Edexcel Biology 2105, also Additional Science 2103

Unit B2

Topic 1 — Inside Living Cells

DNA in the nucleus controls the whole cell and therefore the whole organism. Students will appreciate that our understanding of how cells work owes a lot to our search for cures for cancer.

Energy for the cell is provided by the chemical reaction called respiration, which is driven by proteins. Proteins are important components of the cell and their production is determined by the genes: genes contain codes that determine the sequence of amino acids in proteins.

In this topic, there are opportunities to measure body functions and investigate how they are affected by physical activities. The data can be interpreted in relation to theories about respiration and oxygen debt. Students can practise measuring accurately and understand that they need to consider safety when collecting data.

There is an opportunity to consider the industrial use and benefits of technological developments, including the cultivation of microorganisms in fermenters. How scientific ideas develop can be demonstrated by the DNA story, from data collection to the leap of imagination.

Guidance for students

Have you ever wondered?

What processes in cells keep you alive?
Why are plants and animals so different?
How does my body know which enzymes to produce?
Why does my heart beat faster when I exercise?
Why do I get cramp?

Learning objectives

The chemical reactions essential for life take place inside cells.
Respiring cells require a supply of glucose and oxygen, producing carbon dioxide as a waste
product.
Genes are the template for protein synthesis inside cells.
The digestive, circulatory and respiratory systems provide cells with the basic materials they
need to carry out their functions.

Glossary

You will be expected to be able to recall, explain, describe and use appropriately the following words and phrases:

adenine	cramp	guanine	ribosome
aerobic	cultivated	insulin	RNA
amino acid	cytosine	lactic acid	strand
anaerobic	diffusion	microorganism	thymine
aseptic	DNA	organelle	triplet code
bases	double helix	polypeptide
capillary	fermentation	protein
coding	glucose	respiration
fermenter	plasmid	ventilation
mRNA (messenger RNA)	tRNA (transfer RNA)	rRNA (ribosomal RNA)	transcription	translation

Information for teachers

ICT is an integral part of the way science works, and students should be given opportunities to experience and explore its use. It is expected that ICT will be used where it enhances the learning and teaching of science and helps to make scientific concepts easier to understand.

Some of the learning outcomes have been written deliberately in order to promote discussion and expression of opinion. Where contentious, unresolved or other scientific issues are discussed, it is expected that students will be exposed to the facts, evidence and opinions from all sides of the argument.

Learning outcomes
Learning outcomes, words or statements in bold indicate that this content is designated for Higher tier students only.

Students will be assessed on their ability to:

• describe a DNA molecule as two strands coiled to form a double helix, the strands linked by a series of paired bases (adenine with thymine and cytosine with guanine)	B2 1.1
• explain that DNA controls the joining together of amino acids to make a specific protein in a cell and that the order of bases in a section of DNA decides the order of amino acids in the protein	B2 1.2
• explain that sections of DNA coding for specific proteins can be transferred into microorganisms which are then cultivated in fermenters to produce useful substances, including human insulin	B2 1.3
• explain that microorganisms use an external food source to obtain energy, changing some substances in the medium and recall that this process is fermentation	B2 1.4
• describe a fermenter as a vessel used to cultivate microorganisms and explain the need to supply suitable conditions in fermenters, including aseptic precautions, nutrients, optimum temperature and pH, oxygenation and agitation	B2 1.5
• explain the advantages of using microorganisms for food production - rapid population growth; ease of manipulation - production independent of climate - use of waste products from other industrial processes	B2 1.6
• demonstrate an understanding of the emerging role of genetically modified bacteria in the production of useful substances	B2 1.7
• describe organelles in the cell that are involved with making protein	B2 1.8
• describe the stages of protein synthesis – the coding by triplets of bases to produce RNA – the linking of RNA to ribosomes – the linking of amino acids to form polypeptides	B2 1.9
• explain how ventilation provides oxygen for aerobic respiration which releases energy for work	B2 1.10
• explain how glucose and oxygen diffuse from capillaries into respiring cells, and how carbon dioxide diffuses from respiring cells into capillaries	B2 1.11
• explain why heart rate and breathing rate increase with exercise and interpret data on these measurements	B2 1.12
• explain why respiration is increased in exercising muscles and why diffusion of oxygen and carbon dioxide at the lung surface and muscle cells is increased	B2 1.13
• explain why during vigorous exercise, muscle cells may not receive sufficient oxygen for their energy requirements	B2 1.14
• demonstrate an understanding of how digital thermometers, and breathing rate and heart rate monitors, can provide more reliable data than traditional methods	B2 1.15
• describe that glucose is changed to lactic acid and energy is released, during anaerobic respiration	B2 1.16
• explain why extra oxygen is needed to remove the lactic acid that causes cramp (oxygen debt)	B2 1.17
• discuss why official advice on diet and exercise change over time and consider the scientific basis of current fashionable diets and advice.	B2 1.18