biology - topic 1: cell level systems

What is the definition for magnification?

The degree to which the size of an image is larger than the real object.

What is the definition for resolution?

The ability to distinguish between two points that are close to each other.

What is the process of setting up a microscope?

1. Place the slide onto the stage.

2. Turn on the microscope, so light passes through the slide.

3. Select the lowest powered objective lens, which is usually x4.

4. Look down the eyepiece lens and turn the coarse focus knob, to bring the image roughly into focus. This increases the distance between the objective lens and the slide

5. Adjust the fine focusing knob, to bring the image into focus, producing a clear image.

6. To observe the sample with higher magnification, move the objective lenses, so that an objective lens with a higher magnification power clicks into place.

7. After switching to a different objective lens, you can readjust the focus by using the coarse focus and fine-focusing knobs.

What are the parts of a microscope?

What are the advantages of light microscopes?

They are cheap, do not require specialist training, and can look at living specimens.

What are the disadvantages of light microscopes?

Low resolution (due to the wavelength of visible light), low magnification strength, and staining is required to help see the organelles present.

What are the advantages of electron microscopes?

Can see very small cells and can produce 3D images.

What are the disadvantages of electron microscopes?

Extremely expensive, very large, hard to move, and require specialist training/skills.

What are the structures in both an animal and plant cell, and what are their functions?

Nucleus - Contains the genetic material.

Cytoplasm - Liquid substance where chemical reactions occur.

Cell Membrane - Controls what enters & leaves the cell.

Mitochondria - Aerobic respiration occurs here, provide energy for the cell.

Ribosomes - Where protein synthesis occurs.

What are the three structures in only a plant cell, and what are their functions?

Chloroplasts - Where photosynthesis takes place, which provides food for the plant.

Permanent Vacuole - Contains cell sap.

Cell wall - Helps maintain the cell’s structure.

In plasmid (bacteria) cells, what are plasmids?

Small rings of DNA.

What is a nucleotide and what is it composed of?

The fundamental building of nucleic acids (DNA and RNA). It’s composed of a base, a sugar, and a phosphate group.

What are the four bases of a nucleotide and what are their complimentary base pairs?

Adenine (A), Cytosine (C), Thymine (T), Guanine (G):

A=T

C=G

What are chromosomes?

Chromosomes are made up of long molecules of DNA.

What are the steps of protein synthesis?

Transcription:

• DNA double-helix is ‘unzipped’.

• mRNA nucleotides match to their complimentary base pairs.

• These nucleotides join together to form a template strand of the DNA.

Translation:

• The strand moves into the cytoplasm.

• At the ribosomes, the bases are read in triplets to form the codes for one amino acid.

• It is therefore the triplet code that decides which protein is produced.

What are enzymes?

Enzymes are biological catalysts (speed up a reaction without taking part in it/being used up).

What is denaturation?

The permanent change in an enzyme’s active site that stops the enzyme functioning correctly.

What is the lock and key hypothesis?

Relates to the functions of enzymes: the enzyme is a particular shape (like a lock), so the substrate must be exactly the perfect shape (like a key for the lock) to fit into the active site.

What four things affect the rate of an enzyme reaction?

1. Temperature - Enzyme can become denatured since, when the temperature is too hot, the substrate won’t fit in the active site.

2. pH - Enzyme can become denatured if pH is too high/low.

3. Substrate Concentration - After a while increasing this will not have any affect because the active sites of the enzymes present are full.

4. Enzyme Concentration - After a while increasing this will cause the reaction to stop because not enough substrate molecules can react with all the enzymes

What is the symbol and word formula for aerobic respiration?

C6H12O6 + 6O2 → 6CO2 + 6H2O

Glucose + Oxygen → Carbon Dioxide + Water + ATP

What is the word formula for anaerobic respiration?

In animals: Glucose → Lactic Acid + ATP

In plant/yeast cells (fermentation): Glucose → Ethanol + Carbon Dioxide + ATP

What is the equation for photosynthesis?

6CO2 + 6H2O → C6H12O6 + 6O2

Carbon Dioxide + Water → (light) Glucose + Oxygen

What is the test for sugars?

Benedict’s Test: red/brown precipitate.

What is the test for starch?

Iodine Solution: Blue/black colour.

What is the test for proteins?

Biuret Test: Purple colour

What is the test for fats?

Emulsion Test: Cloudy liquid

What is a eukaryotic cell?

A type of cell found in plants and animals that has a nucleus and other membrane-bound organelles.

What is a prokaryotic cell?

A unicellular organism that lacks a nucleus and other membrane-bound organelles.

What is a limiting factor?

A factor that, when in inadequate supply, limits the rate of reaction