Ch 5

Question 1

Anabolism

Answer 1

requires the input of energy to synthesize large molecules

“building something up”

Question 2

Catabolism

Answer 2

releases energy by breaking down large molecules into small molecules
“breaking something down”

Question 3

Catabolism drives anabolism

Answer 3

The catabolic reactions that break down glucose, fatty acids, and amino acids serve as ENERGY SOURCES for the anabolism of ATP.

Question 4

aerobic cellular respiration

Answer 4

Complete catabolism of glucose requires oxygen as the final electron acceptor.

But…breaking down glucose requires many enzymatically catalyzed steps, the first of which are anaerobic

Question 5

Glycolysis (general)

Answer 5

conversion of glucose into two molecules of pyruvic acid

–> no oxygen needed

Question 6

Glycogenesis

Answer 6

production of glycogen (mostly in skeletal muscles and liver)

Question 7

Glycogenolysis

Answer 7

hydrolysis (breakdown) of glycogen

–> yields glucose 6-phosphate for glycolysis or free glucose that can be secreted in the blood

Question 8

Gluconeogenesis

Answer 8

production of glucose from noncarbohydrate molecules, including lactic acid and amino acids, primarily in the liver

Question 9

Lipogenesis

Answer 9

the form of triglycerides (fat), primarily in adipose tissue

Question 10

Lipolysis

Answer 10

hydrolysis (breakdown) of triglycerides, primarily in adipose tissue

Question 11

Ketogenesis

Answer 11

formation of ketone bodies, which are 4-carbon long organic acids, from fatty acids, occur in the liver

Question 12

Three steps in aerobic respiration of glucose

Answer 12

1. Glycolysis: occurs in cytoplasm, anaerobic
2. Citric Acid (Krebs) Cycle: occurs in matrix of mitochondria, aerobic
3. Electron Transport: occurs in cristae of mitochondria inner membrane, aerobic
   - -> where we get the MOST ATP

Question 13

Glycolysis (detailed)

Answer 13

• First step in catabolism of glucose
• Occurs in the cytoplasm of the cell
• Glucose is split into two pyruvic acid molecules
• 6-carbon sugar–> 2 molecules of 3-carbon pyruvic acid
• C6H12O6 –> 2 molecules C3H4O3
——> (don’t need to know structure, just that it moves from one 6-carbon to two 3-carbon)
• Note loss of 4 hydrogen ions. These were used to reduce
2 molecules of NAD (2NAD + 4H+ –> 2NADH+ H+(2NADH))
——> no need for oxygen

Question 14

Glycolysis equation

Answer 14

Glucose + 2 NAD + 2 ADP + 2 Pi –> 2 pyruvic acid + 2 NADH + 2 ATP
(4 hydrogens reduced to 2 in product)

pyruvic acid –> used in citric acid cycle
NADH –> oxidized to make ATP

Question 15

Lactic Acid Pathway

Answer 15

When there is NO oxygen to complete the breakdown of glucose, NADH has to give its electrons to pyruvic acid.

• ->This results in the reformation of NAD and the conversion of pyruvic acid to lactic acid.
• anaerobic metabolism/lactic acid fermentation
• net yield of 2 ATP

Question 16

muscle cells

Answer 16

can survive for awhile without oxygen by using lactic acid fermentation

Question 17

RBCs

Answer 17

only use lactic acid fermentation because they lack mitochondria

Question 18

Citric Acid Cycle

Answer 18

Acetyl CoA (from pyruvic acid) + oxaloacetic acid = citric acid

• citric acid moves through reactions to produce more oxaloacetic acid
• -> One GTP is produced, which donates a phosphate group to ADP to form ATP
• 3 molecules NAD –> reduced to NADH
• 1 molecule FAD –> reduced to FADH2
• **events occur for each acetic acid, so it happens twice for each glucose molecule

Question 19

Citric Acid Cycle: for each glucose we produce…

Answer 19

• 6 NADH
• 2 FADH2
• 2 ATP
• 4 CO2

Question 20

Electron Transport & Oxidative Phosphorylation

Answer 20

• molecules in the cristae (folds) of the mitochondria act as electron transporters
• -> they accept electrons from NADH and FADH2 (produced in Krebs Cycle). H+ NOT transported.
• -> Oxidized FAD and NAD are reused

Question 21

Electron Transport Chain

Answer 21

Electron transport molecules pass the electrons down a chain, with each being reduced and then oxidized

• exergonic reaction: energy produced - ADP –> ATP
• -> ADP experienced (direct) oxidative phosphorylation - less than 50% efficient (some released as heat)

Question 22

Oxidative Phosphorylation Steps

Answer 22

1. Electron transport fuels proton pumps
   - H+ pumped from the mitochondrial matrix –> space between the inner/outer membranes
2. Creation of a huge concentration gradient between membranes
3. H+ can ONLY move through the inner membrane through structures called respiratory assemblies
4. Movement of H+ across the membrane provides energy to the enzyme ATP synthase, which converts ADP to ATP.

Question 23

Why is the mitochondrial outer membrane important?

Answer 23

**no outer membrane would mean the H would diffuse into cytosol = no concentration gradient, outer membrane is important to get max ATP!!

Question 24

Oxygen

Answer 24

• Final electron acceptor
• citric acid cycle/electron transport require oxygen

Water is formed in the following reaction: O2 + 4e- + 4H+ –> 2H2O

Question 25

Where do we get our total ATP?

Answer 25

Direct (substrate-level) phosphorylation in glycolysis + citric acid cycle = 4 ATP Oxidative Phosporylation = varying amounts of ATP (32-34) --> Theoretical ATP yield is 36-38 per glucose, but actual yield is 30-32 ATP per glucose b/c energy is needed to move ATP from mitochondria to cytoplasm

Question 26

Glycogenesis

Answer 26

* Cells can't store much glucose because it will pull water into the cell via osmosis. * Glucose is stored as a larger molecule called glycogen in the liver, skeletal muscles, and cardiac muscles. * Glycogen is formed from glucose via glycogenesis.

Question 27

Glycogenolysis

Answer 27

• When the cell needs glucose, it breaks glycogen down again. • Produces glucose 1-phosphate (cannot leave muscle or heart cells) --> The liver has an enzyme called glucose 6- phosphatase that removes the phosphate so glucose can reenter the bloodstream • Glycogen phosphorylase is the catalyst (breaks it down)

Question 28

Glycogenolysis: liver

Answer 28

brain is glucose dependent, but doesn’t store it well liver stores the glucose as glycogen —> breaks it down and sends it into the blood where it can get to the heart

Question 29

The Cori Cycle

Answer 29

exchange of lactic acid between skeletal muscles and liver SKELETAL MUSCLE: glycogen --> glucose --> pyruvic acid --> lactic acid *lactic acid enters bloodstream LIVER: lactic acid --> pyruvic acid --> glucose *glucose enters bloodstream

Question 30

Why do you need to warm down after a workout?

Answer 30

so you can keep the blood flowing and wash the lactic acid out of the skeletal muscles

Question 31

Lipid and Protein Metabolism

Answer 31

- can be used for energy by same pathways as metabolism of pyruvic acid - excess food energy (glucose) is then stored as glycogen/fat (none is stored as ATP)

Question 32

Lipid Metabolism

Answer 32

- ATP levels rise --> ATP production inhibited - Glucose doesn t complete glycolysis to form pyruvic acid - -> Acetyl CoA already formed is joined together to produce a variety of lipids, including cholesterol, ketone bodies, and fatty acids. - lipogenesis

Question 33

Lipogenesis

Answer 33

Fatty acids combine with glycerol to form triglycerides in the adipose tissue and liver --> making fat, in fat cells, in times of excess (intake exceeds immediate energy requirements)

Question 34

Fatty Acids as an Energy Source

Answer 34

β-oxidation: Enzymes remove acetic acid molecules from fatty acids to form acetyl CoA * For every 2 carbons on the fatty acid chain, 1 acetyl CoA can be formed. * Each acetyl CoA --> 10 ATP + 1 NADH + 1 FADH2 (decent yield of ATP)

Question 35

Acetyl CoA can turn into....

Answer 35

1. cholesterol (steroids, bile acids) 2. ketone bodies 3. citric acid cycle (CO2) 4. fatty acids (triglycerides, phospholipids)

Question 36

Amino Acid Metabolism

Answer 36

-provides nitrogen for body -Amino acids from dietary proteins are needed to replace proteins in the body (we can only make 12/20) -->essential AA: from diet -If more amino acids are consumed than are needed, the excess amino acids can be used for energy or converted into carbohydrates or fat

Question 37

Amino Acids as Energy

Answer 37

different amino acids enter in at different places/times to drive the reactions (none funnel in during glycolysis) —> can use AA to funnel in for energy

Question 38

Energy Sources

Answer 38

* LIVER: Glucose and ketone bodies * ADIPOSE TISSUE: Fatty acids * MUSCLE: Lactic acid and amino acids

Question 39

Energy Sources: Brain

Answer 39

brain requires lots of glucose, little ketone bodies (can't use fatty acids/lactic acid) --> why it's important to keep blood glucose levels regular