Transcript Cells - singhscience

Additional Biology Smart Teach 2: Cells
Animal, Plant and Bacteria Cell
Organelle
Nucleus
Cell Membrane
Cell Wall
Sap Vacuole
Flagellum/Pili
Plasmid
Chloroplast
Plant Cell
Animal Cell
Bacteria Cell
Plant and Animal Cells
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.
7 Organelles
Function
Cell Membrane
Controls movement into and out of the cell.
Nucleus
Contains DNA. Controls the cell
Cytoplasm
Where chemical reactions take place.
Mitochondria
Where respiration occurs.
Cell Wall
Made of CELLULOSE. Supports the cell.
Vacuole
Contains CELL SAP. Helps support the plant by keeping the cell rigid
Chloroplast
Contains CHLOROPHYLL. Absorbs LIGHT. Where photosynthesis takes place
Differences between the cell
Plant
Animal
Bacteria
Nucleus
Nucleus
No nucleus – chromosomal
DNA and Plasmids
Cell wall
No cell wall
Cell wall
Chloroplasts
No Chloroplasts
No chloroplasts
Mitochondria
Mitochondria
No Mitochondria
No Slime coat/capsule
No Slime coat/capsule
Slime coat/capsule
No pili
No pili
pili
No flagellum
flagellum
flagellum
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
Mitosis
Meiosis
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
(i)
Acceptable
Mark
answers
A description
credit correct
including three of reference to stages
the following
of mitosis:
points:
DNA replication /

cell divides chromosomes
/ cell division / cell duplicate (1)
splits(1)
Chromosomes

two cells
line up along the
produced (1)
equator / middle of

(both)
the cell (1)
diploid (1)
chromosomes

(both) cells pulled to either end
are genetically
of cell (1)
identical (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 disadvantage
Advantage
Advantage
Disadvantage
Disadvantage
Cloning situation
All the new organisms are
genetically identical – they will all
have the desired characteristics.
Organisms that are difficult or
slow to breed normally can be
reproduced quickly.
If a clone is susceptible to disease
or changes in environment, then
all the clones will be susceptible.
It 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
3-4

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
5-6

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.
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
Answer
Mark
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)