What is the function of the Ribsosomes
Site of Protein synthesis;
What is the function of the Nucleus
- Contains genetic material / DNA;
- Controls cell activity;
What is the function of the Mitochondria
- Site of aerobic respiration;
- ATP production;
What is the function of the Smooth Endoplasmic Reticulum
Site of lipid synthesis;
What is the function of the Rough Endoplasmic reticulum
- Encrusted in Ribosomes;
- Site of protein synthesis;
- Transports and stores protein within the cell
What is the function of Golgi Body/Apparatus
- Modifies/packages/sorts proteins;
- Produces vesicles
What is the function of Lysosomes
- Contains hydrolytic enzymes;
- Digests worn out organelles/autolysis;
What is the function of Cell surface membrane
- Made of a Phospholipid Bi-layer;
- Controls what enters the cell/ is selectively permeable;
- Can be folded to increase SA;
What is the function of Chloroplasts
- Contain thylakoids, stacked into Granum;
- Site of photosynthesis;
What is the function of Capsule
- Protects cell from immune systems;
- Aids bacteria sticking together;
What is the function of Plasmid
- Circular DNA;
- Contains antibiotic resistance genes;
What is the function of Cell Wall
- Provides rigid shape / structure;
- Stops osmotic lysis;
What is the function of Flagellum
Allows movement/propulsion;
Eukaryotic cells produce and release proteins. Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells (6)
- DNA in nucleus is code (for protein);
- Ribosomes/rough endoplasmic reticulum produce (protein);
- Mitochondria produce ATP (for protein synthesis);
4 Golgi apparatus package/modify; OR Carbohydrate added/glycoprotein produced by Golgi apparatus;
5 Vesicles transport OR Rough endoplasmic reticulum transports; - (Vesicles) fuse with cell(-surface) membrane;
Describe the differences between Eukaryotic and Prokaryotic cells (7)
Comparisons
1. Nucleotide structure is identical;
2. Nucleotides joined by phosphodiester bond;
OR Deoxyribose joined to phosphate (in sugar, phosphate backbone);
3. DNA in mitochondria / chloroplasts same / similar (structure) to DNA in prokaryotes;
Contrasts
4. Eukaryotic DNA is longer;
5. Eukaryotic DNA contain introns, prokaryotic DNA does not;
6. Eukaryotic DNA is linear, prokaryotic DNA is circular;
7. Eukaryotic DNA is associated with / bound to protein / histones, prokaryotic DNA is not;
State three differences between DNA in the nucleus of a plant cell and DNA in a prokaryotic cell (5)
**Plant v prokaryote
**1. (Associated with) histones/proteins v no histones/proteins;
2. Linear v circular;
3. No plasmids v plasmids;
4. Introns v no introns;
5. Long(er) v short(er);
The structure of a cholera bacterium is different from the structure of an epithelial cell from the small intestine. Describe how the structure of a cholera bacterium is different (7)
- Cholera bacterium is prokaryote;
- Does not have a nucleus/nuclear envelope/ has DNA free in cytoplasm/has loop of DNA
- No membrane-bound organelles/no mitochondria / no golgi/no endoplasmic reticulum (any 2 from)
- Small ribosomes only
- Capsule/flagellum/plasmid / cell wall (any 2 from)
Give one advantage of using a TEM rather than a SEM.
- Higher resolution;
- higher (maximum) magnification / higher detail (of image);
OR - Allows internal details / structures within (cells) to be seen / cross section to be taken;
Give one advantage of using a SEM rather than a TEM.
Thin sections do not need to be prepared / shows surface of specimen / can have 3-D images;
Scientists use optical microscopes and transmission electron microscopes to investigate cell structure. Explain the advantages and limitations of using a TEM to investigate cell structure (7)
**Advantages:
**1. Small objects can be seen;
2. TEM has high resolution;
3. Electron wavelength is shorter;
**Limitations:
**4. Cannot look at living cells;
5. Must be in a vacuum;
6. Must cut section / thin specimen;
7. Preparation may create artefact;
Scientists isolated mitochondria from liver cells. They broke the cells open in an ice-cold, buffered isotonic solution. Explain why the solution was:
a) Isotonic
b) Ice cold
c) buffered
- a) Prevents osmosis / no (net) movement of water So organelle/named organelle does not burst/shrivel;
- b) Reduce/prevent enzyme activity so organelles are not digested / damaged;
- c) Maintain a constant pH so proteins do not denature;
Describe and explain how cell fractionation and centrifugation can be used to isolate mitochondria from a suspension of animal cells (7)
- Cell homogenisation to break open cells and release organelles;
- Filter to remove (large) debris/whole cells;
- Use isotonic solution to prevent osmotic damage to mitochondria / organelles;
- Keep cold to prevent/reduce damage to organelles by enzyme;
- Use buffer to maintain pH and prevent protein/enzyme denaturation;
- Use differential Centrifuge (at high speed/1000 g) to separate nuclei / cell fragments / heavy organelles;
- Re-spin (supernatant / after nuclei/pellet removed) at higher speed to get mitochondria in pellet/at bottom;
- Observe pellet with a microscope to identify mitochondria;
Describe the structure of a phospholipid molecule and explain how phospholipids are arranged in a plasma membrane (3 marks).
- Glycerol joined to two fatty acid tails Phosphate group joined to glycerol on opposite side. (joined by condensation reaction with ester bond).;
- Phospholipid has hydrophilic head (phosphate and glycerol) and hydrophobic tails (fatty acid chains)
- Arrange to form a phospholipid bilayer; (Hydrophilic head facing out. Hydrophobic fatty acid chains facing in)
