Chapter 26: Nutrition and Metabolism

Merged flashcards from Chapter 26, McGraw Hill Anatomy and Physiology Tenth Edition, by Kenneth S. Saladin.

Body weight

Determined by energy balance; gain or loss determined by difference between intake and output around a person’s set point (varies ~30-50% due to heredity, environment, activity, eating)

Appetite

Mechanisms that control feelings of hunger and satiation that can vary with age, weight, and other factors and work over periods of minutes to hours

Appetite regulators

Short-term hormones:

• Ghrelin

• Peptide YY (PYY)

• Cholecystokinin (CCK)

• Amylin

Long-term hormones:

• Leptin

• Insulin

Ghrelin

Short-term appetite regulator made in the stomach’s fundus that causes feelings of hunger and stimulates hypothalamus growth hormone production, nutrient absorption preparation

• Secretion stopped after an hour of eating

Peptide YY (PYY)

Short-term appetite regulator made in the enteroendocrine cells of the ileum and colon that senses food arrival for satiation

Cholecystokinin (CCK)

Short-term appetite regulator secreted in the duodenum and jejunum that simulates bile and pancreatic enzyme secretion for satiation

Amylin

Short-term appetite regulator that promotes satiation and inhibits stomach activity

Leptin

Long-term appetite regulator secreted by adipocytes that indicates fat levels; stimulates nerve fibers to produce norepinephrine for fat breakdown (lipolysis)

• Deficient receptors can cause obesity in some cases

Insulin

Long-term appetite regulator secreted by the pancreas to stimulate glucose and amino acid uptake as well as glycogen and fat synthesis; helps index fat stores with weaker effect than leptin

Hypothalamus

An important center of appetite regulation in the brain

Hunger contractions

Contractions within the stomach after emptying that increase in intensity over a period of hours; can be briefly satisfied by chewing and stomach filling but requires nutrition for satiation

Obesity

Having a body weight more than 20% the recommended norm for one’s age, sex, and height; can be caused by heredity and overfeeding for a shortened life expectancy

Body mass index (BMI)

Number used as an indication of being overweight or obese; calculated based on weight and height

Calorie

A measure of the capacity to do biological work; specifically, the amount of heat required to raise the temperature of 1 gram of water 1 degree celcius

Kilocalorie (kcal)

1,000 calories

4 kcal per gram

The calorie density of carbohydrates and proteins

7 kcal per gram

The calorie density of alcohol and sugars that provide few nutrients and suppress appetite

9 kcal per gram

The calorie density of fats

Nutrient

Any ingested chemical used for growth, repair, or maintenance of the body

Macronutrients

Water, carbohydrates, lipids, and proteins — these are required in larger quantities

Micronutrients

Vitamins and minerals — these are required in small quantities

Carbohydrate

Macromolecule that serves as an easily absorbed source of fuel in greater amounts for cells; regulated by insulin and glucagon and can be found in plants, grains, and milk

130 grams

The recommended daily allowance for carbohydrates

120 grams

The amount of carbohydrates that the brain consumes each day

Hypoglycemia

Blood glucose deficiency that can cause nervous system disturbances, weakness, and dizziness

Glycemic index (GI)

The effect of dietary carbohydrates on blood glucose levels; higher indexes stimulate higher demands and thus increase obesity and type 2 diabetes mellitus risks

Fiber

Fibrous material that resists digestion — not technically a nutrient but allows for smoother digestive function

Lipids (fats)

Macronutrient that accounts for 80-90% of an adult’s resting energy needs through energy stores; very dense at 9 kcal per gram and aids vitamin absorption (lower consumption equates to vitamin deficiency)

High-density lipoproteins (HDLs)

“Good” cholesterol found in healthier fatty foods; indicates cholesterol is being removed from arteries and transported to the liver for disposal

Low-density lipoproteins (LDLs)

“Bad” cholesterol found in unhealthy fatty foods; can be increased via smoking, saturated fat intake, coffee, and stress but is lowered via vigorous exercise

Protein

Macromolecule that constitutes 12-15% of body mass with 65% in skeletal muscles; contributes to muscle contraction, cell components, pH buffers and are made of amino acids from the diet or synthesized by the body

Minerals and vitamins

Micronutrients that are not used as fuel but nutrient absorption aids that mainly come from the diet in small amounts; function in pH buffering, enzymatic action, blood functions

Catabolism

The breakdown of glucose in small steps to be transferred to ATP and heat generation

Glycolysis

The breakdown of glucose into two molecules of pyruvate

Anaerobic fermentation

The reduction of pyruvate to lactate without using oxygen

Aerobic respiration

The more efficient form of cellular respiration that requires oxygen and oxidizes pyruvate to carbon dioxide and water

Enzymes

Proteins that contribute to glucose catabolism and energy production

Glycogenesis

The synthesis of glycogen stimulated by insulin to chain glucose monomers together

Glycogenolysis

The hydrolysis of glycogen to release glucose back into blood

Glycogen

An energy-storage molecule that can aid in glucose level regulation

Glyconeogenesis

The synthesis of glucose from noncarbohydrates, such as glycerol and amino acids, that occurs in the liver and kidneys if necessary

Lipogenesis

The synthesis of fat from other types of molecules, such as amino acids and sugars

Lipolysis

Breaking down fat for fuel in the body; depends on hormone receptors for balance

Proteins

Macromolecules made of amino acids that can be converted to glucose or fat or be used in enzymatic action; synthesis stimulated by growth hormone, thyroid hormone, and insulin with an ample amino acid supply

Liver

Organ that aids in carbohydrate, lipid, and protein metabolism among other nondigestive roles — damage can be life-threatening

Hepatitis

Inflammation of the liver that is caused by a virus; can range from mild inflammation to more serious progression causing cirrhosis or liver cancer

Cirrhosis

An irreversible inflammatory liver disease with poor prognosis; can result from alcohol abuse, hepatitis, gallstones, or pancreatic inflammation ultimately causing scar tissue, jaundice, ascites, impaired clotting, and liver necrosis and failure

Absorptive state (fed state)

State of metabolism during the four hours during and after a meal with nutrient absorption to meet energy and other needs without the need for stored fuels

Postabsorptive state (fasting state)

State of metabolism after meals in the late morning, afternoon, and overnight with an empty stomach to meet needs from stored fuels

Fed state carbohydrates

Where carbohydrates are transported to the liver for transportation throughout the body with any excess producing glycogen or fat

Fed state amino acids

Where amino acids pass through the liver and go to other cells for protein synthesis (liver cells may use them for fuel or fatty acid synthesis)

Insulin

Hormone that regulates glucose uptake by most cells and causes blood glucose levels to fall and index fat stores; can also transport proteins into cells for protein synthesis

Fasting state fats

Where fats are converted to glucose for energy

Fasting state proteins

Where proteins are used as fuel (particularly muscle proteins) when glycogen and fat reserves are depleted

Cachexia

The extreme wasting away seen in some chronic diseases resulting from the loss of appetite (anorexia) as well as altered metabolisms

Cortisol

A hormone released in response to stress that promotes fat and protein catabolism (breakdown) and gluconeogensis as well as growth hormone secretion and insulin inhibition for higher levels

Metabolic rate

The amount of energy used in the body in a given period of time; measured in kcal per hour or day and can depend on physical activity, mental state, absorptive or postabsorptive status, and thyroid or other hormones

Basal metabolic rate (BMR)

Baseline metabolic rate that minimizes the effects of feeding, activity, and hormone levels around 2,000 kcal per day for adult males (slightly less for females)

Total metabolic rate (TMR)

The sum of basal metabolic rates and energy required for voluntary activities; can be increased by physical activity or states like anxiety, pregnancy, fever, or hormonal levels and decreased by mental state and starvation due to weight conservation