Chapter 25: Nutrition, metabolism, and temperature regulation

Nutrition

process by which the body obtains and uses certain component of food

What are the 4 components of nutrition?

1. digestion

2. absorption

3. transportation

4. cell metabolism

Nutrients

substance taken into the body and used by cells to produce energy, synthesize molecules, and to use in chemical reactions

Complex carbohydrates

polysaccarides; require more digestive “work” to break down

Glycolysis

breakdown of glucose into 2 pyruvate molecules and 4 ATP (net 2 ATP)

NADH and pyruvate can be metabolized by ________ _______ or ________ __________

anaerobic fermentation, aerobic respiration

Electron transport chain

series of electron carrier proteins within the inner mitochondrial membrane

Electrons obtained during earlier steps of aerobic respiration are used to create a ________ _________ within the mitochondria

proton gradient

ATP synthase

enzyme that synthesizes ATP molecules within mitochondria during aerobic respiration

Glycogenolysis

breakdown of glycogen and liberation of stored glucose into the blood; stimulated by glucagon

What organ primarily uses glycogen to stabilize blood sugar?

the liver

Absorptive state

period immediately following a meal when nutrients are being absorbed from the digestive systen

Metabolic rate

total amount of energy produced and used by the body per unit of time

ATP production roughly ______ ATP use

equals

How can metabolic rate be estimated?

by measuring the amount of oxygen consumed per unit of time

Metabolic energy is used in 3 ways:

1. basal metabolism

2. thermic effects of food

3. muscular activity

What are the 4 ways that we exchange heat with the environment?

1. radiation

2. conduction

3. convection

4. evaporation

Radiation (part of heat exchange with the environment)

exchange of heat between 2 objects that aren’t in physical contact

Conduction (part of heat exchange with the environment)

exchange of heat between 2 objects in physical contact

Convection (part of heat exchange with the environment)

exchange of heat between the body and air/water as it moves along the surface of the skin

What are the 2 heat loss mechanisms?

1. skin vasodilation

2. sweating

What are the 6 major classes of nutrients?

1. carbohydrates

2. lipids

3. proteins

4. vitamins

5. minerals

6. water

Macronutrients

carbohydrates, lipids, and proteins

Calorie (specifically not capitalized

amount of energy required to increase the temperature of 1 gram of water by 1 degree Celcius

Kilocalorie (Calorie; capitalized)

• 1000 calories

• used to express large amounts of energy in food-metabolism

Carbohydrates

monosaccharides, disaccharides, and polysaccharides

____% of lipids in human diet are triglycerides

95

What are the 2 main categories of lipids?

1. saturated (“unhealthy” fats)

2. unsaturated (“healthy” fats)

Proteins

chains of amino acids

Essential amino acids

9 amino acids that the body cannot synthesize and must be ingested

Conditionally essential amino acids

can normally be synthesized, but not under specific conditions

Complete protein

• contains all 9 essential amino acids

  • meat (including fish and poultry), cheese, eggs, soy, and quinoa

Incomplete protein

• doesn’t contain all 9 essential amino acids

  • leafy green vegetables, grains, and legumes

Vitamins

organic molecules that exist in smaller quantities in food and are essential to metabolism

Essential vitamins

• cannot be produced by the body and must be ingested

  • no single food produced are essential vitamins

Provitamins

• an incomplete vitamin that the body can convert into a functional vitamin

  • function: form coenzymes

Minerals

inorganic nutrients necessary for normal metabolism

What is the function of minerals?

establish resting membrane potential, form coenzymes, act as buffer, etc

Metabolism

the total sum of all chemical reactions in the body

Catabolism

energy-releasing process of breaking molecules into smaller pieces

Anabolism

energy-requiring process of building larger molecules from smaller molecules from smaller molecules

Anaerobic fermentation

in the absence of oxygen, glycolysis products form 2 lactate molecules from 2 pyruvate

Aerobic respiration

catabolism of glucose in the presence of oxygen

True/False: aerobic respiration produces carbon dioxide, water, and 32 ATP

True

What are the 4 phases to aerobic respiration?

1. gylcolysis

2. acetyl-CoA formation

3. citric acid cycle (Kreb’s cycle0

4. electron transport chain

Lipids

primary energy-storage molecules in adipose tissue

Free-fatty acids

circulating fatty acids no longer bound to glycerol

_____ ______ are primarily used for synthesis of proteins

Amino acids

_______ is the primary “fuel” for aerobic respiration and the majority of ATP production

Glucose

What are the 4 processes involved in glucose use and storage?

1. glycogenesis

2. lipogenesis

3. glycogenelysis

4. gluconeogenesis

Glycogenesis

process forming glycogen; stimulated by insulin

Lipogenesis

process of lipid (mainly triglyceride) formation from excess glucose and amino acids

Glycogenolysis

synthesis of glucose by the liver in the absence of glycogen

Postabsorptive state

period between absorptive states when blood glucose is maintained by interconversion of molecules

Basal metabolic rate (BMR)

energy required to keep a resting body functional; typically accounts for 60% of total energy expenditure

Various factors influence BMR such as (5):

• age and sex

• body temperature

• thyroid hormone

• pregnancy

• body composition (muscle mass)

Thermic effect of food

the energy cost of digestion and absorption

Muscular activity uses ~30% of total energy expenditure with:

• skeletal muscle contractions

• cardiac muscle contractions

  • smooth muscle contractions

Free energy

total amount of energy derived from ingested food

What percentage of free energy is derived from catabolism and captured in ATP form?

~43% of energy derived from catabolism is captured in the form of ATP

What percentage of energy is lost as internal body heat?

57%

________ ___________ is maintained by negative feedback mechanisms

Body temperature

2 heat gaining mechanisms are:

1. skin vasoconstriction

2. shivering

Behavioral mechanissm also help heat _____/_____

gain/loss

Substances taken into the body and used by cells to produce energy, synthesize molecules, and to use in chemical reactions are known as what?

nutrients

Which answer best describes complex carbohydrates?

polysaccharides that require more digestive work to break down

Which metabolic pathway breaks glucose down into 2 pyruvate and 4 ATP?

glycolysis

The electron transport chain powers which mitochondrial enzyme during aerobic respiration?

ATP synthase

Which organ stores glycogen for glycogenolysis to stabilize blood sugar?

liver

___________ is the period immediately following a meal when nutrients are being absorbed from the digestive system.

absorptive state

_________ can be estimated by measuring the amount of oxygen consumed per unit of time. 

metabolic rate

__________ is the exchange of heat between 2 objects in physical contact.

conduction

Which is a heat loss mechanism? 

skin vasodilation

The exchange of heat between the body and air/water as air/water moves across the surface of the skin is known as what?

convection