Biochem EX1 - Metabolism Flashcards
Some hormones are released in response to sensing of a condition by the very tissue that synthesizes and secretes the hormone. Give an example of such a hormone and name the tissue that secretes it. What is one stimulus of this hormone release?
Pancreatic B cell: detects glucose and secretes insulin. If glucose too high or low secretes insulin or glucagon.
What are the two hormones that largely control blood glucose? Which is secreted in response to high blood glucose, and brings blood glucose down? Which is secreted in response to low blood glucose, and then increases blood glucose?
Insulin in response to high glucose to bring it down, glucagon in response to low glucose to bring it up.
Other hormones have a more complicated stimulation, a cascade involving sensing of a stimulus, release of a factor from one tissue, the hormone stimulates release of another factor from another tissue, and so on… Give an example of such a hormone and name the tissue that secretes it. What is the stimulus of this hormone release?
Hormone: cortisol (secreted by the anterior pituitary gland)
Tissue: adrenal cortex
In times of stress
What is the name that describes the chemical process by which energy is obtained from biological fuels such as the carbon skeletons of carbs, fatty acids, or amino acids (or any fuel)?
Oxidation
We get much of what we are made along with the energy to keep us going from what we eat. We can also synthesize from scratch much of what we get in our diet. Give three examples of nutrient types animals cannot synthesize themselves that must be obtained from plant or microbial sources.
Essential amino acids (PVT TIM HALL)
Essential fatty acids (linoleic acid, linolenic acid)
Vitamins
Why are all tissues outside the liver often called extrahepatic tissues with respect to metabolism? What organ has priority over all the others for the supply of fuel? What organ can be said to be the “brain” of metabolism? What organ can be said to be the “king” of metabolism?
- The liver has such a central role in metabolism.
- Brain has priority
- Liver is “brain” and brain is “king”
The carbon skeletons of amino acids are degraded to intermediates of carbohydrate metabolic pathways. A different pathway is involved in degrading the other important group on amino acids. What is the other amino acid component group, and what is the pathway that carries this out? Give an example of organs that co-operate with each other in handling amino acids. What are the two organelles that co-operate by participating in this pathway?
- Nitrogen group, handling of nitrogen is carried out in urea cycle
- liver and skeletal muscle
- proteins are broken down into amino acids in skeletal muscle, the amino acids (e.g. Alanine) go into the liver. In the liver, the nitrogen from the amino acid is handled via the urea cycle, and the carbon skeleton is used to make carbohydrate intermediates, which is returned to the skeletal muscle.
- mitochondria, cytosol, and Golgi apparatus
What metabolic pathways are used for energy by skeletal muscles (both at rest and during contractile activity lasting various lengths of time)? For each pathway, what limits the utilization of the pathway (what causes the switch to the next pathway as the time of intense muscular activity goes on)? In terms of the rate of energy supplied as ATP, rank the pathways highest rate to lowest
highest to lowest:
- ATP-used directly for muscle contraction, lasts for a few seconds until supply runs out
- creatine phosphate-also used directly for muscle contraction, lasts for ~10 seconds until creatine phosphates run out
- carbohydrates-supplies ATP via anaerobic glycolysis (includes fermentation to pyruvate to lactic acid), lasts for a few minutes until lactic acid build up and other neural factors
- carbohydrates-supplies ATP via aerobic glycolysis (includes TCA cycle and oxidative phosphorylation), lasts for a few hours until carbs run out
- fatty acids-lasts for ~1 hour
