ch. 18 - metabolic pathways and ATP production

metabolism definition

the chemical reactions that provide the energy and proteins that keep our cells alive and maintain homeostasis

catabolic reactions

molecules are broken down to provide energy, energy as a product

anabolic reactions

energy is used to build large molecules, energy as a reactant

adenosine triphosphate

main energy carrier in our bodies

ATP kcal rate per mol

7.3kcal

ATP kJ per mol

31 kJ

what happens when ATP is hydrolyzed

releases energy due to the high amounts of energy in the phosphate bonds

nicotinamide adenine dinucleotide (NAD)

electron carrier (NADH) that can be oxidized and reduced, turns C-OH into C=O

flavin adenine dinucleotide (FAD)

electron carrier (FADH2) that turns C-C to C=C

Which form of NAD is reduced and which is oxidized

NAD+ is oxidixed, NADH is reduced

which forms of FAD is reduced and which is oxidized

FAD oxidized, FADH2 is reduced

which form of the adenine dinucleotides carries electrons

the reduced forms

what does acetyl CoA carry

carbon

what does coenzyme A contain:

pantothenic acid, ADP, and aminoethanethiol

what are the three steps of catabolism

stage 1: digestion, Stage 2: degradation, Stage 3: release of energy

what happens in stage one of catabolism

proteins, lipids, and polysaccharides are hydrolized

what happens in stage 2 of catabolism

amino acids, fatty acids, and monosaccharides are broken down into smaller molecules. NADH and FADH2 are made

what happens in stage 3 of catabolism

electrons from NADH and FADH2 are used to generate ATP

what reaction keeps occuring in step 1: digestion in catabolism

hydrolysis

step 1 part 1 of catabolism (carbohydrates)

amylose and amylopectin are hydrolyzed into smaller dextrins, maltose, and glucose by enzymes in the saliva and small intestine

step 1 part 2 of catabolism (carbohydrates)

glucose and other monosaccharides are absorbed into the bloodstream and taken to cells

digestion of triglycerides (catabolism)

triglycerides are emulsified and hydrolyzed by enzymes in the small intestine, resulting fatty acids are carried to cells by lipoproteins called chylomicrons

digestion of proteins (catabolism)

proteins are broken down by enzymes in the stomach and small intestines, carried to cells to make new proteins, leftovers are used for energy

what reaction occurs in step 2 of catabolism - degradation

glycolysis

summarize the 10 reactions in degradation

glucose converted into 2 pyruvate molecules, first 5 steps require energy, last 5 steps generate energy

where does degradation occur in the cell

cytosol

what type of enzyme is used to convert ATP to ADP in the first reaction of degradation

transferase

what is the type of enzyme in the second reaction of degradation

isomerase

what type of enzyme is in the third reaction of degradation

transferase (ATP → ADP)

what type of enzyme is in the fourth reaction of degradation

lyase (split molecule into two w/o water)

what type of enzyme is in the fifth reaction of degradation

isomerase (rearranging atoms in molecule)

what type of enzyme is in the sixth reaction of degradation

oxidoreductase (2NAD+ → 2NADH + 2H+)

what type of enzyme is in the seventh reaction of degradation

transferase (2ADP → 2ATP)

what type of enzyme is in the eigth reaction of degradation

isomerase (rearranging atoms in a molecule)

what type of enzyme is in the ninth reaction of degradation

lyase (water taken out, so molecule split w/o water)

what type of enzyme is in the tenth reaction of degradation

transferase (2ADP → 2ATP)

summary of glycolysis

glucose + 2NAD+ + 2ADP + 2 PO43- → 2 pyruvate + 2 NADH + 2 ATP + 4 H+ + 2 H2O

is any oxygen used in this reaction

no

what is the net products of glycolysis

2 ATP and 2 NADH

does glucose get oxidized

yes but not fully

does pyruvate keep reacting?

yes, depending on the conditions it is in

what reaction is acetyl CoA involved in

citric acid cycle

what reaction process is pyruvate involved in if oxygen is available

pyruvate + HS-CoA + NAD+ → acetyl CoA + Co2 + NADH

what reaction process is pyrvuate involved in if oxygen is not available

pyruvate + NADH + H+ → lactic acid + NAD+

what happens to lactic acid after the reaction with no oxygen involved

lactic acid is turned back into pyruvate in the liver, keeps converting to move pyruvate somewhere until oxygen is available (occurs during exercise)

what essentially occurs in the citric acid cycle

8 reactions that extract electrons from acetylCoA through NADH and FADH2

where does the citric acid cycle occur

mitochondria matrix

what enzyme is in the 1st reaction of the citric acid cycle

ligase (molecules combined)

what enzyme is in the 2nd reaction of the citric acid cycle

isomerase (atoms in molecule rearranged)

what enzyme is in the 3rd reaction of the citric acid cycle

oxidoreductase (NAD+ → NADH + H+)

what enzyme is in the 4th reaction of the citric acid cycle

oxidoreductase (NAD+ → NADH + H+)

what enzyme is in the 5th reaction of the citric acid cycle

lyase (removed CoA without water)

what enzyme is in the 6th reaction of the citric acid cycle

oxidoreductase (FAD → FADH2)

what enzyme is in the 7th reaction of the citric acid cycle

hydrolase (combined with water)

what enzyme is in the 8th reaction of the citric acid cycle

oxidoreductase (NAD+ → NADH + H+)

how often does the citric acid cycle happen for each glucose molecule digested

twice

how many electrons are removed from acetylCoA in total by NAD+ and FAD

8 electrons

how much energy is made directly by the citric acid cycle

very little

why is the electron transport chain important for ATP production

the electron transport chain is the body’s way of converting the electrons carried by FADH2 and NADH into ATP

where does the ETC occur in the cell

the matrix and intermembrane space of the mitochondria

step 1 ETC

NADH donates its electrons to complex I. H+ is sent through the membranes

step 2 ETC

FADH2 donates its electrons to complex II. FADH2 enters the chain at lower energy

step 3 ETC

the electrons from complexes I and II are transported by CoQ to complex III

step 4 ETC

complex III sends more H+ through the membrnae and gives electrons to Cyt C

step 5 ETC

Cyt C takes the electrons to complex IV. More H+ go through the membrane

step 6 ETC

in complex IV, the electrons combined with O2 + H+ to make water

step 7 ETC

the H+ gradient that forms is restored as H+ flows through ATP synthase making ATP

ETC summary

each NADH yields 2.5 ATP; each FADH2 yields 1.5 ATP

what occurs when glucose levels are low

Fatty acid degradation: beta oxidation

what does beta oxidation do?

have body degrade fatty acids to keep the citric acid cycle going

what does the degradation of fatty acids yield?

acetyl CoA

what condition must be met in order for fatty acids to be degraded

activated prior to degradation

what occurs as a result of the activation of fatty acids

adds CoA and uses 1 ATP

what is the yield for one molecule of stearic acid

120 ATP

where does the FADH2 and NADH go as a result of being products in beta oxidation

electron transport chain

what can occur when the body is degrading too much fat

acetyl CoA builds up in the liver (ketone bodies)

what is acetyl CoA then converted into as a result of excessive degradation of fat

beta-hydroxylbutyrate and acetone

what happens if the concentration of beta-hydroxylbutyrate and acetone is too high

the body’s pH becomes acidic

what is protein transamination

the transfer of an NH3 group from one molecule to another

what is protein deamination

an NH3 group is removed by NAD+

what does the urea cycle do

dispose of NH3 in the form of urea, then urea is removed from the blood

what organ removes urea from the blood and where is it then excreted

liver, urine