Lecture Quiz 4 Flashcards
What is the overall reaction of the oxication of glucose?
C6H12O6 + 6O2 –> 6H2O + 6CO2 + 32 ATP + heat
What happens during glycolysis (vague)?
glucose is oxidized into pyruvic acid
NAD+ is reduced to NADH + H+
ATP is synthesized by substrate-level phosphorylation
What is the fate of pyruvic acid?
moves on to Krebs cycle in an aerobic pathway
is reduced to lactic acid in an anaerobic environment
What happens during phase one of glycolysis?
sugar activation
2 ATP molecules activate glucose into fructose-1,6-diphosphate
What happens during phase two of glycolysis?
oxidation and ATP formation
3 carbon sugars are oxidized, reducing NAD+
inorganic phosphate groups are attached to each oxidized fragment
terminal phosphates are cleaved and captured by ADP to form 4 ATP
What are the final products of glycolysis?
two pyruvic acid molecules
two NADH+ H+ molecules
net gain of two ATP molecules
What is the importance of glucose?
neurons and RBCs rely almost entirely on glucose for energy
What happens with excess glucose?
converted to glycogen or fat
Where does the Krebs cycle take place?
mitochondrial matrix
What fuels the Krebs cycle?
pyruvic acid and fattys acids
8 step cycle
What happens during the decarboxylation of the Krebs cycle?
carbon is removed from pyruvic acid
CO2 is released into bloodstream
What happens during oxidation of the Krebs cycle?
hydrogen atoms are removed from pyruvic acid
NAD+ is reduced to NAD+ H+
What is the final step of the Krebs cycle?
formation of acetyl CoA
resulting acetic acid is combined with coenzyme A, a sulfur containing coenzyme, to form acetyl coA
What are the final products of the Krebs cycle?
3 NAD+ H+ 1 FADH2 2 CO2 1 ATP 1 glucose = 2 acetyl CoAs entering the Krebs cycle aka 1 glucose = 2 krebs cycles
What happens during the electron transport chain?
glucose is oxidized
hydrogens are transported by coenzymes NADH and FADH2
they enter a chain of proteins bound to metal ions (cofactors)
combine with molecular oxygen to form water
release energy
What happens to the energy released by electron transport chain?
harnessed to attach inorganic phosphate groups to ADP, making ATP through oxidative phosphorylation
Describe what happens to the hydrogens in the mechanisms of oxidative phosphorylation
split into protons and electrons
protons are pumped across the inner mitochondrial membrane by NADH dehydrogenase, cytochrom b-ci, cytochrome oxidase
What happens to the electrons?
electrons are delivered to oxygen, forming oxygen ions
oxygen ions attract H+ to form water
H+ pumped into intermembrane space
diffuses back to the matrix via ATP synthase
releases energy to make ATP
How much ATP is created from NADH + H+?
2.5 ATP
How much ATP is created from FADH2?
1.5 ATP
Break down the energy generated from one glucose molecule
1 glucose
glycolysis - 2 ATP
Krebs - 2 ATP
ETC - 28 ATP
What does the electrochemical proton gradient across the inner membrane do?
creates a pH gradient
generates a voltage gradient
these gradients cause H+ to flow back into the matrix via ATP synthase
Describe ATP synthase
consists of a rotor (membrane), knob (matrix) and rod (connects the two)
current created by H+ causes rotor and rod to rotate
rotation activates catalytic site in the knob where ADP and P are combined
What is glycogenesis?
formation of glycogen when glucose supplies exceed cellular need for ATP synthesis
occurs in liver and skeletal muscle
What is glycogenolysis?
breakdown of glycogen in response to low blood glucose
What is gluconeogenesis?
the process of forming new glucose from noncarbohydrate molecules
takes place in the liver
protects the body and brain from hypoglycemia
What fats are routinely oxidized for energy?
only neutral fats
free fatty acids
glycerol
triglycerides
What happens to glycerol?
converted to glyceraldehyde phosphate
ultimately converted to acetyl CoA
Acetyl CoA enters Krebs cycle
What happens during beta oxidation
fatty acids undergo this and produce
two-carbon acetic acid fragments, which enter the Krebs cycle
reduced coenzymes produced which enter ETC
What happens to excess dietary glycerol and fatty acids?
lipogenesis to form triglycerides
Why is glucose easily converted into fat?
because acetyl CoA is an intermediate in glucose catabolism and the starting molecule for the synthesis of fatty acids
What is lipolysis?
the breakdown of stored fat
essentially lipogensis in reverse
What is oxaloacetic acid’s importance?
necessary for the complete oxidation of fat
without it, acetyl CoA is converted into ketones
What does the liver do involving fats/cholesterol?
synthesizes lipoproteins for transport of cholesterol and fats
makes tissue factor, a clotting factor
synthesizes cholesterol from acetyl CoA
uses cholesterol to form bile salts
Give a summary of liver functions
packages fatty acids to be stored and transported
synthesizes plasma proteins
forms nonessential amino acids
converts ammonia from deamination to urea
stores glucose as glycogen
regulates blood glucose homeostasis
stores vitamins, conserves iron, degrades hormones, detoxifies substances
What is the significance of cholesterol?
structural basis of bile salts, steroid hormones, vitamin D
makes up part of hedgehog molecule - directs embryonic development
transported to and from tissues via lipoproteins
What are the three types of lipoproteins?
HDL - more protein content
LDL - considerable cholesterol component
VLDL - mostly triglycerides
What is the main source of VLDLs?
the liver
these transport glycerides to peripheral tissues, especially adipose
What is the function of LDLs?
transport cholesterol to the peripheral tissues and regulate cholesterol synthesis
What do HDLs do?
transport excess cholesterol from peripheral tissues to the liver
serve the needs of steroid-producing organs
What do high levels of HDL do?
they are thought to protect against heart attack
What do high levels of LDL do?
increase risk of heart attack by promoting plaque formation
When does the liver produce cholesterol?
produces 85%
dietary intake (15%)
produced via negative feedback loop involving serum cholesterol levels
in response to saturated fatty acids
How do fatty acids regulate excretion of cholesterol?
unsaturated fatty acids enhance excretion
saturated fatty acids inhibit excretion
certain unsaturated fatty acids lower the proportions of cholesterol (omega 3)
What are some non-dietary factors affecting cholesterol?
stress, cigarette smoking, coffee increase LDL
aerobic exercise increases HDL
How does body shape correlate with cholesterol levels?
fat carried on upper body = high cholesterol levels
fat carried on lower body = low cholesterol levels
What do amino acids form?
all protein structures
the bulk of the body’s functional molecules
Where do amino acids come from?
all amino acids must be provided from the diet
What does excess dietary protein result in?
amino acids are oxidized for energy
converted into fat for storage
How are amino acids converted into energy?
must be deaminated prior to oxidation
converted into pyruvic acid and one of the keto acid intermediates of the Krebs cycle
What are the events that convert proteins into energy?
transamination
oxidative deamination
keto acid modification
What happens during transamination>
switching of an amine group from an amino acid to a keto acid
typically, glutamic acid is formed in this process
What happens during oxidative deamination?
the amine group of glutamic acid is released as ammonia, combined with CO2 in the liver, exerted as urea by the kidneys
What happens during keto acid modification?
keto acids from transamination are altered to produce metabolites that can enter the Krebs cycle
What metabolic state does the body exist in?
catabolic-anabolic
What is the amino acid pool?
body’s total supply of free amino acids
source for resynthesizing body proteins, forming amino acid derivatives, gluconeogenesis
How do carbohydrates/fat differ from the amino acid pool?
fats and carbohydrates are oxidized directly to produce energy
excess carbohydrate and fat can be stored