1 - Cell Biology

Created by

Harry Parker

Cards (63)

What are eukaryotic cells?
Plants and animal cells (eukaryotes) have a cell membrance, cytoplasm and genetic material enclosed in a nucleus.
What is the function of the nucleus?
The nucleus controls all the activities of the cell and contains the genetic material.
What is the cytoplasm?
The cytoplasm is a liquid gel where the organelles are suspended and where most of the chemical reacions take place.
What is the function of the cell membrane?
The cell membrane controls the passage of substances into and out of the cell.
What are prokaryotic cells?

What are some differences and similarities between
prokaryotes and eukaryotes?

Where is the genetic material in a prokaryotic cell?
Prokaryotes do not have their genetic material enclosed in a nucleus.

Prokaryotes have a cytoplasm and a cell membrance like eukaryotes. However, the cell membrane is surrounded by a bacterial cell wall.

The genetic material of prokaryotes is a single DNA loop and there may be one or more small rings of DNA called plasmids.
What is the function of the mitochondria?
The mitochondria are structures in the cytoplasm where aerobic respiration takes place, releasing energy.
What is the function of the ribosomes?
The ribosomes are where protein synthesis takes place.
What is the function of chloroplasts?
What do chlorophyll do?
Plant cells have chloroplasts which contain chlorophyll.
Chlorophyll absorbs light energy so the plant can make food by photothynthesis.
What is the permanent vacuole important?
The large permanent vacuole is filled with cell sap and this is important because it keeps the cells rigid to support the plant.
What is the function of the cell wall? What is it made out of?
The cell wall is made out of cellulose and it strengthens the cell and gives it support.
What does being 'specialised' mean?
What is 'differentiation'?
Specialised cells have different adaptations which help them carry out their particular function.
'Differentiation' is when cells become specialised.
What is the job of a sperm cell?

What happens during fertilisation?
The sperm cell has to fuse with an ovum (egg cell) to fertilise it.

During fertilisation, the genetic material of both the sperm cell and ovum combine.
How are sperm cells specialised?
- large nucleus contains genetic information

- acrosome stores digestive enzymes for breaking down the outer layers of the ovum

- long tail for swimming

- middle section full of mitochondria to release energy for the tail
What do nerve cells do?
Nerve cells carry electrical impulses around the body and provide a rapid communication system.
How are nerve cells specialised?
- dendrites increase SA so other nerve cells can connect more easily

- long axon carries electrical impulse

- myelin insulates axon + speeds up transmission of nerve impulses

- synapses allow impulse to pass from one nerve cell to another
What do muscle cells do?
Muscle cells contract and relax and work together to form muscle tissue.
How are muscle cells specialised?
- protein fibres can change their length

- lots of mitochondria to relase energy for muscle contraction

- can store glycogen that can be broken down into glucose to be used by mitochondria for respiration
How are root hair cells specialised?
- hairs increase SA for efficient osmosis

- no chloroplasts (underground)

- many mitochondria for active transport
How are xylem cells specialised?
- cell walls made of lignin to withstand water pressure

- dead cells form long hollow tubes so water and dissolved mineral ions can move easily through

- no internal structures so water can flow easier
How are phloem cells specialised?
- cell walls break down to form sieve plates

- each phloem vessel cell has a companion cell containing many mitochondria to transfer energy so phloem vessel cell can move sugars up and down
Describe the method for viewing a prepared slide through an optical microscope.
1) Place the slide on the stage & use the clips to secure it.

2) Select the lowest power OL.

3) By slowly turning the CFD, make sure the OL almost touches the slide.

4) Look through the EL and slowly turn the CFD to increase the distance between the OL and the slide. Do this until the cells come into focus.

5) Slowly turn the FFD to bring the cells into a clear focus.

6) We can now select a higher power OL, but adjust the FFD to bring the cells back into focus.

total magnification = EL x OL
What are the disadvantages of a light microscope?
Disadvantages of a light microscope:

- limited magnification
- limited resolution
What are the key advantages of an electron microscope?
Advantages of an electron microscope:

- much greater magnification
- much greater resolution
How do we calculate magnification? 
magnification = image size /
actual size

i
m x o
How do bacteria divide?

How can we calculate the number of bacteria in a given time?
Bacteria divide by binary fission.

Number = 2^n (rounds)
of bacteria
Describe the method for preparing an uncontaminated bacterial culture.

What 2 ways can bacteria be grown?
Bacteria can be grown using either a nutrient broth solution or as colonies on an agar gel plate.

1) Sterilise all petri dishes, bacterial nutrient broth and agar to kill any unwanted microorganisms + prevents contamination.

2) Sterilise inoculating look by passing it through a bunsen burner flame.

3) Transfer bacteria onto agar gel plate.

4) Attach the lid of the petri dish using adhesive tape top stop the lid falling off + prevent contamination with bacteria in the air.

5) Place the agar plate upside down into an incubator to stop moisture dripping down and disrupting the colonies.
(at school, we normally incubate bacteria at 25 degrees celsius to reduce the chances that harmful bacteria will grow).
Describe a method to investigate the effect of antibiotics on bacterial growth.

What is the zone of inhibition?

How do we calcuate the area where the bactera have not grown?
1) Clean the bench with disinfectant solution to kill microorganisms that could contaminate our culture.

2) Sterilise an inoculating loop by passing it through a bunsen burner flame.

3) Open a sterile agar gel plate near a bunsen burner flame to kill bacteria in the air.

4) Use the inoculating loop to spread the chosen bacteria evenly over the plate.

5) Place sterile filter paper discs containing antibiotic onto the plate.

6) Incubate the plate at 25 degrees celsius.

The region where the bateria have not grown is the zone of inhibition.

area = pi x r^2
Where do we find DNA inside a cell?

How are chromosomes arranged in a body cell?
The nucleus of a body cell contain chromosomes which are made of the molecule DNA.

Chromosomes in the nucleus of a body cell are paired.
What is the function of chromosomes?
Chromosomes carry a large number of genes which determine our features.
What happens in the 1st stage of the Cell Cycle?
1) DNA REPLICATES to form 2 copies of each chromosome;
the cell GROWS and COPIES ITS INTERNAL STRUCTURES.
What happens in the 2nd stage of the Cell Cycle?
2) MITOSIS -
one set of chromosomes pulled to each end of the cell;
nucleus also divides
What happens in the final stage of the Cell Cycle?
3) CYTOPLASM & CELL MEMBRANE DIVIDE =>
2 IDENTICAL DAUGHTER CELLS
What are the functions of mitosis?
- growth & development
- repair
- asexual reproduction
What is a stem cell?
A stem cell is an undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type, and from which certain other cells can arise from differentiation.
Why are early-stage embryonic cells used as stem cells?
Cells in the early stage embryo have not differentiated yet but they are capable of differentiating into any type of body cell.
What can stem cells in bone marrow differentiate to form?
Adult stem cells in the bone marrow can only differentiate to form cells found in blood, e.g. red blood cells, white blood cells, and platelets.
What happens in a bone marrow transplant?

What happens if the donor is not compatible with the patient?
What is another risk of bone marrow transplant.
Leukaemia is a cancer of the bone marrow.

To treat this, the patient's existing bone marrow is first destroyed using radiation.

The patient then receives a transplant of bone marrow from a donor.
The stem cells in the bone marrow now divide and form new bone marrow, they also differentiate and form blood cells.

If the donor is not compatible with the patient, the white blood cells produced by the bone marrow could attack the patient's body.
There is also a risk that viruses can be passed on from the donor.
What happens first in therapeutic cloning?

What does this allow?

What happens after this?

What medical conditions could therapeutic cloning be useful for? 
An embryo is produced with the same genes as the patient.

This means that embryonic stem cells can be transplanted into the patient without being rejected by the patient's immune system.

Once inside the patient, the embryonic stem cells can differentiate to replae cells which have stopped working correctly.

This technique could be useful to treat diabetes or paralysis.
Where are stem cells found in plants?

What is advantageous about these stem cells?

How could we use this type of stem cell?
Roots and buds contain meristem tissue.

These stem cells can differentiate into any type of plant tissue, at any point in the life of the plant.

We could clone a rare plant quickly and cheaply to stop it from extinction.
Farmers could also produce cloned crop plants which are resitant to diseases.
How could substances enter or leave the cell?

What is diffusion?
Substances may move into and out of cells across the cell membranes via diffusion.

Diffusion is the spreading out of particles resulting in a net movement from an area of higher concentration to an area of lower concentration.