Biological Molecules Flashcards
A disaccharide is formed when two monosaccharides bond together, by what reaction and what is the bond?
A condensation reaction occurs (water molecule eliminated) to form a glycosidic bond.
What is a long chain of monosaccharides called and how?
A polysaccharide which is formed by lots of condensation reactions, held together by glycosidic bonds.
What is a glycosidic bond?
A sugar bond
What is a hydrolysis reaction?
Using a molecule of water to break a chemical bond (opposite of a condensation reaction)
Why are carbohydrates/monosaccharides a good energy source?
- Contain carbon, hydrogen, and oxygen
- Large number of carbon-hydrogen bonds
- Monosaccharides are hydrates of carbon
What is the difference between alpha and beta glucose structure (hexose sugar)?
In alpha, the -OH on carbon 1 is below, but its above in beta.
ABBA
What makes maltose?
Two glucose monomers
What makes sucrose?
Glucose and fructose
What makes lactose?
Glucose and galactose
What is the molecular formula of glucose?
C6 H12 O6
Describe glycogen
- A polysaccharide made from a-glucose monomers
- Is branched with 1-4 and 1-6 glycosidic bonds
- Compact, dense and insoluble
in a spiral shape - An energy store and source in animal cells
What types of starch are there?
Amylopectin: 70-80%
Amylose: 20-30%
Describe amylopectin (starch)
- Polysaccharide of a-glucose monomers
- Is branched, therefore as it makes up around 80% of starch, starch is classed as branched
- Has 1-4 and 1-6 glycosidic bonds
- Compact with spiral shape
Describe amylose (starch)
- Polysaccharide of a-glucose monomers
- Unbranched
- 1-4 glycosidic bonds
- Compact with spiral shape
Describe cellulose
- Polysaccharide of b-glucose monomers
- Polymers joined by hydrogen bonds, creating bundles called fibrils.
- 1-4 glycosidic bonds
- Is linear and every other one is rotated 180º to prevent spiralling
What is the function of starch?
Energy store and source for plant cells
What is the function of cellulose?
Is a structural unit for plants within the cell wall.
What is ribose?
A pentose sugar that is involved in respiration as it makes up ATP
What is deoxyribose?
A pentose sugar that is a component of a DNA nucleotide monomer
Briefly explain how you would test for a reducing sugar
- Add an excess of Benedict’s solution to the sample
- Gently heat in a water bath at about 80℃ for 5 minutes
- A positive result would show a colour change from blue→ green, yellow, or brick-red depending on the concentration
Briefly explain how you would test for a NON-reducing sugar
- Add and equal volume of and acid (HCL) to the sample
- Heat at 80℃ where the acid will hydrolyse the disaccharide
- Leave to cool and slowly add an alkaline (sodium hydrogen carbonate) to neutralise the acid
- Add in Benedict’s solution and heat again
- Sugar is non-reducing if there is a blue to green, yellow, or red change.
What sugar is NOT a reducing sugar?
Sucrose
Why is it easier and faster to hydrolyse a carbohydrate that has branched glycosidic bond (1,4 and 1,6)?
There are more ends to cut off from.
Why is it useful for a molecule to be insoluble?
It won’t decrease the water concentration inside of the cell, so water activity does not occur through osmosis
What can we use to test for starch, and what is the colour change?
Iodine
Orange→ Black
What is a triglyceride?
-Macromolecule
-Lipid
What is the structure of a triglyceride?
One glycerol molecule bonded to 3 fatty acids
Explain the structure of a fatty acid
A carboxyl group with a hydrocarbon tail known as the ‘R’ group or variable group.
What is a saturated fatty acid?
There are no double bonds is the hydrocarbon tail/’R’ group -Cn H2n O2
e.g C5 H10 O2
What is an unsaturated fatty acid?
There are double bonds in the hydrocarbon tail/’R’ group
e.g C5 H8 O2
What is monounsaturated?
One double bond in fatty acid
What is polyunsaturated?
More than one double bond in a fatty acid
Why do polyunsaturated fatty acids have lower melting points?
Double bonds give a ‘kink’ in the hydrocarbon which pushes them slightly further apart making the fatty acid more fluid - ?
What reaction occurs to join the glycerol and the fatty acids in a triglyceride?
A condensation reaction
What bond holds the glycerol and the fatty acids together in a triglyceride?
Ester bonds
What is the difference between a triglyceride and a phospholipid?
The glycerol is bonded to only 2 fatty acids and one phosphoric acid at the top called a phosphate head. (the phospholipid)
Is the phosphate head of a phospholipid Hydrophilic or Hydrophobic?
Hydrophilic
-polar
-attracted to water
Is the fatty acids in a phospholipid Hydrophilic or Hydrophobic?
Hydrophobic
-non polar
-repelled by water
How are the phospholipids arranged in the cell membrane (phospholipid bi-layer)?
Drawn as a circle with two lines (fatty acid tails)
O O O O O
l l l l l l l l l l
O O O O O
So that the hydrophobic tails don’t meet the water in/surrounding the cell.
What are triglycerides used for?
Energy storage molecules -as they have long hydrocarbon tails with lots of chemical energy that is released when broken down
Why are triglycerides good energy stores?
-Long hydrocarbon chains that release lots of chemical energy
-They are insoluble so don’t affect water potential; they clump together in droplets so that they are arranged in a ring with the so the hydrophobic fatty acids are protected by the glycerol.
What are proteins made up of?
Long chains of amino acids (monomer)
2 amino acids= dipeptide
more than 2=polypeptide
- Proteins are made up of one or more polypeptides
Explain the general structure of an amino acid
Has an Amine group (NH2), a variable (R) group, and a carboxyl group (COOH)
The variable group determines what amino acid it is.
How many amino acids are there?
20
What bonds hold amino acids together?
Peptide bonds via condensation reactions
Name the 4 structural levels of a protein
Primary
Secondary
Tertiary
Quaternary
What is the primary structure of a protein?
The sequence of amino acids in a polypeptide chain.
-e.g each gene has a unique base sequence so the primary structure will be different that determines its function.
Explain the secondary structure of a protein
Hydrogen bonds form between the amino acids in the polypeptide chain which makes it coil or fold.
-Coils form an alpha helix structure
-Folds form a beta pleated sheet that zig-zags
(bonds between the -NH group and -CO group)
Describe the tertiary structure of a protein
The precise 3D shape the protein held by bonds between the ‘R’ groups that lie close to each other.
-Hydrogen bonds
-Ionic bonds (between charged R groups)
-Weak hydrophobic interactions (between non-polar R groups)
-Disulphide bonds/bridges (only occurs between cysteine amino acids)
What is the quaternary structure of a protein?
Proteins that consist of more than one polypeptide chain bonded together.
-Each polypeptide chain is a subunit of the protein
-e.g haemoglobin
How many bases does a codon have?
3
aka a DNA triplet
What is activation energy?
The minimum amount of energy needed to get a reaction to start
What is the name of the compound made when and active site meets a substrate?
Enzyme-substrate complex
Describe the Lock and Key model
The substrate and the active site are complementary to each other and fit, which then creates an enzyme-substrate complex, that splits the substrate.
Describe the Induced-fit Model
The active site moulds to fit the substrate, changed by the ‘R’ group
Explain the optimum temperature for enzyme activity
Adding more temp increases kinetic energy and increases collisions, yet too far, the enzymes will denature as bonds will break
Describe what a Competitive Inhibitor is
Fits the enzymes active site creating an enzyme-inhibitor complex, preventing any substrates.
-Decrease rate of reaction
-Effect can be overcome by increasing substrate conc
Describe what a Non-competitive Inhibitor is
They don’t fit the active site, therefore will find an alternative binding site called the Allosteric Site.
This will disrupt the tertiary structure and change the active site.
-Irreversible
-Can’t increase the substrate conc to reach normal rate, as the enzyme won’t work
What is the ‘Law of the Minimum’ by Justus Von Liebig?
States growth is dictated not by total resources available, but by the scarcest resource, known as the ‘limiting factor’
What is a monomer?
Monomers are the smaller units from which larger molecules are made.
What is a polymer?
Polymers are molecules made from a large number of monomers joined together.
Monosaccharides, amino acids and nucleotides are examples of monomers.
Name 2 polysaccharides of a-glucose
Glycogen
Starch
Name a b-glucose polysaccharide
Cellulose
What are two groups of lipid?
Triglycerides and phospholipids
What are the bonds in triglycerides between glycerol and fatty acids?
Ester bonds
