Chapter 72

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When is energy stored as fat?

When a person is overfed and energy intake exceeds expenditure

When does starvation occur?

When energy intake is insufficient to meet the body's metabolic needs

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What is 4.1 Calories?

Energy liberated from each gram of carbohydrate as it is oxidized to CO2 and water

Describe the proportion of the carobhdyrates and so on in food?

Carbojhydrates are in vegetable and grain, proteins and arbohydrates are mixed in watery media

What is the average daily requirement for proteins?

30 to 50 grams

What are partial proteins?

Proteins that have inadequate quantities of certain essential amino acids and cannout be used to replace degraded proteins

What is kwashiorkor?

Individuals who consume cornemal as principal source of protein, which is a protein-deficiency syndrome

What does it mean protein spareres?

Carbohydrates and fats are protein sparers because all body's energy is derived fro mthese two components

What happens during state of starvation?

Body's protein stores are consumed instead

What is respiratory quotient?

Ratio of carbon dioxide production to oxygen utilization, which can be used to estimate fat and carbohydratae utilization

What is the respiratory quotient for metabolism of fat averaging?


What is the average respiratory quotient when proteins are oxidizied by cells?


What happens immediately after a mixed meal containing carbohydrates, proteins and fats?

Respiratory quotient approaches 1.0

What happens about 8 to 10 hours after a meal?

Respiratory quotient approaches that for fat metabolism which is about 0,70

What happens in untreated diabetes mellitus?

Little carbohydrate can be used, therefore respiratory quoteint remains near that for fat metabolism which is 0,70

What happens with nitrogen of protein during digestion?

During metabolism of protein, about 90% of nitrogen is excreted in urine in form of urea, uric acid, creatinine,
Remaining 10% is excreted in feces

What does it mean that a person has a negative nitrogen balance?

His or her body stores of protein are decreasing daily

What is needed for stability of body's total amss and composition?

It requries that energy intake match energy expenditure

In athletes and laborers, energy expenditure for high level of muscle activity may be what?

6000 to 7000 Calories per day, compared with only bout 2000Calories per day for sedentary individuals(thus a largrge energy expenditure needs increase in caloric intake)

What does hypothalamus contain?

Hunger and satiety centers

Which neuronal centers of hypothalamus participate in contorl of food intake?

Lateral nuclei of hypothalamus (serving as a feeding center) and stimulation of this areas causes an animal to eat voraciously (hyperphagia)

What happens when there is a destruction of lateral hypothalamus?

It causes lack of desire for food and inanition, weight loss, muscle weakness and decreased metabolism

What does ventromedial nuclei of hypothalamus serve as?

As a major satiety center, sensing of nutritional satisfaction that inhibits feeding center (aphagia-animal refuses to eat)

What happens with destruction of ventromedial nuclei?

It causes voracious and continued eating (obesitey)

What also play a role in regulating food intake?

Paraventricular, dorsomedial and arcuate nuclei of hypothalamus

What does lesion of paraentricular nuclei cause?

Excessive eating

What does lesions of dorsomedial nuclei do?

It depress eating behavior

What does hypothalamus receive+

1) neural signals from GI tract providing sensory information about stomach filling 2)chemical signals from nutrients in blood (glucose, amino acids signify satiety) 3) signals from GI hormones, 4) signals from hormones released by adipose tissue and 5) signals from cerebral cortex (sight, smell and taste)

What are orexigenic substances?

They stimulate feeding

What are anorexigenic substances?

Inhibit feeding

Which are two distinct types of neurons in arcuate nuclei of hypothalamus that are important as controllers of both appetite and energy expenditure)

1) POMC neurons producing alpha-melanocyte-stimulaating hormone (alpha-MSH) together with cocaine- and ampheatmine-relate transcript (CART) and 2) neurons that produce orexigenic substances neuropeptide Y (NPY) and agouti-related protein (AGRP)

What happens with activation of POMC neurons?

It decreases food intake and increases energy expenditure

What happens with activation of NPY-AGRP neurons?

They have opposite effects, increasing food intake and reducing energy expenditure

What regulates appetite?

Leptin, insulin, CCK and ghrelin

What do POMC neurons release?

Releases alpha-MSH, which then acts on melanocortin receptors in neurons of paraventricular nuclei

Given examples of orexigenics?

Neuropeptide Y and Ghrelin)

What is regulation of quantity of food intake divided into+

Short-term regulation (concerned with preventing overeating at each meal) and long-term regulation (concerned with maintenance of normal quantities of energy stores in body)

What inhibits feeding?

When Gi tract becomes distended, stretch inhibitory signals are transmitted by vagi to suppress feeding centers, thereby reducing desire for food

What does CCK has as a role?

It activates receptors on local sensory enrves in duodenum, sending messages to brain via vagus nerve that contribute t o satiation and meal cessation

What is Peptdie YY (PYY)?

It is secreted from GI tract, especially from ileuum and colon, it has an unclear function

What is glucaogn-like peptide (GLP)?

Presence of food in intestines stimulates them to secrete GLP, which enhances insulin production from pancrea, and both GLP and insulin suppress appetite

GLP an insulin tend to do what?

To suppress appetite

What does ghrelin increase?

It increases feeding (blood elvels of ghrelin rise during fasting, peak just before eating and fall rapidly after a meal)

What happens if we give food to an animal which has been starving a lot?

It eats greater quantity than does an animal that has been on a regualt diet

What causes hunger?

A decrease in blood glcusoe concentration

What effect does temperature have on food intake?

When an animal is exposed to cold, it icnrease feeding, when it is exposed to heat, it tends to decresae its caloric intake (increased food intake in a cold animal increases its metabolic rate and provides increased fat for inulation, both of which tend to correct the cold state

From what is leptin released?

From adipocytes

Describe leptin?

When amount aof adipose tissue increases, adipocytes produce increased leptin, released into blood, circulating to breain, occupying leptin receptors in hypothalamus

What does stimulation of leptin receptors cause?

Decrease fat storage including 1) decreased production in hypthalamus of appetite stimulaors such as NPY and AGRP),2) activation of POMC neurons, causing release of alpha-MSH

What does stimulation of leptin receptors cause?

3)increased producton in hypothalamus of substances such as corticotropin-releasing hormone decreasing food intake 4)increased sympathetic nerve activity 5) decreased insulin secretion which decreases energy storage

What does leptin resistance mean?

Leptin receptors or postreceptor signaling pathways activated by leptin may be resistant to activation by leptin in obese people, who continue to eat despite having high levels of leptin

What drugs have been used for decreasing the degree of hunger?

Amphetamines, phentermine, topiramate (which can be dangerous aswell), and lorcaserin which activates serotonin receptors in brain and promotoes increased POMC expression

What is anorexia?

It is a reduction in food intake caused by diminished appetite

What is anorexia nervosa?

An abnormal psychic state in which a person lsoes all desire for food and even becomes nauseated by food, as a result ,svere inanition occurs

What is cachexia?

A metabolic disorder of increased energy expenditure elading to weight lsos greater than that caused by reduced food intake alone (anorexia and cachexia often occur together in cancer)

What can also cause anorexia and cachexia?

Several inflammatory cytokines, including tumor necrossi factor-alpha, interleukin-6, interleukin-1Beta and proteolysis-inducing factor

What effect does starvation have on the food stored of the body?

Quantity of carbohydrate stored in entire body is only a few hundred grams, so progressive depletion of tissue fat and protein occurs more, until most of fat stores in body are gone

What three phages does protein undergo during depletion during starvation?

Rapid depletion at first, followed by slowed depletion and finally rapid depletion shortly before death

What can the ketone bodies do+

They can cross blood-brain barrier like glucose, therefore about two thirds of brain-s energy is derived from ketone bodies principally from Beta-Hydroxybutyrate

What about vitamin deficincies in starvation?

Starvation of some vitamins, especially water-soluble vitmains, vitamin B group and vitamin C do not last long during starvation (can lead to death)

What is scurvy?

Absence of vitamin C in diet can cause symptoms within a few weeks and cause death from scurvy

In what form does vitamin A occur in animal tissues?

As retinol

What does vitamin A deficiency cause?

It causes night blindness and abnormal epithelial cell growth

What is one basic function of vitamin A?

It is its use in formation of retina pigments of eye, itamin A is needed for formation visual pigments and therefore to prevent night blindness

How does vitamin A deficiency manifest itself?

1)scaliness of skin and acne 2) failure fo growth of young animals 3) failure of reproduction 4) keratiniziation of corena

What more hapepns in vitamin A deficiency?

Damaged epithelial structures become infected (e.g. conjunctivate of eyes, linings of urinary tract and respiratory apssage)

What can thiamine defiiency cause?

Degeneration of myelin sheaths of nerve fibers, and also fiber tracts in cord can degenerate to such as extend that paralysis occasionally ersults

What happens with a severe thiamine deficiency?

Cardiac failure because of weakened cardiaca muscle, but also peripheral edema and ascites

What can thiamine deficiency lead to (GI tract)?

Indigestion, severe constipation, anorexia, gastric atony and hypochlorhydria

What happens with a deficiency of niacin?

Normal rate of dehydrogenation cannot be maintained, therefore oxidative delivery of energy from foodstuffs to functioning elements of all cells cannot occur at normal rates

What more happens with niacine deficiency?

Pellagra and black tongue (pellagra is exacerbated in people on a corn diet because orn is deficient in amino acid tryptophan, which can be converted in limitied quantities to niacin in body)

What does deficiency of ribovlavin cause?

Severe dermatitis, vomiting ,diarrhea, muscle spasticity

How does niacin occur?

It is also called nicotinic acid and is in the form of NAD and NAD phosphate

What is the other name for riboflavin?

Vitamin B2

Cobalt atom of vitamin B12 (related) has what role?

It combines reversibly with other substances

What does vitmain B12 deficiency cause?

Pernicious anemmia (a type of anemia caused by failure of red blood cell maturation when vitamin B12 is deficient)

What is the funtion of vitamin B12?

To act as a coenzyme for reducing ribonucleotides to deoxyribonucleotides, 1) promotoion of growth and 2) promotion of red blood cell formation and maturation

What can vitamin B12 defieincy cause?

Demyelination of large nerve fibers of spinal cord

What is the cause of vitamin B12 deficiency?

Deficeicny of formation of intrinsic factor, which is normally secreted by parietal cells of gastric glands and is essential for absorption of vitamin B12 by ileal mucosa

Describe folic acid (pteroylglutamic acid)?

It functions as a carrier of hydroxymethyl and formyl groups, and is part in the synthesis of purines and thymine, which are required for DNA formation

What is one of the significant effects of folic acid defiency?

Development of macrocytic anemia (almost identical to that which occurs in pernicious anemia)

Dietary lack of pyriodxine can casue what?

Dermatitis, decreased rate of growwth, development of atty liver, anemia and evidence of mental deterioration

Pantothenic acid is incorportated in the body into what?

coenzyme A (CoA), which has many metabolic roles in the cells such as 1) conversion of decarboxylated pyruvic acid into acetyl-CoA before its entry into citric acid cycle and 2) degradation of fatty acid molecules into acetyl-CoA

What can lack of pantothenic acid lead to?

It can lead to depressed metabolism of carbohyrates and fats

What can deficieincy of pantothenic acid lead to?

Retarted growth, failure of reproduction, graying of hair, dermatitis, fatty liver and hemorrhagic adrenocortical necrosis

What does ascorbic acid deficiency lead to?

Weakening of collagen fibers throughout body

What is ascorbic acid essential for activating?

The enzyme prolyl hydroxylase, which promotoes hydroxylation st ep in formation of hydroxyproline

What does scurvy lead to?

It leads to failure of wounds to heal, which is caused by failure of cells to deposit collagen fibrils and intercellular cement substances

What does lack of ascorbi acid also cause?

Cessation of bone growth

What happens with blood vessels in persons with scurvy?

Blood vessel walls become extremely fragile because of 1) failure of endothelial cells to be cemented together properly and 29 failure to form collagen fibrils normally presentin vessel walls, so capillaries are to rupture

What does vitamin D do?

It increases calcium absorption from gastrointestinal tract and helps control calcium deposition in bone

What can lack of vitamin E cause?

Degeneration of germinal epithelium in testis and therefore can cause male sterility, lack of vitamin E can also cause resopriton of a fetus after conception in female, so vitamin E is sometimes caleld antisterility vitmain

What is the protective role of vitamin E?

Prevention of oxidation of unsaturated fats

What is magnesium required for?

As a catalyst for many intracellular enzymatic reactions, particularly those related to cabrohydrate metabolism

What does increased extracellular concentration of magnesium do?

It depresses nervosu system activity, as well as skeletal muscle contraction

What can phosphates do?

They have the ability to combine reversibly with coenzyme systems and with multiple other compiunds that are necessary for operation of metabolic processes, for example phosphocreatine, adenosine triphosphate

In what form is iron in the body+

It is in the form of hemoglobin, iron is absolutely essential for both transport of oxygen to tissues and operation of oxidative systems within tissue cells, without which life would cease within a few seconds

What is a trace element?

Elements that are present in body in small quantities

What is iodine essential for?

For formation of thyroxine and triiodothyronine

What is zinc integral part of?

Carbonic anhydrase, lactic dehydrogenase, and peptidases

What effect does fluorine have?

For formation of teeth during period of life, suppressing cariogenic process

What is fluorosis?

Excessive intake of fluorine, which manifests in mild state by mottled teeth and in more severe state by enlarged bones