A&P Lecture Exam III: Metabolism, Nutrients, and Energetics

What is metabolism

The sum of all chemical reactions that occur in an organism

What are the two main types of metabolic reactions?

• Catabolism

• Anabolism

What is catabolism

The breakdown of large molecules into smaller molecules. It releases energy that can be used to make ATP

What is anabolism

The building of larger molecules from smaller molecules. It requires energy and forms new chemical bonds

What is the nutrient pool?

All available nutrient molecules distributed throughout the blood

What are the three major nutrient reserves in the body?

• Triglycerides

• Glycogen

• Proteins

What is the most abundant storage lipid?

Trigycerides

What is the most abundant storage carbohydrate?

Glycogen - a branched chain of glucose molecules

What is the role of coenzymes such as NAD and FAD?

They accept and transfer electrons between molecules during metabolic reactoins?

What is cellular respiration?

The process of breaking down glucose using oxygen to produce carbon dioxide, water, and ATP.

What are the three main stages of cellular respiration?

• Glycolysis

• The Citric Acid Cycle

• Electron Transport Chain

Where does glycolysis occur?

In the cytosol of the cell.

Does glycolysis require oxygen?

No. Glycolysis is an anaerobic reaction.

What does glycolysis break glucose into?

Two 3-carbon molecules of pyruvate

What is the net ATP gain from glycolysis?

• 2 ATP

• 2 NADH

How much ATP can one glucose molecule produce through cellular respiration?

• 30-32 ATP

Where does the citric acid cycle occur?

In the mitochondria

What are the products of the citric acid cycle?

• Carbon Dioxide

• ATP

• NADH

• FADH2

What is the electron transport chain?

A series of protein complexes in the inner mitochondrial membrane that transfer electrons and help produce ATP

What is the final electron acceptor in the electron transport chain?

Oxygen - combines with electrons and hydrogen ions to form water

What is gluconeogenesis?

The production of glucose from noncarbohydrate molecules such as lactic acid, glycerol, and amino acids

What is glycogenesis?

The formation of glycogen from excess glucose

What is lipolysis?

The breakdown of triglycerides into glycerol and three fatty acids

What is beta-oxidation?

A series of reactions in the mitochondria that breaks fatty acids into 2-carbon fragments. to form acetyl-CoA

What is nitrogen balance?

The difference between the amount of nitrogen consumed and the amount excreted in urine and feces

Why must nitrogen be obtained through the diet or recycled compounds?

The body does not store nitrogen

What are minerals?

Inorganic ions released through the dissociation of electrolytes, such as sodium, potassium, chloride, calcium, and iron

What are vitamins

Essential organic nutrients that function as coenzymes in important enzymatic reactions

Which vitamins are fat-soluble?

Vitamins A, D, E, and K

Which vitamins are water-soluble?

Vitamin C and the B-complex vitamins

What is the function of vitamin A?

Maintains epithelial tissues and is needed to make visual pigments

What is the function of vitamin D?

It is converted to calcitriol and is required for normal bone growth

What is the function of vitamin K?

It is essential for the production of blood clotting factors

What is the function of vitamin C?

It is needed for collagen formation

What is metabolic rate?

The average amount of energy the body uses, measured by caloric expenditures

What is a calorie?

The energy required to raise the temperature of 1 gram water by 1 degree celsius

What is a kilocalorie (Calorie)

The energy required to raise the temperature of 1 kilogram of water by 1 degree celsius

What is deamination?

The removal of amino groups from amino acids
Generates ammonium ions, primarily in liver cells

Where does deamination primarily occur?

Liver cells

Why are ammonium ions dangerous?

Toxic to cells

What does the liver do with toxic ammonium ions?

Uses enzymes to convert ammonium into urea

What is the urea cycle?

A series of reactions that produces urea from ammonium ions

How does the body eliminate urea?

Urea is water-soluble and is excreted in urine

When does the body break down proteins for ATP?

When glucose and lipid reserves are inadequate

Why is protein catabolism not an ideal energy source?

• Harder to break down

• Produces toxic ammonium ions

• Important structural and functional components of cells

What are essential amino acids?

Amino acids that the body can’t make in sufficient amounts and must obtain from the diet

What are nonessential amino acids?

Amino acids that the body can make on demand

How many essential amino acids are there?

10 - 8 not synthesized at all, 2 synthesized in insufficient amounts

What is nutrition?

The absorption of nutrients from food

What is a balanced diet?

A diet containing all ingredients needed to maintain homeostasis and prevent malnutrition

What is malnutrition?

An unhealthy state resulting from nutrient imbalance

What are the five food groups in a balanced diet?

• Fruits

• Vegetables

• Grains

• Protein

• Dairy products

What must the digestive tract absorb to maintain homeostasis?

• Fluids

• Organic Nutrients

• Minerals

• Vitamins

Nitrogen-containing compounds

• Purines and pyrimidines

• Amino Acids

• Creatine

Where does aerobic metabolism occur?

Within the mitochondria

Does aerobic metabolism require oxygen?

Yes

What are the main stages of aerobic metabolism?

• Citric Acid Cycle

• Electron Transport Chain

Where does the citric acid cycle occur?

In the mitochondrial matrix

What is the main goal of the citric acid cycle?

To produce NADH and FADH2 for use in the electron transport chain

What is oxidative phosphorylation?

The production of ATP through the transfer of electrons from NADH and FADH2 to oxygen

Approximately what percentage of the body's ATP is produced by oxidative phosphorylation?

Over 90%

Where is the electron transport chain located?

Inner mitochondrial membrane

Which molecules deliver electrons to the electron transport chain?

NADH and FADH2

What happens as electrons move through the electron transport chain?

Release energy that is used to pump hydrogen ions from the mitochondrial matix into the intermembrane space

What is an electrochemical gradient?

A difference in hydrogen ion concentration and charge across the inner mitochondrial membrane

What is ATP synthase?

An enzyme that uses the energy of hydrogen ions flowing down their gradient to convert ADP to ATP

What is chemiosmosis?

The generation of ATP using the energy of hydrogen ions as they pass through ATP synthase

What happens to electrons at the end of the electron transport chain?

They are transferred to oxygen, which combines with hydrogen ions to form water

How much energy do lipids release per gram?

9.46 kcal/g

How much energy do carbohydrates release per gram?

4.18 kcal/g

How much energy do proteins release per gram?

4.32 kcal/gram

Which nutrient provides the most energy per gram?

Lipids

What is calorimetry?

A method that measures the total energy released when chemical bonds in organic molecules are broken

What factors affect metabolic rate?

• Exercise

• Age

• Sex

• Hormones

• Climate

What is basal metabolic rate (BMR)?

The minimum resting energy expenditure of an awake, alert person needed to maintain vital functions

How is basal metabolic rate measured?

Monitoring respiratory activity

What is thermoregulation?

The homeostatic process of keeping body temperature within acceptable limits despite environmental conditions

Why is thermoregulation important?

Enzymes operate within a relatively narrow temperature range

Where is body temperature regulation coordinated?

Hypothalamus which contains heat-gain and heat-loss centers

What are the four mechanisms of heat exchange?

• Radiation

• Convection

• Evaporation

• Conduction

What is radiation?

The loss of heat from an object warmer than its surrounding

Approximately what percentage of indoor heat loss occurs through radiation?

More than 50%

What is convection?

Heat loss to moving air across the body’s surface

Approximately what percentage of indoor heat loss occurs through convection?

About 15%

What is evaporation?

The process in which water absorbs energy and changes into vapor, cooling the surface where evaporation occurs

What is insensible water loss?

Water that crosses body epithelia and evaporates without noticeable sweating

Approximately what percentage of indoor heat loss occurs through insensible water loss?

About 20%

What is sensible perspiration?

Sweat released from seat glands

What is conduction?

The direct transfer of energy through physical contact

What happens when the body's temperature rises above its set point?

The heat-loss center is stimulated

What happens during peripheral vasodilation?

Blood vessels near the skin widen increasing blood flow to the skin and allowing more heat to escape

How does sweating help lower body temperature?

Sweat evaporates from the skin, absorbing heat and cooling the body

What happens when the temperature in the pre-optic area drops?

The heat loss center is inhibited & the heat gain center is activated

What is hypothermia?

A below-normal body temperature

How does the body conserve heat in cold conditions?

The sympathetic vasomotor center reduces blood flow to the dermis, decreasing heat loss

What is countercurrent heat exchange?

Heat transfers from warm arterial blood to cooler venous blood flowing in the opposite direction, helping conserve heat near the body’s core

What happens to blood flow during heat conservation?

Blood returning from the limbs is redirected through deeper veins, reducing heat loss at the skin