glycolysis

Question 1

catabolic pathway

Answer 1

-exergonic rxns, that breakdown complex molecules into simple ones (ATP generation)
-convergent process

Question 2

anabolic pathway

Answer 2

-endergonic rxns, synthesis of complex molecules from simple precursors (requires ATP)
-divergent process

Question 3

metabolism

Answer 3

sum of all chemical changes (rxns) occurring within a cell, tissue or body

Question 4

what helps glucose enter cells?

Answer 4

GLUT transport proteins, through facilitated diffusion

Question 5

GLUT isoforms that are always present in plasma membrane, and their location?

Answer 5

GLUT 1 in RBC’s
GLUT 2 in hepatocytes, pancreatic B cells, and kidneys
brain neurons: GLUT 3

Question 6

GLUT isoforms that are insulin dependent and their location?

Answer 6

GLUT 4 in striated muscle (skeletal/cardiac) and adipose tissue

Question 7

what are SGLT1 and SGLT2 and where are they found?

Answer 7

they are sodium-dependent glucose cotransporters, found in intestinal epithelial cells, and renal tubules
-secondary active transport

Question 8

general info of glycolysis

Answer 8

-occurs in the cytoplasm
-breakdown of glucose in a series of enzyme-catalyzed rxns to yield 2 pyruvate
-anaerobic pathway

Question 9

What form are all sugar derivatives?

Answer 9

D-isomers

Question 10

2 main purposes of glycolysis

Answer 10

1. to oxidate glucose to provide ATP for all tissues
2. provide intermediates for other metabolic pathways

Question 11

2 stages of glycolysis

Answer 11

1. energy investment phase: first 5 steps, phosphorylates intermediates using ATP
2. energy generation phase: last 5 steps, net formation of 2 ATP per glucose by substrate-level phosphorylation

Question 12

kinase

Answer 12

adds phosphate group

Question 13

isomerase

Answer 13

converts a molecule from one chemical structure to another

Question 14

mutase

Answer 14

moves functional group from one position to another on same molecule

Question 15

dehydrogenase

Answer 15

oxidizes the substrate by removing one or more H+ atoms

Question 16

cleaving enzyme

Answer 16

catalyzes the splitting of a molecule into two smaller molecules

Question 17

enolase

Answer 17

removes a molecule of H20

Question 18

energy investment phase

Answer 18

consumes 2 ATP
glucose –>2 Glyceraldehyde-3-phosphate

Question 19

energy generation phase

Answer 19

produce 4 ATP and 2 NADH
2 glyceraldehyde-3-phosphate –>
2 pyruvate

Question 20

rxn 1 of glycolysis

Answer 20

phosphorylation of glucose, uses either hexokinase or glucokinase (pancreas/liver)

Question 21

glucokinase in the liver

Answer 21

initiates metabolism of glucose and helps regulate blood glucose levels

Question 22

hyperglycemic periods

Answer 22

hepatocyte glucose uptake is increased due to increased activity of GLUT 2 and glucokinase

Question 23

hypoglycemic periods

Answer 23

hepatocyte glucose levels are reduced and liver becomes a provider of glucose (breaks down glycogen)

Question 24

glucokinase in the pancreas

Answer 24

functions to modulate insulin secretion to control glucose uptake by muscle/fat cells

Question 25

glucose-6-phosphate

Answer 25

prevents exit from cell due to phosphorylation

Question 26

rxn 3 of glycolysis

Answer 26

uses 1 ATP to change Fructose-6-phosphate to yield fructose-1,6-phosphate, uses enzyme phosphofructokinase-1

Question 27

what step is the rate limiting “committed step” of glycolysis?

Answer 27

rxn 3, enzyme phosphofructokinase

Question 28

rxn 10 of glycolysis

Answer 28

PEP cleaved to form 2 pyruvate, generating ATP, uses enzyme pyruvate kinase

Question 29

3 regulated/irreversible steps of glycolysis

Answer 29

rxn 1, 3, and 10

Question 30

insulin vs glucagon

Answer 30

insulin: promotes glycolysis
glucagon: DOESNT promote glycolysis

Question 31

ATP:AMP ratio

Answer 31

low ATP means high AMP –> activates AMPK stimulating glycolysis

Question 32

what happens to pyruvate in aerobic and anaerobic conditions?

Answer 32

aerobic: pyruvate enters the mitochondria and becomes acetyl-coA
anaerobic: pyruvate becomes lactate

Question 33

lactate dehydrogenase isozymes isozymes

Answer 33

heart (H): supports aerobic metabolism
mucles (M): supports anaerobic metabolism
karkinoma (K): found in cells w/ high metabolic rates (present in retina)

Question 34

corneal epithelium in low oxygen conditions

Answer 34

lactate production via HM3 LDH, often due from lid closure and CL wear

Question 35

ocular lens (LDH)

Answer 35

no mitochondria, so favor lactate, LDH types HM3 and M4 are found in the lens

Question 36

Retina (LDH)

Answer 36

LDH K4 opens the pathway to lactate when the aerobic pathway can’t be used anymore

Question 37

Pentose phosphate pathway

Answer 37

branches from G6P, 3 functions
1. generation of ribose 5-phosphate, needed for nucleotide biosynthesis
2. generation of NADPH for production of FA’s
3. cell detoxification by removal of destructive forms of O2

Question 38

where does the pentose phosphate pathway occur at?

Answer 38

tissues heavily involved in lipid biosynthesis and nucleotide synthesis
- liver, adipose tissue, adrenal cortex (lipids), bone marrow, skin, gastric mucosa (nucleotides)

Question 39

Red blood cell glucose metabolism

Answer 39

insulin independent, metabolized mainly by glycolysis, end product is lactate

Question 40

Brain glucose metabolism

Answer 40

insulin independent, glycolysis to pyruvate

Question 41

muscle and heart glucose metabolism

Answer 41

insulin stimulated, glycolysis to pyruvate, and synthesize a lot of glycogen

Question 42

adipose tissue glucose metabolism

Answer 42

insulin stimulated, either glycolysis, or acetyl-coA for FA synthesis, uses pentose phosphate shunt

Question 43

Liver glucose metabolism

Answer 43

high blood glucose: liver removes glucose from blood and either undergoes glycogenesis or glycolysis
low blood glucose: liver supplies the blood with glucose by glycogenolysis or gluconeogenesis

Question 44

Does glycolysis happen in high or low ATP levels

Answer 44

low ATP