Metabolism And Homeostasis I: Nutrition

Front 1

For an adult, what percentage of the diet should be made up of each of the three macronutrients? (This one really depends on the lecture you look at...)

Back 1

Carbohydrates: 45-65%; Protein: 10-35%; Fat: 20-35%

So basically, Carbs > Fat > Protein

Front 2

How much water (including that in food) is suggested per day for men? For women?

Back 2

Men: 3.7L; Women: 2.7L

Front 3

What nutrient should women who may become pregnant supplement?

Back 3

Folate

Front 4

Neural tube defects have decreased since 1998 due addition of what micronutrient into flour & pasta?

Back 4

Folate

Front 5

Total energy expenditure is based on which 3 factors?

Back 5

BMR; Thermic (Digestion, metabolism, conversion); Activity

Front 6

Caloric requirements peak at approximately what age for males?

Back 6

18

Front 7

Which BMI is classified as underweight?

Back 7

< 18.5

Front 8

Which is the first step in energy generation in cells which is irreversible?

Back 8

Pyruvate => Acetyl-CoA

Front 9

Which of the following has the largest amount of stored energy? (Glycogen, Glucose, Fatty Acids, Pyruvate)

Back 9

Glycogen is considered a large form of stored energy. Glucose and Fatty Acids are intermediate, and mainly used for transport and regulation, while pyruvate is coupled to ATP synthesis.

Front 10

Catabolism refers to _______ of macromolecules, while Anabolism refers to ________ of macromolecules. (Breakdown, Synthesis)

Back 10

Catabolism: Breakdown (causing energy release); Anabolism: Synthesis (requiring energy)

Front 11

Uptake and metabolism of which dietary carbohydrate occurs mainly in the liver, and not in peripheral tissues?

Back 11

Fructose

Front 12

Conversion of glucose to pyruvate is termed what? What is released during this process? Which molecule is required to sustain this conversion?

Back 12

Glycolysis. ATP is generated. NAD+ is required to sustain the process.

Front 13

What are four possible outcomes for pyruvate?

Back 13

ATP via TCA cycle; Lactate; Fatty Acids/TGs; Amino Acid building blocks

Front 14

How does excess glucose get stored as fat in adipose tissue?

Back 14

Some glucose will be converted into pyruvate, which will be converted to Acetyl-CoA, then finally to fatty acids. As this is happening, some glucose gets converted into glycerol. Fatty acids combine with glycerol to form Triglycerides, which are stored in adipose tissue.

Front 15

In hypoxic environments or in mitochondrial defects, what byproduct is produced, and why?

Back 15

Lactate is produced. If the TCA cycle is inhibited, glycolysis will be upregulated to form more ATP. Glycolysis requires NAD+, which is formed by the conversion of pyruvate (the end-product of glycolysis) to lactate. Thus, lactate is secreted in excess.

Front 16

Which cells are entirely dependent on glycolysis for energy production?

Back 16

Red blood cells, as they do not contain mitochondria.

Front 17

What the function of Acetyl-CoA inhibiting its own precursor (pyruvate) upon entering the TCA cycle?

Back 17

Inhibiting the conversion of pyruvate to acetyl-CoA ensures that there is enough pyruvate to fuel certain pyruvate-requiring TCA cycle intermediates.

Front 18

Fatty acid oxidation results in which compound?

Back 18

Acetyl-CoA

Front 19

Ketogenesis occurs primarily in which organ?

Back 19

Liver (and some in kidney)

Front 20

Under what circumstances does ketogenesis occur? Why does it occur?

Back 20

Depletion of glucose-dependent TCA cycle intermediates forces alternative breakdown of fatty acids into Acetyl-CoA. Since the TCA cycle does not have enough intermediates to proceed, and an excess of Acetyl-CoA is being produced, it needs to be converted to another form - ketone bodies.

Front 21

Theoretically, how can protein digestion prevent ketoacidosis in the absence of glucose?

Back 21

Proteins are broken down into amino acids, which can be glucogenically synthesized into TCA cycle intermediates.

Front 22

Why can muscle wasting occur in cases of malnutrition despite adequate fat stores?

Back 22

Despite the presence of fat, breakdown of muscle protein into amino acids occurs in an attempt to replenish TCA cycle intermediates.

Front 23

Can Acetyl-CoA function as a glucose precursor?

Back 23

No. The conversion of pyruvate to acetyl CoA is a one-way step, and cannot go backwards to form glucose.

Front 24

What makes Omega 6 & Omega 3 fatty acids special?

Back 24

They are essential (i.e. we cannot produce them from the conversion of Acetyl-CoA to fatty acids). They have double bonds which are further down the carbon chain that we are capable of synthesizing biologically. These are useful as hormone precursors and cell walls.

Front 25

Following conversion of amino acids to pyruvate, how is the excess ammonium disposed of?

Back 25

Urea is produced, which includes the ammonium/amino group. This is then excreted in the urine.

Front 26

A large factor in cell membrane fluidity is the amount of ________ in the lipids composing the bilayer.

Back 26

Kinks/Double bonds

Front 27

Metabolites of fatty acids that are 20 carbons long are called what?

Back 27

Eicosanoids

Front 28

Eicosanoids are used by the body to serve as which three classes of molecules?

Back 28

Prostacyclin (Antiaggregatory); Thromboxane (Proaggregatory); Leukotriene (Promotes white blood cell adhesion)

Front 29

NSAIDs target cyclooxygenases, which are synthesized from arachidonic acid. What is arachidonic acid metabolized from?

Back 29

Fatty acids. Fatty acid metabolism is a common target in drugs (including steroids)

Front 30

Why is whole milk better for developing children than skim milk?

Back 30

We don't want protein to be burned as a fuel, as excess nitrogen is a strain on the developing kidneys. The fat plays a bit of a structural role, not necessarily a nutrient one.

Front 31

What is one particular problem with the calculation of BMR?

Back 31

It implies that age is a linear variable.

Front 32

What is the energy released per gram for each of the macronutrients?

Back 32

Fat: 9 kcal/g
Protein: 4 kcal/g
Carbohydrates: 4 kcal/g

Front 33

What are seven categories to ask about when assessing malnutrition? (Subjective global assessment)

Back 33

Weight change; Dietary intake; Gastrointestinal symptoms; Functional impairment; Muscle wasting; Subcutaneous fat loss; Edema

Front 34

Why is grapefruit intake important when discussing medications?

Back 34

It is a CYP450 3A4 inhibitor, which is the enzyme used in the metabolism of many drugs.

Front 35

Why are "binders" problematic (eg: calcium, iron, tannins)?

Back 35

They may decrease absorption

Front 36

Iron deficiency, Zinc deficiency and B2 deficiency can all present with which problem?

Back 36

Angular chelitis

Front 37

Small, local, involuntary muscle contraction and relaxation is termed what?

Back 37

Fasciculation

Front 38

Approximately what percentage of meal calories contributes to the body's thermic energy?

Back 38

10%

Front 39

Why is thiamine supplementation important in cases of malnourishment?

Back 39

Thiamine is required for the TCA cycle to occur, thus if carbohydrates are supplemented without thiamine, lactate formation will be induced, causing a toxic byproduct and leading to Wernicke-Korsakoff's syndrome (neurological condition)

Front 40

Metabolization of glucose can occur in which three ways?

Back 40

Conversion to glycogen stores; Conversion to glycerol; Conversion to pyruvate via glycolysis

Front 41

In which three ways does protein contribute to energy production?

Back 41

Conversion to pyruvate (glucogenic); Conversion to TCA cycle intermediates (glucogenic); Conversion to Acetyl-CoA (ketogenic)