B2 – Foundation part 1

Animal, Plant and Bacteria Cell OrganellePlant CellAnimal CellBacteria Cell Nucleus Cell Membrane Cell Wall Sap Vacuole Flagellum Plasmid Chloroplast

Copy these diagrams and label using the keywords off your table.

Exam Question The diagrams show a bacterial cell, a plant cell and an animal cell. Structure X is found in all three cells. Structure X is the (1) A cell membrane B cell wall C cytoplasm D nucleus

Exam Questions Many bacteria have one or more flagella whereas most animal cells have no flagella. State one other difference between a bacterial cell and an animal cell.

Functions Mitochondria produce energy through respiration (lots found in sperm cells and muscle cells for movement) Chloroplast contain chlorophyll and carry out photosynthesis to make glucose (in plants) Cell wall offers support and protection.

Microscopes

Magnification Magnification = image size ÷ actual size 1.An image of a cell measure 30mm across and the actual size of the cell is 0.05mm long. What is the magnification? 2.The nucleus in a photograph of a cell measures 3 mm across. If the magnification in the photograph is × 500, what is the actual size of the nucleus?

How have microscopes improved? Adjustable focus/stage for clearer image. Stronger magnification (objective lens) Brighter light source Clips to hold specimen in place

DNA What is the structure of DNA? Double helix With base pairs Held together by hydrogen bonds What is the function of DNA? To give instruction To make proteins Where is DNA found in an animal/plant cell? In the nucleus

DNA Base pairs match up: Guanine -- Cytosine Adenine -- Thymine

Exam Question The diagram shows part of a DNA molecule. (i) Complete the diagram by writing the letters of the missing bases in the empty boxes. (ii) Name the type of bond that joins the base pairs together.

Exam Question A DNA molecule consists of two coiled strands that form a helix. The strands are held together by bonds between the bases. A is a section of a DNA molecule that codes for a specific protein.

Bacterial DNA No nucleus in bacteria DNA is in the chromosomal DNA and Plasmids

DNA discovery Watson and Crick made the first model of DNA. Franklin took a picture of the double helix using X-ray crystallography.

Exam Question Rosalind Franklin used this image in her study of the structure of DNA. Rosalind Franklin obtained this image using A a light microscope B X-ray crystallography C an electron microscope D a digital camera

Genetic Engineering How are organisms genetically modified? New gene is located Inserted into the organism (often a crop) By genetic engineering.

Exam Question Maize is a crop plant that has been genetically modified. Suggest how maize is genetically modified (3 marks). Answer: New gene is located Inserted into the organism (often a crop) By genetic engineering.

Example Golden Rice: Gene for beta carotene inserted To increase vitamin A levels Reduces night blindness.

Genetic Engineering AdvantagesDisadvantages

Advantages reference to GM crops named GM characteristic e.g. herbicide resistance/longer shelf life/faster growth increased yield less use of chemical pesticides less harm to living things ref to beta carotene/golden rice reduction in vitamin A deficiency/improvement in health reference to GM bacteria rapid population growth increased yield (of product) named GM characteristic e.g. insulin production no animals harmed/used in production less side effects (than bovine insulin) suitable for use by vegans (no animal products) reference to GM animals production of hormones / named GM product Disadvantages reference to cross-pollination/gene transfer production of superweeds/plants with GM characteristics greater competition between plant species reduction in biodiversity/non-target organisms harmed/ negative impact on food chains long term effects on human health unknown/side effects/allergies expensive to produce/buy reliance on GM companies (for GM seeds) farmers cannot afford to buy them risks in culturing microorganisms