Chapter 5 - Essentials of Metabolism Flashcards
PCr produces ATP for how long?
~10 seconds
and if this exercise intensity is sustained, then the energy system has to switch to continue producing ATP to the cells that need it
what is the substrate of glycolysis?
Glucose
enzyme
a substance that acts as a catalyst to bring about a specific biochemical reaction
isoenzyme
A group of enzymes that catalyze the same reaction but have different enzyme forms and catalytic efficiencies
It is thought that isozymes exist to maximize biological capacity
phosphocreatine
Phosphocreatine, sometimes referred to as creatine phosphate (abbreviated to PCr or PC) is a high-energy phosphagen capable of donating its phosphate to ADP and, as a result, resynthesizes ATP
Kinase is the enzyme that triggers this interaction between phosphocreatine and ATP molecules
Creatinine is also a product of the reaction.
burns out quickly because the body only stores a small amount of creatine phosphate
Only supplies energy for up to 10 seconds
how much phosphocreatine (PCr) can be stored in human muscle at once?
Storage of PCr in human muscle is limited to 80 mM/kg dry mass (120g total, less in vegetarian and vegan individuals)
During aerobic recovery, PCr can also be resynthesized in the mitochondrial intermembrane space by the mitochondrial isoform of creatine kinase
what enzyme catalyzes phosphocreatine ATP synthesis?
creatine kinase (CK)
when the body begins to run low on creatine phosphate (and high in adenosine diphosphate), it triggers the chemical action of phosphocreatine molecules donating their phosphate group back to ADP, making it ATP once again
what sports utilize the ATP-PC system?
- 40 meter sprinters
- olympic weightlifters
- golf
- 100 meter sprinters
what are the two primary reactions in the ATP-PC system?
- creatine kinase reaction (uses CP to turn ADP into ATP)
- myokinase reaction (uses 2 ADP molecules to create ATP and AMP. When AMP accumulates, that serves as a signal to start up the glycolitic pathway)
glycolysis
primarily an anaerobic pathway
The anaerobic metabolic pathway that converts glucose into pyruvate
products are 2 pyruvate, 2 ATP, and 2 NADH
literally means the cutting of sugars
occurs in the cytoplasm of the cell
resynthesize
To combine or produce something again
pyruvate
a 3-carbon acid that is naturally produced during glycolysis
a key intermediate in various metabolic pathways such as gluconeogenesis, fermentation, cellular respiration, fatty acid synthesis
An important molecule present at the intersection of multiple biochemical pathways
glucose vs glycogen
Glycogen is essentially glucose molecules bonded together to make a larger storage molecule
Glycogen must first be broken down to release its glucose molecules by a process known as glycogenolysis, catalyzed by the enzyme glycogen phosphorylase.
different GLUT receptors
GLUT 1-4
depends on what type of organ the glycolysis is occuring in
protein
GLUT-4
An insulin-regulated glucose transporter found primarily in adipose, skeletal, and cardiac tissue
responsible for insulin-regulated glucose uptake into fat and muscle cells
glycogenolysis
conversion of glycogen back into glucose, which is then ready to undergo glycolysis to produce ATP
the hormone glucagon (from the liver) stimulates this reaction
the hormone adrenaline controls this process
The process is under the regulation of two key enzymes: phosphorylase kinase and glycogen phosphorylase
glycogen phosphorylase
Enzyme responsible for the breakdown of glycogen into glucose monomers
G-1-P
Glucose-1-phosphate
The first step in glycogen phosphorylase is to break down glycogen into G-1-P
G-6-P
glucose-6-phosphate
The result of the glycogen phosphorylase reaction is G-1-P, which is then converted to G-6-P and available for glycolytic breakdown to release energy
glycolytic breakdown
The breakdown of glucose by enzymes, releasing energy and pyruvic acid (3-carbon molecule intermediate)
AMP
adenosine mononphosphate
consists of the phosphate group, the pentose sugar ribose, and the nucleobase adenine
AMP is used as a dietary supplement to boost immune activity, and is also used as a substitute sweetener to aid in the maintenance of a low-calorie diet
adrenaline (epinepherine)
*catecholamine hormone
A hormone involved in regulating visceral functions, normally produced both by the adrenal glands and by a small number of neurons in the medulla oblongata; also known as epinephrine
In both the liver and muscles, which store glycogen, the process of glycogenolysis is controlled by the hormone adrenaline
how is adrenaline (epinepherine) involved in exercise
Adrenaline is released during exercise and is transported in the circulation to the muscle and liver, where it binds to its receptor on the cell membrane.
When adrenaline is bound to its receptor, glycogen breakdown is initiated
adrenal medulla
Inner part of an adrenal gland that controls hormones that initiate the flight or fight response
Glycolytic Pathway
Step 1
Turn glucose (transported into the cell cytoplasm by GLUT4) into glucose-6-phosphate (G-6-P)
Consists of adding a phosphate group to the 6 carbon of the glucose monomer
Enzyme responsible? hexokinase
lactate shuttling
is best contextualized when considering energy metabolism in fast and slow twitch fibers during exercise
During high-intensity exercise, near VO2 max lactate produced by fast-twitch, glycolytic muscle fibers will be transported out of the fiber and taken up by a neighboring slow-twitch, oxidative muscle fibers, where it is oxidized to pyruvate and used in the tricarboxylic acid cycle (TCA), also known as Krebs cycle
Acetyl coenzyme A (acetyl CoA)
A molecule involved in protein, carbohydrate and lipid metabolism. Its main function is to deliver the acetyl group to the citric acid cycle (krebs) to be oxidized for energy production of ATP
beta oxidation converts lipids into CoA
Enzyme Responsible? pyruvate dehydrogenase (PDH)
link reaction
chemical reaction that links the glycolitic pathways to the oxidative pathway
under aerobic conditions, this reaction catabolizes pyruvate into acetyl CoA
mitochondrion
An organelle found in large numbers in most cells, in which the biochemical processes of respiration and energy production occur; has a double membrane, the inner part being folded inwards to form layers called cristae
a higher concentration of mitochondria in a cells means greater aerobic capacity/fitness
metabolic integration
The coordination between the metabolites of carbohydrates, lipids and proteins, and how the fuels are regulated for energy production
adenosine triphosphate (ATP)
The basic structure of ATP consists of a base (adenine) attached to a sugar (ribose) and three phosphate molecules
Although ATP is the main energy source in cells, it exists in short supply. In muscle, this is approximately 25 mM/kg of dry mass (40–50 g total). In terms of powering muscle contraction during exercise, this only provides enough energy for 2–4 seconds of work
creatine concentration in the muslces based on nutrition status
