IAL Biology Unit 1

Topic 2 – Membranes, Proteins, DNA and Gene Expression

2.1 Properties of gas exchange surfaces

(i) Know the properties of gas exchange surfaces in living organisms (large surface area to volume ratio , thickness of surface and difference in concentration )

(ii) Understand how the rate of diffusion is dependent on these properties and can be calculated using Fick’s Law of Diffusion

(iii) Understand how the structure of the mammalian lung is adapted for rapid gaseous exchange

2.2 Structure and Properties of Cell Membranes

(i) Know the structure and properties of cell membranes

(ii) Understand how models such as the fluid mosaic model of membrane structure are interpretations of data used to develop scientific explanations of the structure and properties of cell membranes

2.3 CORE PRACTICAL 3

Investigate membrane properties including the effect of alcohol and temperature on membrane permeability.

2.4 Osmosis

Understand what is meant by osmosis in terms of the movement of free water molecules through a partially permeable membrane , down a water potential gradient

RECOMMENDED ADDITIONAL PRACTICAL

Investigate tissue water potentials using plant tissue and graded concentrations of a solute.

2.5 Transport Mechanisms

(i) Understand what is meant by passive transport ( diffusion , facilitated diffusion ), active transport (including the role of ATP as an immediate source of energy), endocytosis and exocytosis

(ii) Understand the involvement of carrier and channel proteins in membrane transport

2.6 Structure and Function of Proteins

(i) Know the basic structure of an amino acid

(ii) Understand the formation of polypeptides and proteins ( amino acid monomers linked by condensation reactions to form peptide bonds )

(iii) Understand the significance of a protein’s primary structure in determining its secondary structure , three-dimensional structure and properties ( globular and fibrous proteins and the types of bonds involved in its three-dimensional structure )

(iv) Know the molecular structure of a globular protein and a fibrous protein and understand how their structures relate to their functions (including haemoglobin and collagen )

RECOMMENDED ADDITIONAL PRACTICAL

Use a semi-quantitative method to estimate protein concentration using biuret reagent and colour standards.

2.7 Enzymes

(i) Understand the mechanism of action and the specificity of enzymes in terms of their three-dimensional structure

(ii) Understand that enzymes are biological catalysts that reduce activation energy

(iii) Know that there are intracellular enzymes catalysing reactions inside cells and extracellular enzymes catalysing reactions outside cells

2.8 CORE PRACTICAL 4

Investigate the effect of temperature, pH, enzyme concentration and substrate concentration on the initial rate of enzyme-catalysed reactions.

2.9 Structure of Mononucleotides , DNA and RNA

(i) Know the basic structure of mononucleotides (deoxyribose or ribose linked to a phosphate and a base, including thymine, uracil, adenine, cytosine or guanine) and the structures of DNA and RNA ( polynucleotides composed of mononucleotides linked by condensation reactions to form phosphodiester bonds )

(ii) Know how complementary base pairing and the hydrogen bonding between two complementary strands are involved in the formation of the DNA double helix

2.10 DNA Replication

(i) Understand the process of DNA replication , including the role of DNA polymerase

(ii) Understand how Meselson and Stahl’s classic experiment provided new data that supported the accepted theory of replication of DNA and refuted competing theories

2.11 Nature of the Genetic Code

Understand the nature of the genetic code (triplet code, non-overlapping and degenerate)

2.12 Definition of a Gene

Know that a gene is a sequence of bases on a DNA molecule that codes for a sequence of amino acids in a polypeptide chain

2.13 Process of Protein Synthesis

(i) Understand the process of protein synthesis ( transcription and translation ), including the role of RNA polymerase , messenger RNA (mRNA), transfer RNA (tRNA), ribosomes and the role of start and stop codons

(ii) Understand the roles of the DNA template (antisense) strand in transcription , codons on messenger RNA and anticodons on transfer RNA

2.14 DNA Replication Errors and Mutations

(i) Understand how errors in DNA replication can give rise to mutations (substitution, insertion and deletion of bases)

(ii) Know that some mutations will give rise to cancer or genetic disorders, but that many mutations will have no observable effect

2.15 Basic Genetic Terms

(i) Understand what is meant by the terms gene , allele , genotype , phenotype , recessive , dominant , codominance , homozygote and heterozygote

(ii) Understand patterns of inheritance, including the interpretation of genetic pedigree diagrams , in the context of monohybrid inheritance

(iii) Understand sex linkage on the X chromosome , including red-green colour blindness in humans

2.16 Gene Mutation and Cystic Fibrosis

Understand how the expression of a gene mutation in people with cystic fibrosis impairs the functioning of the gaseous exchange , digestive and reproductive systems

2.17 Uses and Implications of Genetic Screening

(i) Understand the uses of genetic screening , including the identification of carriers, pre-implantation genetic diagnosis (PGD) and prenatal testing, including amniocentesis and chorionic villus sampling

(ii) Understand the implications of prenatal genetic screening

2.18 Ethical and Social Issues of Genetic Screening

Be able to identify and discuss the ethical and social issues relating to genetic screening from a range of ethical viewpoints, including religious, moral and social implications