Exam 2 Lecture 3 (Mignery Overview of Metabolism) Flashcards
Define the following terms:
Metabolism
Catabolism
Anabolism
Metabolism: a series of chemical rxn’s in which product of one reaction is the substrate for the next reaction
Catabolism: chemical reactions that result in the breakdown of more complex organic molecules into simplier substances, release energy (ATP) that is used to drive chemical rxns
Anabolism: chemical reactions in which simplier substances are combined to form more complex, new molecules, usually requires ATP
Explain ATPs role in metabolism and also describe its structure
ATP is the “energy currency of the cell”
High energy phosphate bonds
Explain what oxidation and reduction is.
In order to oxidize and reduce substrates, what has to happen to the electron carriers?
Oxidation refers to the LOSS of electrons (addition of O’s and removal of H’s)
Reduction refers to GAIN of electrons (addition of H’s and loss of O’s)
In order to oxidize a substrate, you have to reduce the e carrier (NAD+ goes to NADH)
In order to reduce a substrate you have to oxidize the e carrier (NADH goes to NAD+)
What are the most important electron carriers?
How do they differ structurally?
Are they oxidizing or reducing agents?
Most important electron carriers are NAD+ and NADP+
NADP+ has an additional phosphate group on the 2’ carbon if the ribose ring
NAD+ and NADP+ are oxidizing agents (they get reduced)
NADH= reduced form of NAD+
NADPH= reduced form of NADP+
Top Hat Question: What are the most important electron carriers?
NAD+, NADH, NADP+, and NADPH (BOTH FORMS)
Explain the role of Acetyl-CoA in metabolism
Acetyl CoA: key molecule used in rxns in carb, protein and lipid metabolism… primary function of acetyl-CoA is to convey the carbon atoms within the acetyl group to the citric acid cycle to be oxidized for energy production
Acetyl Co-A is generated in the mitochondrial matrix, major source of energy.
All metabolic components can give rise to acetyl-coA making it a “common fuel” that can enter the CAC and give rise to energy production through ATP
What are the four fates of Acetyl-CoA?
Fates of Acetyl-CoA:
- primary fate is to oxidize acetyl groups in CAC for energy generation
- lipogenesis: formation of fatty acids
- Ketogenesis: formation of ketone bodies
- Cholesterologenesis: formation of choloesterol which then is turned into steriods
Describe the storage and catabolism of dietary carbodhydrates.
Carbs are metabolized primarily as GLUCOSE.
Glucose —(glycolysis)–> pyruvate—> acetyl coA—-> gets sent into TCA cycle where it undergoes combustion reaction to create ATP
Excess carbs are stored as glycogen, but there’s a limit to how much we can store:
- liver: glycogen is stored to be used as glucose by rest of body later on
- liver and skeletal/heart muscle have largest glycogen stores
Explain the storage and catabolism of dietary fatty acids
Fatty acids go through BETA-OXIDATION in the mitochondria to form acetyl-CoA. (only cells that have mitochondria can have beta oxidation)
Fatty acids can also form triaglycerols which are stored in adipose tissue (breakdown of TAGs into fatty acids is triggered by a hormonal signal)
Explain the storage and catabolism of dietary proteins
Amino acids can be metabolized to either Acetyl CoA or an intermediate in the TCS cycle.
This leads to production of ammonia, which can be toxic at high levels. Amino acids are stored as proteins
Explain the fuel preferences to the following types of tissue: Liver, Adipose Tissue, Skeletal Muscle, Heart Muscle, and Brain Tissue
Preferred Fuel Sources:
Liver: Fatty acids, glucose, AA’s
Adipose Tissue: Fatty Acids
Skeletal Muscle: (fatty acids at rest and glucose during exertion)
Heart Muscle: fatty acids
Brain: (glucose during fed state and ketone bodies during starvation).
BRAIN IS VERY DEPENDENT ON GLUCOSE
What is the driving force for the coordination of metabolism?
During the fed state, the brain has an absolute requirement for glucose. If it does not have access to glucose, nerve cells die very quickly. Therefore, the driving force for the coordination of metabolism is to provide the normal range of glucose levels for the brain.
How are proteins and carbodydrates stored? What about fats?
What is the number of kcal per gram of carbs, proteins, and fats for both dry and wet scenarios?
Proteins and Carbs are stored in a hydrated state. Fats, on the other hand are stored in anhydrous state?
What is the first thing that starts to get utilized when the fed state ends? In other words, during the initial stages of the starved state, what is broken down to maintain the blood glucose level?
LIVER GLYCOGEN is broken down first in order to maintain blood glucose levels
Explain lactose intolerance
Lactose intolerance results from a decrease level of production for the enzyme lactase
High levels of intestinal lactose causes osmosis of water into intestine, leading to the poops. Anaerobic bacteria use lacctose to create H2 and CH4 gas
Draw the “OVERVIEW of Carbphydrate Metabolism” pathway slide
Define the following terms:
Insulin
Glucagon
Hypoglycemia
Hyperglycemia
Insulin: peptide hormone secreted by pancreas beta cells that regulates glucose metabolism (maintains low glucose by promoting glycolysis and glycogen synthesis)
Glucagon: peptide hormone secreted by alpha cells of the pancreas when blood glucose is low (between meals or during exercise) causes the liver to release glucose into the blood
Hypoglycemia: low blood glucose
Hyperglycemia: high blood glucose
Explain what happens during the fed state.
Fed state: we have plenty of glucose in our blood stream, so glucose will proceed to other fates
- Glucose can get stored as glycogen in the liver via glycogenesis
- Glucose can turn into Glucose-6-P and enter the pentose phosphate pathway
- Glucose can undergo glycolysis and be turned into lactate and pyruvate. Pyruvate is then oxidized into acetyl coA, which is then converted into triacylglycerol OR oxidized again into CO2 and water by the CAC.
Explain what happens during the fasted state
During starvation, glucose levels are falling. Glucose needs to be maintained in order to keep up brain activity.
The alpha cells of pancrease release glucagon. Adrenal medulla releases Epi. (both act via second messenger pathway)
Promotes glycogenolysis (breakdown of glycogen into glucose)
Promotes glycogenogenesis
Inhibits glycolysis
Explain GLUT 2 and GLUT 4
GLUT 2: insulin independent, low affinity, high capacity transporter in the liver, it’s BIDIRECTIONAL
GLUT 4: insulin dependent transporter in muscle, heart, and adipocytes, higher affinity for glucose
