Nutrition review exam2

Nutrition 101 Exam 2 Review Session

TAs: Helen Corless

and Delma Betancourt

Chapter 6Protein: Amino Acids

Which of the following atoms is not a component of carbohydrate or fat?

a) Hydrogen

b) Nitrogen

c) Oxygen

d) Carbon

Carbohydrates, lipids, and proteins are all composed of carbon, hydrogen and oxygen in various arrangements

But…protein is unique in that it also contains nitrogen

Which of the following differentiates amino acids from each other?

a) Number of carbon-carbon double bonds

b) The side group

c) The amino group

d) Hydrogenation

There are 20 different amino acids, each with its own unique side group

An amino acid that the body can synthesize is called:

a) Indispensable

b) Essential

c) Conditionally essential

d) Non-essential

Most amino acids are nonessential, meaning the body can synthesize them for itself (as long as building blocks are available)

Essential amino acids must come from the diet, because the body cannot make these in sufficient quantities (indispensable)

Conditionally essential: normally nonessential but must be supplied by diet under special circumstances (e.g. PKU -> tyrosine)

Proteins form when _______ bonds join amino acids in a ________ reaction.

a) Carbon; hydrolysis

b) Carbon; anabolic

c) Peptide; condensation

d) Peptide; catabolic

Peptide bonds link amino acids through condensation reactions (anabolic process) to form proteins

Remember: amino acids are the building blocks of proteins!

Which of the following describes the structure of a protein that is folded into complex, tangled shapes such that hydrophilic groups are on the surface and hydrophobic side groups are tucked inside

a) Primary

b) Secondary

c) Tertiary

d) Quaternary

Primary Structure

Secondary Structure

hydrophobic

hydrophilic

Tertiary Structure

Quaternary Structure

True or False: the sequence of amino acids determines the function of a protein

a) True

b) False

Sequence -> Shape -> Function

If there is a mutation in the sequence, then the protein may not function properly (e.g. sickle cell anemia)

This also explains why proteins that are denatured (uncoiled) no longer can perform their functions

Which of the following is true about protein digestion

a) Pepsin in the stomach begins break down of proteins into amino acids

b) Proteins are only uncoiled in the stomach, but are not digested

c) Hydrochloric acid in the stomach cleaves proteins into smaller polypeptides and amino acids

In stomach:Hydrochloric acid denatures proteins (uncoils them)Pepsin begins protein digestion by cleaving denatured proteins into smaller polypeptides and amino acids (hydrolysis)

In small intestine: Pancreatic and intestinal proteases and peptidases complete protein digestion

Which of the following is true of protein absorption?

a) Absorbed amino acids may be used by intestinal cells for energy

b) Amino acids enter the lymph system and bypass the liver to enter blood stream

c) Most proteins are absorbed intact and travel to the cells where they are needed

Once absorbed, amino acids may be used by the intestinal cells for energy or to synthesize needed compounds

Unused amino acids enter the blood stream and are transported to the liver

Most proteins are broken down into amino acids before absorption

Which of the following describes how proteins differ from carbohydrates and lipids

a) Protein is not a macronutrient

b) Protein cannot be used for energy

c) Protein has no specialized storage form

d) Protein is needed in larger amounts

Protein is a macronutrient, meaning it is a nutrient the body requires in relatively large amounts (many grams daily).

Protein can be used as a source of energy during times of starvation or inadequate carbohydrate intake (gluconeogenesis). Protein yields 4kcal/g

AMDR for protein is 10-35% which is actually the lowest of macronutrients (recommendation for fat is 20-35% and for carbohydrate is 45-65%)

The body does not make a specialized storage form of protein as it does for carbohydrate or fat

Glucose is stored as glycogen in the liver and fat as triglycerides in adipose tissue, but protein in the body is available only from the working and structural components of the tissues.

Over time, energy deprivation always causes wasting of lean body tissue

Amino acids in the “amino acid pool” of a cell can be used to make…

a) Protein

b) Energy

c) Fat

d) All of the above

The amino acid pool is made up of amino acids from protein turnover and from the diet

These amino acids can be used to make body proteins or other nitrogen-containing compounds, or they can be stripped of their nitrogen and used for energy (either immediately or stored as fat for later use)

Positive nitrogen balance occurs in which of the following situations:

a) Healthy adult

b) Starving child

c) Pregnant woman

d) Burn victim

Nitrogen balance refers to the amount of nitrogen consumed as compared to the amount of nitrogen excreted in a given time.

During periods of growth, such as pregnancy, nitrogen intake > nitrogen output (positive nitrogen balance)

In people who are starving or suffering other severe stresses, such as burns, injuries, infections, and fever, nitrogen intake < nitrogen output (negative nitrogen balance)

Which of the following organs filters urea out of the blood

a) Pancreas

b) Liver

c) Kidneys

d) Small intestine

Liver creates urea from the products of amino acid breakdown (NH3) and releases it into the bloodstream.

The kidneys filter urea out of the bloodstream for excretion in the urine

So...if you have liver disease, you will have high levels of ammonia in your blood (because the liver is not converting ammonia to urea), but if you have kidney disease, you will have high levels of urea circulating in your blood (because the kidneys are not filtering urea out of the blood.

Which of the following is not a function of protein in the body?

a) Acid base balance

b) Energy storage

c) Hormones

d) Antibodies

e) All of the above

The body does not have a specialized storage form of protein

The following are all functions of protein- Growth and maintenance- Enzymes- Hormones- Fluid balance- Acid-base balance- Transportation- Antibodies- Energy and glucose

A protein that contains all the essential amino acids is called a/an…

a) Complementary protein

b) Complete protein

c) Essential protein

A complete protein contains all the essential amino acids in the amounts we require (e.g. animal proteins, soy proteins)

An incomplete protein lacks one or more essential amino acids (e.g. most plant proteins)

Complementary proteins are two or more dietary proteins whose amino acid assortments complement each other, such that aa’s missing from one are supplied by the other

Which of the following describes the condition of chronic, severe protein-energy malnutrition that is characterized by muscle wasting

a) Marasmus

b) Kwashiorkor

Kwashiorkor results from acute protein deficiency and is characterized by abdominal swelling, edema, and muscle wasting with subcutaneous fat retention

Kwashiorkor may also result from an infection or illness

Chapter 7Energy Metabolism and

Alcohol

The only form of energy that can be used directly by the cells to do the work they need to do is called

a) Glucose

b) Pyruvate

c) Acetyl-CoA

d) ATP

ATP (adenosine triphosphate) is one of the main energy storage molecules and is the only form of energy that can be used directly by cells to do work

When the high energy bonds between phosphate groups in ATP are broken, energy is released; this energy can fuel another energy-requiring action (coupled reactions)

Energy released from the breakdown of carbohydrates, fats and proteins is captured in the form of ATP

TRUE or FALSE: Anabolic reactions release energy.

a) Trueb) False

Anabolic reactions require energy.ex. Creating bonds between glucose molecules to form glycogen

Catabolic reactions release energy.ex. Breaking down glycogen into glucose molecules

The break down of glucose is called:

a) Gluconeogenesisb) Glycolysisc) Glycogenolysis

Glycolysis is the metabolic breakdown of glucose, it does not require oxygen (anaerobic reaction)

Gluconeogenesis is the making of glucose from a non-carbohydrate source

Glycogenolysis is the breakdown of glycogen into individual glucose units

Glycolysis yields…

a) No energyb) 2 molecules of glucosec) 2 molecules of pyruvated) 2 molecules of acetyl CoA

Glycolysis is the metabolic breakdown of glucose to pyruvate.

1 glucose -> 2 pyruvate

Net energy yield from glycolysis is 2 ATP (releases 4 ATP, requires 2 ATP)

H atoms and electrons released in the process are carried by coenzymes (niacin) to the electron transport chain

Which of the following is not true of coenzymes?

a) They are facilitators of metabolic reactions

b) They are organicc) They associate with enzymesd) They are required for a metabolic

reaction to take place

While coenzymes themselves are not the facilitators of metabolic reactions, without them enzymes cannot function.

We can think of coenzymes as facilitators of enzymes.

Which of the following can be converted back into glucose

a) Acetyl CoA

b) Pyruvate

c) Fatty acids

Glycolysis is reversible, so pyruvate can be converted back to glucose to some extent in the body (kidneys and liver)

The conversion of pyruvate to acetyl CoA is not reversible, so acetyl CoA cannot be converted to glucose.

Recall that triglycerides are broken down into a glycerol head and three fatty acid tails.

Glycerol can be converted to pyruvate, which can then be converted to glucose

Fatty acids, however, can only be converted to acetyl CoA, which cannot be converted to pyruvate. Therefore fatty acids cannot be converted into glucose

In the anaerobic pathway, pyruvate is converted into

a) Lactate

b) Acetyl CoA

c) Oxaloacetate

d) Glucose

When the body needs energy quickly and not enough oxygen is available, pyruvate will enter the anaerobic pathway.

The lack of oxygen prevents the ETC from accepting the hydrogen ions attached to the coenzymes (from glycolysis).

In the anaerobic pathway, pyruvate is able to accept these hydrogens, becoming lactate (i.e. lactic acid).

This frees the coenzymes, allowing them to accept more hydrogens from glycolysis reactions (allows glycolysis to continue).

Remember glycolysis is an anaerobic rxn.

This is not efficient and not sustainable!

QUESTION:

If the anaerobic breakdown of glucose (to pyruvate to lactate) cannot be sustained for long periods of time, then how can runners sprint for minutes at a time?

ANSWER:

Endurance training can actually increase the number of mitochondria in the muscle cells. This increases the mitochondrias’ ability to keep pace with the muscles’ demand for energy.

TRUE or FALSE: Lactic acid can be converted back to pyruvate

a) True

b) False

TRUE or FALSE: Lactic acid can be converted back to pyruvate

a) True

b) False

Lactic acid can be converted back to pyruvate in the CORI cycle!

In the aerobic pathway, pyruvate is converted into…

a) Lactate

b) Acetyl CoA

c) Oxaloacetate

d) Glucose

e) None of the above

When oxygen is available, pyruvate will enter the aerobic pathway.

In this pathway, a carbon is cleaved from pyruvate and released as CO2

You can’t get that carbon back (you breathe it out) so this step is irreversible!

Which of the following is true about the TCA cycle?

a) It is the final step in energy metabolism

b) It generates lots of ATP

c) It generates lots of hydrogens and electrons

d) It requires energy

(FYI this is probably more difficult of a question than she would ask you)

The TCA cycle generates a lot of hydrogen ions and electrons which then enter the electron transport chain and power the synthesis of ATP.

The TCA cycle does not require any energy inputs and it does, in fact, yield some energy (but not much!)

The TCA cycle is not the last step in energy metabolism. It precedes the ETC which is the final step.

True or false: Increasing protein intake will not increase muscle development

a) True

b) False

A person cannot grow muscle simply by overeating protein, rather they will likely grow fat!

When a person overeats protein…1. Surplus used to replace normal daily

losses2. Increases protein metabolism

(displaces fat in the fuel mix)3. Additional protein is deaminated,

converted to fatty acids -> stored as fat

When excess carbohydrate is consumed…

a) The body uses more glucose for fuelb) Excess is stored as glycogenc) Excess is converted to fat directlyd) Both a and be) All of the above

When excess carbohydrate is consumed, the excess is stored as glycogen (limited)

Body uses more glucose for fuel when there is an excessive diet intake of carbohydrate (displaces fat in fuel mix)

Glucose can also be converted to fat directly, but this pathway is relatively minor and only occurs after glycogen stores have been filled

How glucose can be converted to fat:

Glucose -> Pyruvate -> Acetyl CoA

Acetyl CoA -> fatty acids

Fatty acids -> triglycerides stored in adipose tissue

Some important things to note about this diagram:• Glycerol can be converted to either glucose and pyruvate BUT neither

glycerol nor fatty acids can be used to make amino acids• Some amino acids can be converted to pyruvate (reversible), others

can be converted to acetyl CoA (irreversible) -> depends on the AA• Fatty acids can be converted to acetyl CoA (reversible), but since

acetyl CoA cannot be converted back to pyruvate, fatty acids cannot generate glucose

True or false: Increasing dietary fat intake will increase fat metabolism

a) True

b) False

Unlike excess protein and carbohydrate, which both enhance their own metabolism, eating too much fat does not promote fat metabolism.

Instead, excess dietary fat moves efficiently into the body’s fat stores

Possible short answer question:

Describe what happens when someone fasts for a short time. Explain where their body gets energy from and what it is used for.


Describe a few ways in which alcohol can negatively impact your health.

Possible answer:

• Nutrient displacement– Getting calories from alcohol displaces

calories from healthy foods– Can lead to nutrient deficiencies

• Interference with nutrient metabolism, especially the B vitamins (Folate, B6, B12, Thiamin)


What are some of the possible health benefits of consuming alcohol (within the recommended limits of 1 drink per day for women and 1 drink per day for men)?

Possible answer :

– Reduce risk of developing heart disease

– Reduce risk of dying of a heart attack

– Possibly reduce risk of strokes

– Lower risk of gallstones

– Possibly reduce risk of diabetes

Chapter 8 & 9Energy Balance and Weight

Management

What I think you should know…

• What are considered normal ranges for percentage body fat (men vs. women)

• Concept of energy balance as it relates to weight gain/loss

• Energy outputs: BMR, TEF, exercise

• Hyperplasia vs. hypertrophy

Possible short answer questions

• Describe some of the different ways to measure body composition and list a pro and con for each

• Explain one problem with using BMI to measure body fat

• Describe some of the causes of obesity

• Describe some treatment options for obesity

Nutrition review exam2

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