ch 7: energy metabolism

energy balance

the amount consumed (energy in) vs the amount expended (energy out) in a day

physiological fuel value

the amount of energy the human body derives from foods

most of the body's cells can use glucose, fat, or both for energy, the body must have ____ to fuel the activities of the brain and nerves and the red blood cells

glucose

during digestion, the body breaks down fats into smaller molecules of ___ to be absorbed

glycerol and fatty acids

as the fast continues, the body finds a way to use its fat to fuel the brain. It adapts by combining acetyl CoA fragments derived from fatty acids to produce an alternative energy source, _____

ketone bodies

to enable high intensity exercise to continue pyruvate is converted to____ and coenzymes are released, which allows glycolysis to continue

lactate

the _____ is the most active processing center in the body

liver

ATP

(adenosine triphosphate) main energy source that cells use for most of their work

fatty acids to acetyl CoA

-Fatty acid oxidation: 2 carbon units at a time join with CoA Hydrogens and electrons carried to electron transport chain

symptoms of starvation

-Muscle wasting -Decreased heart rate, respiratory rate, metabolic rate, and body temperature -Impaired vision -Organ failure -Decreased immunity -Depression, anxiety, and food-related dream

direct measure of bomb calorimeter

-amount of heat given off

intermittent fasting

-appears to sustain optimal nutrient use and promote good health

in fasting, adaptation: conserving energy (slowing of metabolism)

-hormones -reduces energy output -supports weight loss but not fat loss

1 glycerol yields ____ acetyl CoA

1 (1:1)

______ enters the TCA cycle, and energy is harnessed through the electron transport chain

ACETYL COA

___ is released during breakdown of glucose, fatty acids, and amino acid

ATP

___ provides energy for all cell activities

ATP

basal metabolism

amount of energy required to carry out involuntary activities of the body at rest

enzyme helpers are claled

coenzymes

fasting vs starving

fast = can be short or long term, choosing not to eat starving = no food available, no choice

in fasting, low blood glucose levels signal

fat breakdown release of amino acids from muscles

in fasting, adaptation: making glucose

for nervous system and RBCs -amino acids yielding pyruvate -- gluconeogenesis -breakdown of body proteins

____ causes loss of appetite

ketosis

____ cells are the most versatile and metabolically active

liver

fasting begins with

release of glucose and fatty acids

in low carb diets, dieters can know when glycogen depletion has occurred and gluconeogensis has begun by monitoring ____

their urine

ATP is made up of ____ phosphate groups

three

in low carb diets, once the body depletes its glycogen reserves, it begins making glucose from the amino acids of protein (gluconeogenesis)

true

t/f: nCarbohydrate, fat, and protein are all eventually used for energy

true

in fasting, adaptation: creating an alternate fuel (shift to ketosis)

use fat to fuel brain -ketone bodies -slows rate of body protein breakdoqn

how does urine monitoring work

whenever glycogen or protein is broken down, water is released and urine production increases. Low-carbohydrate diets induce ketosis, and ketones can be detected in the urine. Ketones form whenever glucose is lacking and fat breakdown is incomplete

what happens with low carb diets

-metabolism similar to fasting --uses glycogen stores first --gluconeogenesis when glycogen is depleted ---body tissues used somewhat even when protein provided in diet -urine monitoring -ketosis

adverse side effects of low carb, ketogenic diets

-nausea -fatigue -constipation -low bp -elevated uric acid -bad breath

glucose enters the energy pathway (aerobic)

1. a small amount of energy (ATP) is required to start glycolysis. in a series of reactions, the 6-c glucose is converted into two 3-c pyruvate 2. coenzymes carry the hydrogens and their electrons to the ETC 3. a small amount of ATP is released 4. 3-c pyruvate picks up CoA, loses a carbon as carbon dioxide, and yields 2-c acetyl CoA, which then goes to TCA cycle

Simplified Overview of Energy-Yielding Pathways

1. all of the energy yielding nutrients -- protein, carbs, fat -- can be brokem down to acetyl coa 2. acetyl coa can enter the tca cycle 3. most of the reactions aboce release H atoms with their electrons, which are carried by coenzymes to the ETC 4. ATP is synthesized 5. H atoms react with oxygen to produce water and carbon atoms react with oxygen to produce carbon dioxide

steps of fat entering pathway

1. glycerol enters the glycolysis pathway about midway between glucose and pyruvate 2. in the first step of fatty acid oxidation, the fatty acid is activated by CoA and a small amount ot ATP is used 3. coenzymes carry H atoms and their electrons to the ETC 4. another CoA joins the chain, and the bond at the second carbon (the beta carbon) weakens. acetyl coa spits off, leaving a fatty acid that is two carbons shorter. 5. the shorter fatty acid enters the pathway and the cycle repeats. these rxns produce more acetyl CoA for the TCA cycle and coenzymes carry more Hs with their electrons to the ETC. 5. cycle repeats, leaving 1 acetyl CoA for every 2C fatty acid CoA

amino acids entering energy pathway

1. most aa can be converted to pyruvate, which can be used to make glucose (they are glucogenic) 2. some aa are converted directly to acetyl CoA (they are ketogenic) 3. some aa can enter the TCA cycle directly (they are glucogenic)

acetyl CoAis a __C structure and (can/canno)t be used to make glucose

2C cannot

pyruvate is a __C structure and (can/cannot) be used to make glucose

3C can

according to acceptable macronutrient distribution ranges, AMDR, a healthy diet provides _____ carbs, ____ protein, and _____ fat

45-65% 10-35% 20-35%

transition from feasting to fasting

As the body shifts from a fed state to a fasting state, it begins drawing on stores of glucose, glycerol, and fatty acids. Glycogen and fat are released from storage to provide more glucose, glycerol, and fatty acids for energy. The body's top priority is to meet the cell's need for energy, and it normally does so by periodically refueling (eating). If we do not to eat, body starts to break down its own tissues for fuel.

some of the ___ vitamins serve as coenzymes that participate in the energy metabolism of glucose, glycerol, fatty acids, and amino acids

B

during digestion, the body breaks down proteins into smaller molecules of ___ to be absorbed

amino acids

condensation reactions are (anabolic/catabolic); they build/assemble things and require energy

anabolic

when the body needs energy quickly—as occurs when you run a quarter mile as fast as you can—pyruvate proceeds without oxygen on an ______ pathway. this pathway yields energy quickly, but it cannot be sustained for long—a couple of minutes at most

anaerobic

during high-intensity exercise, however, the muscles rely heavily on _______ to produce ATP quickly, and the concentration of lactate increases dramatically. The rapid rate of glycolysis produces abundant pyruvate and releases hydrogen-carrying coenzymes more rapidly than the mitochondria can handle

anaerobic glycolysis

enzymes (are/are not) proteins

are

coenzymes (are/are not) proteins

are not

in many cases, the enzymes need assistance in facilitating the metabolic reactions, which is done by ___

coenzymes

different forms of energy

electrical mechanical electrical chemical

________ is the process in which the body obtains and uses energy from food

energy metabolism

____ are helpers in metabolic reactions by being facilitators of metabolic reactions

enzymes

metabolic reactions almost always require _____ to facilitate their action

enzymes

what are the two helpers in metabolic reactions

enzymes and coenzymes

when a person feasts (eats too much) metabolism favors ___ formation

fat

during digestion, the body breaks down carbs into smaller molecules of ___ to be absorbed

glucose (and other monosaccharides)

the first pathway glucose takes on its way to yield energy is called _____ (glucose splitting)

glycolysis

metabolic work of the liver

hen nutrients enter the body from the digestive tract, the liver receives them first; then it metabolizes, packages, stores, or ships them out for use by other tissues. When alcohol, drugs, or toxins enter the body, they are also sent directly to the liver, where they are detoxified and their by-products shipped out for excretion

In the body, hunger is the physiological response to a need for food triggered by nerve signals and chemical messengers originating and acting in the brain, primarily in the _____

hypothalamus

pyruvate to acetyl CoA (aerobic)

if a cell needs energy and oxygen is available, pyruvate enters the mitochondria of the cell. There a carbon group from the 3-carbon pyruvate is removed to produce a 2-carbon compound that bonds with a molecule of CoA, becoming acetyl CoA. The carbon group from pyruvate becomes carbon dioxide , which is released into the blood, circulated to the lungs, and breathed out

glycolysis

in a series of reactions, the 6-carbon glucose is converted to similar 6-carbon compounds before being split in half, forming two 3-carbon compounds. These 3-carbon compounds continue along the pathway until they are converted to pyruvate. Thus the net yield of one glucose molecule is two pyruvate molecules.

during ______, the body releases energy, water, and carbon dioxide (and other waste products)

metabolism

the ___ charges on the phosphate groups of ATP make ATP vulnerable to hydrolysis

negative

which energy yielding nutrient endpoint(s) do not yield energy

none; they all yield energy

excess carbs

ompared with protein, the proportion of carbohydrate in the fuel mix changes more dramatically when a person overeats. The body handles abundant carbohydrate by first storing it as glycogen, but glycogen storage areas are limited and fill quickly. Because maintaining glucose balance is critical, the body uses glucose frugally when the diet provides only small amounts and freely when supplies are abundant. In other words, glucose oxidation rapidly adjusts to the dietary intake of carbohydrate. Like protein, excess glucose can also be converted to fat and new body fat is made whenever carbohydrate intake is excessive. Excess dietary carbohydrate can also displace fat in the fuel mix. When this occurs, carbohydrate spares both dietary fat and body fat from oxidation. The net result: excess carbohydrate contributes to body fat.

fat provides more energy because the bonds in fat molecules are easily ____ and result in more ATP

oxidized

photosynthesis

plants make simple sugars from carbon dioxide and capture the sun's light energy into the chemical bonds of those sugars

two new compounds appear in metabolism called

pyruvate acetyl CoA

catabolism (breaking apart)

releases energy

anabolism (building up)

requires energy

excess protein

the body cannot store excess amino acids as such; it has to convert them to other compounds. Contrary to popular opinion, a person cannot grow muscle simply by overeating protein. Lean tissue such as muscle develops in response to stimuli such as hormones or physical activity. When a person overeats protein, the body uses the surplus first by replacing normal daily losses and then by increasing protein oxidation. If excess protein is still available, the amino acids are deaminated and the remaining carbons are converted to ketone bodies, which are stored as fat in adipose tissue. Thus, eating too much protein contributes to body fat.

couple reactions

the body uses ATP to transfer the energy released during catabolic reactions to power anabolic reactions that require energy. The body converts the chemical energy of food to the chemical energy of ATP with about 50 percent efficiency, radiating the rest as heat. Some energy is lost as heat again when the body uses the chemical energy of ATP to do its work—moving muscles, synthesizing compounds, or transporting nutrients, for example

bomb calorimeter

the medium in which a scientist burns food. the amount of heat given off provides a direct measure of the food's energy value. these reactions also generate carbon dioxide and water, just like the body's cells do when they metabolize the energy yielding nutrients from food

fats enter the energy pathway

the process of breaking down fats to yield energy begins with triglycerides breaking down to glycerol and fatty acids. Glycerol enters the pathway that converts glucose to pyruvate, which can then make acetyl CoA. The fatty acids are broken apart in a series of reactions known as fatty acid oxidation. Fatty acid oxidation yields 2-carbon fragments that combine with CoA to form abundant acetyl CoA

(t/F) amino acids that yield pyruvate can be used for gluconeogenesis—the making of glucose from noncarbohydrate source

true

(t/F): to protect this protein tissue, the body needs foods that provide glucose—primarily carbohydrate. Eating only fat provides abundant acetyl CoA, but forces the body to break down protein tissue to make glucose. Eating only protein requires the body to convert protein to glucose

true

(t/f) Normally produced and used only in small quantities, ketone bodies can efficiently provide fuel for brain cells. Ketone body production rises until, after about 10 days of fasting, it is meeting much of the nervous system's energy needs.

true

(t/f) a person performing the same exercise following endurance training actually experiences less discomfort—in part because the number of mitochondria in the muscle cells has increased. This adaptation improves the mitochondria's ability to keep pace with the muscles' demand for energy

true

(t/f) amino acids entering the TCA cycle directly can continue in the cycle and generate energy; alternatively, they can generate glucose

true

(t/f) amino acids that are used to make pyruvate can provide glucose, whereas those used to make acetyl CoA can provide additional energy or make body fat but cannot make glucose

true

(t/f) fat cells enlarge regardless of whether the excess in kcalories derives from protein, carbohydrate, or fat. The pathway from dietary fat to body fat, however, is the most direct (requiring only a few metabolic steps) and the most efficient (costing only a few kcalories)

true

(t/f) on average, storing excess energy from dietary fat as body fat uses only 5 percent of the ingested energy intake, but storing excess energy from dietary carbohydrate as body fat requires 25 percent of the ingested energy intake

true

(t/f) protein, unlike fat, is a fairly good source of glucose when carbohydrate is not available

true

(t/f) the accumulation of lactate in the muscles coincides with—but does not seem to be the cause of—the subsequent drop in blood pH, burning pain, and fatigue that are commonly associated with intense exercise. In fact, making lactate from pyruvate removes two hydrogen ions, which actually diminishes acidity and improves the performance of tired muscles

true

(t/f): during hydrolysis, the bonds between the phosphate groups readily break, splitting off one or two phosphate groups and releasing energy. In this way, ATP provides the energy that powers all the activities of living cells

true

(t/f): metabolic activity varies with cell type

true

the cells' work that maintains all life processes without any conscious effort represents about ____-thirds of the total energy a person expends in a day.

two

excess fat

unlike excess protein and carbohydrate, which both increase oxidation, eating too much fat does not promote fat oxidation. Instead, excess dietary fat efficiently fills the body's fat stores; almost all of the excess is stored.

fuel mix from various nutrients

usually, protein's contribution to the fuel mix is relatively minor and fairly constant, but protein oxidation does increase when protein is eaten in excess. Similarly, carbohydrate eaten in excess significantly enhances carbohydrate oxidation. In contrast, fat oxidation does not respond to dietary fat intake. Instead of being oxidized, fat accumulates in storage

molecules of glucose (from carbs), glycerol & fatty acids (from fats), and amino acids (from proteins) are then broken down into

C, N, O, H

fasting - inadequate energy

Carbohydrate, fat, and protein • All eventually used for energy Begins with release of glucose from liver stored as glycogen and fatty acids released from adipose tissue's stored as fat, travel to the cells • Acetyl CoA Low blood glucose levels signal: • Fat breakdown • Release of amino acids from muscles

feasting - excess energy

-Metabolism favors fat formation --Regardless of excess from protein, fat, or carbohydrates -Excess protein -Excess carbohydrate -Excess fat - most direct and efficient conversion -Fuel mix

indirect measure of bomb calorimeter

-amount of oxyhen consumed

amino acid deamination

-first step of proteins entering energy pathway -when amino acids lose their nitrogen-containing amino group to produce ammonia (NH3+) in order to enter metabolic pathways

16C fatty acid yields ___ acetyl CoA

8 (2:1)

energy yielding macronutrients' paths meet at _____, where the most intense action begings

acetyl coa

what entrance points of aa into energy pathway are glucogenic

aa -> pyruvate -> glucose and aa entering TCA cylce directly

what entrance points of aa into energy pathway are ketogenic

aa converted directly to acetyl CoA

when energy expenditure proceeds at a slow to moderate pace—as occurs when you jog around the track for an hour—pyruvate enters an ____ pathway. this pathway produce energy slowly, but because they can be sustained for a long time, their total energy yield is great

aerobic

pyruvate's pathway options are

aerobic or anaerobic

which energy yielding nutrient endpoint(s) yields fat stores

all four of them -carbs (glucose) -lipids (fatty acids) -lipids (glycerol) -proteins (aa)

which energy yielding nutrient endpoint(s) yields energy

all of them -carbs (glucose) -lipids (fatty acids) -lipids (glycerol) -proteins (aa)

___ are helpers in metabolic reactions by associating with enyzmes

coenzymes

amino acids and glycerol can be converted to pyruvate and therefore (can/cannot) provide glucose for the body

can

fatty acids (can/cannot) make glucose

cannot

fatty acids can be converted to acetyl CoAand therefore (can/cannot) provide glucose for the body

cannot

for RBCS and brain and nervous system cells, they rely primarily on glucose as fuel. when carbohydrate is unavailable, liver cells can make glucose from pyruvate and other 3-carbon compounds, such as glycerol. Importantly, cells _____ make glucose from the 2-carbon fragments of fatty acid

cannot

which energy yielding nutrient endpoint(s) yyields glucose

carbs (glucose) lipids (glycerol) -when carbs are unavailable proteins (aa) - when carbs are unavailable

which energy yielding nutrient endpoint(s) yields aa and body proteins

carbs(glucose) - when N is available, can yield nonessential aa lipids (glycerol) - when N is available, can yield nonessential aa proteins (aa)

hydrolysis reactions are (anabolic/catabolic); they break down things and release energy

catabolic

______ energy stored in food and body

chemical

pyruvate to lactate (anaerobic)

coenzymes carry the hydrogens from glycolysis to the electron transport chain. If the electron transport chain is unable to accept these hydrogens, as may occur when cells lack sufficient mitochondria or in the absence of sufficient oxygen, pyruvate can accept the hydrogens. By accepting the hydrogens, pyruvate becomes lactate, and the coenzymes are freed to return to glycolysis to pick up more hydrogens. In this way, glucose can continue providing energy anaerobically for a while

the hydrolysis of ATP occurs simultaneously with reactions that will use that energy—a metabolic duet known as

coupled reactions

coenzymes are (organic/inorganic)

organic

(T/F): without its coenzyme, an enzyme cannot function

treu