Homeostasis, metabolism, and bioenergetics 2 Flashcards
bioenergetics
study of flow of energy through biological systems
ATP
adenosine triphosphate
special carrier for free energy
provides most of the energy for cell functions
made of adenine, ribose, and three linked phosphates
made by adding a phosphate group to an ADP molecule
which bonds in ATP are the high energy bonds
two outer most phosphates - they have the most amount of stored energy
ATP-PC system
anaerobic pathway that occurs in the cytoplasm
most rapid way of making ATP because it’s only a one enzyme reaction
ADP + phosphocreatine (PC) -> ATP + Creatine
explain the anaerobic glycolysis pathway for glucose
1.) glucose molecule enters cell
2.) glucose is phosphorylated to become glucose-6-phosphate by hexokinase
-1 ATP
3.) glucose-6-phosphate is rearranged into fructose-6-phosphate by glucose-6-phosphate isomerase
4.) fructose-6-phosphate is phosphorylated to form fructose-1,6-biphosphate by phosphofructokinase
-1 ATP
5.) fructose-1,6-biphosphate molecule splits into two glyceraldehyde-3-phosphate molecules (G3P)
6.) each G3P molecule is converted to pyruvate
two main aerobic pathways
citric acid cycle (Krebs cycle)
electron transport chain
cellular respiration
metabolic pathway where organic molecules are oxidized and disassembled in a controlled manner by a series of enzymes
what enzyme breaks down ATP
ATPase
why don’t we store a lot of ATP
the molecule is large and would make us large
only storing a little causes us to make more as soon as we need it (ex. starting to exercise)
which enzyme donates the phosphate group of phosphocreatine to create an ATP molecule
creatine kinase
why can we not solely use the ATP-PC system to make ATP
we do not have an unlimited amount of phosphocreatine
what is the limiting factor in the anaerobic glycolysis of glucose
phosphfructokinase (enzyme that phosphorylates fructose-6-phophate)
what are the products of the anaerobic glycolysis of glucose
4 ATP (net 2)
2 NADH+ + 2H+
2 pyruvate or lactate
why must glucose be phosphorylated after entering the cell
phosphorylation prevents it from leaving the cell through the glucose channel
prevents the build up of glucose in the cell and maintains the chemical gradient
what does a hexokinase do
adds phosphate group
explain the anaerobic glycolysis pathway for glycogen
1.) glycogen already in the cell is converted to glucose-6-phosphate
2.) glucose-6-phosphate is rearranged into fructose-6-phosphate by glucose-6-phosphate isomerase
3.) fructose-6-phosphate is phosphorylated to form fructose-1,6-biphosphate by phosphofructokinase
-1 ATP
4.) fructose-1,6-biphosphate molecule splits into two glyceraldehyde-3-phosphate molecules (G3P)
5.) each G3P molecule is converted to pyruvate
what are the products of the anaerobic glycolysis of glycogen
4 ATP (net 3)
2 NADH+ + 2H+
2 pyruvate or lactate
where is glycogen stored
in liver and skeletal muscle
what happens to pyruvate if there is sufficient oxygen present
the pyruvate will be changed to acetyl CoA where it can start the Krebs cycle
what happens to pyruvate if there is not sufficient oxygen present
pyruvate is converted to lactic acid because we don’t want pyruvate building up
what is the equation for converting pyruvate to lactic acid
pyruvate + NADH + H+ -> lactic acid + NAD+
then
lactic acid -> lactate + H+
what enzyme catalyzes converting pyruvate into lactic acid
lactate dehydrogenase (LDH)
explain the preparatory phase of pyruvate of acetyl-CoA
occurs in the mitochondria
pulls off a carbon group and adds a CoA group by pyruvate dehydrogenase complex (PDC) - irreversible
NAD+ is also converting back and forth to NADH + H+ to send electrons to the electron transport chain
what enzyme catalyzes the conversion of pyruvate to acetyl-CoA
pyruvate dehydrogenase complex (PDC)
multi-enzyme complex
what 5 things can be converted to acetyl-CoA
pyruvate, amino acids, fatty acids, glycerol, and ketone bodies
explain the citric acid cycle (Krebs cycle)
occurs in the mitochondria
1.) acetyl group is transferred to oxaloacetate to form citrate
2.) citrate is eventually converted back into oxaloacetate
3.) oxalocetate is converted back to citrate to continue the cycle as long as there is sufficient intermediates
what enzyme transfers an acetyl group to oxaloacetate to form citrate
citrate synthesis
what is the reaction for the transfer of an acetyl group to oxaloacetate
acetyl-CoA + oxaloacetate -> citrate + CoA
what is the rate limiting enzyme of the citric acid cycle
isocitrate dehydrogenase
what are the products for one turn of the Krebs cycle
1 ATP
3 NADH + H+
1 FADH2
2 CO2
*double the quantities for one glucose molecule
explain the electron transport chain
occurs in the mitochondria
1.) NADH + H+ and FADH2 are brought to the electron transport chain from previous processes and release high energy electrons
2.) NAD+ and FAD are recycled to go get more
3.) pairs of high energy electrons move across the ETC to create energy
4.) this energy created fuels the cytochrome pumps
5.) pumps pump H+ from mitochondrial matrix to the mitochondrial intermembrane space, thus creating an electrochemical gradient
6.) H+ move down the concentration gradient through the protein ATP synthase
7.) ATP synthase transfers the kinetic energy into ATP from ADP and phosphate
8.) 1 ATP for every 3 H+
9.) high energy electron pairs that come to the end of the ETC combines with H+ and oxygen to form water
what is the equation for the high energy electrons to become water
2H+ + 1/2O2 + 2e- -> H2O
what enzyme catalyzes the creation of water from high energy electrons
cytochrome oxidase
what is the rate limiting enzyme of the electron transport chain
cytochrome oxidase - if we don’t have enough of this enzyme, we cannot do the conversion of electrons to H2O which stops the electron transport chain
what is oxygen’s role in the electron transport chain
final acceptor of electrons
how much ATP is made from each NADH + H+ and FADH2 molecule that goes through the electron transport chain
NADH + H+ = 2.5
FADH2 = 1.5
what is the grand total of net ATP from one glucose molecule (explain how you got to the number)
32 ATP
what is the grand total of net ATP from one glycogen molecule (explain how you got to the number)
33 ATP
(one more ATP molecule from glycolysis)
explain how fatty acids are used for energy
go through beta oxidation to yield ATP
occurs in the mitochondria
what are the products of each round of beta oxidation
1 acetyl-CoA (except for last round which yields 2)
1 NADH + H+
1 FADH2
what is the equation to determine the number of rounds of beta oxidation a fatty acid will go through
of carbons / 2 -1
ex. 14 carbon fatty acid will go through 6 rounds
what is the equation to determine the number of acetyl-CoA molecules you will get out of a fatty acid
of carbons / 2
ex. 14 carbon fatty acid will make 7 acetyl-CoA molecules
why are amino acids (proteins) not usually a major source of energy
we need proteins for so many other things that we only use them as fuel when absolutely necessary
ex. long starvation
what is the amino acid structure
amino group, carboxyl group, alpha carbon with attached H, and R group (variant)
what are the 3 ways to use proteins as an energy source
1.) convert them to glucose via gluconeogenesis
2.) convert them to acetyl-CoA
3.) convert them to citric acid cycle intermediates
what is ATP cycling
formation and breakdown of ATP
ATP is formed when energy is released (exergonic reactions)
ATP is oxidized to aid in exergonic reactions
