Leyland 4 Catabolism

Question 1

Stage 1

Answer 1

• Extracellular (GI tract)
• Complex molecules à building block molecules (bbm)
• bbm absorbed into circulation
• No energy produced.

Question 2

Stage II

Answer 2

•	 Intracellular 
(cytoplasmic & mitochondrial)
•	 Many pathways 
(not all in all tissues)
•	 bbm à even simpler molecules
•	 Oxidative 
(require NAD+, NADP+, FAD)
•	 Some energy (as ATP) produced

Question 3

Stage III

Answer 3

Mitochondria
•	A single pathway – 
Citric acid (Tricarboxylic acid)          
		cycle 
- Oxidative 
- Acetyl converted to 2CO2
- Produces precursors for 
                           biosynthesis
•	Oxidative phosphorylation                                        
(Electron transport and ATP 
		synthesis)
•	NADH & FAD2H re-oxidised
•	O2 required (reduced to H2O)
•	Lots of energy (ATP) produced

Question 4

Carbohydrates

Answer 4

• General formula (CH2O)n
• Contain aldehyde (-CHO) or keto (-C=O) groups
• Multiple –OH gps
• Monosaccharide – single sugar units (3-9 C-atoms)

Question 5

trioses

Answer 5

3-carbon monosaccharides

Differ in spatial organization of the asymmetric carbon atom furthest from the aldehyde or ketone group
5-carbon monosaccharides ( Pentoses )
6-carbon monosaccharides (hexoses)
Hexoses usually exist in cyclic forms

Question 6

Pentoses

Answer 6

5-carbon monosaccharides

Question 7

hexoses

Answer 7

6-carbon monosaccharides

Hexoses usually exist in cyclic forms

Question 8

Types of Carbs

Answer 8

Aldohexoses: aldose sugars
Aldopentose: aldose sugars
Ketohexose: ketose sugar

Question 9

Epimers:

Answer 9

Differ at one of several different asymmetric carbon atoms

Question 10

Sugar molecules are not planar…

Answer 10

…assume a ‘chair’ (or ‘boat’) conformation.
axial bonds
equatorial bonds

Question 11

Most important monosaccharide metabolically in mammals …

Answer 11

glucose.

Question 12

Monosaccharides are linked to form

Answer 12

complex carbohydrates

Question 13

Disaccharides

Answer 13

alpha 1,4, glycosidic bond between 2 monosaccharides

Question 14

Maltose

Answer 14

glucose + glucose

Question 15

Sucrose

Answer 15

Glucose + fructose

Question 16

Lactose

Answer 16

galactose + glucose

Question 17

Polysaccharides

Answer 17

(10 – 1000 units)

Question 18

Glycogen

Answer 18

• main storage polysaccharide of animal cells (liver & skeletal muscle)
• a1-4 and a1-6 glycosidic bonds
• highly branched

Question 19

Starch

Answer 19

• plants
  
  • a1-4 and a1-6 glycosidic bonds
• less branched

Question 20

Cellulose

Answer 20

• plants
• b1-4 glycosidic bonds
• unbranched

Question 21

Dietary CHO

Answer 21

Starch, glycogen lactose maltose sucrose glucose fructose

Question 22

a-1,4 bonds of glycogen & starch digested in the mouth by:

Answer 22

salivary amylase to produce dextrins

Question 23

Other enzymes in small intestine (attached to brush border membrane of epithelial cells)

Answer 23

pancreatic amylase (a-1,4 bonds)
isomaltase (a-1,6 bonds)
sucrase (sucrose)
lactase (lactose)

Question 24

Absorption of monosaccharides (sugars)

Answer 24

• Actively transported into intestinal epithelial cells & then, via blood supply, to target tissues.
• Uptake into cells via facilitated diffusion using transport proteins (GLUT1 - GLUT5).
- different distribution and affinities
- can be hormonally controlled (insulin)

Question 25

Glucose requirements of tissues.

Answer 25

• All tissues can metabolise glucose
• Blood [glucose] regulated (~5mM).
- because some tissues (rbc, wbc, kidney medulla, lens of the eye) have an absolute requirement &
uptake by these tissues depends on [blood]
• CNS (brain) prefers glucose