W4 Carbohydrates (Fructose Metabolism) Flashcards
What’s the role of CHO in the body? (List 3)
- Energy provider for the body
- CHO is stored in the Liver/Muscles.
- Glycated proteins
- Glycosaminoglycans
Terminology: What does... mean? - Olysis = ... - Genesis/Synthesis = ... - Glucose Uptake = ... - Glucose Synthesis = ... - Glycolysis = ... - Gluconeogenesis = ...
- Olysis = Breaking down
- Genesis/Synthesis = Building Up
- Glucose Uptake = Tissue take glucose from blood into them
- Glucose Synthesis = Making glycogen from glucose
- Glycolysis = Breaking down of glucose
- Gluconeogenesis = Making glucose from carbon sources
Where does Fructose Metabolism occur?
Is fructose bad for the body?
- Mainly in the Liver
- No if active but yes if sedentary
What does the Pancreas do?
- Secrets enzymes that help with digestion
- Exocrine (Digestive enzymes)
- Endocrine (body hormones into blood stream)
- Insulin (increases glucose uptake)
Why is insulin important with glucose in the liver?
- It increases Glucokinase volumes which change glucose into glycogen in the liver cell.
(therefore, maintaining a higher gradient of glucose in the blood compared to the liver cell - meaning more glucose will keep entering the liver)
What is the importance of Blood Glucose in the brain?
Glucose is important for:
- Turnover
- Neurotransmitter Synthesis
- 20% glucose in the brain (LOADS!)
- Not insulin mediated (VERY GOOD)
“Glucose is taken in through … then either fully oxidised or converted into lactate.”
Which Glut is used in the sentence above?
“Glucose is taken in through Glut 3 then either fully oxidised or converted into lactate.”
What do Glut 1-5 do?
Glut 1: Sit in cell membrane & transports glucose into the cell from the blood stream.
Glut 2: Glucose Uptake, facilitates the diffusion of glucose across the cell’s membranes.
Glut 3: Facilitates the transport of glucose across the cell’s plasma.
Glut 4: Glucose Transporter, Translocated too membrane. It’s an insulin-regulated transporter to help with glucose.
Glut 5: Transports fructose from the intestinal lumen into the enterocyte via diffusion.
Name another way to increase glucose in a cell.
Calcium increases glucose in the cell (its released when the muscle is contracted).
What is glucose important for?
- Brain (ketones)
- Turnover
- Neurotransmitter synthesis
Once glucose has entered the skeletal muscle cell can it leave again?
- Glucose cannot leave once it has entered because of the concentration gradient.
- It is either stored or oxidised (used as energy)
Where are the main storage points for CHO? Which storage place is the biggest?
- Liver & Muscles
- The liver has a bigger capacity however, there are more muscles
Why is insulin important in the liver?
- Insulin in the liver is important because it increases Glucokinase which change glucose in to glycogen. Therefore, maintaining a lower concentration gradient in the cell so glucose keeps flooding into the liver cell.
Storing glycogen in the brain as astrocytes (cell in CNS) is important because…
- It means the brain doesn’t have to store glycogen in the neurones but the neurones can still use the glycogen because its stored as astrocytes in the support cells.
What is the role of insulin in skeletal muscle cells?
- Moves GLUT 4 to the membrane (which allows extra glucose into the cell)
- This doesn’t happen in the liver!
Describe the 4 steps of glycogen building and 1 fact about why branch structuring is good.
- Glucose attaches to glycogenin (enzyme that acts as primer for changing glucose into glycogen)
- Once there is 8-10 glucose units (pro-glycogen) glycogen synthase (regulated by insulin) takes over creating macro-glycogen
- Then a branching enzyme starts connecting different macro-glycogen = creating a branched structure!
- 12 residues break off at about 7 bonds & attach to neighbour.
- The branch structure is space efficient meaning more glucose can be stored in glycogen!
How is glycogen synthase regulated?
- Phosphate groups block the catalytic site
- Which means UDP-glucose cannot be converted into glycogen
- Glycogen synthase is normally inactive but when activated by insulin protein phosphatase removes a phosphate allowing glycogen to be produced.
What does Protein Phosphatase (enzyme) do?
What does Protein Kinase A (enzyme) do?
- Protein Phosphatase removes a phosphate from the glycogen synthase process making it an active site!
- Regulated by insulin
- Protein Kinase A adds a phosphate from glycogen synthase process making it an inactive site!
Can you give 3 key points about insulin (hormone)?
- It’s released after the ingestion of CHO
- Reduces breakdown of CHO
- It stimulates storage of CHO
Can you give 3 key points about Glucagon (hormone)?
- Released after periods of no food
- Stimulates food breakdown
- Inhibit/prevents storage
During exercise Glycolysis begins. Why during glycolysis is there no insulin produced?
- Insulin is used for storage which we do not need during exercise.
- We will want to use glucose in glycolysis to create ATP.
What are 3 things Glycolysis generates?
What is NADP & ATP net result after glycolysis?
- ATP
- Co-enzymes
- Energy independent of oxygen
Net results:
- 2 molecules of NADP
- 2 molecules of ATP
- PDH (Pyruvate Dehydrogenase) converts … into …
- PDH increases the influx of … from glycolysis into the …
Fill in the blanks
- PHD (Pyruvate Dehydrogenase) converts pyruvate into Acetyl-coA.
- PDH increases the influx of Acetyl-coA from glycolysis into the TCA cycle.
What are 4 functions of the TCA cycle?
- Decarboxylation (eliminate a carbon acid) of Acetyl-coA
- ATP production
- FADH2 production
- NADH production
During the Electron transport chain (ETC) how do electrons travel through the chain?
- Electrons pass from donors to electron receptors
- Each electron receptor wants the last one more than the last!
What is Gluconeogenesis?
- It is a metabolic pathway that results in the generation of glucose.
- Because Acetyl-coA from fatty acids cannot from glucose.
- We want to reverse the process so we can create more glucose however, it isn’t very easy
Gluconeogenesis:
- What is the only carbon backbone that we can use during this process?
- OAA or Oxaloacetate
