Carbohydrates Part 2 Flashcards
What level energy requirements does the neural retina require? How does the aerobic glucose consumption compare to other tissues?
High energy requirements
Highest aerobic glucose consumption
In what ways does the retina use glucose?
Aerobically and anaerobically
Describe the pathway of aerobic glycolysis. Is this more or less common compared to anaerobic?
NADH is oxidized to NAD+
Glucose converted to pyruvate
TCA
Oxidative phosphorylation
*This is the typical pathway of glucose
What pathway follows anaerobic glycolysis.
Followed by lactate fermentation (glucose is converted to lactate)
What is the Warburg effect? What kind of cells is it observed in?
Increase in rate of glucose uptake, lactate production is preferred even when oxygen is present
Observed in rapidly dividing cancer cells
What is the predominant cells in the retina that have high glucose needs?
Photoreceptors (rods)
What does NADPH function as? In what process is it required?
H+ donor
Required to produce ATP
What process is necessary for photoreceptor cell survival? What occurs when this pathway is impaired? Upregulated?
Glycolysis
Retinal degeneration
Neuroprotection
For what processes do photoreceptors require copious amounts of NADPH?
Did membrane biogenesis
Antioxidant metabolism
Reduction of all trans-retinal
Detoxifies the retina
What is aerobic glycolysis necessary for? What does it prevent?
For normal rod function
Prevent cone degeneration in retinitis pigmentosa
How do rod and cone photoreceptor cells (PRs) interact with the RPE and muller cells? What does PR deliver to them?
PRs are in close contact with RPE and muller
PRs deliver lactate
A metabolic ecosystem exists between them
Where does cellular respiration occur?
Cytosol and mitochondria
How many pyruvate are synthesized from one glucose molecule during glycolysis?
2
Describe glycolysis. Does it require oxygen? What does it release? Where does it occur?
Breakdown of glucose by enzymes
Releases energy and pyruvate
Does not require oxygen
Occurs in the cytosol/ cytoplasm (part of the cytoplasm = cytosol + organelle
What is the free energy from glycolysis used to form?
ATP and NADH (used to make ATP)
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?
Liver
Skeletal muscle
Carbohydrates
Describe liver glycogen? Where is it released to? Do liver cells use this glucose for their own energy needs?
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
Describe muscle glycogen. When is it used, what does it support (aerobic or anaerobic)? Can it be released into blood? Why or why not?
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
In what part of the body is glucose homeostasis controlled? What pathways are controlled?
Liver
Glycolysis, gluconeogenesis, glycogenesis, glycogenolysis
*genesis (formation)
Where does the Krebs cycle and ETC take place?
Mitochondria
How many reactions are involved in glycolysis?
What are the 2 phases of the glycolysis pathway, what occurs during each?
10
Investment phase: ATP is consumed
Yield phase: more ATP is produced than originally consumed
What is NAD made up of?
Adenine (nitrogenous base)
2x the sugar ribose
2x phosphate
Nicotinamide (form of vitamin B3)
What reactions is NAD involved in? (5 answers)
Oxidation–reduction reactions critical for glycolysis,
Fatty acid oxidation
TCA cycle
Complex I of the mitochondrial respiratory chain
Autophagy
Define NAD+ and NADH. Are they each oxidizing or reducing agents? What are they both oxidized/reduced to? What do they both transport?
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
What are the components of ATP? What does it function as?
Nitrogenous base adenine
Sugar ribose
Triphosphate
Energy source
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?
Anion
Multiple biochemical pathways
End product of glycolysis, transported to mitochondria for citric acid cycle
Pyruvate goes through fermentation to produce lactate
What two components can be used to regenerate glucose? What is this process called?
Pyruvate and lactate
Gluconeogenesis
What is produced when pyruvate undergoes anabolic synthesis? What else can it directly influence?
Fatty acids and Amino acids
Nuclear activity and epigenetic modifications forming interface between genome and metabolic state
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?
Consume energy to convert glucose
Glucose enters cells and undergoes phosphorylation to glucose-6-phosphorylation
Phosphate comes from ATP
Enzyme is hexokinase
