Topic 1 - Key Concepts in Biology

Question 1

What is an electron microscope?

Answer 1

They use electrons rather than light to produce higher magnification and resolution than light microscope. Allowed to understand better how cells and subcellular structures work.

Question 2

What is meant by instruments resolution?

Answer 2

How well a microscope distinguishes between two points that are close together.

Question 3

How can cell structures (some) only be seen with an electron microscope but not light microscope?

Answer 3

Due to electron microscopes having a higher resolution than light microscopes, it allows us to see greater details of internal structure of mitochondria and chloroplasts.

Question 4

What is the magnification formula? (Total magnification)

Answer 4

Eyepiece lens magnification x objective lens magnification.

Question 5

What is magnification formula including sizes?

Answer 5

Image size / real size

Question 6

What is the order of units starting with millimetre and how do we reach next level down?

Answer 6

Millimetre x 1000 micrometre x nanometre x 1000 picometre multiply to go down / to go up

Question 7

Name parts in a plant cell

Answer 7

Cell wall, large permanent vacuole, chloroplasts, mitochondria, nucleus, ribosomes, cytoplasm, cell membrane.

Question 8

Name parts of animal cells

Answer 8

Cell membrane, nucleus, ribosomes, cytoplasm, mitochondria

Question 9

Recall the purposes of sub-cellular structures of: Nucleus

Answer 9

Contains genetic material

Question 10

Recall the purposes of sub-cellular structures of: Cytoplasm

Answer 10

Where chemical reactions take place

Question 11

Recall the purposes of sub-cellular structures of: Vacuole

Answer 11

Weak solution of sugar and salts and keeps internal structure

Question 12

Recall the purposes of sub-cellular structures of: Ribosomes

Answer 12

Translation of genetic material in synthesis of proteins

Question 13

Recall the purposes of sub-cellular structures of: Mitochondria

Answer 13

Reactions for respiration take place

Question 14

How are sperm cells adapted for their function?

Answer 14

• Lots of mitchondria to provide energy for respiration needed to swim the distance
• Has an acrosome at front of head where enzymes are stroed to break through membrane of the egg cell
• Haploid nucleus
• Tail/flagellum to swim to egg

Question 15

How are egg cells adapted to their function?

Answer 15

• Nutrients in cytoplasm feed the embryo
• Haploid nucleus
• after fertilisation, membrane changes structure to stop any more sperm getting in so embryo has right amount of DNA

Question 16

How are ciliated epitherial cells adapted for their function?

Answer 16

• Cilla hair-like structures on surface to move substances in one direction along survace (like mucus)
• Large surface area to take in nutrients
• Hairs stop mucus getting into lungs

Question 17

What are the common parts of a bacteria cell?

Answer 17

Flagellum to power along away from harmful toxins and towards nutrients and oxygen. Ribosomes, cell membrane, chromosomal DNA, PLasmid DNA for replication (small loops of extra DNA contains genes for drug resistance)

Question 18

Why are bacteria prokoryotic?

Answer 18

Because it has no nucleus

Question 19

What’s the difference between prokoryotic and eukoryotic cells?

Answer 19

Eukoryotic cells have a nucleus, prokoryotic are single celled organisms

Question 20

What are enzymes?

Answer 20

Proteins made from amino acids. It is a biological catalyst.

Question 21

What are the substrate concentrations of: Carbohydrates?

Answer 21

(Carbohydrases) carbohydrates to simple sugars amalyase

Question 22

What are the substrate concentrations of: Proteins?

Answer 22

(Proteases used) amino acids

Question 23

What are the substrate concentrations of: Lipids?

Answer 23

(Lipases) glycerol and fatty acids

Question 24

What does an enzyme do?

Answer 24

Break down large molecules by speeding up the rate of a reaction for growth and life processes

Question 25

How do we test for starch (a carbohydrate) in food?

Answer 25

Iodine test: positive = black, negative = brown/red

Question 26

How can we test for sugars in food?

Answer 26

Benedict reagent: positive = brick red ranges to negative = blue (take sample and add to hot water bath 75ºC

Question 27

How can we test for proteins in food?

Answer 27

• Biuret Test is used for proteins, first add potassium hydroxide to make it alkaline then add copper sulfate solution (blue)
• If no protein it stays blue (negative)
• If there is it turns purple (positive)

Question 28

How can we test for lipids?

Answer 28

Emulsion test - Take sample and shake to mix with ethanol for a minute so it dissolved then pour into water

• Positive = milky emulsion (precipitate)
• Negative = clear

Question 29

How can we use calorimetry to measure the energy in food?

Answer 29

• First get food sample which burns easily (dry)
• Weigh the food and skewer it on a needle and hold under boiling tube
• Add set volume of water to boiling tube and measure initial temperature of water
• Set fire to food sample and heat boiling tube with it until burnt out
• Measure water again and use formula:
  Energy in food (J) = Mass of water x temp change x 4.2

Question 30

What does enzyme specificity mean?

Answer 30

Enzymes only work with one substrate which they have a high specificity for. The substrate is the molecules changed in a reaction

Question 31

What is an active site? (Explain the role)

Answer 31

Every enzyme has an active site where the substrate joins it to catalyse the reaction. The substrate has to fit into the active site and if it doesn’t fit, the reaction wont be catalysed. This is called a lock and key mechanism.

Question 32

How can an enzyme become denatured?

Answer 32

An enzyme can be denatured if the temperature is too high (above 40ºC) or pH is too high or low. This is usually pH7 (neutral) but some enzymes are optimum at pH2 (acidic conditions).

Question 33

What is the effect of substrate concentration on enzymes?

Answer 33

The higher the substrate concentration, the faster the reaction as more likely enzyme will meet with substrate molecules. This is only up to a point as after certain point, all active sites are full so forms a plateau.

Question 34

What is the formula for enzyme activity?

Answer 34

Rate = 1000 / time

Question 35

What are the 3 processes which transport substances around an organism?

Answer 35

• Diffusion - net movement of particles from an area of higher concentration to lower concentration (down concent. gradient)
• Osmosis - net movement of water molecules across a partially permeable membrane from a region of high to low centration of water
• Active transport - movement of particles across membrane for a low to high concentration using energy transferred during respiration (against concentration gradient).

Question 36

What is the effect of osmosis on cells and tissues?

Answer 36

Plant cells have rigid cell wall and when plant placed in hypotonic solution, it takes up water by osmosis and starts to swell but cell wall stops it bursting.

Question 37

How can we investigate osmosis with potatoes?

Answer 37

• Get sucrose solution in ranging concentration from pure water to very concentrated sucrose
• Use a potato corer to have evenly sized potato cores
• Use mass balance to measure mass before then place into test tubes of different concentrations and leave for 40mins
• Then remove and pat dry and measure mass again (for accuracy)
• Then work out percentage change = difference mass / original x 100