Human Nutrition Exam 2

Define peptide

chain of less than 50 amino acids

Define dipeptide

Chain with 2 amino acids

Define tripeptide

Chain of 3 amino acids

Define polypeptide

Chain of more than 10 amino acids

Define protein (structure relating to amino acids)

Chain of more than 50 amino acids

Define peptide bond

Bonds that link amino acids together

Define pepsinogen

The inactive form of pepsin

Define pepsin

Enzyme that breaks down proteins in the GI tract

What compound is needed to convert pepsinogen to pepsin?

Hydrochloric acid

Define kwashiorkor

buildup of fluids (edema) caused by a disruption in fluid balance from protein deficiency

Name all essential amino acids

1. Histidine

2. Isoleucine

3. Leucine

4. Lysine

5. Methionine

6. Phenylalanine

7. Threonine

8. Tryptophan

9. Valine

List some roles of proteins/amino acids in the body

1. synthesize new compounds

2. Gluconeogenesis

3. Converted to ATP or adipose tissue

What is an amino acid pool?

Collections found in cells or blood made of amino acids recycled from degraded proteins

Define transamination

synthesis of nonessential amino acids

Define deamination

Removal of an amine group from an amino acid

What happens to excess proteins in the body?

They are deaminated and converted to fatty acids, which allows them to be stored in adipose tissue

Define nitrogen balance

The amount of nitrogen (in protein) consumed compared to how much is excreted (in urea)

What are complete proteins?

Proteins that are digestible, contain all essential amino acids, and provide a sufficient amount of amino acids to synthesize nonessential amino acids

List a few sources of complete proteins

Animal products (meat and dairy), soy, quinoa

Define complementary proteins

combinations of food that provide all essential amino acids

What are some consequences of low protein intake?

• Slow cell turnover rate

• Impair immune function

• Disrupts fluid balance, possibly resulting in edema

• Marasmus

Define electrolyte

charged ions in a solution that can conduct current

Define ethanol

Type of alcohol that is safe for consumption

List some key roles of water in the body

• Key component of body fluids

• Transports nutrients and waste products

• Thermoregulation

• Lubrication of joints

• Component of mucus membranes

• Enables hydrolysis and condensation reactions

How does fluid balance affect blood pressure?

• High blood sodium levels stimulate the release of ADH

• ADH stimulates water reabsorption in the kidneys —> increasing blood volume and blood pressure

• Low blood sodium levels stimulate release of aldosterone

• Aldosterone promotes vasoconstriction —> increasing blood pressure

What minerals are typically found in tap water?

Calcium, magnesium, fluoride

What is hyponatremia?

Condition of low sodium levels in the blood caused by water intoxication

What is the standard drink size for beer?

12 oz

What is the standard drink size for wine?

5 oz

What is the standard drink size for hard liquor?

1.5 oz

How is alcohol metabolized?

It is either absorbed in the stomach or small intestine. In the stomach, alcohol can be metabolized by alcohol dehydrogenase. In the liver, alcohol is converted to acetate, and then fatty acids. Fatty acids are then stored in adipocytes

What are the short term effects of alcohol consumption?

• Diminished senses and judgement

• Impaired memory

• Loss of emotional control

• Impaired balance and movement

• Compromised breathing and heart rate

• Sleep disruption

• Hangovers

• Alcohol poisoning

What are the long term effects of alcohol consumption?

• Impaired digestion, absorption, and metabolism

• Weight gain

• Fatty liver disease

• Alcoholic hepatitis

• Cirrhosis

• Cancer

• Fetal alcohol syndrome

Define heme (ferrous) iron

Iron with a +2 charge that is a key component of hemoglobin and myoglobin. More bioavailable than nonheme iron

Define nonheme (ferric) iron

Iron with a +3 charge found in plant foods. This is the type of iron used in fortification

What vitamin improves the absorption of nonheme iron?

Vitamin C

What are the major roles of magnesium?

• Maintains bone health

• Needed for muscle and nerve function

• Cofactor in enzymatic reactions

What are some dietary sources of magnesium?

• Leafy greens

• whole grains

• nuts and legumes

• fruit

What is an important role of sulfate?

Important component of amino acids and some B vitamins

Food sources of sulfate

Animal products

What is the most common nutrient deficiency both in the US and worldwide?

Iron

Important functions for iron

• Component of hemoglobin and myoglobin

• Cofactor in energy metabolism

• Needed to produce WBCs

• Cofactor in antioxidant systems and neurotransmitter synthesis

Can iron be excreted?

No

Most common form of iron loss

Menstruation

How is iron absorption impacted by the environment of the GI tract?

• HCl in the stomach is needed to convert pepsinogen to pepsin and digest proteins

• MFP factor improves absorption

• Absorption increases when iron is low

• Excess minerals that use the same carrier proteins as iron inhibit iron absorption

Outline how iron is absorbed

1. Ferrous iron is converted to ferric iron

2. Ferric iron binds to ferritin for temporary storage

3. Transferrin transports ferric iron to the bloodstream

Important function of zinc

• Antioxidant

• Component of hormones and immune cells

• Taste perception

Food sources of zinc

Oysters

How is zinc absorbed?

Passively diffuses into enterocytes and is bound to albumin in blood

What are key functions of copper?

• Component of proteins needed for oxidation reaction

• Component of enzymes needed to oxidize iron

• Component of ETS

What are some food sources of copper?

Organ meats, seafood, nuts, seeds, whole grain

What is a key role of selenium?

Involved in thyroid hormone synthesis

What is a key function of fluoride?

Increases osteoblast activity

What is a major dietary source of fluoride?

Water

What is the key function of iodine and what can happen if one is iodine deficient?

Iodine is essential for proper thyroid function. Iodine deficiency can cause enlarged thyroid (goiter)

What can happen if a person experiences chronic zinc deficiencies in childhood?

Delayed sexual maturation and slow growth

How can overconsumption of minerals cause deficiencies of other minerals?

Minerals compete with each other for absorption

What is the biggest cause of iron toxicity and iron poisoning in children?

Supplements

Define creatine phosphate

storage form of phosphate in muscles that can rapidly convert ADP to ATP

Define ketogenic amino acids

Amino acids that can be converted to acetyl CoA

Define glucogenic amino acid

Amino acids that can be converted to glucose

Define beta oxidation

process of cleaving 2 carbon groups at a time from a fatty acid chain

What is the big picture process for how glucose is converted to ATP?

1. Glucose is converted to pyruvate via glycolysis

2. Pyruvate is converted to acetyl CoA

3. Acetyl CoA fuels the TCA cycle

4. TCA cycle fuels ETS

5. ETS generates ATP

What is the importance of vitamin B3 in glycolysis?

Vitamin B3 (Niacin) serves as an important coenzyme in the form of NAD+

How many pyruvate molecules are created per glucose molecule? How many carbons do they have?

1 6-carbon glucose is converted to 2 3-carbon pyruvates

What B vitamin other than niacin plays an important role in the TCA cycle?

Riboflavin (FAD2)

How much ATP is created at the end of the ETS?

30 ATP molecules

Are water-soluble vitamins stored in the body?

No - they are excreted in urine

How are water-soluble vitamins digested?

They are bound to proteins and separated in the stomach

How are water-soluble vitamins destroyed?

Heat, oxidation, light, or pH changes

What are some key functions of vitamin B1 (thiamin)?

• Key component of TPP in energy metabolism

• Needed for pentose synthesis for DNA and RNA synthesis

What are some dietary sources of vitamin B1/thiamin?

Whole grains, nuts, legumes, pork, enriched grains

Define beriberi

memory symptoms, nervous system impairment, and heart failure caused by thiamin deficiency

Define Wernicke-Korsakoff Syndrome

neurological disorder caused by extreme thiamin deficiency

What group of people are at a higher risk of thiamin deficiency? Why?

Alcoholics because alcohol contributes to malabsorption of thiamin

What is a major role of vitamin B2 (riboflavin)?

Component of FAD/FADH in the TCA cycle

What are some dietary sources of vitamin B2 (riboflavin)?

Milk, yogurt, enriched grains, spinach, almonds, eggs

What happens when someone is deficient in riboflavin?

Stomatitis (inflammation of the lining of the mouth), glossitis (inflammation of the tongue), and cheilosis (cracked lips)

What is a key role of vitamin B3 niacin?

Component of NAD/NADH

What are some dietary sources of B3 niacin?

Meat, fish, poultry, enriched grains, and fortified cereals

Define pellagra

Dermatitis, dementia, diarrhea, and death caused by niacin deficiency. Often associated with populations who eat a lot of corn

How can pellagra be avoided in populations who eat a lot of corn?

Soaking corn in water - niacin leached into the water and increases its bioavailability

What is a major role of pantothenic acid?

Component of acetyl CoA

What are some dietary sources of pantothenic acid?

Whole grains, nuts, legumes, meat, milk, eggs

Symptoms of pantothenic acid deficiency

Nausea, vomiting, fatigue

What is a key role of biotin?

Facilitates cell growth by acting as a coenzyme in energy metabolism

What are some dietary sources of biotin?

Peanuts, egg yolk, whole grains, fish, organ meats

Define egg white injury (avidin)

dermatitis, hair loss, lethargy, and depression caused by biotin deficiency

What are some roles of vitamin B6 (pyridoxine)?

• Component of PLP which is needed to create nonessential amino acids

• RBC synthesis

• Reduces morning sickness in pregnancy

Symptoms of B6 (pyridoxine) deficiency

microcytic hypochromic anemia, skin inflammation, depression

What is the biggest role of folate?

Prevents neural tube defects in pregnancy

Dietary sources of folate

Enriched refined grains, leafy greens, asparagus, legumes, seeds

Define cobalamins

Group of vitamin B12s

Define intrinsic factor (IF)

protein needed to absorb vitamin B12

Define pernicious (macrocytic) anemia

anemia caused by vitamin B12 deficiency

Define ketogenesis

formation of ketone bodies

What are some major roles of B12

• Activates folate

• Component of RBCs and myelin sheaths

• Required for osteoblast stimulation

Dietary sources of B12

Only found in animal products; fortified cereals and non-dairy milks contain synthetic B12

What populations are at a higher risk of B12 deficiency?

Elderly, vegans, vegetarians

What are some roles of vitamin C?

• Collagen synthesis

• Component of serotonin and norepinephrine

• Antioxidant

• Assists in the absorption of nonheme iron

• WBC synthesis