cellular metabolism Flashcards
what is a metabolic pathway?
a metabolic pathway is a series of chemical reactions occurring within a cell
what is the initial chemical in a pathway?
the initial chemical (metabolite) is modified by a sequence of chemical reactions
what are chemical reactions catalysed by?
these reactions are catalyzed by enzymes
what do you need in order to carry a chemical reaction?
in order to carry out these reaction a cell requires energy
what is the main aim of the metabolic pathway?
generation of ATP
what results in the depletion of ATP?
cellular stress from nutrient starvation or reduced oxygen supply results in the depletion of ATP
what does sufficient ATP depletion trigger?
sufficient ATP depletion may trigger apoptosis
what happens if ATP is not required?
if ATP is not required energy can be stored
what is ATP?
ATP is energy carrying molecule
what are catabolic pathways?
.break down foodstuffs into smaller molecules with the release of energy
.results in ATP production and transfer of energy
. breakdown macromolecules
what are anabolic pathways?
use the energy released by catabolism to synthesise molecules that the cell requires
what are examples of activated carrier molecules?
.ATP
.NADH
where do activated carrier molecules store energy?
energy is stored in the chemical bonds of carrier molecules
how do activated carriers store energy?
activated carriers store energy in an easily exchangeable form
what is the structure of ATP?
ATP is a nucleotide that consists of 3 main structures
- nitrogenous base (adenine)
- ribose (sugar)
- chain of 3 phosphate groups bound to the ribose
where is available energy contained in ATP?
available energy is contained in the bonds between the phosphates
when is energy in ATP released?
energy is released when phosphate bonds are broken through the addition of water molecule ( hydrolysis)
when is ATP converted to ADP?
this occurs when the outer phosphate is removed from ATP to transfer energy
therefore ADP only has two phosphates
what are electron carriers?
they are involved in redox reactions- carrying electrons from one reaction to another
what are examples of electron carriers?
. NAD+ is a 2-electron oxidising agent reduced to NADH
.NADH is a 2-electron reducing agent oxidised to NAD+
what is glycolysis?
breaking down of carbohydrates to harness energy in ATP
describe the process of glycolysis?
. converts a 6C glucose molecule into two 3C molecules of pyruvate
. we use ATP to make more ATP
where is the energy released in glycolysis trapped?
energy released in this process is trapped within ATP and NADH
where does glycolysis occur?
glycoclysis occurs in the cytoplasm of the cell
what are the 2 phases of glycoclysis?
. energy investment (ATP CONSUMED)
. energy generation (ATP produced)
what is the net gain of glycolysis?
glycolysis results in a net gain of 2 molecules of ATP and 2 molecules of NADH for each molecule of glucose
what is the rate of production of ATP in glycolysis?
fast ATP production but low yield
what happens to pyruvate during anaerobic oxidation?
enzyme (lactate dehydrogenase) will turn pyruvate into lactate which forms lactic acid
what happens to pyruvate during aerobic oxidation?
convert pyruvate 3C into acetyl-coA
oxygen is produced which is reactive
what is the waste product during aerobic oxidation?
carbon dioxide which goes to the cardiovascular system then to respiratory system and then breath out
where does the conversion of pyruvate to acetyl-coA occur?
occurs in the membrane of the mitochondria (transition reaction/link reaction)
what happens in a transition reaction/link reaction?
pyruvate+coA+NAD+ ——-> acetylcoA +co2 +NADH
what is the energy trapped in NADH used?
energy trapped inside NADH can be used for oxidative phosphorylation
why is acetylcoA a key intermediate in transition reaction/link reaction?
.acetylcoA is a key intermediate to transfer 2C atom into the krebs cycle
.acetylcoA feeds stright into krebs cycle and gets oxidised
what are other names for the krebs cycle?
.citric acid cycle
.TCA cycle
where does krebs cycle take place?
takes place inside mitochondrial matrix
what happens to acetyl-coA in the krebs cycle?
krebs cycle reaction oxidise the remaining acetyl fragments of acetyl-coA to co2
what is the energy released from the oxidation of acetyl used for?
energy released from this oxidation is used to reduce co enzymes
NAD+ and FAD
and phosphorylate
ADP to ATP
what happens in each turn of krebs cycle?
.2C enter in the acetyl fragment of acetyl-coA
.2 separate carbons are oxidised and leave as co2
.3NADH AND 1 FADH2 and 1 GTP produced
how is ATP made?
GTP+ADP ——-> GDP+ATP
where are NADH and FADH2 produced?
.they are produced by the krebs cycle , transitio/link reaction and glycolysis
.they are carriers of high energy electrons
how do NADH and FADH2 generate ATP ?
. each contain a pair of electrons
. these electrons are used to reduce oxygen to water liberating a large amount of free energy
. this free energy is used to generate ATP
what is oxidative phosphorylation?
. the process in which ATP is formed as result of transfer of electrons from NADH or FADH2 to O2 by series of electron carriers
why is oxidative phosphorylation a major source of ATP in aerobic respiration?
generate 26 of 30 molecules of ATP that are formed when glucose is completely oxidized to CO2 and H20
describe the process of oxidative phosphorylation?
- NADH or FADH2 transfer energy into proteins
- this induces proteins to pump h+ ions across the membrane to outside
- accumulation of H+ on one side of the membrane- intermembrane space
- ATP is synthesised when protons flow back through the mitochondrial matrix through an enzyme complex (ATP synthase)
what is ATP synthesis?
pumps hydrogen ions into mitochondrial matrix
what is ATP hydrolysis?
pumps hydrogen ions in the opposite direction
. requires energy
how many energy tokens are produced by one glucose?
1 glucose = 32 energy tokens
how can glucose be stored?
glucose availability may exceed need for ATP
glucose energy can be stored as glycogen
what are the 2 process in which glucose can be stored as glycogen?
. glycogenesis
. glycogenolysis
what is the process of glycogenesis?
glucose + ATP ——-> G-6-P —–> glycogen
.stored in liver and skeletal muscle cell
. storage stimulated by insulin ( endocrine system)
. insulin is secreted when blood glucose levels are high
what is the process of glycogenolysis?
glycogen+P —-> G-6-P —->GLUCOSE
liver breakdown stimulated by glucagon
glucagon is secreted when blood glucose levels are low
what is proteolysis?
protein breakdown
how do polypeptides breakdown to amino acids?
by hydrolysis
what is deamination
.removal of NH3 from a molecule as it can be toxic if on its own
. NH3 forms ammonia
-neutralises into urea
. remaining carbon skeleton ( keto acid) can be used to make ATP
what is the fate of carbon skeleton of amino acids?
the carbon skeletons to amino acids can be utilised in the krebs cycle
what happens to ammonia after deamination?
.ammonia is toxic and must be removed from the body
. the urea cycle produces urea from ammonia
.takes place in the liver
. need to put in ATP to convert ammonia to urea
what is the process of transmination?
. transfer of NH2 to another carbon skeleton to form new aminoacid
what is two step process of catabolism of lipids?
- triglyceride breakdown
2. beta- oxidation
what happens during triglyceride breakdown?
triglyceride+h2o ——-> 3 fatty acid+glycerol
what happens during beta-oxidation?
. oxidation of fatty acid chains
.cleaved off into 2 carbon chains
.reaction binds coA to end and cleaves
. AcetylcoA —-> can enter krebs cycle
does beta-oxidatipn of long chain fatty acids produce more ATP than glucose?
yes as
ATP yield from palmitate C16 - producing 106 ATP and
ATP yield from glucose C6 - producing 36 ATP
what do fatty acids do when broken down?
fatty acids can be broken to create ATP down when there is oxygen
what are the non-carbohydrate building blocks that glucose can be formed from?
glycerol - from lipid breakdown
keto acids - carbon skeletons from amino acids breakdown
what is gluconeogenesis?
.when glucose can be formed from non-carbohydrate building blocks
process occurs in the liver and kidney (stimulated by hormones)
. stimulated in times of great need
summary of building blocks of life formation?
. transamination-
glucose -> keto acids (plus NH2) -> amino acid
. gluconeogenesis
amino acids -> keto acids -> glucose
. lipid synthesis (occurs when glycogen stores are full)
glucose -> acetyl coA -> fatty acid
What does aerobic respiration involve?
Krebs cycle
What are the 2 components of oxidative phosphorylation?
electron transport chain
What protein is the ATP synthase?
intergral
What is proton motive force?
In oxidative phosphorylation
where H+ pumped in mictochondrial matrix
What can Amino acids be used for?
used as a source of energy to harness into ATP (energy production)
How do we convert ammonia to urea?
via ATP
