Lecture: Nutrition & Metabolism Flashcards
Define: nutrition.
process by which necessary food substances are taken in and utilized by the body
Define: nutrients.
ingested chemicals that are used for growth, repair, or maintenance of the body
Define: macronutrient. Name 4 examples.
nutrient that must be consumed in relatively large quantities;
ex. water, carbohydrates, proteins, lipids
Define: micronutrient. Name 2 examples.
nutrient only required by the body in small quantities;
ex. vitamins & minerals
Describe the prevalence of carbohydrates in various parts of the body.
~440 g in body
- ~325 g in muscle glycogen
- ~100 g in liver glycogen
- ~15 g in blood glucose
In what forms are carbohydrates found within the body?
polysaccharides: starch
disaccharides: sucrose, lactose, & maltose
monosaccharides: glucose, galactose, & fructose
In what forms are lipids found within the body?
triglycerides; cholesterol; phospholipids; lipoproteins: -chylomicrons -high-density lipoproteins (HDLs) -low-density lipoproteins (LDLs) -very low-density lipoproteins (VLDLs)
In what forms are proteins found within the body?
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
What are minerals? What is their role? What are their 2 classifications?
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)
What are vitamins? What is their role? What are their 2 classifications?
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)
Define: metabolism.
all chemical reactions in body
Define: anabolism.
energy-requiring building processes;
construct complex structures, including cells, molecules, and hormones, from smaller units
Define: catabolism.
energy-releasing processes;
complex structures are broken down;
chemical reactions produce ATP
Define: carbohydrate metabolism. What are the 3 major pathways?
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
What is glycolysis? What 5 things does it require?
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
Explain the 7 step process of glycolysis.
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
What are the end products of glycolysis?
4 ATP (2 net);
2 pyruvic acid or pyruvate;
2 reduced NADH + 2 H+
Is glycolysis reversible or irreversible?
all steps reversible except for the first phosphorylation of glucose
Is glycolysis an anaerobic or aerobic process?
anaerobic
After glycolysis, where does the energy that was originally in glucose end up?
ATP, NADH, some lost as heat
What is anaerobic fermentation?
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+
What is aerobic respiration?
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
Explain the conversion step of the citric acid cycle.
pyruvic acid is converted to an acetyl group;
acetyl group binds to coenzyme A, forming acetyl-coenzyme A (acetyl-CoA)
What is the citric acid (Krebs) cycle?
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
What are the end products of one cycle of the citric acid (Krebs) cycle?
2 CO2 4 reduced coenzymes: -3 NADH + 3 H+ -1 FADH2 1 ATP
What are the end products of a complete citric acid (Krebs) cycle?
4 CO2 8 reduced coenzymes: -6 NADH + 6 H+ -2 FADH2 2 ATP
Where is the electron transport chain? What are the 2 purposes of the electron transport chain?
mitochondrial membrane;
1) oxidize NADH and FADH2 to make ATP
2) regenerate NAD+ and FAD
Name the 5 members of the electron transport chain.
1) flavin mononucleotide
2) iron-sulfur centers
3) coenzyme Q
4) copper
5) cytochromes
Explain the chemiosmotic mechanism.
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
About how many ATP does the electron transport chain produce?
~34
Define: glycogenesis.
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
Define: glycogenolysis.
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
