Exam 2 Lecture 15 Glycolysis Flashcards
glycolysis occurring in the absence of O2:
provides ATP quickly and for short amount of time (more efficient in sprinting)
glycolysis metabolizes: anaerobic
1 molecule of glucose gets:
1 molecule of glucose to 2 molecules of pyruvate and generates 2 molecules of ATP
glycolysis metabolizes: aerobic
1 molecule of glucose gets:
2 pyruvate, 2 ATPs, 2 NADH; pyruvate enters the mitochondria to enter TCA cycle to generate more ATP
is anaerobic of aerobic glycolysis more efficient?
complete oxidation more energy efficient than anaerobic glycolysis
sources of glucose in diet:
- disaccharides (present in foods we consume): sucrose made from fructose and glucose and lactose made from galactose and glucose
- starch (plant)
- glycogen (animal)
under conditions of non-starvation, the brain uses _ as fuel
glucose
_ is the only fuel that RBCs can use
glucose
how does gluconeogenesis occur?
pyruvate and lactate are salvaged and re-synthesized to glucose
glucose uptake occurs via protein transporters called _; ECF into cell’s cytoplasm
glucose transporters (GLUTs)
Types of GLUTs:
ubiquitous but expressed highly in brain and RBCs. High affinity to glucose and unregulated
GLUT1
Types of GLUTs:
main transporter in liver (pancreas); low affinity to glucose and unregulated
GLUT2
Types of GLUTs:
main transporter in neurons; high affinity to glucose and unregulated
GLUT3
Types of GLUTs:
present in skeletal muscle, heart, adipose tissue; insulin dependent (regulated by insulin)
GLUT4
GLUT1 has a Km of _ which is advantageous because?
Km = 1 mM (high affinity) advantageous because even if there is very little glucose, will still pick it up because it is sensitive to glucose
RBCs use only glucose because
there is no mitochondira ie no oxygen
_ is the center of glycolysis
liver
GLUT2 has Km of _ which makes sense because:
Km = 10 mM (low affinity) makes sense because liver (pancreas) is a high capacity system for glucose
GLUT3 has Km of _
Km = 1 mM (high affinity)
GLUT4 has Km of _
Km = 5 mM
exercise enhances which GLUT?
GLUT4
stored in vesicles under the plasma membrane (fusion of vesicle to plasma membrane); present in sub-specialized tissues describes which GLUT?
GLUT4
GLUT1-3 uses _ which is why they are unregulated
gradients
glycolysis happens where?
occurs in the cytoplasm of eukaryotic cells
what are the 2 stages of glycolysis?
- trapping of glucose and its cleavage into 2 inter-convertible 3-carbon molecules
- generation of ATP
the 1st stage of glycolysis begins with _ of glucose and ends with _
1st stage of glycolysis begins with the PHOSPHORYLATION of glucose and ends with the isomerization of dihydroxyacetone phosphate to GAP IE GLYCERALDEHYDE 3-PHOSPHATE
Trapping of glucose and preparation phase:
what is consumed and generated?
2 ATPs consumed and no ATP generated
Trapping of glucose and preparation phase:
consists of 3 reactions:
- phosphorylation
2/ isomerization - and a second phosphorylation
Trapping of glucose and preparation phase:
strategy of this phase is to:
TRAP THE GLUCOSE in the cell and form a compound that can be readily cleaved into 2 PHOSPHORYLATED 3-CARBON UNITS
Steps 1-5 of stage 1 of glycolysis:
at which step is glucose phosphorylated to G6P, ATP is consumed, and either enzyme hexokinase or glucokinase is responsible?
step 1
hexokinase is found where?
in all tissues
glucokinase is found where?
in liver
which enzymes catalyze irreversible reactions?
- glucokinase/hexokinase
- PFK-1
- pyruvate kinase
Steps 1-5 of stage 1 of glycolysis:
at which step is G6P isomerized to F6P
step 2
which enzyme converts glucose into G6P?
either hexokinase or glucokinase
which enzyme converts G6P into F6P?
phosphoglucoisomerase
Steps 1-5 of stage 1 of glycolysis:
at which step does F6P phosphorylated to F1,6BP and ATP is consumed?
step 3 rate limiting step
which enzyme converts F6P into F1,6BP?
phosphofructokinase (rate limiting enzyme of glycolysis)
Steps 1-5 of stage 1 of glycolysis:
at which step is F1,6BP broken down to glyceraldehyde-3-phosphate (G3P) and dihydroxyacetone phosphate (DHAP)
step 4 (reversible)
which enzyme breaks F1,6BP into G3P and DHAP?
aldolase
Steps 1-5 of stage 1 of glycolysis:
at which step is DHAP isomerized to G3P?
step 5
which enzyme isomerizes DHAP into G3P ?
triose phosphate isomerase
stage 2 of glycolysis is when:
energy is harnessed in GAP used to form ATP
Steps 1-5 of stage 2 of glycolysis:
at which step does oxidative phosphorylation of GAP to form 1,3-BPG and NAD+ is reduced to NADH happen?
step 1 of stage 2
which enzyme coverts GAP into 1,3-BPG
GAPDH and reduces NAD+ to NADH
NADH contains a pair of “high energy” e-s that are sent to:
ETC; play a role in oxidative phosphorylation
Steps 1-5 of stage 2 of glycolysis:
at which step is 1,3-BPG is converted into 3-PG and ADP is phosphorylated to form ATP (ATP is synthesized) and 3-PG?
step 2 of stage 2
what enzyme converts 1,3-BPG into 3-PG?
phosphoglycerate kinase
Steps 1-5 of stage 2 of glycolysis:
at which step is 3-PG converted to 2-PG?
step 3 of stage 2
what enzyme converts 3-PG to 2-PG?
phosphoglycerate mutase
Steps 1-5 of stage 2 of glycolysis:
at which step is 2-PG dehydrated to form PEP and the phosphoryl group is transferred from PEP to ADP to form ATP?
step 4 of stage 2
PEP:
an enol with HIGH PHOSPHORYL-TRANSFER POTENTIAL (unstable)
what is the enzyme that dehydrates 2-PG into PEP?
enolase
Steps 1-5 of stage 2 of glycolysis:
at which step is PEP converted from unstable enol to pyruvate, a stable ketone?
step 5 of stage 2
what enzyme converts PEP to pyruvate?
pyruvate kinase IRREVERSIBLE STEP
what is the fate of pyruvate?
- formation of NAD+ to regenerate glycolysis and form lactate
- formed into acetyl-CoA to enter TCA (lipid metabolism)
- converted into ethanol (fermentation) for microorganisms
glycolysis will stop if _ is not regenerated
NAD+
sucrose is a disaccharide of:
glucose and fructose
lactose is a disaccharide of:
galactose and glucose
fructose and galactose can be converted into _
glycolytic intermediates
fructose is quickly turned into _ in times of high energy, why?
fat; fructose metabolism lacks rate limiting step (designed to bypass rate limiting step) and is making fats disproportionally
UDP attached to sugar means:
a synthetic pathway; it is indirect
the goal of regulation of glycolysis in muscle is:
to generate ATP during activity; ATP levels regulate glycolysis
the goal of regulation of glycolysis in liver is:
to maintain blood glucose levels and provide building blocks for other pathways
phosphofructokinase is activated by _ and inhibited by _
activated by F-2,6-BP and inhibited by citrate
glucokinase is not inhibited by G6P which means:
glucose permanently trapped
pyruvate kinase is regulated by _
allosteric effectors and coavalent modification
high blood glucose level want to _ pyruvate kinase which can be achieved by high levels of _ to inhibit glycolysis
want PHOSPHORYLATE pyruvate kinase which is achieved by high levels of ATP
low blood glucose level want to _ pyruvate kinase which can be achieved by _ which stimulates glycolysis
want to DEPHOSPHORYLATE pyruvate kinase which is stimulated by F1,6-BP
why is hexokinase Km (very) low?
means high affinity for glucose. Hexokinase is present in every cell so needs to be able to detect even the smallest amount of glucose
why is glucokinase Km high?
mean low affinity for glucose. Glucokinase is present in liver and liver is constantly presented with glucose bc of what we eat and is focuses on distributing glucose
How does one result in having obesity and/or a fatty liver?
- fructokinase and triose kinase bypass the rate limiting step in glycolysis: the phosphofructokinase-catatlyzed rxn
- fructose derived G3P and DHAP are processed by glycolysis to pyruvate and acteyl CoA in an UNREGULATED fashion
- Excess acetyl CoA is converted into fatty acids which can be transported to adipose tissue to form triacylglycerols resulting in obesity
- Liver also begins to accumulate fatty acids resulting in a fatty liver
what is lactose intolerance caused by?
deficiency in enzyme lactase
disruption of galactose metabolism is called _
galactosemia
CLASSIC GALCTOSEMIA is an inherited deficiency in _ activity
galactose 1-phosphate uridyl transferase activity
absence of galactose 1-phosphate uridyl transferase in _ is a diagnostic criterion
RBCs
How does the onset of cataracts occur?
Galactose not normally entering glycolysis because its been reduced to GALACTITOL which is not soluble so deposits around the lens of the eye
rapidly growing tumor cells metabolize glucose to lactate in a process called
aerobic glycolysis or the Warburg effect
visualization of tumor effectiveness of treatment is detected via _
combination of positron emission tomography (PET) and computer-aided tomography (CAT)