Lecture 6. Carbohydrate Metabolism

Question 1

Has something to do with both synthesis (anabolism) and degradation or breakdown (catabolism) of carbohydrates in plants.

Answer 1

CARBOHYDRATE METABOLISM

Question 2

anabolism

Answer 2

synthesis of carbohydrates in plants.

Question 3

catabolism

Answer 3

degradation or breakdown of
carbohydrates in plants

Question 4

general ratio of C, H, and O is 1:2:1. They are polyhydroxy aldehydes and polyhydroxy ketones.

Answer 4

Carbohydrate

Question 6

What is carbohydrate metabolism?

Answer 6

It involves both the synthesis (anabolism) and breakdown (catabolism) of carbohydrates in plants.

Question 7

What are carbohydrates composed of?

Answer 7

Carbon, hydrogen, and oxygen in a 1:2:1 ratio. They are polyhydroxy aldehydes or ketones.

Question 8

Name three functions of carbohydrates in plants.

Answer 8

1) Store energy, 2) Form structural tissue, 3) Provide carbon skeletons for biomolecules.

Question 9

What is a monosaccharide?

Answer 9

The simplest carbohydrate; building blocks of complex carbohydrates.

Question 10

What is the difference between aldopentoses and ketopentoses?

Answer 10

Aldopentoses have 3 chiral centers (e.g., D-xylose); ketopentoses have 2 (e.g., D-ribulose).

Question 11

What is optical rotation in sugars?

Answer 11

The rotation of polarized light by mirror-image sugars—either to the left (levorotatory) or right (dextrorotatory).

Question 12

What are oligosaccharides?

Answer 12

Carbohydrates with 2–10 monosaccharides linked by glycosidic bonds.

Question 13

Name 3 examples of disaccharides and their components.

Answer 13

Sucrose: Glucose + Fructose
Maltose: Glucose + Glucose (α 1-4 bond)
Cellobiose: Glucose + Glucose (β 1-4 bond)

Question 14

What is raffinose made of?

Answer 14

Glucose, fructose, and galactose (a trisaccharide).

Question 15

What are polysaccharides?

Answer 15

Large carbohydrates composed of many monosaccharides; usually not sweet and insoluble in water.

Question 16

What are the two components of starch?

Answer 16

Amylose: Linear α(1-4) glucose, turns blue-black with iodine
Amylopectin: Branched, α(1-4) & α(1-6), red-purple with iodine

Question 17

What is cellulose made of?

Answer 17

β(1-4) glucose chains; structural component of the plant cell wall.

Question 18

What are pectic substances?

Answer 18

Polymers like pectin and protopectin in the cell wall that help in structure and gel formation.

Question 19

What is phosphorylation in carbohydrate metabolism?

Answer 19

A key transformation step where a phosphate group is added to sugars, initiating metabolism.

Question 20

How is sucrose synthesized?

Answer 20

Via UDP-glucose + fructose → sucrose, catalyzed by sucrose phosphate synthase.

Question 21

How is cellulose degraded?

Answer 21

Enzymes like cellulase break β(1-4) bonds to release glucose.

Question 22

What are the reactants and products of photosynthesis?

Answer 22

Reactants: CO₂, H₂O, sunlight
Products: Glucose (C₆H₁₂O₆), O₂

Question 23

Where do light reactions occur?

Answer 23

In the thylakoid membranes (grana) of the chloroplast.

Question 24

What does Photosystem I do?

Answer 24

Converts NADP⁺ to NADPH using light energy.

Question 25

What does Photosystem II do?

Answer 25

Splits water to release O₂ and produces ATP.

Question 26

What is the Calvin Cycle?

Answer 26

A light-independent process in the chloroplast stroma that synthesizes sugars from CO₂.

Question 27

What is the Hatch-Slack (C₄) pathway?

Answer 27

A CO₂ fixation method using PEP carboxylase; efficient in hot climates and not inhibited by O₂.

Question 28

What is glycolysis?

Answer 28

The breakdown of glucose into pyruvate, producing 2 ATP and 2 NADH, occurs in the cytoplasm.

Question 29

What is the Krebs (TCA) cycle?

Answer 29

A mitochondrial process that oxidizes pyruvate into CO₂, generating NADH and FADH₂.

Question 30

What is oxidative phosphorylation?

Answer 30

The production of ATP using energy from the electron transport chain and a proton gradient.

Question 31

What is the total ATP yield from one glucose molecule?

Answer 31

Up to 38 ATP: 2 from glycolysis, 2 from Krebs, ~34 from ETC.

Question 32

What are the products of anaerobic respiration?

Answer 32

Ethanol or lactic acid, CO₂, and 2 ATP.

Question 33

What is chemiosmosis?

Answer 33

The movement of H⁺ across a membrane to drive ATP synthesis via ATP synthase.

Question 34

What is a metabolic pathway?

Answer 34

A series of enzymatic reactions transforming molecules into new products in cells.

Question 35

What is the role of ATP synthase?

Answer 35

Synthesizes ATP from ADP using the proton gradient in mitochondria and chloroplasts.