Exam Questions Flashcards
Describe the chemical reactions involved in the conversion of polymers to monomers and monomers to polymers.
Give 2 named examples of polymers and their associated monomers to illustrate your answer (5)
For the conversion of monomers to polymers a condensation reaction joins monomers together to form a chemical bond and also releases water. For the conversion of polymers to monomers a hydrolysis reaction breaks a chemical bond between monomers and uses water. Polymers must contain many monomers. For example beta glucose is the monomer of cellulose. The polymer cellulose has 1-4 glycosidic bonds to form the polymer. Another example is a nucleotide which is the monomer for DNA and RNA. DNA and RNA is the polymer and within them contains phosphodiester bonds.
What is a monomer? (1)
A monomer is a smaller repeating unit which forms larger molecules
The general structure of a fatty acid is RCOOH. Name the group represented by COOH. (1)
carboxyl
Describe how a triglyceride is formed. (3)
A triglyceride is made up on one glycerol and three fatty acids. They are formed through condensation reactions and the removal of 3 molecules of water. Ester bonds are also removed.
Describe how an ester bond is formed in a phospholipid molecule. (1)
Condensation reactions between the glycerol and fatty acid
Describe how the structure of a protein depends on the amino acid it contains. (5)
The structure is determined by the position of amino acids. The primary structure is the sequence of amino acids. The secondary structure is formed by hydrogen bonds between amino acids. The tertiary structure of a protein is formed by interactions between R groups. The quaternary structure is formed by interactions between polypeptides
Describe the role of iron ions, sodium ions and phosphate ions in cells. (5)
Iron ions is used in haemoglobin. The role is for haemoglobin to bind to oxygen. Sodium ions are used in the co- transport of glucose into cells. Sodium is moved out by active transport in the Na/K pump. This creates a sodium concentration gradient. This affects osmosis. Phosphate ions joins nucleotides in the backbone of DNA. They’re used to produce ATP. Phosphate ions also phosphorylates other compounds which can make them more reactive.
Describe how a sample of chloroplasts could be isolated from leaves. (4)
Break open the cells and filter. In a cold, pH controlled solution with the same water potential centrifuge and remove nuclei. Centrifuge at a higher speed for the chloroplasts to settle out.
Eukaryotic cells produce and release proteins. Outline the role of organelles in the production, transportation and release of proteins from eukaryotic cells. (4)
The DNA in a nucleus is code for a protein. Ribosomes produce protein. Mitochondria produces ATP which is required for protein synthesis. The Golgi apparatus modifies the proteins ready for them to be released.
Describe binary fission in bacteria. (3)
The circular DNA is replicated as well as the plasmids also being replicated. The cytoplasm divides to produce daughter cells.
Describe the appearance and behaviour of chromosomes during mitosis. (5)
During prophase, the chromosomes condense and appear as 2 sister chromatids joined at the centromere.
In metaphase, the chromosomes line up at the equator and are attached to spindle fibres by their centromere.
During anaphase, the centromere splits and the sister chromatids are pulled to opposite ends of the cells.
In telophase, the chromosomes unwind.
Name and describe 5 ways substances can move across the cell-surface membrane into a cell
Simple diffusion: small non-polar molecules move down a concentration gradient.
Facilitated diffusion: molecules move down a concentration gradient via a protein carrier.
Osmosis: of water down a concentration gradient.
Active transport: molecules go against the concentration gradient via a protein carrier using ATP.
Co-transport: 2 different substances using a carrier protein.
The movement of substances across cell membranes is affected by membrane structure. Describe how.
The phospholipid bilayer allows diffusion of lipid-soluble substances. The phospholipid bilayer prevents the diffusion on lipid insoluble substances. Carrier proteins allow active transport. The carrier determines which substances move. The number of carriers determines how much movement will occur.
Describe how HIV is replicated. (4)
Attachment proteins attach to receptors on helper T cells. RNA enters the cell. Reverse transcriptase converts RNA to DNA. A viral protein is produced. Virus particles are assembled and released from the cell.
Describe how a phagocyte destroys a pathogen present in the blood. (3)
A phagocyte engulfs the pathogen. This forms a phagosome and fuses with a lysosome. Lysozymes hydrolyse the engulfed pathogen.
