Edexcel SNAB A Level Biology - Topic 2 Exam Questions & Answers 2024, Exams of Nursing

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Exam Question & Answers 2024

What are the monomers of proteins? - Correct Answers ✅Amino acids Dipeptide - Correct Answers ✅Two amino acids bonded together Polypeptide - Correct Answers ✅A polymer (chain) of more than two amino acids bonded together What are proteins made of? - Correct Answers ✅One or more polypeptides What is the general structure of amino acids? - Correct Answers ✅A carboxyl group, an amine/amino group, a carbon-containing R group How many amino acids are there? - Correct Answers ✅ 20 What is the difference between amino acids? - Correct Answers ✅Their R group How are amino acids linked? - Correct Answers ✅Condensation reaction

Exam Question & Answers 2024

What is released in a condensation reaction? - Correct Answers ✅Water molecule What type of bond is formed between amino acids? - Correct Answers ✅Peptide bond What are the 4 structural levels of proteins? - Correct Answers ✅Primary, Secondary, Tertiary, Quaternary What is the primary structure of a protein? - Correct Answers ✅The sequence of amino acids in the polypeptide chain What is the secondary structure of a protein? - Correct Answers ✅The 2D arrangement of the chain of amino acids. Alpha helix or Beta pleated sheet What determines the secondary structure of a protein? - Correct Answers ✅Hydrogen bonds between amino acids What is the tertiary structure of a protein? - Correct Answers ✅The 3D structure of a protein

Exam Question & Answers 2024

What determines the tertiary structure of a protein? - Correct Answers ✅Hydrogen bonds, ionic bonds, disulphide bridges, hydrophobic and hydrophilic interactions What is the quaternary structure of a protein? - Correct Answers ✅Some proteins are made of more than one polypeptide chains linked together. The quaternary structure is the way these polypeptide chains are assembled together What is the primary structure of proteins held together by? - Correct Answers ✅Peptide bonds between amino acids Ionic bonds in proteins - Correct Answers ✅Attractions between negative and positive charges on different parts of the molecule Disulphide bridge/bond in proteins - Correct Answers ✅Covalent bond between sulphur atoms of two cysteine amino acids Hydrophobic interactions in proteins - Correct Answers ✅When hydrophobic groups are close together, they tend to clump together Hydrophilic interactions in proteins - Correct Answers ✅Hydrophilic groups get pushed to the outside

Exam Question & Answers 2024

What do hydrophilic/phobic interactions affect tertiary structure? - Correct Answers ✅They affect how the protein folds up How does a proteins primary structure determine its 3D structure and properties - Correct Answers ✅The amino acid sequence of a protein determines what bonds will form and how the protein folds into its 3D structure. The 3D structure determines its properties and function in the body Globular proteins - Correct Answers ✅- Round, compact proteins made up of multiple polypeptide chains.

• Complex tertiary/quaternary structures.
• Form colloids in water How are the chains structured in globular proteins? - Correct Answers ✅Coiled up so that hydrophilic parts are on the outside and hydrophobic parts face inwards What are the two types of protein 3D structure? - Correct Answers ✅Globular

Exam Question & Answers 2024

Fibrous How does the structure of globular proteins make it good for their function? - Correct Answers ✅Makes them soluble, so they're easily transported in fluids Hydrogen bonds - Correct Answers ✅Weak bonds between a slightly positively charged hydrogen atom in one molecule and a slightly negatively charged atom in another molecule Example of globular protein - Correct Answers ✅Haemoglobin Haemoglobin strucutre - Correct Answers ✅Globular protein made of 4 polypeptide chains. It has iron-contains haem groups that bind to oxygen What is the function of haemoglobin? - Correct Answers ✅Carries oxygen around the body How is haemoglobin suited for its function? - Correct Answers ✅Its soluble so can easily be transported in the blood

Exam Question & Answers 2024

Collagen structure - Correct Answers ✅Fibrous protein made up of 3 polypeptides Fibrous proteins - Correct Answers ✅- Long, insoluble polypeptide chains, tightly coiled round each other to form a rope shape

• Chains are held together by lots of bonds, making the proteins strong
• Little tertiary/quaternary structure
• Occasional cross linkages which forms microfibres for tensile strength
• Insoluble How are fibrous proteins suited for their function? - Correct Answers ✅They are strong so are often found in supportive tissue How is collagen suited for its function? - Correct Answers ✅High tensile strength due to hydrogen and covalent bonds and forms the structure of bones, cartilage and connective tissue in animals

Exam Question & Answers 2024

What do enzymes do? - Correct Answers ✅Catalyse metabolic reactions Intracellular enzymes - Correct Answers ✅Catalyse reactions inside the cell Extracellular enzymes - Correct Answers ✅Secreted by cells to catalyse reactions outside of cells Are enzymes proteins? - Correct Answers ✅Yes Activate site of enzymes - Correct Answers ✅Has a specific shape where the substrate molecules bind to What makes enzymes specific? - Correct Answers ✅Their tertiary structure How do enzymes catalyse reactions? - Correct Answers ✅They lower the activation energy needed for a reaction Enzyme-substrate complex - Correct Answers ✅A complex formed when an enzyme binds to its substrate molecule(s).

Exam Question & Answers 2024

Activation energy - Correct Answers ✅Energy needed to get a reaction started How does an enzyme substrate complex lower activation energy? - Correct Answers ✅- If 2 substrate molecules need to be joined, being attached to the enzyme holds them close together, reducing and repulsion between the molecules so they can bond more easily

• In a breakdown reaction, fitting into the active site puts a strain on the bonds in the substrate so the molecule breaks up more easily Induced fit model - Correct Answers ✅Change in the shape of an enzyme's active site that enhances the fit between the active site and its substrate(s) How do enzyme properties relate to their tertiary structure? - Correct Answers ✅- Enzymes are very specific and usually only catalyse one reaction because only one complementary substrate will fit into the active site
• The enzyme's active site is determined by it's tertiary structure
• Each enzyme has a different tertiary structure and so a different shaped active site

Exam Question & Answers 2024

• If the substrate doesn't match the active sit, the enzyme-substrate complex won't be formed and the reaction won't be catalysed What can the tertiary structure of an enzyme be altered by? - Correct Answers ✅Changes in pH or temperature What is the primary structure of a protein determined by? - Correct Answers ✅The sequence of nucleotides in the gene encoding for amino acids How does enzyme concentration affect enzyme activity? - Correct Answers ✅The more enzyme molecules there are in a solution, the more active sites present and the more likely a substrate molecule is to collide with an active site and form an enzyme-substrate complex What is the limiting factor in enzyme catalysed reactions? - Correct Answers ✅Substrate concentration What does DNA stand for? - Correct Answers ✅Deoxyribosenucleic Acid What does RNA stand for? - Correct Answers ✅Ribonucleic acid

Exam Question & Answers 2024

What are mono nucleotides made from? - Correct Answers ✅- Pentose sugar

• Nitrogen-containing organic base
• Phosphate group Pentose sugar - Correct Answers ✅Sugar with 5 carbon atoms DNA and RNA are polymers of what? - Correct Answers ✅Mononucleotides What is the pentose sugar in a DNA mononucleotide called? - Correct Answers ✅Deoxyribose Each DNA mononucleotide has the same _____ and a _________/_____ - Correct Answers ✅- Sugar
• Phosphate group What varies between DNA/RNA mononucleotides? - Correct Answers ✅Their base 4 bases (DNA) - Correct Answers ✅- Adenine (A)

Exam Question & Answers 2024

• Thymine (T)
• Cytosine (C)
• Guanine (G) What is the pentose sugar in a RNA mononucleotide called? - Correct Answers ✅Ribose Each RNA mononucleotide has the same _____ and a _________/_____
• Correct Answers ✅- Sugar
• Phosphate group 4 bases (RNA) - Correct Answers ✅- Adenine (A)
• Uracial (U)
• Cytosine (C)
• Guanine (G) Polynucleotide - Correct Answers ✅A polymer consisting of many mononucleotide monomers in a chain What are polynucleotides joined by? - Correct Answers ✅Condensation reaction between the phosphate of one mononucleotide and the sugar group of another

Exam Question & Answers 2024

How many polynucleotide strands is DNA made up of? - Correct Answers ✅Two How many polynucleotide strands is RNA made up of? - Correct Answers ✅One How do two DNA polynucleotide strands join together? - Correct Answers ✅Hydrogen bonding between bases What are the DNA base pairs? - Correct Answers ✅Adenine - Thymine (A-T) Cytosine - Guanine (C-G) Complementary base pairing - Correct Answers ✅Hydrogen bonding between particular pyrimidines and purines Pyrimidines - Correct Answers ✅- Cytosine

• Thymine
• Uracil

Exam Question & Answers 2024

Purines - Correct Answers ✅- Adenine

• Guanine How many hydrogen bonds form between A and T? - Correct Answers ✅Two How many hydrogen bonds form between C and G - Correct Answers ✅Three DNA double helix - Correct Answers ✅Two antiparallel polynucleotide strands twist to form the DNA double-helix Who and when determined the double-helix structure of DNA - Correct Answers ✅Watson and Crick - 1953 Gene - Correct Answers ✅Sequence of mononucleotide bases on a DNA molecule that codes for the sequence of amino acids in a polypeptide Different proteins have a different ______ and _____ or amino acids - Correct Answers ✅- Number
• Order

Exam Question & Answers 2024

How many bases code for one amino acid? - Correct Answers ✅Three Does DNA move out of the nucleus? - Correct Answers ✅No, It is too large so is copied into mRNA (transcription). The mRNA leaves the nucleus and joins with a ribosome in the cytoplasm, where it can be used to synthesise a protein (translation) Two types of RNA - Correct Answers ✅- Messenger RNA (mRNA)

• Transfer RNA (tRNA) When and where is mRNA made? - Correct Answers ✅In the nucleus during transcription What does mRNA do? - Correct Answers ✅Carries the genetic code from the DNA to a ribosome in the cytoplasm, where it's used to make a protein during translation Codon - Correct Answers ✅A specific sequence of three adjacent bases on a strand of DNA or RNA that provides genetic code information for a particular amino acid

Exam Question & Answers 2024

Where is tRNA found? - Correct Answers ✅The cytoplasm What does tRNA have at each end? - Correct Answers ✅Amino acid binding site at one end and an anticodon at the other end Anticodon - Correct Answers ✅A sequence of three bases of a tRNA molecule that pairs with the complementary three-nucleotide codon of an mRNA molecule during protein synthesis. What does tRNA do? - Correct Answers ✅Carries the amino acids that are used to make proteins, to the ribosomes during translation What are codons and anticodons sometimes referred to as? - Correct Answers ✅Triplets Genetic code - Correct Answers ✅The sequence of base triplets (codons) in DNA or mRNA which codes for specific amino acids Features of genetic codes - Correct Answers ✅- Degenerate (more than one genetic code corresponds to one amino acid)

• Non-overlapping (base triplets don't share their bases, each is separate from the triplet before)

Exam Question & Answers 2024

How many possible triplets are there? - Correct Answers ✅ 64 Start and Stop codons - Correct Answers ✅Triplets used to tell the cell when to start and stop the production of the protein. Found at the beginning and end of the gene What is the first stage of protein synthesis called? - Correct Answers ✅Transcription Stage 1 of transcription: - Correct Answers ✅Transcription starts when RNA polymerase attaches to the DNA double-helix at the beginning of a gene (start codon) Transcription starts when RNA polymerase attaches to the DNA double- helix at the beginning of a gene (start codon)... Stage 2 of transcription: - Correct Answers ✅The hydrogen bonds between the two DNA strands in the gene break, separating the stands and causing the DNA molecule to unwind. The hydrogen bonds between the two DNA strands in the gene break, separating the stands and causing the DNA molecule to unwind...

Exam Question & Answers 2024

Stage 3 of transcription: - Correct Answers ✅One of the strands is used as a template to make an mRNA copy One of the strands is used as a template to make an mRNA copy... Stage 4 of transcription: - Correct Answers ✅RNA polymerase lines up free RNA mononucleotides alongside the template strand. Complementary base pairing means the mRNA ends up being a complementary copy of the DNA strand (with T being replaced with U) RNA polymerase lines up free RNA mononucleotides alongside the template strand. Complementary base pairing means the mRNA ends up being a complementary copy of the DNA strand (with T being replaced with U)... Stage 5 of transcription: - Correct Answers ✅Once the RNA mononucleotides have paired with their specific bases on the DNA strand they're joined by RNA polymerase, forming an mRNA molecule Once the RNA mononucleotides have paired with their specific bases on the DNA strand they're joined by RNA polymerase, forming an mRNA molecule...

Exam Question & Answers 2024

Stage 6 of transcription: - Correct Answers ✅The RNA polymerase moves along the DNA separating the strands and assembling the mRNA strand The RNA polymerase moves along the DNA separating the strands and assembling the mRNA strand... Stage 7 of transcription: - Correct Answers ✅The hydrogen bonds between the unwound strands of DNA re-form once the RNA polymerase has passed by. The strands wind back into a double-helix The hydrogen bonds between the unwound strands of DNA re-form once the RNA polymerase has passed by. The strands wind back into a double-helix... Stage 8 of transcription: - Correct Answers ✅When RNA polymerase reaches a stop codon its stops make mRNA and detaches from the DNA When RNA polymerase reaches a stop codon its stops make mRNA and detaches from the DNA... Stage 9 of transcription: - Correct Answers ✅The mRNA moves out of the nucleus through a nuclear pore and attaches to a ribosome in the cytoplasm, where the next stage of protein synthesis takes place

Exam Question & Answers 2024

What is the second stage of protein synthesis called? - Correct Answers ✅Translation Stage 1 of translation: - Correct Answers ✅The mRNA attaches itself to a ribose and tRNA molecules carry amino acids to the ribosome The mRNA attaches itself to a ribose and tRNA molecules carry amino acids to the ribosome... Stage 2 of translation: - Correct Answers ✅A tRNA molecule, with an anticodon that's complementary to the start codon on the mRNA, attaches itself to the mRNA by complementary base pairing A tRNA molecule, with an anticodon that's complementary to the start codon on the mRNA, attaches itself to the mRNA by complementary base pairing... Stage 3 of translation: - Correct Answers ✅A second tRNA molecule attaches itself to the next codon on the mRNA in the same way A second tRNA molecule attaches itself to the next codon on the mRNA in the same way...

Exam Question & Answers 2024

Stage 4 of translation: - Correct Answers ✅The two amino acids attached to the tRNA molecules are then joined together by a peptide bond. The first tRNA molecule moves away, leaving its amino acid behind The two amino acids attached to the tRNA molecules are then joined together by a peptide bond. The first tRNA molecule moves away, leaving its amino acid behind... Stage 5 of translation: - Correct Answers ✅The ribosome moves along to the next codon The ribosome moves along to the next codon... Stage 6 of translation: - Correct Answers ✅A third tRNA molecule binds to that codon on the mRNA. Its amino acid binds to the first two and the second tRNA molecule moves away A third tRNA molecule binds to that codon on the mRNA. Its amino acid binds to the first two and the second tRNA molecule moves away...

Exam Question & Answers 2024

Stage 7 of translation: - Correct Answers ✅This process continues, producing a chain of linked amino acids (a polypeptide chain), until there's a stop codon on the mRNA molecule This process continues, producing a chain of linked amino acids (a polypeptide chain), until there's a stop codon on the mRNA molecule... Stage 8 of translation: - Correct Answers ✅The polypeptide chain moves away from the ribosome and translation is complete DNA replicates by ____-____________ replication - Correct Answers ✅Semi-conservative What is it called semi-conservative replication? - Correct Answers ✅Because half the strands in each new DNA molecule are from the original DNA molecule What does semi-conservative replication create? - Correct Answers ✅Genetic continuity Genetic continuity - Correct Answers ✅The continuation of genes, passed from parents to offspring.

Exam Question & Answers 2024

Stage 1 of DNA replication: - Correct Answers ✅DNA helicase breaks the hydrogen bonds between bases on the two polynucleotide DNA strands, causing the helix to unwind to form two single strands DNA helicase breaks the hydrogen bonds between bases on the two polynucleotide DNA strands, causing the helix to unwind to form two single strands... Stage 2 of DNA replication: - Correct Answers ✅Each original single strand acts as a template for a new strand. Complementary base pairing means that free-floating DNA nucleotides are attracted to their complementary exposed bases on each original template strand Each original single strand acts as a template for a new strand. Complementary base pairing means that free-floating DNA nucleotides are attracted to their complementary exposed bases on each original template strand... Stage 3 of DNA replication: - Correct Answers ✅Condensation reactions join the nucleotides of the new strands together, catalysed by DNA polymerase. Hydrogen bonds form between the bases on the original and new strands.

Exam Question & Answers 2024

Condensation reactions join the nucleotides of the new strands together, catalysed by DNA polymerase. Hydrogen bonds form between the bases on the original and new strands... Stage 4 of DNA replication: - Correct Answers ✅Each new DNA molecule contains one strand from the original DNA molecule and one new strand Who provided evidence for semi-conservative replication? - Correct Answers ✅Meselson and Stahl Mutations - Correct Answers ✅Changes to the base sequence of DNA, they can be caused by errors during DNA replication Types of errors in DNA replication - Correct Answers ✅- Substitution

• Deletion
• Insertion
• Duplication
• Inversion DNA replication erros - substitution - Correct Answers ✅One base is substituted with another

Exam Question & Answers 2024

DNA replication erros - deletion - Correct Answers ✅One base is deleted DNA replication erros - insertion - Correct Answers ✅An extra base is added DNA replication erros - duplication - Correct Answers ✅One or more bases are repeated DNA replication erros - inversion - Correct Answers ✅A sequence of bases is reverse How can mutations change a protein? - Correct Answers ✅The order of DNA bases in a gene determines the order of amino acids in a particular protein. If a mutation occurs, the primary structure of the protein could be altered and could change the final 3D shape of the protein so it doesn't work properly What does cystic fibrosis affect? - Correct Answers ✅Respiratory, digestive and reproductive systems Is CF dominant or recessive? - Correct Answers ✅Recessive

Exam Question & Answers 2024

Will a person with CF be homozygous or heterozygous for the allele? - Correct Answers ✅Homozygous Will a carrier of CF be homozygous or heterozygous for the allele? - Correct Answers ✅Heterozygous How does CF affect the respiratory system? - Correct Answers ✅- Mucus is abnormally thick and sticky so cilia are unable to move it towards the throat

• Mucus builds up in the airways
• Some airways can become completely blocked by the mucus so gas exchange can't take place in the area below the blockage
• The surface area for gas exchange is reduced, causing breathing difficulties
• People with CF are prone to lung infections as mucus containing microorganisms cannot be removed How does CF affect the digestive system? - Correct Answers ✅- The tube that connects the pancreas to the small intestine can become