A small molecule involved in the

1. Degredation of biopolymers and the

2. Interconversion of chemical compounds

The breakdown of biomolecules to produce

1. Energy

2. Building blocks

It is the conversion of fuel into energy - It produces energy

The biosynthesis of complex molecules from small precursor molecules from reductive (energy using) pathways.

The synthesis of larger molecules from smaller ones.

It store energy and build molecules

It is conserved in 3 types of molecules

1. Nucleoside triphosphates (ex- ATP, GTP)
2. Reduced coenzymes (ex- NADH, NADPH, FADH2, FMNH2)
3. Acetyl Coenzyme A (acetyl CoA)

Metabolic pathways are designed to meet specific cellular needs.

One pathway can create metabolites for use in other pathways

5.1. What is a substrate cycle?

5.2. How is futile cycling avoided?

5.1. One pathway that uses separate, "reciprocally related" enzymes to move forward and backward.

• Ex- Glycolysis & Gluconeogenesis

5.2. The "reciprocally related" enzymes control which way the metabolites of the reaction go.

• When the enzymes of 1 pathway are "on," the other set is "off," thereby preventing futile cycling

Metabolic pathways are compartmentalized

1. In cells, pathways are compartmentalized in specific organelles. - Ex- Glycolysis occurs in cytoplasm and ETC occurs in mitochondria
2. In multicellular organisms, matabolic pathways are compartmentalized by specialization of tissues

8-9. How many Kcals are obtained by the complete oxidation of food to CO2 and H2O for. . .

1. Carbs
2. Proteins
3. Fats and
4. Alcohol

1. Carbs     = 4 Kcal/g
2. Proteins  = 4 Kcal/g
3. Fat         = 9 Kcal/g 4
4. Alcohol   = 7 Kcal/g

1. Linoleic Acid

2. ɑ-Linolenic Acid

We have 9 essential proteins.

Having the proper nitrogen balance is essential

Food is broken down by enzymes into its smallest units

1. Carbs -----> Monosaccharides (ex- glucose)
2. Fats ------> Emulsified in the intestine by bile salts forming Chylomicrons
3. Proteins ------> Amino Acids

These nutrients are absorbed by the intestinal epithelia

1. It stimulates the production of insulin by the pancreas
2. It stimulates cells to take up glucose
3. It decreases glucagon levels in the blood

1. Liver- Glucose is metabolized to form ATP for immediate needs and stored as glycogen
2. Brain- Brain can't use fats so glucose is the brain's major energy source
3. Red Blood Cells- RBCs have no mitochondria so glucose is its only source of energy
4. Muscles- Glucose used for energy and stored as glycogen
5. Adipose Tissue- Glucose provides glycerol moiety for making triacylglycerols for storage

1. Liver- Fat is converted to Chylomicrons and vLDL by the Liver (they transport TGs and cholesterol in the blood)
2. vLDL binds to adipose cells where the TG is degraded to a free FA, which is transported into adipose cell, reformed to Triacylglycerol (using glycerol formed from blood glucose), and stored as fat droplet in cell
3. vLDL cleared by liver or converted to LDL

1. Taken up by tissues (mostly muscle)
2. Used to synthesize new proteins
3. Oxidized to yield energy or important metabolites (Ex- ATP, hormones, neuotransmitters, etc.)
4. Dietary AAs are mixed with AAs from degraded proteins to form new proteins

1. Fats- converted to triglycerides and stored as adipose tissue
2. Carbs- converted to glucose and stored as glycogen OR converted to fatty acids and stored as triglycerides in adipose tissue
3. AAs stored in muscles

1. Glucose comes from Liver
2. Fats come from Adipose Tissue
3. AAs come from Muscle

Adipose Tissue provides Triacylglycerol, which provides FAs (the major source of fuel when fasting)

1. FAs are oxidated to acetyl CoA to make ATP
2. Glycerol backbone is used for gluconeogenesis

1. Maintains blood glucose levels (for brain and RBCs)
2. Takes FAs and produces Ketone Bodies (which are used by muscle and kidneys for energy)

1. Emphasis shifts away from producing glucose as the major fuel source, which results in
   1. Muscle being spared since AAs aren't used to make glucose
   2. Less AA degradation means less excess nitrogen means less urea 
2. Muscle uses FA oxidation as primary fuel source

1. Brain utilizes Ketone Bodies to make acetyl CoA
2. Brain uses less glucose
   • More glucose available for RBCs

Pathways that require O2 to produce ATP

Ex- ETC

Pathways that operate (and produce ATP) in the absense of O2

Ex- Glycolysis

1. The ETC shuts down and doesn't use NADH
2. NADH builds up as a result
3. Glycolysis is inhibited

The body:

1. Utilizes what fuels it needs for immediate energy needs
2. Stores excess fuels.

1. What does insulin do
2. It signals what state

1. It stimulates cells to take in glucose
2. It signals the Fed State

To ensure enough glucose is provided to:

1. The Brain and
2. The RBCs

Low Insulin

&

High Glucagon

High Insulin

&

Low Glucagon

1. When do blood glucose levels peak?
2. What do blood glucoes levels signal?
3. What happens when insulin decreases?

1. About an hour after eating
2. Blood glucose signals the pancreas to produce insulin
3. Glucagon increases and liver goes from making glycogen (from glucose) to breaking down glycogen to glucose

1. How long after eating is the body in the "fasting range"?
2. What is the "fasting range"?

1. About 2 hours after eating
2. The "fasting range" is 80-100 mg/dL of glucose in blood

The basal state is the "post absorptive state." Occurs after having not eaten for ~ 12 hrs

1. Insulin is low
2. Glucagon is rising
3. Glycogen stores are low
4. Gluconeogenesis starts supplying glucose into blood
5. FAs directly oxidized to yield energy

1. Liver maintains blood glucose levels
2. FAs provide major source of energy
3. Ketone Bodies become an important source of energy
4. Brain continues to rely on blood glucose
   1. Comes from gluconeogenesis (primarily from AAs from protein degradation)
5. AA use in gluconeogenesis produces Nitrogen as a byproduct (converted to urea)

1. What is a long fast?
2. How can you differentiate between a short fast and a long fast?

1. Days and days with no food
2. In the Long Fast
   1. Brain uses Ketone Bodies (not glucose)
   2. Muscle is not giving up AAs as readily
   3. Liver is depleted

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Dashed lines indicate that the process is not easily done