Carbohydrates Part 2

Question 1

What level energy requirements does the neural retina require? How does the aerobic glucose consumption compare to other tissues?

Answer 1

High energy requirements
Highest aerobic glucose consumption

Question 2

In what ways does the retina use glucose?

Answer 2

Aerobically and anaerobically

Question 3

Describe the pathway of aerobic glycolysis. Is this more or less common compared to anaerobic?

Answer 3

NADH is oxidized to NAD+
Glucose converted to pyruvate
TCA
Oxidative phosphorylation
*This is the typical pathway of glucose

Question 4

What pathway follows anaerobic glycolysis.

Answer 4

Followed by lactate fermentation (glucose is converted to lactate)

Question 5

What is the Warburg effect? What kind of cells is it observed in?

Answer 5

Increase in rate of glucose uptake, lactate production is preferred even when oxygen is present
Observed in rapidly dividing cancer cells

Question 6

What is the predominant cells in the retina that have high glucose needs?

Answer 6

Photoreceptors (rods)

Question 7

What does NADPH function as? In what process is it required?

Answer 7

H+ donor
Required to produce ATP

Question 8

What process is necessary for photoreceptor cell survival? What occurs when this pathway is impaired? Upregulated?

Answer 8

Glycolysis
Retinal degeneration
Neuroprotection

Question 9

For what processes do photoreceptors require copious amounts of NADPH?

Answer 9

Did membrane biogenesis
Antioxidant metabolism
Reduction of all trans-retinal
Detoxifies the retina

Question 10

What is aerobic glycolysis necessary for? What does it prevent?

Answer 10

For normal rod function
Prevent cone degeneration in retinitis pigmentosa

Question 11

How do rod and cone photoreceptor cells (PRs) interact with the RPE and muller cells? What does PR deliver to them?

Answer 11

PRs are in close contact with RPE and muller
PRs deliver lactate
A metabolic ecosystem exists between them

Question 12

Where does cellular respiration occur?

Answer 12

Cytosol and mitochondria

Question 13

How many pyruvate are synthesized from one glucose molecule during glycolysis?

Answer 13

2

Question 14

Describe glycolysis. Does it require oxygen? What does it release? Where does it occur?

Answer 14

Breakdown of glucose by enzymes
Releases energy and pyruvate
Does not require oxygen
Occurs in the cytosol/ cytoplasm (part of the cytoplasm = cytosol + organelle

Question 15

What is the free energy from glycolysis used to form?

Answer 15

ATP and NADH (used to make ATP)

Question 16

In what areas of the body are cells that control glucose levels and regulate glycolysis found? From what energy source do these cells receives nutrients to begin this process?

Answer 16

Liver
Skeletal muscle
Carbohydrates

Question 17

Describe liver glycogen? Where is it released to? Do liver cells use this glucose for their own energy needs?

Answer 17

Short term energy source
Stores and releases glucose
Releases into blood to maintain blood glucose
Liver cells DO NOT use this glucose for their own energy needs

Question 18

Describe muscle glycogen. When is it used, what does it support (aerobic or anaerobic)? Can it be released into blood? Why or why not?

Answer 18

Readily available source of glucose
Released during exercise to support aerobic AND anaerobic pathways
Cannot be released into blood because muscle cells lack the enzyme glucose-6-phosphatase

Question 19

In what part of the body is glucose homeostasis controlled? What pathways are controlled?

Answer 19

Liver
Glycolysis, gluconeogenesis, glycogenesis, glycogenolysis
*genesis (formation)

Question 20

Where does the Krebs cycle and ETC take place?

Answer 20

Mitochondria

Question 21

How many reactions are involved in glycolysis?
What are the 2 phases of the glycolysis pathway, what occurs during each?

Answer 21

10

Investment phase: ATP is consumed
Yield phase: more ATP is produced than originally consumed

Question 22

What is NAD made up of?

Answer 22

Adenine (nitrogenous base)
2x the sugar ribose
2x phosphate
Nicotinamide (form of vitamin B3)

Question 23

What reactions is NAD involved in? (5 answers)

Answer 23

Oxidation–reduction reactions critical for glycolysis,
Fatty acid oxidation
TCA cycle
Complex I of the mitochondrial respiratory chain
Autophagy

Question 24

Define NAD+ and NADH. Are they each oxidizing or reducing agents? What are they both oxidized/reduced to? What do they both transport?

Answer 24

NAD+ is a two-electron oxidizing agent and is reduced to NADH
NADH is a two-electron reducing agent and is oxidized to NAD+
NAD+ and NADH are also hydrogen ion transporting molecules

Question 25

What are the components of ATP? What does it function as?

Answer 25

Nitrogenous base adenine Sugar ribose Triphosphate Energy source

Question 26

Describe pyruvate. Anion or cation? Where is it found? What pathways can it be found in? What happens to pyruvate when oxygen is not present?

Answer 26

Anion Multiple biochemical pathways End product of glycolysis, transported to mitochondria for citric acid cycle Pyruvate goes through fermentation to produce lactate

Question 27

What two components can be used to regenerate glucose? What is this process called?

Answer 27

Pyruvate and lactate Gluconeogenesis

Question 28

What is produced when pyruvate undergoes anabolic synthesis? What else can it directly influence?

Answer 28

Fatty acids and Amino acids Nuclear activity and epigenetic modifications forming interface between genome and metabolic state

Question 29

What occurs during the investment phase of glycolysis? What is glucose converted to after phosphorylation? Where does the phosphate come from? What enzyme is involved?

Answer 29

Consume energy to convert glucose Glucose enters cells and undergoes phosphorylation to glucose-6-phosphorylation Phosphate comes from ATP Enzyme is hexokinase