Carbohydrates

Question 1

what sort of bond is formed?

Answer 1

glycosidic

Question 2

3 main types of monosaccharides

Answer 2

1. glucose
2. galactose
3. fructose

Question 3

3 main disaccharides

Answer 3

1. maltose - from plant starch, a reducing sugar (oxidizable)
2. lactose - milk, reducing
3. sucrose - common sugar, non reducing

Question 4

2 types of polysaccharides

Answer 4

1. starch - many non reducing ends, few reducing ends.

2. glycogen - branched structure of glucose monomers

Question 5

3 reasons why glucose is stored in polymers:

Answer 5

1. compactness
2. many reducing ends in branched structures
3. polymers are not soluble, so it won’t contribute to tonicity

Question 6

glycosaminoglycans (GAGs)

Answer 6

unbranched chain of disaccharide units

slimy and are found in synovial fluid and mucous

Question 7

proteoglycans (PGs)

Answer 7

core proteins with dangling long chains of sugar
95% carbs by weight
holds cells together in ECF

Question 8

glycoproteins

Answer 8

more proteins than carbs

forms matrix that hold cells together

Question 9

oligosaccharides

Answer 9

(alpha 1 –> 6) linked galactose

found in peas and beans

Question 10

3 main sites of carb digestion

Answer 10

1. mouth - amylase breaks a 1–>4 linkage
2. stomach - THERE IS NO CARB DIGESTION IN THE STOMACH
3. duodenum - pancreatic amylase does the same thing as mouth
4. jejunum - many enzymes

Question 11

4 main enzymes for carb digestion in the jejunum

Answer 11

1. isomaltase - breaks a 1–>6 bonds
2. glucoamylase - hydrolysis of glucose monomers from the chain one by one.
3. sucrase - hydrolysis of sucrose
4. lactase - hydrolysis of lactose

Question 12

glucose absorption in the intestine

Answer 12

coupled with Na+ passive diffusion into the intestinal wall (Na+/K+ pump keeps the Na+ concentration inside the cell low so that Na+ and gluc from lumen could come in)
after it is in the cell, GLUC2 transporter transports glucose into the blood.
since na/k pump is used, ATP is required

Question 13

example of disaccharide deficiency

Answer 13

lactose intolerance

- breakdown by bacteria instead and causes diarrhoea

Question 14

glucokinase vs. hexokinase

Answer 14

enzymes that provide glucose 6 phosphate for synthesis of glycogen (Glucose + ATP –> G6P + ADP)
glucokinase is only present in liver cells while hexokinase is present in all cells.
glycokinase: high km (lower binding affinity), high Vmax, controlled by insulin
hexokinase: low Km (higher binding affinity), low Vmax

low bg: hexokinase works, not glcokinase
high bg: hexokinase already working at full speed, glycokinase activated and liver takes up the excess glucose

Question 15

von Gierke’s disease

Answer 15

unable to break down glycogen

also unable to convert lactate back into pyruvate in liver.

Question 16

Mcardle’s disease

Answer 16

high muscle glycogen because it can’t be broken down.
during exercise when glycogen needs to be broken down but isn’t the body does not have enough energy and symptoms include muscle weakness and cramps.

Question 17

mechanism used in glycolysis (1 word)

Answer 17

substrate-level phsohporylation

Question 18

2 phases of glycolysis and the number of ATPS involved

Answer 18

1. energy expending phase: 2 ATsS used (first 5 steps)

2. energy generation phase: 4 ATPs produced and 2NAD+

Question 19

3 rate-limiting steps in glycolysis

Answer 19

Step 1: glucose → G6P
Step 2: F6P → F-1, 6-bisp
Step 10: PEP → pyruvate

Question 20

how does fructose enter glycolysis?

Answer 20

as G3P

through fructose 1 phosphate pathway

Question 21

how does galactose enter glycolysis?

Answer 21

galactose –> G1P –> OPD glucose –> G1P

Question 22

pentose phosphate pathway functions (3)

Answer 22

1. produces NADH
2. produces pentose sugar
3. metabolizes some pentose sugar in the diet.

Question 23

pentose phosphate pathway is used in

Answer 23

liver - fatty acid, steroid synthesis, drug metabolism
mammary gland - fatty acid synthesis
adrenal cortex - steroid synthesis
RBCs - antioxidant

Question 24

NAD+ vs NADP+

Answer 24

NAD+ is used in metabolism of dietary sugars in redox reactions of glycolysis and the citric acid cycle

NADP+ is used to convert simple precursors to fatty acids.

Question 25

effect of drinking on glycolysis

Answer 25

decreases glycolysis, because ethanol acts as alternate energy source, can convert to acetyl CoA, which can be stored as fat, or put through the citric acid cycle and then through oxidative phosphorylation to form ATP

also inhibits gluconeogenesis, because the process above uses up NAD+, leading to increased lacteal and decreased bg

Question 26

black water fever define

Answer 26

G6P dehydrogenase deficiency
since this enzyme is used in PP pathway, this may lead to lack of NADH in RBCs, and consequencial build up of toxins H2O2 that can’t be converted to H2O

Question 27

3 steps of enzyme pyruvate dehydrogenase

Answer 27

E1 - decarboxylation of pyruvate
E2 - transfers acetyl group to coenzyme !
E3 - recycles liopogllysine through reduction of FAD and passing the electrons to NAD+

Question 28

4 enzyme complexes in the electron trasnport chain

Answer 28

1. NADH - q - oxidoreductase
2. Succinate - q - oxidoreductase
3. Q - cytochrome C oxidoreductase
4. cytochrome C oxidase

Question 29

NADH q oxidoreductase

Answer 29

NADH oxidation for 2e- and pass it on to ubiquinol (QH2)

• the e- is passed along the chain FMN (flavin monocleotide) and through Fe-S centers
• 2 more H+ molecules is needed to complete the electron transfer Q –> QH2 and start pumping H+ out

Question 30

succinate q reducatse

Answer 30

FADH2 give electron to QH2
Fe-S centers direct the electron
heme group is present to keep e- in the complex and not leak out before passing on to Qh2

Question 31

cytochrome C oxidoreducatase

Answer 31

e- from QH2 is passed to this complex, goes through 4 heme groups that keep it inside the complex, and pass on to cytochrome c molecules, all the while pumping H+

Question 32

cytochrome C oxidase

Answer 32

takes e- from cytochrome C and passes it on to O2 to form water, all the while pumping H+

Question 33

structure of the ATP synthase

Answer 33

F0 : inside the mitochondrial inner membrane, is the part that moved when H+ comes in
F1: protrudes inside the mitochondrial inner matrix, is the part that produced ATP

Question 34

uncoupling define

Answer 34

present in malignant hyperthermia
H+ gradient cannot be established, and therefore, no ATP is form, and the energy from the electron transport chain is released as heat –> high body temperature

Question 35

intentional uncoupling define

Answer 35

found in brown fat in babies
fat is brown due to the heme group in the mitochondria
contains thermogenin that sits on the inner mitochondrial membrane and lets H+ diffuse back in without going through ATP synthase.
done to generate heat and warm them up
also seen in winter plants like stink cabbage