Topic 1 - Genes And Enzymes

Question 1

What do animal and plant cells BOTH have and the purposes?

Answer 1

Nucleus- controls cell and contains all the DNA
Cytoplasm - gel like substance where most of the chemical reactions take place.
Cell membrane- holds the cell together and controls what goes in and out
Mithochondria- this is where the reactions for respiration take place
Ribosomes- where proteins are made

Question 2

Organelles that only the plant cells have?

Answer 2

Rigid cell wall- made of cellulose and gives the cell support
Large vacuole- contains cell sap, helps the cell keep its shape.
Chloroplasts- where photosynthesis occurs because it holds chlorophyll

Question 3

Bacteria cell organelles?

Answer 3

Chromosomal DNA- controls the cells activities and replication, no nucleus so floats free
Plasmid DNA- contain genes for things like drug resistance and can be passed between bacteria
Flagellum- long hair like structure that rotates to make the bacteria move
Cell is supported by a cell wall

Question 4

Magnification formula

Answer 4

Length of image divided by length of specimen

Question 5

What are the base pairs?

Answer 5

Adenine and thymine

Guanine and cytosine

Question 6

Describe the shape of DNA

Answer 6

Double helix
Has two strands held together by chemicals called bases
Bases are linked by weak hydrogen bonds

Question 7

What is a gene?

Answer 7

A section of DNA

Question 8

Who and how discovered shape of DNA

Answer 8

Rosalind Franklin and Maurice Wilkins discovered shape by bouncing beams of xrays off crystallised DNA and looking at the patterns the xrays formed
James Watson and Francis crick used idea that amount of a + t is equal to amount of c+g to create a model showing the structure

Question 9

Practical to extract DNA from cells

Answer 9

Chop onion
Put in beaker of detergent and salt
Detergent breaks down cell membranes, salt will make the DNA stick together
Beaker in 60°c water bath for 15minutes to denature enzymes that could break down the DNA
Beaker in ice to stop DNA from breaking down
Put in blender to break down cell walls and release DNA
Cool then filter
Add ice cold alcohol
DNA will come out of solution as its not soluble with the alcohol

Question 10

What does a gene contain?

Answer 10

The instructions to make a specific protein

Question 11

What are three bases called and what do they do?

Answer 11

A codon codes for one amino acid

Question 12

How does protein synthesis work?

Answer 12

Instructions need to get out of the nucleus
The DNA unzips
DNA is used as a template to make the mRNA
They use uracil instead of thymine. The mRNA is complementary to the DNA strand it’s based off. Once the mRNA is made, it’s called transcription.
The mRNA molecule moves out of the nucleus through the nuclear pore and joins with the ribosome. The ribosome reads the bases in a codon (three bases) tRNA is an anticodon. This is called translation. There’s one tRNA for each codon. The tRNA brings the appropriate amino acids in the right order to the ribosome. Ribosome links together the amino acids in the order given by mRNA to form a polypeptide (protein)

Question 13

What can mutations be!

Answer 13

Harmful- could cause a genetic disorder like cystic fibrosis or cancer
Beneficial- produce new characteristics that is beneficial to the organism e.g natural selection
Neutral- neither harmful nor beneficial

Question 14

What are enzymes?

Answer 14

Biological catalysts they’re made of proteins

Question 15

What is a catalyst

Answer 15

A substance which increases the speed of a reaction without being changed or used up in the reaction.

Question 16

What can enzymes be used for?

Answer 16

DNA replication
Protein synthesis
Digestion

Question 17

What is the substrate

Answer 17

The molecule being catalysed by the enzyme

Question 18

What is the active site of an enzyme?

Answer 18

The part that binds to the substrate to catalyse the reaction

Question 19

Enzymes only work on one substrate, what does this mean?

Answer 19

They have a high specificity for their substrate.

Question 20

Explain the lock and key theory

Answer 20

The substrate fits into its matching enzyme like a key fits into a lock. If the substrate doesn’t match the active site then the reaction won’t be catalysed

Question 21

What’s the experiment for rate of enzyme controlled reactions

Answer 21

Use amylase as the enzyme and starch as the substrate. Mix the amylase and starch together then take regular drops of the solution and put it into a spotting tile whilst timing. Add iodine solution, if it’s blue or black starch is still present. Record the time the solution no longer turns blue or black. You can have different factors affecting the reaction.

Question 22

What are the variables for the experiment?

Answer 22

Temperature- put test tubes into water bath at different temps
PH- pH buffers
Substrate concentration- vary conc. Of starch solution

Question 23

Temp results

Answer 23

Best around 37°c as body temp. To high enzyme denatures too low substrates lose energy and don’t collide with the enzymes. Increases with temp up to 37 because substrates gain energy and collide more.

Question 24

pH results

Answer 24

Each enzyme works in a different place so each enzyme has a different optimum pH. E,g stomach enzymes like acidic (HCL) too high or too low from the optimum means denaturing

Question 25

What is denaturing

Answer 25

When the shape of an enzyme is is changes so that the active site doesn’t fit the substrate anymore.

Question 26

Substrate conc. Results

Answer 26

The higher the substrate conc. The faster the rate of reaction. It will level off when the number of substrates matches or surpasses the number of enzymes available

Question 27

What is the human genome project?

Answer 27

Lots of scientists collaborate to try and find and order the 25000 human genes. Collab meant that genes were found more quickly and the data could be made public.

Question 28

Good part of human genome project

Answer 28

Predict and prevent diseases- if we knew what genes predisposed people to what disease then we could get individually tailored lifestyle plans to try and avoid it. Could cure things like cystic fibrosis
Develop new and better medicines
Accurate diagnosis
Improve forensic science- get a DNA fingerprint and in future could tell what the suspect looks like

Question 29

Bad parts

Answer 29

Increased stress- if you knew you were susceptible to something you would panic when you were only slightly I’ll.
Genesism- people affected would feel pressured to not have kids
Discrimination from employers and insurers- may not want to hire and insure these people

Question 30

How do people make human insulin using genetic engineering?

Answer 30

Human insulin gene is identified. Gene is cut from human DNA using enzymes. A loop of bacterial DNA is cut open. Human insulin gene is inserted into the bacterial cell. The bacterial cell produces insulin for humans. The transgenic bacterium is cloned to make lots of copies.

Question 31

What is genetic engineering?

Answer 31

The transfer of DNA from one organism to another

Question 32

How can it benefit humans?

Answer 32

Reducing vitamin a deficiency- beta carotene is used by our bodies to make vitamin a. Vitamin a deficiency can make you go blind. Golden rice is GM rice. It contains two genes from other organisms that make vitamin a.
Producing human insulin - through bacteria
Increasing crop yield - GM crops have genes that make them resistant to herbicides so fields can be sprayed and kill the weeds not the plants. There’s then less competition for resources

Question 33

Why do people worry about GM crops?

Answer 33

Will affect the number of weeds and flowers growing around the crops and will reduce farmland biodiversity
People think they’re unsafe to eat
Concerns transplanted genes will get into the weeds and create super weeds

Question 34

Why does mitosis happen?

Answer 34

To grow and repair.