Lecture: Nutrition & Metabolism

Question 1

Define: nutrition.

Answer 1

process by which necessary food substances are taken in and utilized by the body

Question 2

Define: nutrients.

Answer 2

ingested chemicals that are used for growth, repair, or maintenance of the body

Question 3

Define: macronutrient. Name 4 examples.

Answer 3

nutrient that must be consumed in relatively large quantities;
ex. water, carbohydrates, proteins, lipids

Question 4

Define: micronutrient. Name 2 examples.

Answer 4

nutrient only required by the body in small quantities;

ex. vitamins & minerals

Question 5

Describe the prevalence of carbohydrates in various parts of the body.

Answer 5

~440 g in body

• ~325 g in muscle glycogen
• ~100 g in liver glycogen
• ~15 g in blood glucose

Question 6

In what forms are carbohydrates found within the body?

Answer 6

polysaccharides: starch
disaccharides: sucrose, lactose, & maltose
monosaccharides: glucose, galactose, & fructose

Question 7

In what forms are lipids found within the body?

Answer 7

triglycerides;
cholesterol;
phospholipids;
lipoproteins:
-chylomicrons
-high-density lipoproteins (HDLs)
-low-density lipoproteins (LDLs)
-very low-density lipoproteins (VLDLs)

Question 8

In what forms are proteins found within the body?

Answer 8

amino acids:
-essential (body cannot synthesize from other organic compounds when they are not available from the diet);
-inessential (body can synthesize from other organic compounds when they are not available from the diet)
food sources:
-complete proteins: provide all essential AAs in the necessary proportions for human tissue growth, maintenance, and nitrogen balance;
-incomplete proteins: lack one or more AAs

Question 9

What are minerals? What is their role? What are their 2 classifications?

Answer 9

inorganic elements in food;
not used for fuel, but are essential to our ability to use other nutrients;
classifications:
-major (body needs lots)
-trace (body needs little)

Question 10

What are vitamins? What is their role? What are their 2 classifications?

Answer 10

organic compounds necessary for metabolism;
not used for fuel, but are essential to our ability to use other nutrients;
classifications:
-water-soluble: B-vitamins and Vitamin C
-fat-soluble: Vitamins A, D, E, & K)

Question 11

Define: metabolism.

Answer 11

all chemical reactions in body

Question 12

Define: anabolism.

Answer 12

energy-requiring building processes;

construct complex structures, including cells, molecules, and hormones, from smaller units

Question 13

Define: catabolism.

Answer 13

energy-releasing processes;
complex structures are broken down;
chemical reactions produce ATP

Question 14

Define: carbohydrate metabolism. What are the 3 major pathways?

Answer 14

catabolic process by which carbohydrates are transformed into glucose;
complete catabolism of glucose overall reaction:
C6H12O6 + 6O2 → 6CO2 + 6H2O
3 major pathwways:
1) glycolysis
2) anaerobic fermentation
3) aerobic respiration

Question 15

What is glycolysis? What 5 things does it require?

Answer 15

series of enzymatic rxns in cytoplasm;
6-C glucose molecule to 2 3-C molecules of pyruvate;
requires:
-glucose
-cytoplasmic enzymes
-ATP & ADP
-nicotinamide adenine dinucleotide (NAD)
–coenzyme
–organic molecule, usually derived from vitamins
–removes H atoms
–must be present for enzymatic rxn to occur

Question 16

Explain the 7 step process of glycolysis.

Answer 16

1) phosphorylation: glucose enters cell by facilitated diffusion and is phosphorylated by ATP, producing G6P
2) priming: G6P isomerized (rearranged) to fructose 6-phosphate
3) F6P phosphorylated, forming fructose-1,6-diphosphate
4) cleavage: fructose-1,6-diphosphate splits into 2 3-carbon chains, 2 phosphoglyceraldehyde (PGAL)
5) oxidation: PGAL oxidized; electrons are picked up by NAD+
6) dephosporylation: phosphate groups transferred to ADP, producing ATP
7) pyruvic acid formed

Question 17

What are the end products of glycolysis?

Answer 17

4 ATP (2 net);
2 pyruvic acid or pyruvate;
2 reduced NADH + 2 H+

Question 18

Is glycolysis reversible or irreversible?

Answer 18

all steps reversible except for the first phosphorylation of glucose

Question 19

Is glycolysis an anaerobic or aerobic process?

Answer 19

anaerobic

Question 20

After glycolysis, where does the energy that was originally in glucose end up?

Answer 20

ATP, NADH, some lost as heat

Question 21

What is anaerobic fermentation?

Answer 21

reduction of pyruvic acid to lactic acid without using O2;
occurs in absence of O2;
NADH donates a pair of electrons to pyruvic acid, reducing it to lactic acid and regenerating NAD+

Question 22

What is aerobic respiration?

Answer 22

occurs when O2 is available;
pyruvic acid enters the mitochondria and is oxidized; this occurs in 2 steps:
1) matrix reactions (so called b/c their controlling enzymes are in the fluid of the mitochondrial matrix)
-citric acid (Krebs) cycle
2) membrane reactions (so called b/c their controlling enzymes are bound to the membranes of the mitochondrial cristae)
-electron transport chain

Question 23

Explain the conversion step of the citric acid cycle.

Answer 23

pyruvic acid is converted to an acetyl group;

acetyl group binds to coenzyme A, forming acetyl-coenzyme A (acetyl-CoA)

Question 24

What is the citric acid (Krebs) cycle?

Answer 24

occurs in matrix of mitochondria;
acetyl-CoA (generated during the conversion step) combines with oxaloacetic acid, forming citric acid;
reactions continue and produce many intermediates

Question 25

What are the end products of one cycle of the citric acid (Krebs) cycle?

Answer 25

2 CO2
4 reduced coenzymes:
-3 NADH + 3 H+
-1  FADH2
1 ATP

Question 26

What are the end products of a complete citric acid (Krebs) cycle?

Answer 26

4 CO2
8 reduced coenzymes:
-6 NADH + 6 H+
-2 FADH2
2 ATP

Question 27

Where is the electron transport chain? What are the 2 purposes of the electron transport chain?

Answer 27

mitochondrial membrane;

1) oxidize NADH and FADH2 to make ATP
2) regenerate NAD+ and FAD

Question 28

Name the 5 members of the electron transport chain.

Answer 28

1) flavin mononucleotide
2) iron-sulfur centers
3) coenzyme Q
4) copper
5) cytochromes

Question 29

Explain the chemiosmotic mechanism.

Answer 29

energy liberated by electrons as they pass down the electron transport chain drives respiratory enzyme complexes;
each works collectively as a proton pump, removing H+ from the mitochondrial matrix and pumps it into the space between the inner and outer mitochondrial membranes;
this creates an electrochemical gradient;
ATP synthase, the collective name for specific channel proteins, uses the gradient to drive ATP synthesis

Question 30

About how many ATP does the electron transport chain produce?

Answer 30

~34

Question 31

Define: glycogenesis.

Answer 31

the synthesis of glycogen, a molecule which is better suited for energy storage than glucose;
stimulated by insulin and facilitated by glycogen synthase, which cleaves off the phosphate group and adds the 6C monomer to a growing polysaccharide chain

Question 32

Define: glycogenolysis.

Answer 32

the hydrolysis of glycogen; releases glucose between meals when glucose is not being ingested;
stimulated by glucagon and epinephrine;
glycogen
4/2 lecture 51:30 for more clarification