Ch.10 Carb Metabolism

Question 1

Where does starch digestion start? What enzyme is found in saliva?

Answer 1

Starts in the mouth; enzyme α-amylase

Question 2

What happens when food enters the small intestine?

Answer 2

Mixes with pancreatic juice, which contains more α-amylase.

Question 3

What 3 oligosaccharides are formed after entering the small intestine?

Answer 3

maltose, maltotriose, alpha-dextrin

Question 4

What is the last step of starch digestion?

Answer 4

convert maltose, maltotriose, and alpha-dextrin into glucose

Question 5

What two enzymes play a role in oligosaccharide conversion to glucose during starch digestion?

Answer 5

maltase and α-dextrinase

Question 6

Where are maltase and α-dextrinase located?

Answer 6

Microvilli (Tiny finger-like structures that line the small intestine)

Question 7

What 2 disaccharides do our diets consist of?

Answer 7

sucrose (sweet foods) and lactose (milk)

Question 8

What enzymes break down disaccharides? What do they breakdown to?

Answer 8

Sucrase and lactase; glucose, fructose, galactose

Question 9

What is absorbed into the cells lining the small intestine after digestion?

Answer 9

monosaccharides (simple sugars)

Question 10

What helps moves sugars into the cells?

Answer 10

transport proteins

Question 11

What is the completing step to carbohydrate absorption?

Answer 11

monosaccharides exit cells, enter bloodstream, making sugars available for bodily use

Question 12

Where do sugars in the bloodstream travel to?

Answer 12

Liver –> acts as a distribution center for carbs

Question 13

How does the liver store sugar?

Answer 13

Stores some as glycogen, releases the rest to bloodstream

Question 14

List characteristics of the liver

Answer 14

• manages carbs
• turns sugar into glycogen
• glycogen typically amounts to 3-7% of overall weight

Question 15

List characteristics of muscles

Answer 15

• store glycogen for energy
• glycogen amounts to 1-1.5% of overall muscle weight

Question 16

Which contains more glycogen in the body?

Answer 16

Liver has higher percentage of glycogen, but muscles store more glycogen overall

Question 17

Where is glycogen found?

Answer 17

cytosol of liver/muscle cells; forms tiny granules in the cells

Question 18

What is glycogenesis?

Answer 18

builds glycogen for energy storage; adds glucose molecules together making long chains

Question 19

Where does energy come from to make glycogen?

Answer 19

ATP and UTP (uridine triphosphate)

Question 20

First step of glycogenesis

Answer 20

Turn ATP into glucose 1-phosphate

Question 21

Second step of glycogenesis

Answer 21

Mix glucose 1-phosphate with ATP to create UDP-glucose

Question 22

What enzyme helps add glucose molecules to glycogen chain?

Answer 22

Glycogen synthase

Question 23

What happens to UDP when glucose is added?

Answer 23

UDP is released, ready to be used again in later formations of UDP-glucose, allowing further glycogen synthesis

Question 24

What is the starting point for glycogen synthase? What protein makes this up?

Answer 24

primer made up of glycogenin

Question 25

What is glycogenin's role?

Answer 25

adds 8 glucose molecules to itself, then glycogen synthase adds more glucose to the chain

Question 26

What makes glycogen a branched chain?

Answer 26

branching enzyme (moves parts of chain inside the glycogen molecule to form branches)

Question 27

What is glycogenolysis?

Answer 27

Breaking down of glycogen into glucose 1-phosphate and plain glucose

Question 28

What bonds are breaking during glycogenolysis? What causes the breaking?

Answer 28

glycosidic linkages broken through phosphorolysis (Pi helps break bonds)

Question 29

What is created through breaking of glycosidic linkages? What enzyme causes this?

Answer 29

glucose 1-phosphate; glycogen phosphorylase

Question 30

What is phosphorylase's role?

Answer 30

goes through glycogen and removes glucose until it's 4 glucose residues away from a branch point

Question 31

What happens when the chain becomes really short?

Answer 31

Debranching enzyme helps phosphorylase

Question 32

What 2 jobs does the debranching enzyme have?

Answer 32

1. moves 3 of the 4 glucose residues from a branch to the end of another branch 2. breaks bond at the branch point, leaving plain glucose

Question 33

Both glycogenesis and glycogenolysis are ________. Meaning what?

Answer 33

Anaerobic processes; occur without the need for oxygen

Question 34

What speeds up glycogenolysis in the muscles?

Answer 34

Exercise/ physical activity

Question 35

What 4 factors speed up glycogenolysis?

Answer 35

1. Pi concentration increase 2. Ratio of AMP to ATP 3. Calcium ion concentration 4. Hormonal control

Question 36

How does the increase of Pi concentration contribute to speeding up glycogenolysis?

Answer 36

It contributes to the conditions that favor phosphorylase activation.

Question 37

As AMP levels ____ (while ATP levels ____), it activates ________, facilitating glycogenesis.

Answer 37

rise, decrease, phosphorylase b

Question 38

While AMP binding activates Phosphorylase b, this activation is only _______.

Answer 38

temporary

Question 39

The phosphorylation of phosphorylase b (to form a) is a more ______ and longer-lasting activation mechanism.

Answer 39

stable