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MEH > Carbs 1 > Flashcards

Carbs 1 Flashcards

1
Q

What is the general formula for carbs

A

(CH2O) n

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2
Q

What is a carb with a ketone group called

A

ketose

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2
Q

What is a carb with an aldehyde group called

A

aldoes

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3
Q

Describe the structure of a monosaccharide

A

have an asymmetrical carbon
exist as either D or L forms
natural forms are D

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4
Q

How are disaccharides made

A

condensation reaction between two monosaccharides to form a glycosidic bond

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5
Q

how many units is an oligosaccharide

A

3-12

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6
Q

give examples of polysaccharides

A

glycogen
cellulose
starch

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7
Q

What are two important features of sugars

A

hydrophilic
partially oxidised (require less oxygen)

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8
Q

What are the 4 stages of metabolism

A

1) extracellular breakdown
2) glycolysis/ pentose phosphate
3) TCA cycle
4) ETC and ox phosphorylation

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9
Q

List all the dietary carbs

A
  • glucose
  • fructose
  • sucrose
  • lactose
  • maltose
  • starch
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10
Q

Name the enzymes involved in extracellular breakdown

A

glycosidase enzymes
- salivary amylase
- pancreatic amylase

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11
Q

Where are the glycosidase enzymes found

A

large glycoproteins that are attached to the brush border membranes of epithelial cells lining small intestine

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12
Q

Where do the pancreatic amylase enzymes work

A

duodenum

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13
Q

what enzymes breakdown diasaccharides

A

diasaccharidases
- lactase
- sucrase
- isomaltase
- glycomaltase

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14
Q

After stage 1 how and where are sugars transported

A
  • actively transported to cells lining gut
  • facilitated diffusion to blood then tissues by glucose transport proteins (GLUT1 - GLUT5)
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15
Q

Which GLUT transports glucose to skeletal muscle and adipose tissue

A

GLUT 4

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16
Q

Which cells are dependent only on glucose

A

RBC
neutrophils
CNS prefers
kidney medulla
lens of eye

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17
Q

Where does glycolysis occur

A

cytoplasm

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18
Q

Why is glycolysis important

A
  • oxidation of glucose to pyruvate
    -NADH production
  • ATP synthesis
  • important intermediates
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19
Q

How many enzyme catalysed steps are there in glycolysis

A

10

20
Q

Why is phase 1 of glycolysis known as investment phase

A

uses 2 ATP molecules

21
Q

What is the enzyme of reaction 1 in glycolysis

A

hexokinase
glucokinase in liver

22
Q

What happens in reaction one of glycolysis

A

glucose is phosphorylated to glucose-6-phosphate

23
Q

Why does reaction one of glycolysis require ATP

A

to phosphorylate glucose

24
Q

Why is reaction 1 of glycolysis important

A

it phosphorylates glucose so
- makes it neg charge so cannot leave cell
- increases reactivity
- allows for substrate level phosporylation

25
Q

What is the enzyme for reaction 3 in glycolysis

A

phosphofructokinase-1

26
Q

What is the main regulatory enzyme in glycolysis

A

phosphofructokinase-1

27
Q

What happens in reaction 2 of glycolysis

A

glucose-6-phosphate is isomerised to fructose-6-phosphate

28
Q

What happens in reaction 3 of glycolysis

A

fructose-6-phosphate is phosphorylated to fructose-1,6-bisphosphate

29
Q

What are some important features of reactions 1 and 3 of glycolysis

A
  • large neg delta G
  • irreversible
30
Q

why is phase 2 of glycolysis known as payback

A

4 ATP molecules are made to replace the two used and generate two new

31
Q

What is the enzyme for reaction 10 of glycolysis

A

pyruvate kinase

32
Q

In which reactions of glycolysis does substrate phosphorylation occur

A

7 & 10

33
Q

What reaction is NADH produced

A

6

34
Q

Why must a constant supply of NAD be available for glycolysis

A

to make NADH in reaction 6

35
Q

Why must the NADH be reoxidised to NAD

A

to be used again to make NADH

36
Q

When does NADH get reoxidised

A

in stage 4 in cells with a mitochondria ETC
however in cells without mitochondria or lack of O2 NADH is converted back to NAD by lactate dehydrogenase in anaerobic glycolysis

37
Q

What enzyme converts NADH to NAD in cells without mitochondria or anaerobic resp

A

lactate dehyrogenase

38
Q

What are the important intermediates in glycolysis

A
  • 1,3- bisphosphoglycerate
  • DHAP (dihydroxyaetone-p)
39
Q

What is the importance of the intermediate 1,3- bisphosphoglycerate

A

is converted to 2,3- bisphosphoglycerate by the enzyme bisphosphoglycerate mutase

produced in RBC regulates affinity of Hb to oxygen

40
Q

What is the importance of DHAP intermediate

A
  • converted to glycerol phosphate by enzyme glycerol-3-phosphate dehydrogenase
  • this is important for triaclyglyceride and phospholipid synth
  • produced in adipose and liver
41
Q

Why can humans not digest cellulose

A

humans do not have the enzymes to break β-1,4 linkages in cellulose

42
Q

What are symptoms of lactose intolerance

A

bloating (colonic bacteria releases gas)
diahorrea (lactose in colon means higher oncotic pressure so more water drawn out)

flatulence
vomiting

43
Q

What happens to lactase activity after infancy in most populations

A

declines

44
Q

what is the phenotype name for lactase enzyme remaining after infancy

A

lactase persistance phenotype

45
Q

What is the primary deficiency of lactose intolerance and who does it affect

A

absence of lactase persistant allele
high prevalence in NW euope
adults only

46
Q

What is a secondary deficiency of lactose intolerance cause by and who does it affect

A

caused by injury to small intestine
(coeliac, Crohns, ulcerative colitis, gastroenteritis)
infants and adults
generally reversible

47
Q

What is a congenital deficiency to lactose caused by

A

rare defect in lactase gene
cannot digest breast milk

48
Q

What is the treatment for lactose intolerance

A

remove all lactose from diet

MEH (12 decks)

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