Chapter 25. Metabolism And Nutrition

Question 1

Metabolism

Answer 1

Sum total of all chemical reactions occurring within the cells of an organism
- ATP is the primary energy-carrying molecule of the cell

Question 2

How many stages occur in the processing of nutrients

Answer 2

3 stages, stage two has two different parts

Question 3

Stage one of nutrient processing

Answer 3

Digestion occurs in the GIT and absorbed nutrients enter the blood to reach tissue cells

Question 4

Stage Two of nutrient processing

Answer 4

• Occurs in the cytoplasm of tissue cells.
• Absorbed nutrients are:
  I) used o build complex molecules (lipids, proteins, glycogen) by ANABOLIC pathways
  Or
  II) broken down by CATABOLIC pathways to harvest their bond energy to form pyruvic acid and acetyl CoA

Question 5

Stage Three of Nutrient Porcessing

Answer 5

• Occurs in the mitochondria and is almost entirely catabolic (“breakdown”).
• Requires oxygen and completes the breakdown of food to CO2 and H2O, generating large amounts of ATP through oxidative phosphorylation

Question 6

Anabolic Reactions

Answer 6

Takes the last phosphate and uses it to make new nutrients

40% is used
60% is released by heat

Question 7

Carbohydrate metabolism

Answer 7

• Carbohydrates are broken down into monosaccharides: glucose (about 80%), fructose and galactose.
• can transfer energy from glucose to ATP
• other nutrients (fats, amino acids) can generate ATP and are linked to glucose breakdown pathways
• Glucose is the major fuel for cellular respiration to produce ATP (it is the most that gets broken down)

Question 8

What does liver cells (hepatocytes) do to fructose and galactose

Answer 8

Converts fructose and galactose into glucose

Question 9

Cellular respiration

Answer 9

• Is the process (series of catabolic reactions) that releases energy from glucose and makes it available for cellular use.
• in involves oxidation and reduction reactions (redox rxns)
• a substance is oxidized when it loses and electron
• a substance is reduced when it gains an electron

Question 10

What happens when hydrogens are removed

Answer 10

They are attached to coenzymes

Question 11

Coenzymes

Answer 11

Are assisting enzymes and they help grab on to hydrogen atoms and help lead them where they need to go.

Question 12

Two coenzymes

Answer 12

• Nicotinamide adenine dinucleotide (NAD+)
• Flavin adenine dinucleotide (FAD)

Question 13

Cellular respiration

Answer 13

Involves four sets of reactions:
1. Glycolyses
2. Formation of acetylene CoA
3. Krebs cycle (critic acid chain cycle)
4. Electron transport chain reaction (ETC)

Question 14

Glycolysis

Answer 14

• Occurs in the cell cytoplasm
• is an anaerobic process (does not need oxygen)
• series of 10 reactions which convert 1 (6C) glucose into 2 molecules of pyruvic acid (3C)
• glucose loses 4 hydrogen atoms which are now bound to 2 molecules of NAD+
• Produces 2 NADH + 2H+
• this results in a net gain of 2 ATP

Question 15

Formation of Acetyl CoA

Answer 15

• If oxygen is available ( aerobic conditions), them pyruvic acid is converted to acetyl coenzymes A (CoA)
• when Pyruvic acid enters the mitochondria, it loses a C atom and a pair of H atoms
• 2 C molecule formed (acetic acid) is attached to coenzymes A to produce acetyl CoA (form 2 for every molecule of glucose
• H’s are transferred to NAD+ TO PRODUCE NADH + H+
• Acetyl CoA Exeter’s the Krebs cycle

Question 16

Krebs Cycle

Answer 16

• Occurs in matrix o if mitochondria
• an aerobic process (requires O2)
• series of 8 cyclical reactions
• beings with 1 acetyl CoA and results in
  
  • formation of 2 CO2
  • H’s are picked up by FAD to form 1 FADH2
    -H’s are picked up by NAD+ to form 3 NADH
  • Formation of 1 ATP

Question 17

Electron Transport Chain

Answer 17

• each par of electrons donated to ETC by NADH provides enough energy to pump enough protons to produce about 2.5 molecules of ATP ( 1.5 ATP for each FAH2)
• oxygen acts as the final electron acceptor at the end of the ETC
• electrons are recombined with protons (H+) to form hydrogen which is combined with oxygen to form water (6 H2O)

Question 18

Cellular Respiration Numbers

Answer 18

ATP Produced by Glycolysis = 2 ATP
ATP produced by Krebs cycle = 2 ATP
NADH produced by glycolysis = 2 x 2.5 ATP = 5 ATP
NADH produced in formation of acetyl CoA from pyruvic acid = 2 x 2.5 ATP = 5 ATP
NADH produced in Krebs cycle = 6 x 2.5 ATP = 15 ATP
FADH2 produced in Krebs cycle = 2 x 1.5 ATP = 3 ATP
TOTAL = 32 ATP

Question 19

NADH + H+ shuttles

Answer 19

Shuttle number 1
- found in liver, kidney, and heart muscle
- NADH passes e-‘s to a shuttle molecule that delivers e-‘s to beginning of ETC
- Anything that starts at the beginning generates 2.5 ATP

Question 20

Shuttle Number 2

Answer 20

• Found in skeletal muscle and brain cells
• NADH passes e-‘s to a different shuttle that deliver e-‘s farther down ETC
• only generates 1.5 ATP, just like FADH2.