Transcript File - singhscience

B2 – Foundation part 1
Animal, Plant and Bacteria Cell
Organelle
Nucleus
Cell Membrane
Cell Wall
Sap Vacuole
Flagellum
Plasmid
Chloroplast
Plant Cell
Animal Cell
Bacteria Cell
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
Advantages
Disadvantages
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