5/24 Lecture E3 Flashcards
What is weight determined by?
The body’s energy balance; combination of heredity (30-50%) and environmental influences
What is involved in the control of weight?
several peptide hormones and regulatory pathways that control sort and long-term appetite
What do short term regulators of appetite do?
make one feel hungry or satiated to begin or end eating.
What do short term regulators of appetite include?
peptides ghrelin, peptide YY, cholecystokinin, and amylin
What is Ghrelin?
A substance secreted from parietal cells in the fundus of an empty stomach that produces the sensation of hunger.
What gland does Ghrelin stimulate?
stimulates the hypothalamus to secrete growth hormone releasing hormone
What is Peptide YY? (PYY)
a substance secreted by enteroendocrine cells of the ileum and colon that can sense that food has arrived in the stomach, in order to signal satiety and terminate eating.
How much PYY is secreted?
the amount is proportional to the number of calories consumed
What is Cholecystokinin (CCK)
a substance secreted by enteroendocrine cells in the duodenum and jejunum that stimulates the secretion of bile and pancreatic enzymes.
What does CCK do?
stimulates brain and sensory fibers of vagus nerve, suppressing appetite.
What is Amylin?
A substance secreted from beta cells of the pancreas that produces satiety and inhibits stomach activity.
What substances act as a signal to stop eating?
Peptide YY, Cholecystokinin and Amylin
What substance produces the sensation of hunger?
Ghrelin
What do long-term regulators of appetite do?
Govern caloric intake and energy expenditure over periods of weeks to years.
What peptides inform the brain of how much adipose the body has?
Leptin and Insulin
What secretes Leptin?
adipocytes throughout the body
What does leptin do?
informs the brain on how much fat it has.
What secretes insulin?
pancreatic beta cells
What does insulin stimulate?
glucose and amino acid uptake
What does insulin promote?
glycogen and fat synthesis
Which has a greater effect on appetite: insulin or leptin
leptin
What has receptors for all short and long term chemical signals?
The Arcuate nucleus of the hypothalamus
What are the two substances secreted by the arcuate nucleus of the hypothalamus that affect appectite?
Neuropeptide Y and melanocortin
What is neuropeptide Y?
a potent appetite stimulant
what is melanocortin?
an eating inhibitor
What stimulates neuropeptide Y?
Gherlin
What inhibits neuropeptide Y?
insulin, PPY, and leptin
What stimulates Melanocortin?
Leptin
What does melanocortin inhibit?
the secretion of appetite stimulants (endocannabinoids)
What partly stimulates hunger?
gastric peristalsis
Does gastric peristalsis affect the amount of food consumed?
NO. Its the PYY and CCK that shut off food intake.
What are the lasting effects of satiety due to?
nutrients absorbed into the blood.
What do neurotransmitters do?
stimulate the desire for different types of food.
What food type does the neurotransmitter norepinephrine stimulate the desire for?
carbohydrates
What food type does the neurotransmitter galanin stimulate the desire for?
fats
What food type does the neurotransmitter endorphins stimulate the desire for?
protein
What is one calorie?
the amount of heat required to raise temperature of 1 g of water 1 degree C.
What is one Calorie (in dietetics)
1,000 calories, or 1 kcal in physiology
What is a calorie measure?
the capacity to do biological work.
How many kcal/g do carbs and proteins yield?
about 4 kcal/g
why are sugar and alcohol considered “empty” calories?
they provide few nutrients and suppress appetite
how many kcal/g do fats yield?
about 9 kcal/g
what is a nutrient?
any ingested chemical used for growth repair, or maintenance of the body.
What are the 6 classes of nutrients
water, carbs, lipids, proteins, vitamins, minerals
What are considered macronutrients?
nutrients that must be consume in relatively large quantities: water, carbs, lipids, proteins
What are considered micronutrients?
nutrients that are only needed in small quantities: vitamins and minerals
What are DRIs?
dietary reference intakes: RDAs (recommended dietary allowances) and AIs (adequate intake)
What are essential nutrients
nutrients that cannot be synthesized in the body: minerals, most vitamins, eight amino acids, and 1-3 of the fatty acids
A well-nourished adult body has what amount of carbs?
440 g:
325 g of muscle glycogen
90-100 g of liver glycogen
15-20 g of blood glucose
what are the functions of sugars?
1) structural components of other molecules including nucleic acids, glycoproteins, glycolipids, ATP, and related nucleotides (GTP, cAMP)
2) most serve as fuel
Why does most sugar serve as fuel for the body?
because they are easily oxidized source of chemical energy
What body components depend solely on carbohydrates?
Neurons and erythrocytes
What is hypoglycemia?
deficiency of blood glucose
What does hypoglycemia cause?
nervous system disturbances such as weakness and dizziness
How is plasma glucose concentration carefully regulated?
interplay of insulin and glucagon; balance between glycogen and free glucose
how does carb intake influence metabolism of other nutrients?
fats used as fuel when glucose and glycogen levels are low, and excess carbs are converted to fat.
What nutrient is required in greater amounts than any other nutrient?
carbohydrates
What is the RDA for carbs?
130 g
how many carbs does the brain consumer daily?
120 g of glucose per day
What is the average consumption of sugar and corn syrup per year?
60 lb of sugar and 46 lb of corn syrup
Dietary carbs come in what three principal forms?
glucose, galactose, and fructose
where do dietary carbs mainly come from?
mainly from digestion of starch and disaccharides.
What organs convert galactose and fructose to glucose?
small intestine and liver
What is a normal blood sugar (glucose) concentration?
70-110 mg/dL
What are the disaccharides?
sucrose (table sugar), maltose, lactose
What are the polysaccharides (complex carbs)?
starch, glycogen, and cellulose
is cellulose a nutrient?
no, because it is not digested, but is important as a dietary fiber.
where do nearly all dietary carbs come from?
plants
Where does sucrose come from?
Sucrose is refined from sugarcane and sugar beets
where does fructose come from?
Fructose is present in fruits and corn syrup
Where does maltose come from?
Maltose is present in some cereal grains
Where does Lactose come from?
Lactose is found in cow’s milk.
What is dietary fiber?
All fibrous material of plant and animal origin that resists digestion: cellulose, pectin, gums, and lignins
What is the RDA for fiber?
25 g/day for females, 38 g/day for males
Where is water soluble fiber found?
In oats, beans, peas, brown rice, and fruits
What role does water-soluble fiber play in the body?
decreases blood cholesterol and LDL levels
What are some types of water-insoluble fiber?
cellulose, hemicellulose, lignin
Do water-insoluble fibers have an effect no cholesterol and LDL levels?
no
What does water-insoluble fiber do?
absorbs water in intestines
softens stool and increases its bulk
stretches the colon
stimulates peristalsis (quickens passage of feces
What can excessive intake of water-insoluble fiber do?
interfere with absorption of some elements such as iron, calcium, magnesium, phosphorous, and others
What is the average body fat percentage for females and males?
females: 25%
males: 15%
A well-nourished adult meets 80-90% of resting energy needs from what?
fat
which is superior for energy storage and why?
fat is superior to carbs because:
1) carbs are hydrophilic, absorbs water, and expands, occupying more space in tissue, whereas fat is hydrophobic and is more compact energy storage
2) fat contains over twice as much energy: 9 kcal/g for fat; 4 kcal/g for carbs
What are the glucose sparing effects of fat?
Glucose is spared for consumption by cells that cannot use fat, like neurons
What are the protein sparing effects of fat?
Protein is spared as fuel as long as there is enough fat.
What are the fat soluble vitamins that are absorbed with dietary fat?
A, D, E, K
How much fat is needed per day in order to absorb the necessary amount of fat soluble vitamins?
20 g/day
What other diverse functions does fat have besides an energy source?
1) structural: phospholipids and cholesterol (components of plasma membranes and myelin
2) chemical precursors:
3) important protective and insulating functions
What are the chemical precursors that fat assists with?
cholesterol (precursor of steroids, bile salts, vitamin D
thromboplastin (an essential blood-clotting factor; a lipoprotein)
fatty acids (arachidonic acid and linoleic acid: precursors for prostaglandins and other eicosanoids
What are the daily fat requirements?
less than 35% of daily calorie intake:
1) less than 10% of fat as saturated
2) limit saturated fat and cholesterol
how much fat does the typical American get?
40-50%
Where are most fatty acids found?
they are synthesized by the body
Where are saturated fats from?
Animal origins (meat, egg yolks, dairy products) some in coconut and palm oils
Where are unsaturated fats from?
nuts, seeds, and most vegetable oils
Where is cholesterol from?
egg yolks, cream, shellfish, meats
only in tiny, trace amounts of food of plant origin
How much protein makes up the total body mass?
12-15%
Where is most of the body’s protein found?
in skeletal muscle (65%)
What are the functions of proteins? (5)
1) Muscle contraction
2) motility of cilia and flagella
3) structural components
4) Buffer pH of body fluids
5) resting membrane potential of all cells
What structural components do proteins contribute to?
1) all cellular membranes
2) fibrous proteins
3) globular proteins
4) plasma proteins
What is the protein RDA?
46-56 g/day
How is protein RDA calculated?
weight in pounds x 0.37
When is higher protein necessary?
stress, infection, injury, and pregnancy
What can excessive protein intake do?
overload the kidneys with nitrogenous waste and cause kidney damage
What are the 8 out of 20 essential amino acids that cannot be synthesized by the body?
isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine
In addition to the 8 out of 20, what other two essential amino acids cannot be synthesized by an infant’s body?
histidine and arginine
Can cells store surplus amino acids for later use?
no
What happens if a particular amino acid is missing when a protein is being synthesized?
The protein cannot be synthesized
What are complete proteins?
high-quality dietary proteins that provide all essential amino acids in the necessary proportions for human tissue growth, maintenance and nitrogen balance
What are incomplete proteins?
lower quality proteins that lack on or more essential amino acids
What is net protein utilization?
the percentage of amino acids in a protein that the human body uses
What percentage of animal and plant proteins do we use?
80% of animal
50% of plant
What are the advantages of decreasing meat intake and increasing plant intake?
more vitamins, mineral and fiber,
less saturated fat
no cholesterol
less pesticide
What are complete animal proteins?
meat, eggs, and dairy products
What is nitrogen balance?
Rate of nitrogen ingested equals the rate of nitrogen excreted
What is the chief dietary source of nitrogen?
proteins
what causes a positive nitrogen balance?
nitrogen ingestion exceeds its excretion (more into the body than out in the urine?)
When does a positive nitrogen balance most often occur?
in children because they retain protein for tissue growth, and pregnant women and athletes in resistance training
What two things promote protein synthesis and positive nitrogen balance
growth hormone and sex steroids
What is a negative nitrogen balance?
When nitrogen excretion exceeds ingestion (more in urine than going into the body)
What causes a negative nitrogen balance?
1) Body proteins being broken down for fuel; muscle atrophy
2) Glucocorticoids (like cortisol) promote protein catabolism in states of stress
Why does muscle atrophy sometimes occur?
1) Muscles and liver proteins are more easily broken down than others
2) carb and fat intake is insufficient to meet body’s energy needs
What are minerals?
inorganic elements that plants extract from soil or water and introduce into the food web
What are vitamins?
small dietary organic compounds that are necessary for metabolism
Why are vitamins and minerals important?
They are essential to our ability to use other nutrients
Can minerals and vitamins be used as fuel?
no
What percent of minerals is our body mass?
about 4%
What part of the body contains the most minerals?
calcium and phosphorous in bones and teeth (3/4)
What 4 minerals acts as cofactors for enzymes?
calcium, iron, magnesium, and manganese
What is important about phosphorous?
1) key structural component of phospholipids, ATP, cAMP, GTP, and creatine phosphate
2) basis for the phosphate buffer system
What is iron essential for?
the oxygen carrying capacity of hemoglobin and myoglobin
Where is chlorine found in the body?
It is a component of stomach acid
What is the function of mineral salts?
electrolytes and govern functions of nerve and muscle cells, osmotically regulate the content and distribution of water in the body, and maintain blood volume
What are the best sources of minerals?
vegetables, legumes, milk, eggs, fish, shellfish, and some other meats
What is the recommended daily sodium intake?
1.5 g/day
How much sodium does the typical American diet contain?
3.4 g/day
what can cause or contribute to hypertension?
elevated salt intake
Where must most vitamins be obtained from?
the diet
What are provitamins?
precursors that allow the body to synthesize some vitaims
What vitamins can the body synthesize using precursors?
Niacin Vitamin A Vitamin D Vitamin K Some B vitamins
How is niacin synthesized?
from amino acid tryptophan
How is vitamin A synthesized?
from carotene
How is vitamin D synthesized?
from cholesterol
How is vitamin K synthesized?
by bacteria of the large intestine
What are water-soluble vitamins?
vitamins that are absorbed with water in the small intestine and quickly excreted by the kidneys (not stored)
What are the water-soluble vitamins?
Vitamin C (ascorbic acid) and vitamin B
Why is vitamin C important to the body?
1) promotes hemoglobin synthesis, collagen synthesis, and sound connective tissue structure
2) an antioxidant that scavenges free radicals and possibly reduces the risk of cancer
Why are B vitamins important?
1) Function as coenzymes or parts of coenzyme molecules
2) Assist enzymes by transferring electrons from one metabolic reaction of cancer
3) Make it possible for enzymes to catalyze these reactions
What are the fat soluble enzymes?
Vitamin A, D, E and K
How are fat-soluble vitamins absorbed?
They are incorporated into lipid micelles in the small intestine and absorbed with dietary lipids
Why is Vitamin A important?
1) component of visual pigments
2) promotes proteoglycan synthesis and epithelial maintenance
Why is Vitamin D important?
Promotes calcium absorption and bone mineralization
Why is Vitamin K important?
Essential for prothrombin synthesis and blood clotting
Why are Vitamins A and E important?
They are antioxidants like ascorbic acid
What is the effect of vitamin A excess?
anorexia, nausea and vomiting, headache, pain and fragility in the bones, hair loss, an enlarged liver and spleen, and birth defects
What are the effects of vitamin A deficiency?
night blindness; dry skin, hair, and conjunctiva; cloudy cornea; increased incidence of infections
What is the world’s most common vitamin deficiency?
vitamin A
What three processes are considered cellular respiration?
Krebs Cycle, Electron Transport Chain, Oxidative Phosphorylation
Where does glycolysis occur?
in cytoplasm
Where does the krebs cycle occur?
in mitochondrial matrix
Where does the electron transport chain occur?
inner mitochondrial membrane
where does oxidative phosphorylation occur?
inner mitochondrial membrane
Where is most cellular energy stored?
in the chemical bonds of storage molecules such as adenosine triphosphate (ATP)
When is chemical energy captured by cells?
during glucose breakdown when oxygen is available
What are two general “rules” about ATP?
1) ATP is NOT transported from one cell to another
2) ATP is NOT stored by cells to any substantial extent
What does a cell’s work rate depend on?
the rate at which that cell is able to produce ATP
What are heterotrophs?
Consumers of organic materials to acquire energy (eating meats and veggies)
What are autotrophs?
Producers of their own energy (photosynthesis by plants and algae etc)
What is the ultimate source of cellular energy?
photosynthesis
what do autotrophs store their energy in the form of?
glucose
what processes do heterotrophs and autotrophs use to break down glucose?
glycolysis and cellular respiration
What is the equation for photosynthesis?
6 CO2 + 6 H2O + light energy –> C6H12O6 + 6 O2
What is the equation for complete glucose breakdown?
C6H12O6 + 6 O2 –> 6 CO2 _ 6 H2O + ATP energy + heat energy
How do plants use glucose as a source of energy?
convert glucose to sucrose or starch for storage
How is energy stored in humans?
as long chains of glucose, called glycogen, or as fat.
What are the two general phases of the breakdown of glucose?
1) glycolysis
2) cellular respiration (kreb’s cycle, ETC, Ox Phos)
What is the process of glycolysis?
the splitting of glucose (a 6 carbon sugar) into two molecules of pyruvate (3-carbon sugars)
Does glycolysis make ATP or use ATP?
both: glycolysis has energy investment and energy harvesting stages
How does glycolysis begin breaking down glucose?
an initial investment of 2 ATP molecules
How does the addition of phosphates effect the fructose biphosphate?
makes it highly reactive
What is the net gain of ATPs per glucose molecule?
2 ATP
What is the “empty” electron carrier?
NAD+
What is added to the NAD+?
2 high-energy electrons and a hydrogen ion
What is made when 2 high-energy electrons and a hydrogen ion are combined with NAD+?
NADH
How many NADH carriers are produced per glucose molecule?
2
During glycolysis, what is fructose biphosphate broken down into?
2 G3P molecules
What are the two G3P molecules are converted into?
2 pyruvate molecules
What results from the 2 pyruvate molecules?
4 ATP and 2 NADH
What is the net result?
2 ATP and 2 NADH
How does cellular respiration extract energy from glucose?
It breaks down the 2 pyruvate molecules into 6 carbon dioxide molecules and 6 water molecules
How many ATP molecules are formed during cellular respiration?
36 (2 from glycolysis and 34 from cellular respiration)
what organelles are specialized for the aerobic breakdown of pyruvate?
mitochondria
what is contained in the inner mitochondrian membrane?
a central compartment containing the fluid matrix
what does the outer mitochondrian membrane form?
the outer surface of the organelle
What lies between the outer and inner mitochondrian membranes?
an intermembrane space
What two stages does cellular respiration occur in?
1) the conversion of pyruvate to acetyl CoA, as it moves through the Krebs cycle
2) Electrons move through the ETC and ATP is created by chmiosmosis (oxidative phosphorylation)
Where is pyruvate synthesized?
in the cytosol
Where does cellular respiration begin?
In the mitochondrial matrix?
Once pyruvate is transported into the mitochondrion matrix, further breakdown occurs in what two stages?
1) the formation of acetyl CoA
2) the Krebs cycle
What results when pyruvate is split?
acetyl group is formed and CO2 released
Who discovered the Krebs cycle?
Hans Krebs: he won the nobel prize in 1953
What else is the Krebs cycle called?
1) citric acid cycle (CAC)
2) tricarboxylic acid cycle (TCA)
How does the Krebs cycle begin?
Combining acetyl CoA with a 4-carbon molecule to form 6-carbon citrate, and releasing CoA.
How much CO2 is released during the Krebs cycle?
2
In the Krebs cycle, how much ATP is produced by each acetyl CoA?
1
In the Krebs cycle, how much NADH is produced by each acetyl CoA?
3
In the Krebs cycle, how much FADH2 is produced by each acetyl CoA?
1
What is FAD?
a high-energy electron carrier (similar to NAD)
What is generated as a waste product during the mitochondrial reactions?
CO2
In the Krebs cycle, how is chemical energy released?
by breaking down each acetyl group
In the Krebs cycle, how is the released chemical energy captured?
in energy-carrier molecules
For every glucose molecule that was broken down, how many high-energy electrons are captured in carrier molecules?
10 NADH and 2 FADH2
How many electrons are released by the carriers and where do thy go?
2 electrons into the ETC
What is the flow of electrons through the whole ETC called?
oxidative phosphorylation
In the ETC, what is the buildup of H+ in the intermembrane space used for?
to generate ATP
At the end of the ETC, what happens to the energy-depleted electrons?
they are transferred to oxygen (which acts as an electron acceptor)
What do energy-depleted electrons, oxygen, and hydrogen ions combine to form?
water
How many water molecules are produced in the ETC?
1 water molecule is produced for every 2 electrons
What is most needed to allow the ETC to function and for ATP synthesis to continue?
Oxygen
What is the final electron acceptor in the ETC?
oxygen
How much metabolic water is produced per day in the process of voiding electrons from cells?
0.8 L
What is chemiosmosis?
the process by which energy is first used to generate a gradient of H+ and then captured in the bonds of ATP as H+ flows down its gradient
During ETC, where is the concentration of H+ the highest?
in the intermembrane space.
During ETC, where is the concentration of H+ the lowest?
in the matrix
When H+ flows across the membrane through the ATP synthase channels, what is generated by this movement?
ATP from ADP and Phosphate
For each molecule of glucose, how many molecules of ATP are synthesized due to the flow of H+ through the synthase channel?
32
After leaving the mitochondrion, where does the ATP go?
into the cytoplasm to be used by the cell
How much ATP do people produce, use, and regenerate daily?
The equivalent of their body weight.
What does cyanide poisoning do to the process?
inhibits Cyt C oxidase enzyme (phase IV) which “uncouples” the ETC (suffocation from the inside at every cell)
What are the three components of a cyanide antidote package?
amyl nitrite, sodium nitrite, and sodium thiosulfate
What does a cyanide antidote do?
helps convert cyanide to thiocyanate, which is excreted renally.
What does fermentation produce?
lactate or alcohol and carbon dioxide
What is the second stage of glucose breakdown if oxygen is not available?
fermentation
Does fermentation produce any ATP?
no
In fermentation, what happens to the pyruvate?
remains in the cytoplasm and is converted into lactate or ethanol and CO2
How does fermentation allow an organism to continue to function?
it regenerates NAD+, which must be available for glycolysis to continue
What does lactate fermentation produce?
lactic acid from pyruvate
What happens during alcoholic fermentation?
pyruvate is converted into ethanol and CO2. It also converts NADH to NAD+, which is then available for glycolysis
