AS GCE EDEXCEL Biology Specification Revision topics 3 and 4

To be able to distinguish between eukaryote a prokaryote cells. 

Describe the ultrastructure of animal cells for example, rough er, smooth er and golgi  apparatus, lysomes, centrioles and mitochondria. You need to be able to identify these under an electron microscope. 

Explain the role of the rough endoplasmic reticulum (rER) and the Golgi apparatus in protein transport within cells and including its role in formation of extracellular enzymes.

Describe how the cells of multicellular organisms can be organised into tissues, tissues into organs and organs into systems.

Explain the role of mitosis and the cell cycle for growth and asexual reproduction.

Explain the role of meiosis in the production of gametes and genetic variation through recombination of alleles and genes including independent assortment and crossing over (details of the stages of meiosis are not required).

Explain how mammalian gametes are specialised for their functions.

Describe the process of fertilisation in mammals and flowering plants (starting with the acrosome reaction in mammals and pollen tube growth in plants and ending with the fusion of the nuclei) and explain the importance of fertilisation in sexual reproduction.

Explain what is meant by the terms stem cell, pluripotency and totipotency and discuss the way society uses scientific knowledge to make decisions about the use of stem cells in medical therapies (eg regulatory authorities relating to human embryo research, ability of stem cells to develop into specialised tissues, potential sources of stem cells, who could benefit from the therapies, procedures to obtain stem cells and their risks).

Explain how cells become specialised through differential gene expression, producing active mRNA leading to synthesis of proteins, which in turn control cell processes or determine cell structure in animals and plants (details of transcription factors are not required at AS).

Explain how a phenotype is the result of an interaction between genotype and the environment (eg animal hair colour, human height, monoamine oxidase A (MAOA) and cancers), but the data on the relative contributions of genes and environment is often difficult to interpret.

Explain how some phenotypes are affected by alleles at many loci (polygenic inheritance) as well as the environment (eg height) and how this can give rise to phenotypes that show continuous variation.