Carbohydrates & Lipids (Cambridge (CIE) AS Biology): Flashcards
Exam code: 9700
1/500Still learning
Know0
Define monomer.
Was this flashcard helpful?
Cards in this collection (50)
Define monomer.
A monomer is a small molecule that is a single repeating unit used to build a polymer.
Define polymer.
A polymer is a large molecule made of many monomers joined together.
Define macromolecule.
A macromolecule is a very large biological molecule, such as a polysaccharide, protein or nucleic acid.
Define monosaccharide.
A monosaccharide is a single sugar unit (the monomer of carbohydrates), e.g. glucose.
Define disaccharide.
A disaccharide is a sugar made of two monosaccharides joined by a glycosidic bond.
Define polysaccharide.
A polysaccharide is a polymer of many monosaccharides joined by glycosidic bonds.
What is the difference between the ring forms of α-glucose and β-glucose?
In α-glucose, the hydroxyl (–OH) group on carbon 1 is below the ring.
In β-glucose, the –OH group on carbon 1 is above the ring.
In -glucose, the hydroxyl group on carbon 1 points above the ring.
In beta-glucose, the hydroxyl group on carbon 1 points above the ring.
What is the role of covalent bonds in polymers?
They join smaller molecules (monomers) together to form polymers.
What type of reaction joins monomers together with covalent bonds?
A condensation reaction, which releases a molecule of water each time a bond forms.
Define condensation reaction.
A condensation reaction joins two molecules with a covalent bond, releasing a molecule of water.
Monomers are joined together by bonds to form polymers.
Monomers are joined together by covalent bonds to form polymers.
True or False?
Covalent bonds hold the individual monomers within a polymer together.
True.
Strong covalent bonds link the monomers along the polymer chain.
Name three reducing sugars.
Glucose, fructose and maltose.
Name a common non-reducing sugar.
Sucrose.
Define reducing sugar.
A reducing sugar is a sugar that can donate electrons (reduce another molecule), giving a positive Benedict's test.
is a non-reducing sugar.
Sucrose is a non-reducing sugar.
True or False?
Maltose is a non-reducing sugar.
False.
Maltose is a reducing sugar; sucrose is the non-reducing sugar.
Define glycosidic bond.
A glycosidic bond is the covalent bond that links two monosaccharides together in disaccharides and polysaccharides.
How is a glycosidic bond formed?
By a condensation reaction between two monosaccharides.
A molecule of water is released as the bond forms.
How is the disaccharide sucrose formed?
By the condensation of glucose and fructose, forming a glycosidic bond.
How is a glycosidic bond broken?
By hydrolysis — a molecule of water is added, splitting the bond into separate sugars.
How does hydrolysis relate to the non-reducing sugar test?
Acid hydrolyses the glycosidic bonds in a non-reducing sugar (e.g. sucrose).
This releases reducing monosaccharides, which then give a positive Benedict's test.
A glycosidic bond is formed by a reaction.
A glycosidic bond is formed by a condensation reaction.
Glycosidic bonds are broken by the addition of water in a reaction called .
Glycosidic bonds are broken by the addition of water in a reaction called hydrolysis.
What two polysaccharides make up starch, and how do they differ?
Amylose — unbranched, coiled (helical) chain of α-glucose with 1,4 glycosidic bonds.
Amylopectin — branched, with 1,4 and 1,6 glycosidic bonds.
Describe the structure of glycogen.
A polymer of α-glucose that is highly branched (more than amylopectin).
It has 1,4 and 1,6 glycosidic bonds.
How is the structure of starch related to its function as a storage molecule in plants?
It is insoluble, so it has no osmotic effect and does not leave the cell.
Amylose coils into a compact shape for storage, and amylopectin's branches allow rapid hydrolysis to release glucose.
Why is glycogen a good energy store in animals?
It is highly branched, giving many free ends for rapid enzyme hydrolysis and fast glucose release.
It is also insoluble, so it has no osmotic effect.
The two components of starch are amylose and .
The two components of starch are amylose and amylopectin.
True or False?
Glycogen is more highly branched than amylopectin.
True.
Glycogen's greater branching allows even faster glucose release, suiting the higher metabolic rate of animals.
Describe the structure of a cellulose molecule.
A polymer of β-glucose joined by 1,4 glycosidic bonds.
Alternate β-glucose units are flipped 180°, giving long, straight, unbranched chains.
How do cellulose molecules form microfibrils?
Many parallel cellulose chains are held together by hydrogen bonds, forming strong microfibrils.
How does the arrangement of cellulose contribute to the function of the plant cell wall?
Strong microfibrils give the wall high tensile strength and rigidity.
This provides support and stops the cell bursting when it takes in water.
Why are cellulose chains straight rather than coiled?
Alternate β-glucose units are inverted (flipped 180°), so the chains stay straight and can line up alongside each other.
Cellulose is a polymer of -glucose.
Cellulose is a polymer of beta-glucose.
True or False?
Cellulose chains are held together by hydrogen bonds to form microfibrils.
True.
Many hydrogen bonds between parallel chains make the microfibrils strong.
Describe the molecular structure of a triglyceride.
One glycerol molecule joined to three fatty acids.
They are linked by ester bonds, formed by condensation.
Define ester bond.
An ester bond is the covalent bond formed between glycerol and a fatty acid in a triglyceride, by a condensation reaction.
What is the difference between saturated and unsaturated fatty acids?
Saturated fatty acids have no carbon-carbon double bonds.
Unsaturated fatty acids have one or more C=C double bonds.
Why are triglycerides described as non-polar and hydrophobic?
Their hydrocarbon fatty acid tails have no charged or polar regions, so they do not interact with water.
How is the structure of triglycerides related to their functions in living organisms?
Many C–H bonds store a lot of energy, so they are an excellent energy store.
Being hydrophobic/insoluble means no osmotic effect; they also provide thermal insulation and buoyancy (less dense than water).
A triglyceride is made of glycerol and three fatty acids joined by bonds.
A triglyceride is made of glycerol and three fatty acids joined by ester bonds.
True or False?
Unsaturated fatty acids contain one or more carbon-carbon double bonds.
True.
Saturated fatty acids, by contrast, have no C=C double bonds.
Describe the molecular structure of a phospholipid.
A glycerol backbone joined to a phosphate group (the head) and two fatty acid tails.
Define hydrophilic.
Hydrophilic means attracted to water — like the polar phosphate head of a phospholipid.
Define hydrophobic.
Hydrophobic means repelled by water — like the non-polar fatty acid tails of a phospholipid.
Which part of a phospholipid interacts with water?
The phosphate head, because it is hydrophilic (polar).
The fatty acid tails are hydrophobic (non-polar) and face away from water.
The phosphate head of a phospholipid is because it is polar.
The phosphate head of a phospholipid is hydrophilic because it is polar.
True or False?
The fatty acid tails of a phospholipid are hydrophilic.
False.
The fatty acid tails are hydrophobic (non-polar); only the phosphate head is hydrophilic.
Sign up to unlock flashcards
or