L2 - Organisation of Cells

Question 1

Are virus and mitochondria cells and if not why?

Answer 1

Virus aren’t cells as they can’t produce on their own. Use DNA of another cell to reproduce. Have RNA genome whereas all cells have DNA.

Mitochondria is an organelle not cell.

Question 2

Cell theory (Schleiden and Schwann 1838/39):

Answer 2

Cells are the fundamental units of life.

Question 3

Definition of cell:

Examples of single cell organisms:

Answer 3

Can carry out life processes and can reproduce independently.

Examples:
Protozoans
Yeast - Eukaryotic
Bacteria - Prokaryotic

Question 4

Functions of Plasma Membrane:

Answer 4

Barrier - maintains different composition of external and internal compartments

Communication between cells

Import and export

Question 5

Two types of organisms depending on whether they contain nucleus and organelles:

Answer 5

Prokaryotes: no nucleus, single cell (bacteria)

Eukaryotes: nucleus, single or multicellular

Question 6

Prokaryotes have two types: Bacteria and Archaea

Answer 6

Bacteria:
They are the familiar ones including pathogens.
E.g. E. Coli
Cyanobacteria - photosynthetic. Have specialised cells which fix CO2. Have resistant spore cells that can resists changes in environ.

Archaea:
Live in unusual environments. 
Thermoacidophiles - low pH and high temps 
Enzymes adapted to conditions. 
Halophiles - high salt environments

Both derived from common ancestor.

Question 7

Features of bacteria:

Answer 7

Size 1um 
Different shapes 
Can reproduce quickly 
Has cell membrane
Has peptidoglycan cell wall which is protein and oligosaccharide. 
Can resist osmotic pressure outside
Has ribosomes in Cytosol. 
Has single circular DNA containing proteins.

Question 8

Examples of eukaryotes:

Answer 8

Can be single called or multicellular.

Multicellular:
Plants
Animals
Fungi

Single celled:
Protozoans
Algae
Yeast

Question 9

Features of eukaryotes:

Answer 9

Size 5-50um
Have nucleus and organelles.
Have DNA in nucleus.
Have cytoskeleton.

Question 10

Examples of specialised cells:

Answer 10

Carry out different functions in body. All from single cell which changes and becomes specialised.

E.g. 
Red blood cells
Bone cells
Neurons 
Kidney cells
Heart muscle cells

Question 11

Cellular processes of development of organism (6 steps):

Answer 11

1. Cell division
   Single cell solid ball with lots of nutrients divide forming hollow ball of cells = cleavage division
2. Cell movement
   Gastrulation - simple ball of cells become three layered structure.
   Cells change shape from short to fat and long to thin. Cells move outside to inside.
3. Cell signalling
   Embryonic induction which changes fate of cells. Signals from one part to another. Can cause formation of red types of cells (mesoderm)
4. Cell differentiation
   Stem cells can become neurons/glial cells. Have specific function.
5. Gene expression
   Make different proteins using different parts of gene.
6. Cell death
   Metamorphosis of frogs so lose tails from tadpoles. Cell death of extremities giving shape of hand. Has to be controlled as it remodels tissues.

Question 12

Fate maps:

Germ layers:

Answer 12

Fate maps:
Show the origin of embryonic tissues. If we label one cell (on ball of cells) then you can find where it is as organism.

Germ layers:
Endoderm (inside) - gut liver lungs
Mesoderm (middle) - skeleton muscle kidneys heart and blood
Ectoderm (outside) - nervous system and epidermis of skin.