Chapter 7 - Metabolism Flashcards
What is metabolism?
- sum total of all chemical reactions to go on in living cells
- generation of energy from carbohydrates, proteins, & fats
what is aerobic metabolism?
- with oxygen
- produces energy more slowly b/c can be sustained for a long time
- total energy yield is greater (than anaerobic)
- ex. pyruvate breaking down slowly to acetyl CoA
what is anaerobic metabolism?
- not requiring oxygen
- yields energy more quickly, but can’t be sustained for long
- ex. pyruvate to lactate
catabolic vs. anabolic metabolism
catabolic reactions break down larger molecules into smaller compounds & release energy (ATP & heat)
anabolic reactions use ATP to combine smaller molecule, like glucose, into larger compounds, like glycogen, & release small amounts of heat
mitochondria (structural features)
inner compartment - site of pyruvate-to-acetyl CoA, fatty acid oxidation, & TCA Cycle
inner membrane - site of electron transport chain
outer membrane - site of fatty acid activation
what is pyruvate?
- amino acids, glycerol, & glucose can be converted to pyruvate
satiety
feeling of being full after eating
gherlin
appetite stimulating hormone
what is glycolysis?
- the metabolic breakdown of glucose to pyruvate
- is anaerobic (doesn’t require oxygen)
- takes place in cytosol of cell where enzymes are located to breakdown glucose
- one glucose molecule = 2 pyrite molecules
Is ATP used for glycolysis?
yes, 2 ATP needed to begin it
- 4 ATP yielded at end of process
- net gain of 2 ATP
can glucose be made from pyruvate?
yes, process can go either way
glucose pyruvate
what is the fate of pyruvate w/o oxygen?
- anaerobic (glucose -> pyruvate -> lactate)
- yields energy quickly, but cannot be sustained for long
what is the fate of pyruvate with oxygen?
- aerobic (glucose -> pyruvate -> acetyl CoA
- produces energy more slowly
Cori cycle
- done in the liver
- a recycling process of lactate
- process of converting lactate from muscles to glucose that can be returned to the muscles
is the step from pyruvate to acetyl CoA reversible?
No
- A cell cannot retrieve the carbons from CO2 to remake pyruvate & then glucose
- it’s one way only
how are fats converted to energy?
- break down to glycerol & fatty acids
- glycerol converts to pyruvate
- fatty acids convert to acetyl CoA thru fatty acid oxidation
fatty acid oxidation
- takes place in the mitochondria
- 2 carbons at a time are cleaved off chain & combine with CoA to make acetyl CoA
can fatty acids make glucose?
cells cannot make glucose from the 2-carbon fragments of fatty acids
how is glucose obtained from fats (triglyceride)?
- only the glycerol can yield glucose, but only a very small amount
- fatty acids can provide abundant acetyl CoA
what are ketones?
- the byproduct when the body uses fat for energy instead of glucose
- back up fuel for brain & nerve function when glucose is limited
glucogenic
glycerol b/c can me transformed into glucose
ketogenic
fatty acids – b/c can be transformed into ketone bodies
what is ketoacidosis?
- when there is a toxic level of ketones in the blood
- causes the blood to become acidic
how are proteins converted to energy?
- before entering the metabolic pathways, amino acids are deaminated (lose their nitrogen-containing amino group)
- can enter pathway as pyruvate (are glycogenic), acetyl CoA (are ketogenic) or directly into TCA cycle (are glycogenic).
why is deamination important?
amino acids must drop their N-containing amine group before they can be used for energy
glucogenic amino acids
can be used to make glucose
- 14 amino acids
ketogenic amino acids
can be transformed into ketone bodies
- leucine
- lysine
which amino acids are both glycogenic & ketogenic?
- isoleucine
- tryptophan
- phynylalanine
- tyrosine
what is deamination?
removal of the amine (N-containing) group
why is deamination important?
an amino acid needs to be deaminated in order to be used for:
- energy
- production of glucose, ketones, cholesterol or fat
- to make nonessential amino acids
oxaloacetate
- primarily made from pyruvate
- can also be made from certain amino acids
- CANNOT be made from fat
- must be available for acetyl CoA to enter the TCA cycle (underscores how important carbohydrates are in the diet)
what are the products of the TCA cycle?
Each cycle produces:
- 2 Carbons that are lost to CO2 (breathed out)
- 8 H+ atoms & their electrons
- small amount of energy at GTP
How does the TCA cycle contribute to protein synthesis?
it provides the starting material for creating non-essential amino acids through transamination
how are non-essential amino acids made from essential amino acids?
by transamination - the transfer of an amino group from one amino acid to an alpha-keto acid to form a new non-essential amino acid
why is transamination important?
allows cells to make amino acids they need to synthesize protein
where is the TCA cycle carried out?
in the inner compartment of mitochondria
what is coenzyme Q?
ubiquinone (CoQ10)
- made in the body to help with cell function
- is critical to converting fats, proteins, & carbs into energy
what is the entrance point to the TCA cycle?
Acetyl CoA combines with oxaloacetate to form citrate in the first step of the TCA cycle
what is the electron transport chain?
- the final stage of metabolism when electrons are transferred from one complex to another
- products are ATP & H2O
- takes place in the inner mitochondrial membrane of cell
in what way is the electron transport chain related to photosynthesis?
In both cases the electron transport chain uses the energy to pump hydrogen ions across a membrane.
cell - uses process to make ATP
photosyn - use energy to make molecules
What is the location of the electron transport chain?
happens in the mitochondrial membrane
what are the products of the electron transport chain?
ATP (90% of the ATP used by the body)
H20
digestion pathway of alcohol
stomach - alcohol dehydrogenase (enzyme): begins to break down alcohol in stomach
small intestine - rapidly absorbs it, before metabolizing any other nutrients
liver - also makes alcohol dehydrogenase
Alcohol metabolism - pathway 1
- alcohol dehydrogenase (ADH) w/niacin, oxidizes alcohol to acetaldehyde
- acetaldehyde dehydrogenase (ALDH) removes more H & forms acetate
- acetate forms acetyl CoA & enters TCA cycle
alcohol metabolism - pathway 2 (when too much)
used when too much alcohol present & liver enzymes can’t keep up
1. MEOS - at high concentrations or repeated exposure, alcohol stimulates synthesis of enzymes in the MEOS.
Microsomal ethanol-oxidizing system
MEOS
- chronic alcohol abuse increases the # of enzymes in this pathway
- used to metabolized drugs & other foreign bodies
- alcohol takes precedence over drugs (may interfere w/metabolism of drugs
- can increase alcohol tolerance
blood alcohol concentration (bac)
- if there is too much alcohol for the liver to metabolize, some stays in the blood
- amount of alcohol in blood measured in grams/dL
Wernike-Korsakoff syndrome
malnutrition - mental confusion & uncontrolled muscle movement due to thiamin deficiency’s affect on brain
- paralysis of eye muscles
- poor muscle coordination
- impaired memory
- damaged nerves
malnutrition
- heavy drinking displaces nutrients from diet
- interferes with body’s metabolism of nutrients
- affects B vitamin folate
- affects liver’s ability to retain folate & kidneys excrete more
fatty liver
- presence of too much alcohol in liver stops liver from packaging & sending fatty acids to tissues
- fat can build up
cirrhosis of the liver
- fatty liver is reversible if stop drinking
- fibrosis - alcoholic hepatitis - 2nd stage of liver deterioration - some cells can regenerate w/good nutrition & no drinking
- cirrhosis - advanced stage of damage; least reversible
Consequences from excessive alcohol consumption:
- liver disease
- malnutrition
- impaired digestion & absorption
- weight gain
- changes in nutrient metabolism
- interaction w/hormones
- cardiovascular disease
- irreversible damage to fetus
phenylkeonuria
PKU
- born without ability to properly breakdown amino acid phenylalanine
- example of a diet-related single-gene disorder
- can be controlled by diet
- symptoms include:
- delayed mental & social skills
- head size significantly below normal
- hyperactivity
- jerking movements of arms or legs
- mental retardation
- seizures
- skin rashes
- tremors
- unusual positioning of hands
role of liver in metabolism
- most metabolically active organ in body
- first organ to metabolize, store & distribute nutrients after absorption
- proteins, carbs, & fats are converted to: usable forms of energy; storage forms -> glycogen, triglycerides
how is energy defined?
ATP
creatine phosphate
energy storage
creatine phosphate
- a high energy compound found in muscle cells
- acts as a reservoir of energy
- can maintain a steady supply of ATP for short bursts of activity
- can donate an inorganic phosphate to ADP to make ATP
