Molecules of Life

Molecules of Life

SET B QUESTIONS

FOO YONG THAI MS2213300726 H6T01A



CARBOHYDRATES MONOSACCHARIDES
DISACCHARIDES

POLYSACCHARIDES

MONOSACCHARIDES

STRUCTURES CHARACTERISTICS
Straight-chain form , ring form in aqueous state
Has carbonyl group (C = O) Sweet-tasting
Has many hydroxyl groups (-OH)
Has a single monomer Soluble in water

Has simple , linear , unbranched structures Can be crystallized

Has a single ring structure As reducing agent : has a free ketone or aldehyde
group , can donate electron to other group

General formula (CH2O)n
-n=number of C atoms in the molecule , where n =
3,5,6

DISACCHARIDES

STRUCTURES CHARACTERISTICS
Sweet
A double sugar molecule consists of 2
monosaccharides Water soluble
Can be crystallized
Linked by glycosidic linkage

Glycosidic linkage is a covalent bond formed
between two monosaccharides by a condensation
reaction

Has simple , linear , unbranched or branched
structures

Has two ring structures

POLYSACCHARIDES

STRUCTURES CHARACTERISTICS
Large / Macromolecule
Hundreds of monosaccharides joined by glycosidic
linkage through condensation process No taste sweet
Breakdown by hydrolysis Insoluble in water

The chain formed may be variable in length

Has a complex branched or unbranched Cannot be crystallised
Folded : ideal for energy storage Non – reducing carbohydrates
Straight or coiled
Has a number of ring structures

Humans are unable to digest vegetables but herbivores are able to do so

-This is because plant cell has abundant Cellulose which is a complex organic compound
-It is a polymeric carbohydrate molecule consisting of a linear chain having thousand of glycosidic linkages.
-It consists of long unbranched chains of glucose .
-They are straight chains linked by hydrogen bonds producing a substance that is inert and insoluble in
water.
-The chain arranged in parallel (cellulose microfibrils) stick together through formation of cross linkages.
-Formation of cross linkage in the hydrogen bonds between the hydroxyl groups of one cellulose chain and
hydrogen atoms of adjacent chain.
-Beta-glucose monomers linked (upside down to each other) by Beta-1,4 glycosidic bonds.
-The presence of beta acetal linkages in cellulose makes it different from starch and is a deciding factor in
its digestibility.
-Humans lack of enzyme(cellulase) required to break down the linkages.
-While herbivores able to digest vegetables because when a herbivore swallow it , it will first enter the
compartment of the stomach called the rumen.
-The rumen contains a salty solution and bacteria that helps to break down bond in cellulose.

4) Organelle which synthesis carbohydrates in plant cell is chloroplast.

-Chloroplast is the site to carry out photosynthesis.

-During photosynthesis , the sun solar energy is converted to chemical energy.

-The chemical energy is stored in the form of glucose(monosaccharide-carbohydrates)

-The anabolic process will generates ATP (light independent reaction) and sugar (light independent

reaction)
-Chlorophyll present in the thylakoid membrane absorbs energy from the sunlight and is involved
in the formation of ATP and NADPH in the light reaction of photosynthesis through electron
transport chains.
-Chlorophyll in thylakoid membrane trap light energy

-At light independent reaction , the electron carried by NADPH convert carbon dioxide to carbohydrate

through CO2 fixation process. Hence carbohydrate and other organic molecules can be stored and used for

energy.

-Stroma in chloroplast contains enzymes that work with ATP and NADPH to fix carbon from carbon dioxide

into molecules that can be used to build glucose.

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