more work for the kidneys; if eating a high protein diet increase water intake to keep urea soluble
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