Metabolism Flashcards
What is metabolism?
sum of all of the chemical reactions in the body
What are the various forms of energy?
- Kinetic energy - motion
- Potential energy - position, chemical energy stored in bonds
- Activation energy - energy needed to start reaction; the collision energy needed to break the chemical bonds of reactants
Compare exergonic and endergonic reactions and how they relate to metabolism.
Exergonic - releases energy; catabolism (break down) (I.e., breakdown of nutrients such as glucose)
Endergonic - absorbs energy; anabolic (build up)
- energy released from an exergonic reaction can be used to drive an endergonic reaction (I.e. energy released from breakdown of glucose can become trapped into the covalent bonds of ATP which drive endergonic reaction to build body structures like muscle and bone)
Digestion breaks down proteins, carbs, and fats into what components?
Proteins => amino acids
Carbohydrates => simple sugars
Fats => fatty acids
What are the 3 uses that come from digestion of complex substances into simpler components?
- Energy
- Building blocks
- Stored for future
What is activation energy?
the energy required for a reaction to occur
What are 2 factors that influence the chance that a collision occurs and causes a chemical reaction?
- Concentration of reactants - the more particles in a fixed space, the greater the chance they will collide
- temperature - increase in T causes an increase in particle movement which increases chance of collision
What is the relationship between catalysts and activation energy?
catalysts speed up the reaction by lowering the activation energy required to start a reaction (not requiring as much energy to be absorbed by reactants for a reaction to start) and, therefore, lowering the temperature and concentration of reactants needed to start a reaction
____ are the catalysts of organisms
enzymes
Why are catalysts needed if increase in concentration of reactants and increase in temperature can achieve the required activation energy needed to start a reaction?
- normal body temps and concentration of molecules in body fluids are too low for most chemical reactions to occur rapidly enough to maintain life
- the body can only handle so much of an increase in temperature and concentration of reactants even though this can increase amount of collisions and increase rate of reactions (we have limits), so catalysts help with not exceeding those limits but also allowing for the reaction to occur
List the properties of enzymes.
- Protein
- Active site - where substrate/ligand binds
*3. Highly specific - permits binding of a specific substrate and catalyzes a specific reaction
*4. Efficient
*5. Subject to controls - rate of synthesis and concentration of an enzyme are controlled by a cell’s genes; substances within cell may enhance or inhibit activity of an enzyme; enzyme outside cell is controlled by ECF’s chemical environment
How do enzymes function?
- Enzyme and substrate (reactant(s)) combine/bind at active site of enzyme forming enzyme-substrate complex
- Enzyme catalyzes reaction and transforms substrate into products
- Once reaction is complete, enzyme is unchanged and free to catalyze same reaction again on a new substrate
(I.e. sucrose binds to enzyme specific for sucrose, enzyme catalyzes reaction and sucrose becomes fructose and glucose, fructose and sucrose are released and enzyme is unchanged and ready to catalyze another reaction for sucrose)
List the factors that influence the rate of an enzymatic reactions and how they influence it.
- Temperature - rate of reaction increases with increasing temperature until optimal temperature (37 C) is reached in which the rate of reaction severely drops after this point (denatures the enzyme)
- pH - reaction rate is greatest at an enzyme’s optimal pH (typically pH = 7.4 which is the pH of most body fluids, but it depends on the enzyme (I.e., pepsin of the stomach’s optimal pH = 2)) and decreases at pH lower or higher than optimal pH due to changes in the [H+] which alters charges of amino acids at active site and causes enzyme to denature
- Substrate concentration - rate of reaction increases with increasing substrate concentration until all enzymes are occupied with a substrate (no more enzymes available to catalyze reactions)
What are examples of non-substrate chemical substances that bind to an enzyme and how do they function?
- Competitive inhibitors - inhibitor resembles substrate and competes with it to bind at active site of enzyme, binding of inhibitor to enzyme decreases reaction rate or prevents reaction from occurring (no catalyzing of reaction occurs)
- reversible binding - weak, noncovalent bonds - Allosteric modulators - chemical substance (non-substrate) binds reversibly to allosteric site causing a conformational change of the active site
- Allosteric inhibitors - changes shape of active site resulting in decreased affinity for substrate (decreases reaction rate)
- Allosteric activators - changes the shape of active site resulting in increased affinity for substrate (increases reaction rate)
Concept of a metabolic pathway
A metabolic pathway is a sequence of reactions in which an initial substrate is converted into an end product via a series of intermediates
Each reaction is catalyzed by a separate enzyme and the product of one reaction serves as the substrate for the next reaction.
A => B => C => D => E
A is initial substrate, E is end product, and B, C, and D are intermediates
How does an enzyme function in a metabolic pathway?
Each reaction is catalyzed by a separate enzyme and the product of one reaction serves as the substrate for the next reaction.
How are metabolic pathways controlled?
Feedback/end product inhibition - process in which the end product of a metabolic pathway shuts down the pathway by binding to and inhibiting an enzyme which catalyzed a previous reaction in the pathway
How does the end product of a metabolic pathway shut down the entire pathway?
by binding to the first enzyme which catalyzed the initial substrate preventing the next product from being formed
What type of feedback is feedback inhibition?
negative feedback - excess of end product causes feedback inhibition to occur and metabolic pathway to come to a halt; metabolic pathway resumes when end product becomes too low
What kind of inhibitor does the end product of a metabolic pathway typically serve as during feedback inhibition?
allosteric inhibitor; but competitive inhibitors also exist
“energy currency” of a living cell
ATP
What is the importance of ATP in metabolism?
couples energy releasing catabolic reactions (exergonic) with energy absorbing anabolic reactions (endergonic)
Role of ATP in anabolism.
Anabolic reactions transfer energy from ATP to complex molecules such as glycogen, proteins, and triglycerides (takes energy to build)
Role of ATP in catabolism.
Catabolic reactions transfer energy from complex molecules to ATP (breaking of complex molecules releases energy which can further be used in anabolic reactions)
- breakdown of complex molecules to form simple molecules such as glucose, amino acids, glycerol, and fatty acids
Compare substrate-level phosphorylation with oxidative phosphorylation.
Substrate-level phosphorylation - phosphate is transferred from phosphorylated intermediate to ADP to form ATP
Oxidative phosphorylation = chemiosmosis (process in which a H+ gradient is used to produce ATP) + ETC
- mitochondria
- electron transport chain (of the inner membrane of mitochondria)
- oxygen final electron acceptor
Where would there be a high [H+] in the mitochondria?
intermembranous space (space between the inner and outer membrane)
How do NAD+ and FAD help in the generation of ATP?
by picking up and carrying electrons in the form of hydrogen atoms to the electron transport chain where H is spit into H+ ions (establishes H+ ion gradient) and electrons (goes through the ETC)
What is cellular respiration?
breakdown of a nutrient molecule (glucose, amino acid, fatty acid) into CO2, H2O and energy (ATP) in the presence of O2
Outline the components of cellular respiration under aerobic conditions.
Glycolysis (cytosol)
=> pyruvate processing (mitochondria)
=> Krebb’s cycle (mitochondrial matrix)
=> Electron transport chain (inner mitochondrial membrane)
How much ATP is produced from aerobic cellular respiration?
30-32 ATP
Outline the components of cellular respiration under anaerobic conditions.
Pyruvic acid => lactic acid
How much ATP is produced from anaerobic cellular respiration?
2 ATP
When does anaerobic cellular respiration occur?
strenuous exercise, hypoxia/ischemia
How much ATP is produced from glycolysis during aerobic respiration?
2 ATP
What is produced from pyruvate processing during aerobic respiration?
2 CO2
What is produced from the Krebs cycle during aerobic respiration?
4 CO2 & 2 ATP
How much oxygen is used as a final electron acceptor at the end of the electron transport chain?
6 O2
What is produced at the end of the electron transport chain from aerobic respiration?
26/28 ATP
Glucose anabolism includes _____ and _____
glycogenesis; gluconeogenesis
synthesis of glycogen
glycogenesis
synthesis of new glucose molecules from the products of protein and lipid breakdown (amino/keto/lactic acids)
gluconeogenesis
What occurs to glucose molecules that are not needed immediately to produce ATP?
glucose combines with many other forms of glucose to form glycogen - a polysaccharide that’s the only stored form of carbohydrates in our bodies
The body can store about ____ of glycogen; ___ in skeletal muscle and the rest in ____
500 g;
75%
liver
Where does gluconeogenesis occur?
liver
What is lipid metabolism?
lipids are catabolized to produce ATP
What happens to lipids if they are needed immediately for ATP production?
they are stored as triglycerides in adipose tissue and the liver
What’s the first step to lipid metabolism?
Lipolysis: triglycerides => glycerol + fatty acids
What occurs to glycerol if ATP supply is high?
glycerol converts to glucose for storage (gluconeogenesis)
What occurs to glycerol if ATP supply is low?
glycerol enters catabolic pathway to form pyruvic acid
Fatty acid catabolism begins with a series of reactions collectively called _____
B-oxidation
Where does B-oxidation occur?
in mitochondrial matrix
B-oxidation converts fatty acids into ____
acetyl CoA
After b-oxidation, acetyl CoA can do what 2 processes?
- enter krebs cycle
- undergo ketogenesis in liver cells to form ketone bodies which will then leave the liver and enter body cells where they’d be broken down into acetyl CoA and subsequently enter the Krebs cycle
Outline the steps to lipid metabolism.
triglycerides => glycerol = fatty acids
glycerol => pyruvate processing => krebs cycle => ETC
fatty acids => b-oxidation/acetyl CoA => krebs cycle => ETC
- After acetyl CoA formation, liver converts some acetyl CoA into ketone bodies such as acetoacetic acid, beta-hydroxybutyric acid, and acetone (ketogenesis). Once produce, they leave the liver and enter body cells where they are broken down into acetyl CoA and enter krebs cycle, etc.
the level of ketone bodies in the blood is normally very ____; why?
low; other tissues use them for ATP production as they are formed
What can occur as a result of excessive B-oxidation?
production of ketone bodies exceeds their uptake and use by body cells
- higher than normal ketone bodies in blood = ketosis
- too many ketone bodies accumulate causing blood pH to fall = ketoacidosis
Outline the steps to protein metabolism.
- breakdown of proteins into amino acids via digestion
- Deamination - removal of NH2 from amino acid (liver) producing ammonia (NH3) and a keto acid
- ammonia => urea (partially excreted in urine)
- keto acid => pyruvic acid, intermediate of krebs cycle or acetyl CoA (depends on the type of amino acid deaminated)
Where does deamination occur?
in the liver
What are the 6 main types of nutrients?
- Water
- Carbohydrates
- Lipids
- Proteins
- Minerals
- Vitamins
Minerals are ____ elements, and vitamins are _____
inorganic; organic
List the minerals with known functions of the body.
Sodium, calcium, potassium, magnesium, phosphorous
Most vitamins with known functions are _____
coenzymes
3 groups of vitamins:
- Fat-soluble - A, D, E, & K (absorbed in blood stream and can be stored in cells and especially hepatocytes)
- Water-soluble - several B vitamins and vitamin C (dissolved in body fluids; excess is not stored but excreted in urine)
- Antioxidants (C, E, and beta-carotene) - inactivate oxygen free radicals
