AS Biology Midterm Study Guide 2016

Assignment: for each bullet point and topic in each bullet point, write an exam style question and mark scheme (answer key) for it or find a previous test question and rewrite it.

Due: Tuesday, December 13, 2016

Cell Structure

• 1.1a) compare the structure of typical animal and plant cells by making temporary preparations of live material and using photomicrographs

• 1.1b) calculate the linear magnifications of drawings, photomicrographs and electron micrographs

• 1.1d) explain and distinguish between resolution and magnification, with reference to light microscopy and electron microscopy

• 1.1e) calculate actual sizes of specimens from drawings, photomicrographs and electron micrographs
• 1.2a) describe and interpret electron micrographs and drawings of typical animal and plant cells as seen with the electron microscope

• 1.2b) recognise the following cell structures and outline their functions:

• cell surface membrane

• nucleus, nuclear envelope and nucleolus

• rough endoplasmic reticulum

• smooth endoplasmic reticulum

• Golgi body (Golgi apparatus or Golgi complex)

• mitochondria (including small circular DNA)

• ribosomes (80S in the cytoplasm and 70S in chloroplasts and mitochondria)

• lysosomes

• centrioles and microtubules

• chloroplasts (including small circular DNA)

• cell wall

• plasmodesmata

• large permanent vacuole and tonoplast of plant cells

• 1.2c) state that ATP is produced in mitochondria and chloroplasts and outline the role of ATP in cells
• 1.2d) outline key structural features of typical prokaryotic cells as seen in a typical bacterium (including: unicellular, 1-5μm diameter, peptidoglycan cell walls, lack of organelles surrounded by double membranes, naked circular DNA, 70S ribosomes)

• 1.2e) compare and contrast the structure of typical prokaryotic cells with typical eukaryotic cells (reference to mesosomes should not be included)

• 1.2f) outline the key features of viruses as non-cellular structures (limited to protein coat and DNA/RNA)

Biological Molecules

• 2.1a) carry out tests for reducing sugars and non-reducing sugars, the iodine in potassium iodide solution test for starch, the emulsion test for lipids and the biuret test for proteins to identify the contents of solutions
• 2.1b) carry out a semi-quantitative Benedict’s test on a reducing sugar using dilution, standardising the test and using the results (colour standards or time to first colour change) to estimate the concentration
• 2.2a) describe the ring forms of α-glucose and β-glucose
• 2.2b) define the terms monomer, polymer, macromolecule, monosaccharide, disaccharide and polysaccharide
• 2.2c) describe the formation of a glycosidic bond by condensation, with reference both to polysaccharides and to disaccharides, including sucrose
• 2.2d) describe the breakage of glycosidic bonds in polysaccharides and disaccharides by hydrolysis, with reference to the non-reducing sugar test
• 2.2e) describe the molecular structure of polysaccharides including starch (amylose and amylopectin), glycogen and cellulose and relate these structures to their functions in living organisms
• 2.2f) describe the molecular structure of a triglyceride with reference to the formation of ester bonds and relate the structure of triglycerides to their functions in living organisms
• 2.2g) describe the structure of a phospholipid and relate the structure of phospholipids to their functions in living organisms
• 2.3a) describe the structure of an amino acid and the formation and breakage of a peptide bond
• 2.3b) explain the meaning of the terms primary structure, secondary structure, tertiary structure and quaternary structure of proteins and describe the types of bonding (hydrogen, ionic, disulfide and hydrophobic interactions) that hold these molecules in shape
• 2.3c) describe the molecular structure of haemoglobin as an example of a globular protein, and of collagen as an example of a fibrous protein and relate these structures to their functions (The importance of iron in the haemoglobin molecule should be emphasised. A haemoglobin molecule is composed of two alpha (α) chains and two beta (β) chains, although when describing the chains the terms α-globin and β-globin may be used. There should be a distinction between collagen molecules and collagen fibres)
• 2.3d) explain how hydrogen bonding occurs between water molecules and relate the properties of water to its roles in living organisms (limited to solvent action, specific heat capacity and latent heat of vapourisation)

Enzymes

• 3.1a) explain that enzymes are globular proteins that catalyse metabolic reactions
• 3.1b) state that enzymes function inside cells (intracellular enzymes) and outside cells (extracellular enzymes)
• 3.1c) explain the mode of action of enzymes in terms of an active site, enzyme/substrate complex, lowering of activation energy and enzyme specificity (the lock and key hypothesis and the induced fit hypothesis should be included)
• 3.1d) describe the progress of an enzyme-catalysed reaction by measuring rates of formation of products (for example, using catalase) or rates of disappearance of substrate (for example, using amylase)
• 3.2a) explain the effects of the following factors on the rate of enzyme-catalysed reactions:

• temperature

• pH (using buffer solutions)

• enzyme concentration

• substrate concentration

• inhibitor concentration

• 3.2b) explain that the maximum rate of reaction (Vmax) is used to        derive the Michaelis-Menten constant (Km) which is used to compare the affinity of different enzymes for their substrates
• 3.2c) explain the effects of reversible inhibitors, both competitive and non-competitive, on the rate of enzyme activity
• 3.2d) explain the effect of immobilising an enzyme in alginate on its activity as compared with its activity when free in solution

Cell membranes and transport

• 4.1a) describe and explain the fluid mosaic model of membrane structure, including an outline of the roles of phospholipids, cholesterol, glycolipids, proteins and glycoproteins
• 4.1b) outline the roles of cell surface membranes including references to carrier proteins, channel proteins, cell surface receptors and cell surface antigens
• 4.1c) outline the process of cell signalling involving the release of chemicals that combine with cell surface receptors on target cells, leading to specific responses
• 4.2a) describe and explain the processes of diffusion, facilitated diffusion, osmosis, active transport, endocytosis and exocytosis (no calculations involving water potential will be set)
• 4.2b) describe simple diffusion using plant tissue and non-living materials, such as glucose solutions, Visking (dialysis) tubing and agar
• 4.2c) calculate surface areas and volumes of simple shapes (e.g. cubes) to illustrate the principle that surface area to volume ratios decrease with increasing size
• 4.2d) describe the effect of changing surface area to volume ratio on diffusion using agar blocks of different sizes
• 4.2e) describe the effects of immersing plant tissues in solutions of different water potential, using the results to estimate the water potential of the tissues
• 4.2f) explain the movement of water between cells and solutions with different water potentials and explain the different effects on plant and animal cells