CELL STRUTURE AND WATER

Question 1

Eukaryotic Cells
Eukaryotes include animal, plant & fungal cells.

Answer 1

Cell surface membrane
* Controls passage of entry of substance into the cell
* Site of cell communication via receptors
nucleus
* Stores DNA
* Nuclear pores allow mRNA & ribosomes to pass through
Mitochondria
* Carry out aerobic respiration to produce ATP
Lysosomes
* Contains digestive enzymes to break down pathogens, old organelles, cells & food molecules
Ribosomes (80s)
* Site of protein synthesis
Rough endoplasmic reticulum
* Provide a large surface area for protein synthesis
Smooth endoplasmic reticulum
* Synthesise, store and transport lipids and carbohydrates.
Golgi Apparatus
* Modifies proteins
* Sort, package, and transport molecules around the cell

Question 2

Eukaryotic cells - special

Answer 2

There are additional organelles in plants, algae & fungi:
Chloroplasts
* Site of photosynthesis
Cell vacuole
* Maintains cell structure
* Act as a temporary energy store
Cell wall (cellulose or chitin)
* Provides support & mechanical strength

• In complex multicellular organisms, eukaryotic cells become
• Specialised for specific functions.
• Specialised cells are organised into tissues, tissues into organs
  and organs into systems

Question 3

Prokaryotic cells

Answer 3

• no nucleus
• DNA is circular and floating in the cytoplasm
• cell membrane
• no membrane bound organelles
• 70s ribosomes
• peptidoglycan cell wall
• flagellum
• capsule
• plasmids

Question 4

Water

Answer 4

• Water molecules consist of 2 hydrogen molecules covalently to
  an oxygen molecule.
• The molecules are slightly polar because the oxygen nucleus
  pulls the shared electrons away from the hydrogen nuclei.
  Giving the oxygen nuclei a δ- charge, and the hydrogen nuclei
  a δ+ charge.
• The polarity of water causes attraction between water
  molecules. This force of attraction is called a hydrogen bond

Question 5

Water continued…
(properties)

Answer 5

Liquid medium- Provides habitats for aquatic organisms, medium for chemical reactions & used for transport
Important metabolite - Used in hydrolysis & condensation reactions
High specific heat capacity - Keeps aquatic & cellular environments stable
High latent heat of vaporisation - Evaporation has a cooling
effect on organisms
Cohesion of molecules - Water is drawn up the xylem
Surface tension - Allows pond-skaters to walk on the surface
Good solvent and transport medium - Dissolves ionic and polar molecules, allowing them to easily be transported
Good reaction medium - The cytoplasm in cells is an aqueous solution where many chemical reactions happen
Incompressible - Can prevent plants from wilting & act as a hydrostatic skeleton for invertebrates

Question 6

Methods of Studying Cells