Additional Biology Smart Teach 2: Cells

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

Plant and Animal Cells 7 OrganellesFunction Cell MembraneControls movement into and out of the cell. NucleusContains DNA. Controls the cell CytoplasmWhere chemical reactions take place. MitochondriaWhere respiration occurs. Cell WallMade of CELLULOSE. Supports the cell. VacuoleContains CELL SAP. Helps support the plant by keeping the cell rigid ChloroplastContains CHLOROPHYLL. Absorbs LIGHT. Where photosynthesis takes place Plant and animal cells can be studies in greater detail using a light microscope. Light passes through a thin slice of the specimen. Lenses magnify the specimen many times.

Differences between the cell PlantAnimalBacteria Nucleus No nucleus – chromosomal DNA and Plasmids Cell wallNo cell wallCell wall ChloroplastsNo ChloroplastsNo chloroplasts Mitochondria No Mitochondria No Slime coat/capsule Slime coat/capsule No pili pili No flagellumflagellum

Cell division Two types resulting in different cells: – Mitosis – Meiosis You could be asked to compare and contrast the two processes, or you could be asked to describe in detail one process with a diagram.

Copy the table and use the information on the following slides to compare mitosis and meiosis MitosisMeiosis

Mitosis Key words Growth Cell repair Diploid – 46 chromosomes 2 daughter cells which are genetically identical

Meiosis Keywords Gametes Haploid – 23 chromosomes 4 genetically different daughter cells

Now lets have a look at an exam question about this

Questions Q1. Corals are animals that live on the sea bed. The photograph shows some species of coral. After fertilisation, mitosis takes place to form an embryo. The embryo develops into new coral. (i) Describe mitosis. (3)

Answer Acceptable answers Mark (i)A description including three of the following points:  cell divides / cell division / cell splits(1)  two cells produced (1)  (both) diploid (1)  (both) cells are genetically identical (1) credit correct reference to stages of mitosis: DNA replication / chromosomes duplicate (1) Chromosomes line up along the equator / middle of the cell (1) chromosomes pulled to either end of cell (1) cytokinesis / cytoplasm splits (1) (3)

Cloning Process by which organisms are copied exactly. – Can apply to plants (taking a cutting) – Can apply to animals You could be asked to describe the stages of cloning, or evaluate cloning. Evaluating means giving the advantages and disadvantages.

Stages of cloning – Nuclear transfer Remove the nucleus from an unfertilised egg cell. Transfer the nucleus from the adult body cell (somatic cell) of the organism you wish to clone into the egg cell. Apply an electric shock to cause the egg cell to begin to divide Implant the embryo cells into a host mother.

Dolly the Sheep – First cloned mammal

Advantages and disadvantages Advantage or disadvantageCloning situation AdvantageAll the new organisms are genetically identical – they will all have the desired characteristics. AdvantageOrganisms that are difficult or slow to breed normally can be reproduced quickly. DisadvantageIf a clone is susceptible to disease or changes in environment, then all the clones will be susceptible. DisadvantageIt will lead to less variation, and less opportunity to create new varieties in the future.

Now lets have a look at an exam question about this

*(ii) A cloned animal contains genetic information that is identical to its parent. Describe the stages in the production of a cloned mammal. (6)

Did you get all these points into your answer? A description including · use of body cell · nucleus removed from body / parent cell · use of egg cell · nucleus removed from egg cell/enucleated egg · nucleus (from body cell) transferred to enucleated egg · electric shock; · to stimulate cell division · mitosis · formation of embryo; · embryo implanted · into surrogate

1 - 2  Limited description of 2 of the stages involved in cloning and the sequence of events is confused  the answer communicates ideas using simple language and uses limited scientific terminology  spelling, punctuation and grammar are used with limited accuracy  a simple description of 3 or more of the stages involved in cloning but some of the steps may be missing or out of sequence  the answer communicates ideas showing some evidence of clarity and organisation and uses scientific terminology appropriately  spelling, punctuation and grammar are used with some accuracy  a detailed description of 5 or more of the stages involved in cloning but the sequence is largely in order and complete  the answer communicates ideas clearly and coherently uses a range of scientific terminology accurately  spelling, punctuation and grammar are used with few errors

Genetic engineering This is altering an organisms genetic code to give desired characteristics such as resistance to disease in crops or producing desirable products such as insulin. You could be asked about the stages of genetic engineering and give examples.

Examples of GM organisms GM insulin Golden rice that produce extra beta carotene that is used to make Vitamin A Herbicide resistant crop plants

Stages of genetic engineering Select the desired characteristic. Isolate the gene responsible for the characteristic. Insert that gene into another organism usually by using a bacterium as a vector. Replicate the transgenic organism.transgenic

Now lets have a look at an exam question about this

Organisms can be genetically engineered to make them more useful to humans. Suggest how wheat could be genetically engineered to allow it to grow in wet, marshy land. (3)

Question number AnswerMark an answer describing the process that includes three of the following: identify gene that allows plant to grow in wet or marshy area (1) extract/cut out the gene with a restriction (endonuclease)/enzyme (1) use vector/agrobacterium/ plasmid/to put desired gene into wheat/crop (1) (3)