Mock Revision Topic 1 Flashcards
Biological Molecules + Enzymes
What is a monomer?
Smaller units from which larger molecules are made.
What is a polymer?
Molecules made from a large number of monomers joined together.
Name 3 examples of monomers and their
polymer.
- Monosaccharides e.g. alpha glucose – polymer
glycogen and starch, beta glucose – polymer cellulose - Amino acids – polypeptide/protein
- Nucleotides - DNA/RNA
What is a condensation reaction?
Joins two molecules together with the formation of a chemical bond and involves the elimination of a molecule of water.
What is a hydrolysis reaction?
Breaks a chemical bond between two molecules and involves the use of a water molecule.
When 2 monosaccharides join, name the
reaction and the type of bond formed.
Condensation and glycosidic bond.
Name 3 disaccharides and their constituent
monomers. For all state which are reducing
and which are non-reducing sugars.
Maltose (reducing sugar) = Glucose and Glucose
Lactose (reducing sugar) = Glucose and Galactose
Sucrose (non-reducing sugar) = Glucose and Fructose
Draw α and β glucose.
a - H O H
HO OH
b - H O OH
HO O H
Name 3 polysaccharides; for each which type
of organism are they found in and name the
monomer.
Plants: Starch – alpha glucose
Cellulose – beta glucose
Animals: Glycogen – alpha glucose
Describe the biochemical test for:
a) Reducing sugar
b) Non-reducing sugar
c) Starch
for each name the reagent and make clear
what a positive and negative result is.
Reducing sugar:
1. Heat with Benedict’s solution
2. Brick red precipitate = reducing sugar present
3. Blue = no reducing sugar
Non-Reducing sugar:
1. Heat with Benedict’s solution to confirm a negative result (Blue)
2. Heat a new sample with acid
3. Cool and neutralise with alkali
4. Heat with Benedict’s solution
5. Brick red precipitate = Non-reducing sugar present
6. Blue – No non-reducing sugar present
Starch:
1. Add iodine solution to a sample
2. Blue/Black = Starch present
3. Yellow = No starch present
What reaction forms a triglyceride, what is it
made up of and name the type of bond
formed.
Glycerol and 3 fatty acids
Condensation reaction
Ester bond
What is the difference between a
saturated/unsaturated fatty acid?
Saturated fatty acid – no double bonds between carbon atoms in the hydrocarbon chain.
Unsaturated fatty acid – one or more double bonds between carbon atoms in the hydrocarbon chain
How does a phospholipid differ from a
triglyceride?
Phospholipid has a phosphate group and two fatty acids
attached to glycerol whereas a triglyceride has three
fatty acids attached to glycerol
Describe the emulsion test for lipids and the
positive and negative result (3)
Add ethanol, shake/mix to dissolve any lipids then add
water
White emulsion = lipid present
Colourless = no lipid present
Draw an amino acid
R
H2N C COOH
H
How is a dipeptide formed? - name the bond,
exactly which groups the bond forms between
and the type of reaction.
Two amino acids join by a condensation reaction and a
peptide bond is formed.
Describe each level of structure in a protein -
name the bonds involved at each level
Primary structure – sequence of amino acids joined by
peptide bonds in a polypeptide
Secondary structure - polypeptide chain can coil/fold to
form a beta pleated sheet or an alpha helix. Hydrogen
bonds are present
Tertiary structure – further folding and coiling of the
secondary structure. Hydrogen, ionic and
(maybe) disulphide bonds
Quaternary protein – made from more than one
polypeptide chain. Hydrogen, ionic, disulphide bonds,
hydrophobic interactions
Describe the test for a protein - include the
name of the reagent and what a positive and
negative result look like.
Add Biuret reagent to the sample
Purple = Protein is present
Blue = No protein present
Which type of energy does an enzyme lower?
Activation energy
What is the induced fit model? (2)
- This suggests that the active site of an enzyme is
flexible and can slightly change its shape - When the substrate binds to the active site, this
causes the active site to change in shape and become
complementary to the shape of the substrate
What is a non-competitive inhibitor? (5)
- Not similar in shape to the substrate
- Binds at a position on the enzyme away from the active
site (allosteric site) - Changes the shape (tertiary structure) of the active site
- Active site is no longer complementary to the substrate
- Substrate unable to bind to the enzyme to form and
enzyme-substrate complex
What is a competitive inhibitor? (4)
- Similar shape to the substrate
- Binds to the active site
- Prevents the substrate binding to the active site
- Fewer enzyme-substrate complexes are formed
In an experiment how would you show
whether an inhibitor is competitive or non-
competitive? (4)
- Add more substrate
- If the rate of reaction increases to the maximum = competitive inhibitor.
- If it remains below the maximum = non-competitive inhibitor
- The effects of a competitive inhibitor can be overcome
by the addition of more substrate
What does DNA stand for?
Deoxyribonucleic acid
What are the components of a DNA monomer?
Pentose sugar deoxyribose
Nitrogen-containing base
Phosphate group
What are ribosomes made from?
RNA and protein.
How does the monomer of RNA differ from DNA?
Ribose instead of deoxyribose
Uracil instead of thymine
Name the DNA and RNA bases
DNA: Adenine, Thymine, Guanine and Cytosine
RNA: Adenine, Uracil, Guanine and Cytosine
Name the bond formed between adjacent nucleotides and the bond formed between a complementary base pair.
Phosphodiester bond
Hydrogen bond
Compare and contrast DNA and mRNA (5)
DNA - Deoxyribose
mRNA - Ribose
DNA - Thymine
mRNA - Uracil
DNA - Double stranded
mRNA - Single stranded
DNA - Hydrogen bonds
mRNA - No hydrogen bonds
DNA - Double helix
mRNA - Linear shape
What process ‘ensures the genetic continuity between generations of cells’?
DNA replication
List 5 steps in DNA replication
- Unwinding of double helix
- Breakage of hydrogen bonds between complementary bases in the polynucleotide strands by DNA helicase (both strands act as templates)
- Free DNA nucleotides attracted to exposed bases on template and base pairing (A-T and C-G)
- DNA polymerase joins adjacent nucleotides by phosphodiester bonds in a condensation reaction
- Each new DNA molecule consists of one original and one new strand = semi-conservative replication
How does the specification describe ATP?
A single molecule of adenosine triphosphate (ATP) is a nucleotide derivative and is formed from a molecule of ribose, a molecule of adenine and three phosphate groups.
What is the full name of ATP?
Adenosine triphosphate
Describe the reaction catalysed by ATP
hydrolase
ATP is hydrolysed into ADP and Pi with the release of energy
Why do we hydrolyse ATP? (2)
- The hydrolysis of ATP can be coupled to energy- requiring reactions within cells.
- The inorganic phosphate released during the hydrolysis of ATP can be used to phosphorylate other
compounds, often making them more reactive.
Describe the reaction catalysed by ATP
synthase
- ADP and Pi (with the use of energy from respiration) are joined
- In a condensation reaction to form ATP and
water - This is a phosphorylation reaction
List 5 properties of water and give their
importance in biology
- It’s a metabolite in many metabolic reactions, including condensation and hydrolysis reactions.
- It’s an important solvent in which metabolic reactions occur.
- High specific heat capacity, buffering changes in temperature.
- High specific latent heat of vaporisation, providing a cooling effect with little loss of water through evaporation.
- Strong cohesion between water molecules; supports strong column in the tub-like transport cells of plants and produces a surface tension when water meets air.
Describe the role of each of the following ions:
Hydrogen
Iron
Sodium
Phosphate
Hydrogen ions - pH
Irons ions - component of haemoglobin
Sodium ions - co-transport of glucose and amino acids
Phosphate ions - components of DNA and ATP
