Bio 233 @ Oit - Unit 4

Front 1

Define metabolism and explain the difference between catabolism and anabolism.

Back 1

Metabolism includes all chemical reactions necessary to maintain life.
Anabolic reactions – synthesis of larger molecules from smaller ones.
Catabolic reactions – hydrolysis of complex structures into simpler ones
Energy-containing nutrients are processed in three major stages. Digestion – breakdown of food;
nutrients are transported to tissues. Anabolism, where nutrients are built into lipids, proteins, and glycogen; and catabolism, where nutrients are broken down to pyruvic acid and acetyl-CoA, and then catabolized to carbon dioxide, water, and ATP.

Front 2

Describe oxidation and reduction and list their importance of these reactions in metabolism.

Back 2

Oxidation was originally defined as the combination of oxygen with other elements. Later it was discovered that oxidation also occurs when hydrogen atoms are removed from compounds and so the definition was expanded to its current form: Oxidation is the gain of oxygen or the lost of hydrogen.
Whenever one substance loses electrons (is oxidized), another substance gains them (is reduced). Thus, oxidation and reduction are coupled reactions and we speak of oxidation-reduction reactions.
(p 957)

Front 3

Describe the role of coenzyme in cellular oxidation reaction.

Back 3

Most vitamins function as coenzymes (or parts of coenzymes), which act with an enzyme to accomplish a particular chemical task.
(p 948)

Front 4

Describe the difference between substrate-level phosphorylation and oxidative
phosphorylation in ATP synthesis.

Back 4

Substrate-level phospohorylation occurs when high-energy phosphate groups are transferred directly from phosphorylated substrates (metabolic intermediates such as glyceraldehyde phosphate) to ADP. Essentially, this process occurs because the high-energy bonds attaching the phosphate groups to the substrates are even more unstable than those in ATP. ATP is synthesized by this route during one of the steps in glycolysis, and once during each turn of the Krebs cycle.
Oxidative phosphorylation is much more complicated, but it also releases most of the energy that is eventually captures in ATP bonds during cellular respiration. This process, which is carried out by electron transport proteins forming part of the mitochondria cristae, is an exxample of a chemiosmotic process. Chemiosmotic processes couple the movement of substances across membranes to chemical reaction. In this case, some of the energy released during the oxidation of food fuels (the "chemi" part of the term) is used to pump (osmo=push) protons (H+) across the cristae membrane into the intermembrane space. This creates a steep concentration gradient for protons across the membrane. Then, when H+ does flow back across the membrane (trhough a membrane channel protein called ATP synthase) some of this gradient energy is captured and used to attach phosphate groups to ADP.

Front 5

Follow the oxidation of glucose in body cells. Describe important steps and
products of glycolysis, the Krebs cycle, and electron transport. Provide an
accurate ATP count in these processes. Name the process responsible for CO2 release. What process uses oxygen?

Back 5

Glycolysis
Glucose is the major source of energy for ATP synthesis. Glucose may be obtained directly
from the blood or from glycogen. In glycolysis glucose is broken down to 2 piruvate molecules
and yields 2 ATP. This process includes 10 biochemical reactions. Each reaction is facilitated
by a specific enzyme. Only the 1st reaction is irreversible. 1st and 3rd reactions each require 1ATP (energy investment phase). Later reactions yield production of 4ATPs.

This process generates:
 3 (NADH + H+)
 1 FADH2
 2 CO2
 1 ATP
For each molecule of glucose
entering glycolysis, two
molecules of acetyl CoA enter the Krebs cycle
Fate of Piruvate
In the absence of oxygen
piruvate is converted into
the lactic acid. With the
oxygen present, piruvate
enters Krebs cycle, and
then oxidative
phosphorylation.

Krebs Cycle
Krebs cycle = citric acid
cycle is an eight-step cycle
in which each piruvate
molecule is first converted
into acetyl-CoA,
decarboxylated and
oxidized.

Front 6

Define glycogenesis, glycogenolysis, and glyconeogenesis. Describe the role of insulin, glucagon, cortisole, and epinephrine in blood glucose regulation.

Back 6

Glycogenesis is formation of glycogen when glucose supplies exceed cellular need for ATP
synthesis
Glycogenolysis is breakdown of glycogen in response to low blood glucose
Gluconeogenesis is the process of forming sugar from noncarbohydrate molecules (fatty acids,
amino acids) It takes place mainly in the liver. Gluconeogenesis protects the body, especially
the brain, from the damaging effects of hypoglycemia by ensuring ATP synthesis can continueGlycogenesis is formation of glycogen when glucose supplies exceed cellular need for ATP
synthesis
Glycogenolysis is breakdown of glycogen in response to low blood glucose
Gluconeogenesis is the process of forming sugar from noncarbohydrate molecules (fatty acids,
amino acids) It takes place mainly in the liver. Gluconeogenesis protects the body, especially
the brain, from the damaging effects of hypoglycemia by ensuring ATP synthesis can continue
High blood glucose triggers release of insulin from pancreatic -cells. This hormone
 Increases glucose uptake by the muscle and fat cells
 Increases glycogen synthesis (glycogenesis)
 Increases ATP production from glucose (glycolysis)
Low blood glucose triggers release of glucagon from pancreatic -cells. This hormone acts as
insulin antagonist, it
 Induces glycogenolysis: synthesis of glucose from glycogen (liver and muscle tissue)
 Induces breakdown of fats into fatty acids
 Induces glyconeogenesis: synthesis of glucose from the fatty acids and amino acids)
Additional signals, ACTH and growth hormone, released from the pituitary act to increase blood
glucose by inhibiting uptake by extrahepatic tissues. Glucocorticoids also act to increase blood
glucose levels by inhibiting glucose uptake. Cortisol, the major glucocorticoid released from the
adrenal cortex, is secreted in response to the increase in circulating ACTH. The adrenal
medullary hormone, epinephrine, stimulates production of glucose by activating glycogenolysis
in response to stressful stimuli.

Front 7

Describe the processes by which fatty acids are oxidized for energy.

Back 7

BIO 233 Unit II, Lecture 3 Dr. Tanya McVay
The biochemical conversion of carbohydrates and proteins into fat uses up about 25% of the
inherent energy value in the process. One can eat more kcal in the form of carbohydrate and
protein and make less fatLipid Metabolism
As fats enter the cells, they are stored in adipose granules or metabolized. Lipolysis is a
metabolic break-down of triglycerides to fatty acids and glycerol. Then glycerol is converted to
glyceraldehyde phosphate. Glyceraldehyde is ultimately converted into acetyl-CoA that enters
the Krebs cycle. Fatty acids undergo -oxidation which produces two-carbon acetic acid
fragments, which enter the Krebs cycle, and NADH and FADH2, which enter the electron
transport chain.
Excess dietary glycerol and fatty acids undergo lipogenesis, - a formation of triglycerides. They
can also be formed from glucose or amino acids.
Fat is the most efficient way of storing excess dietary energy because it has over twice the
energy density of either carbohydrate or protein (9 kcal/g vs. 4 kcal/g). A small amount (less
than 1 pound) of glucose is stored as glycogen, but excess carbohydrate (glucose) is converted
into fatty acids and hence into fat. Likewise, excess protein is also converted into fatty acids.

Front 8

Define lipogenesis and lipolysis.

Back 8

Triglyceride synthesis, or lipogenesis, occurs when cellular ATP and glucose levels are high. Excess ATP also leads to an accumulation of acetyl CoA and glyceraldehyde-PO4, two intermediates of glucose metabolism that would otherwise feed into the Krebs cycle. But when these two metabolites are present in excess, they are channeled into triglyceride synthesis pathways. Acetyl CoA molecules are condensed together, forming fatty acid chains that grow two carbons at a time.
Lipolysis, the breakdown of stored fats into glycerol and fatty acids, is essentially lipogenesis in reverse.

Front 9

Describe some of the metabolic functions of liver.

Back 9

Lipolysis in adipose tissues and the liver. Adipose and liver cells produce glycerol by lipolysis and the liver converts the glycerol to glucose (gluconeogenesis), which is released to the blood. Because of acetyl CoA, a product of the beta oxidation of fatty acids, is produced beyond the reversible steps of glycolysis, fatty acids cannot be used to bolster blood glucose levels.

Front 10

Classify lipoproteins and describe their functions in cholesterol transport

Back 10

Lipid Transport
Lipoproteins that carry fat-soluble substances in blood are called serum lipoproteins.
 Chylomicrons are the largest out of four types. They are synthesized in intestinal wall and transport large dietary lipids (triglycerides (mostly), phospholipids and cholesterol) from intestine to the rest of the body. In tissues special receptors recognize chylomicrons and allow unload lipids into the cell. Once unloaded, the remnants can be dismantled in liver.
Fatty acid BIO 233 Unit II, Lecture 3 Dr. Tanya McVay
 VLDL, Very Low Density Lipoproteins. Liver synthesizes cholesterol, different fatty acids
and phospholipids de novo using lipids, carbohydrates and proteins as substrates. These
newly synthesized compounds are packaged into VLDL and are carried to the tissues.
VLDLs unload new lipids in tissues and acquire cholesterol through the exchange with HDL.
Now they become LDL.
 LDL, Low Density Lipoproteins, contain mostly cholesterol (up to 50%) which they deliver to peripheral tissues. They are small enough to get into intercellular space where they
deposit cholesterol on the cellular membranes. High LDL concentration is associated with increased incidence of atherosclerosis (heart attack, stroke, etc.)
 HDL, High Density Lipoproteins are synthesized in liver and carry cholesterol and
phospholipids from tissues back to liver for recycling or excretion. They lower damage by cholesterol on tissues (arteries)

Front 11

Describe how plasma cholesterol level is regulated

Back 11

Cholesterol, though an important dietary lipid, has recieved little attention in this discussion so far, primarily because it is not used as an energy source. It serves instead as the structural basis of bile salts, steroid hormones, and vitamin D and as a major component of plasma membranes.
A negative feedback loop partially adjusts the amount of cholesterol produced by the liver according to the amount of cholesterol in the diet. A high cholesterol intake inhibits its synthesis by the liver, but is not a one-to-one relationship because the liver produces a certain basal amount of cholesterol (about 85%) even when dietary intake is excessive.
The relative amounts of saturated and unsaturated fatty acids in the diet have an important effect on blood cholesterol levels. Saturated fatty acids stimulate liver synthesis of cholesterol and inhibit its excretion from the body. In contrast, unsaturated (mono- and polyunsaturated) fatty acids (found in olive oil and in most vegetable oils respectively) enhance excretion of cholesterol and its catabolism to bile salts, thereby reducing total cholesterol levels.

Front 12

Define ketone bodies, and indicate the mechanisms underlying its formation.
Explain the effects of ketone bodies on blood pH

Back 12

Without oxaloacetic acid, fat oxidation is incomplete, acetyl CoA accumulates, and via a process called ketogenesis, the liver converts acetyl CoA molecules ot ketone bodies, or ketones, which are released into the blood. Ketone bodies include acetoacetic acid, B-hydroxybutric acid, and acetone, all formed from acetic acid.
When ketone bodies accumulate in the blood, ketosis results and large amounts of ketone bodes are excreted in the urine. Ketosis is a common consequence of starvation, unwise dieting, and diabetes mellitus.
Because most ketone bodies are organic acids, the outcome of ketosis is metabolic acidosis. The body's buffer systems cannot tie up the acids (ketones) fast enough, and blood pH drops to dangerously low levels.

Front 13

Describe how amino acids are metabolized for energy.

Back 13

When dietary protein (and hence Nitrogen) intake exceeds actual protein needs, it is called positive nitrogen balance. When dietary calorie intake is inadequate to meet
energy needs, the body may break down protein in order to supply energy. This results in
a net loss of protein and is called negative nitrogen balance.Protein Metabolism
Excess dietary protein results in amino acids being:
 Oxidized for energy
 Converted into glucose (gluconeogenesis)
 Converted into fat for storage (lipogenesis)
Nitrogen should be first removed from amino acids via one of the following processes:
 Deamination, where nitrogen is removed and excreted with urea
 Transamination, where nitrogen is transferred to another amino acid
Deaminated amino acids are converted into pyruvic acid or one of the intermediates of the Krebs cycle.

Front 14

Describe the need for protein synthesis in body cells

Back 14

Proteins are important structural materials of the body, including, for example, keratin in skin, collagen and elastin in connective tissues, and muscle proteins. In addition, functional proteins such as enzymes and some hormones regulate an incredible variety of body functions. Whether amino acids are used to synthesize new proteins or are burned for energy depends on a number of factors.
1. The all-or none rule
2. Adequacy of caloric intake
3. Nitrogen balance
4. Hormonal controls.

Front 15

Describe the concept of amino acid or carbohydrate-fat pools and describe pathways by which substances in these pools can be interconverted

Back 15

The amino acid pool is the body's total supply of free amino acids. Small amounts of amino acids and proteins are lost daily in urine and in sloughed hairs and skin cells. Typically, these lost molecules are replaced via the diet; otherwise amino acids arising from tissue breakdown return to the pool. This pool is the source of amino acids used for protein synthesis and in the formation of amino acid derivaties.

Front 16

Distinguish between fat- and water- soluble vitamins, and list vitamins in each
group.

Back 16

Vitamins include two major groups: water soluble and fat-soluble.

Water Soluble Vitamins include vitamins group B, folic acid and vitamin C.
 Thiamin = B1 helps catalyze the reactions that chip off carbons in the form of CO2
yielding energy. For example conversion of pyruvate into acetyl-CoA requires thiamine.
 Riboflavin= B2 is needed to produce FADH2
 Niacin = Nicotinic acid= B3, is essential for production of NADH
 Biotin is essential in making adding carboxyl groups in intermediate molecules in the
Krebs cycle. It also has roles in gluconeogenesis, fatty acid synthesis and breakdown of
amino acids.
 Pantothenic Acid = B5 is a component of Coenzyme A (CoA)
 Pyridoxine = B6 is active in amino acid metabolism: it transfers amine groups from 1
molecule to another (transamination) or removes amino groups during catabolic
processes (deamination).
 Folate = Folic Acid and vitamin B12 = Cobalamin are critical for cell division and protein
synthesis.
 Ascorbic Acid = Vitamin C acts as an antioxidant or as coenzyme in the synthesis of
neurotransmitters (norepinephrine), hormones (thyroxin) and collagen. It also increases
absorption and bioavailability of iron.

Fat Soluble Vitamins include vitamins
 Vitamin A found in 3 forms: retinol (sperm and fetal development), retinal (part of
rhodopsin, important for vision) and retinoic acid (promotes differentiation of epithelial
cells of skin, GI tract and goblet cells. Vitamin A also promotes growth of the bone.
Children deficient in Vitamin A have accelerated growth when given vitamin A
supplements.
 Vitamin D3 = Cholecalciferrol. Active vitamin D maintains calcium concentrations in
blood: it increases calcium and phosphates absorption, decreases loss of calcium with
urine and affects Ca mobilization from bone in presence of parathyroid hormone
 Vitamin K = Phylloquinone, is required in the synthesis of prothrombin and clotting
factors II, VII, IX and X, essential proteins in the clotting process.
 Vitamin E acts as an antioxidant, particularly important in lungs and WBC.

Front 17

For each vitamin, list important sources, body functions, and consequences of its
deficit or excess

Back 17

Vitamins include two major groups: water soluble and fat-soluble.

Water Soluble Vitamins include vitamins group B, folic acid and vitamin C.
 Thiamin = B1 helps catalyze the reactions that chip off carbons in the form of CO2
yielding energy. For example conversion of pyruvate into acetyl-CoA requires thiamine.
 Riboflavin= B2 is needed to produce FADH2
 Niacin = Nicotinic acid= B3, is essential for production of NADH
 Biotin is essential in making adding carboxyl groups in intermediate molecules in the
Krebs cycle. It also has roles in gluconeogenesis, fatty acid synthesis and breakdown of
amino acids.
 Pantothenic Acid = B5 is a component of Coenzyme A (CoA)
 Pyridoxine = B6 is active in amino acid metabolism: it transfers amine groups from 1
molecule to another (transamination) or removes amino groups during catabolic
processes (deamination).
 Folate = Folic Acid and vitamin B12 = Cobalamin are critical for cell division and protein
synthesis.
 Ascorbic Acid = Vitamin C acts as an antioxidant or as coenzyme in the synthesis of
neurotransmitters (norepinephrine), hormones (thyroxin) and collagen. It also increases
absorption and bioavailability of iron.

Fat Soluble Vitamins include vitamins
 Vitamin A found in 3 forms: retinol (sperm and fetal development), retinal (part of
rhodopsin, important for vision) and retinoic acid (promotes differentiation of epithelial
cells of skin, GI tract and goblet cells. Vitamin A also promotes growth of the bone.
Children deficient in Vitamin A have accelerated growth when given vitamin A
supplements.
 Vitamin D3 = Cholecalciferrol. Active vitamin D maintains calcium concentrations in
blood: it increases calcium and phosphates absorption, decreases loss of calcium with
urine and affects Ca mobilization from bone in presence of parathyroid hormone
 Vitamin K = Phylloquinone, is required in the synthesis of prothrombin and clotting
factors II, VII, IX and X, essential proteins in the clotting process.
 Vitamin E acts as an antioxidant, particularly important in lungs and WBC.

Front 18

List minerals essential for health; note important dietary sources and describe how
each is used

Back 18

Minerals
Seven minerals are required in moderate amounts: calcium, phosphorus, potassium, sulfur,
sodium, chloride and magnesium. Dozens are required in trace amounts. Minerals work with
nutrients to ensure proper body functioning. Calcium, phosphorus, and magnesium salts harden
bone. Sodium and chloride help maintain normal osmolarity, water balance, and are essential in
nerve and muscle function. Iron is essential for hem synthesis.