Carbohydrates (2.1.1)

What is the function of carbohydrates?
Energy source- used for respiration. Energy store (glycogen in animals, starch in plants). Structural roles, like plant cell walls.
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What elements do carbohydrates contain?
Carbon, hydrogen and oxygen.
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What are monosaccharides?
The simplest carbohydrates. They are basic monomers.
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Give 3 features of monosaccharides.
Soluble in water. Sweet tasting. Ability to form crystals.
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What are hexoses?
The most common type of monosaccharide. They contain 6 carbon atoms.
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Give 2 examples of hexoses.
Glucose and fructose.
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What are the two ring structures that glucose can form?
Alpha glucose (OH group is below plane of the ring). Beta glucose (OH group is above plane of the ring).
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How are monosaccharides joined together?
They join together in a condensation reaction to form a disaccharide. A new covalent bond is formed- glycosidic bond.
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How do you make maltose and sucrose.
Maltose is alpha glucose + alpha glucose. Sucrose is alpha glucose + fructose.
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What are the properties of disaccharides?
The same as monosaccharides: sweet, water soluble, and forms crystals.
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By what process is glucose broken down in our body?
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Why can't glucose be stored?
Because it is a small, soluble, reactive molecule.
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Give two examples of polysaccharides.
Starch and glycogen.
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How is starch made?
Thousands of alpha-glucose molecules are joined together by 1,4-glycosidic bonds. Some coil up into a spring shape- amylose. Some become highly branched structures- amylopectin. Amylose and amylopectin combined gives starch.
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Where is starch stored?
Inside starch grains in the chloroplasts in leaves. It will be broken down by hydrolysis to form glucose when the plant needs it.
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How is glycogen made?
Thousands of alpha-glucose molecules joined together. The chains are shorter with more branches, and there is no coil arrangement. This makes glycogen more compact than starch.
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Where is glycogen found?
It forms storage granules in most animal cells. Especially in the liver and muscles.
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Give 2 features of starch & glycogen that make them good storage molecules.
Insoluble- won't dissolve in cells where they're stored. Unreactive- They don't dissolve, so won't interfere with reactions inside cells/
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Give 2 more features of starch & glycogen that make them good storage molecules.
Compact- can store a lot of energy in a small space. Easily hydrolysed- glucose molecules are released from the many end points of branches when needed for cell respiration.
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What sort of polysaccharide is cellulose?
A structural one. Found in plant cell walls.
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How do two molecules of beta glucose line up?
Ever other molecule is rotated to give along, straight cellulose chains. The OH on C1 can only line up with the OH on C4 if one of the 2 molecules is flipped upside down.
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What is the structure of cellulose?
Many chains of beta-glucose molecules stack on top of each other. Joined by H-bonds to form a microfibril. Many of these bundled together, held by H-bonds, give macrofibrils. Interwoven & criss cross at different angles. Embedded in pectins.
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What are the main functions of plant cell walls?
Gives plant great mechanical strength- helps to support whole plant. Fully permeable to water, so water can move from cell-cell- apoplastic pathway. When full of water, becomes turgid but doesn't burst. Arrangement of macrofibrils can influence shape
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Give 2 examples of other structural polysaccharides.
Chitin- exoskeleton of insects. Peptidoglycan- bacteria cell walls.
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Card 2


What elements do carbohydrates contain?


Carbon, hydrogen and oxygen.

Card 3


What are monosaccharides?


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Card 4


Give 3 features of monosaccharides.


Preview of the front of card 4

Card 5


What are hexoses?


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