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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

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
Why is reaction 1 of glycolysis important
it phosphorylates glucose so - makes it neg charge so cannot leave cell - increases reactivity - allows for substrate level phosporylation
25
What is the enzyme for reaction 3 in glycolysis
phosphofructokinase-1
26
What is the main regulatory enzyme in glycolysis
phosphofructokinase-1
27
What happens in reaction 2 of glycolysis
glucose-6-phosphate is isomerised to fructose-6-phosphate
28
What happens in reaction 3 of glycolysis
fructose-6-phosphate is phosphorylated to fructose-1,6-bisphosphate
29
What are some important features of reactions 1 and 3 of glycolysis
- large neg delta G - irreversible
30
why is phase 2 of glycolysis known as payback
4 ATP molecules are made to replace the two used and generate two new
31
What is the enzyme for reaction 10 of glycolysis
pyruvate kinase
32
In which reactions of glycolysis does substrate phosphorylation occur
7 & 10
33
What reaction is NADH produced
6
34
Why must a constant supply of NAD be available for glycolysis
to make NADH in reaction 6
35
Why must the NADH be reoxidised to NAD
to be used again to make NADH
36
When does NADH get reoxidised
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
What enzyme converts NADH to NAD in cells without mitochondria or anaerobic resp
lactate dehyrogenase
38
What are the important intermediates in glycolysis
- 1,3- bisphosphoglycerate - DHAP (dihydroxyaetone-p)
39
What is the importance of the intermediate 1,3- bisphosphoglycerate
is converted to 2,3- bisphosphoglycerate by the enzyme bisphosphoglycerate mutase produced in RBC regulates affinity of Hb to oxygen
40
What is the importance of DHAP intermediate
- converted to glycerol phosphate by enzyme glycerol-3-phosphate dehydrogenase - this is important for triaclyglyceride and phospholipid synth - produced in adipose and liver
41
Why can humans not digest cellulose
humans do not have the enzymes to break β-1,4 linkages in cellulose
42
What are symptoms of lactose intolerance
bloating (colonic bacteria releases gas) diahorrea (lactose in colon means higher oncotic pressure so more water drawn out) flatulence vomiting
43
What happens to lactase activity after infancy in most populations
declines
44
what is the phenotype name for lactase enzyme remaining after infancy
lactase persistance phenotype
45
What is the primary deficiency of lactose intolerance and who does it affect
absence of lactase persistant allele high prevalence in NW euope adults only
46
What is a secondary deficiency of lactose intolerance cause by and who does it affect
caused by injury to small intestine (coeliac, Crohns, ulcerative colitis, gastroenteritis) infants and adults generally reversible
47
What is a congenital deficiency to lactose caused by
rare defect in lactase gene cannot digest breast milk
48
What is the treatment for lactose intolerance
remove all lactose from diet

MEH (12 decks)

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