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Edexcel Additional Biology > Topic 1 - Genes and Enzymes > Flashcards

Topic 1 - Genes and Enzymes Flashcards

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1
Q

What are the features of an animal cell ?

A

A nucleus, cytoplasm, cell membrane mitochondria and ribosomes.

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2
Q

Function of the nucleus ?

A

contains DNA and controls what the cell does.

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3
Q

Function of cytoplasm ?

A

gel like substance where most chemical reactions happen.

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4
Q

Function of cell membrane ?

A

holds cell together and controls what goes in and out of the cell.

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5
Q

Function of mitochondria ?

A

respiration takes place here which releases energy for the cell to work.

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6
Q

Function of ribosomes ?

A

all the proteins needed for the cell are synthesized here.

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7
Q

What 3 extra features does a plant cell have and what are their functions ?

A

rigid cell wall : made of cellulose and gives support.
Large Vacuole : contains cell sap , a weak solution of sugar and salts
Chloroplasts: contain chlorophyll and photosynthesis occurs here.

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8
Q

What features does a bacterial cell have ?

A

Chromosomal DNA , Plasmids, flagellum and cell wall.

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9
Q

Role of Chromosomal DNA ?

A

Chromosomal DNA controls cells activities and replication. It floats free in the
cytoplasm.

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10
Q

Role of plasmids ?

A

Small loops of extra DNA that aren’t part of the chromosome.

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11
Q

Role of flagellum ?

A

long, hair like structure that rotates to move the bacterium.

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12
Q

Role of cell wall ?

A

supports the cell.

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13
Q

When was the light microscope invented and how much magnification does it have ?. What does it enable us to see ?

A

invented in the 1590’s and has x1500 magnification. we can see things like nuclei,chloroplasts and mitochondria.

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14
Q

When was the electron microscope invented and how much magnification does it have ?. What does it enable us to see ?.

A

invented in the 1930s and has x2,000,000 magnification. We can see things smaller things like plasmids.

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15
Q

Magnification formula ?

A

m= image/actual

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16
Q

What is DNA ?

A

A double Helix of paired bases of Adenine to Thymine and Guanine to Cytosine. Bases are joined together by weak hydrogen bonds.

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17
Q

What is a gene ?

A

a gene is a section of DNA and the sequence of bases in a gene code for a specific protein

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18
Q

How and who discovered the structure of DNA?

A

Franklin and Wilkins directed beams of x-rays onto crystallised DNA and looked at the patterns the x-rays formed as they bounced off. Watson and Crick made a model of DNA using the idea that the amount of adenina and guanine matched the amount of thymine and cytosine.

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19
Q

How to extract DNA from cells ?

A
  1. chop up onion and put it in a solution of detergent ( to break down cell membrane ) and salt ( to stick DNA together ) in a beaker.
  2. put beaker in 60 c for 15 mins to denature enzymes that could digest DNA and soften cells.
  3. put beaker in ice to cool to stop DNA from breaking down
  4. once ice cold, put solution in blender to break open cell walls and release DNA
  5. cool mixture again then filter to get froth and big bits of cell out
  6. add ice cold alcohol to solution. DNA will come out of solution because it isn’t soluble. it will appear as a stringy white substance which can be taken out using glass rod.
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20
Q

What does DNA determine ?

A

what genes are switched off. therefore which proteins the cell produces which in turn determines what kind of cell it is.

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21
Q

Describe Transcription ( stage 1 in protein synthesis ) ?

A
  1. DNA unravels to show bases
  2. complementary free bases attach to the unraveled DNA to form mRNA.
  3. mRNA goes through the nuclear pores into the cytoplasm.
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22
Q

Describe Translation ( stage 2 in protein synthesis )?

A
  1. mRNA attaches to ribosome in cytoplasm
  2. the codon is read in triplets
  3. the complementary tRNA brings a certain amino acid to the ribosome
  4. the amino acids join to the mRNA to make a polypeptide
  5. eventually a stop codon forms and the polypeptide breaks off and folds. This is now a protein.
23
Q

Are mutations always harmful ?

A

No, they can cause genetic disorders like Cystic fibrosis but they can also be beneficial by producing a beneficial new characteristic. Sometimes the mutations are neutral as they don’t affect a protein’s function.

24
Q

Define a catalyst ?

A

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

25
Q

What are enzymes specific to ?

A

temperature , pH and the substrate it works on.

26
Q

Give 3 examples where enzymes are used ?

A

DNA replication : enzymes copy cells DNA before it divides by mitosis or meiosis.
Protein synthesis : enzymes hold amino acids in place and form bonds between them.
Digestion : enzymes are secreted in the gut to digest food molecules.

27
Q

How do enzymes work ?

A
  1. the substrate sucrose consists of glucose and fructose bonded together.
  2. the substrate binds to the enzyme forming an enzyme substrate complex.
  3. the binding of the substrate and enzyme places stress on the glucose-fructose bond and the bond breaks
  4. products are released and the enzyme is free to bind other substrates.
28
Q

How do enzymes work in biological washing powders ?

A

Biological washing powders contain enzymes that break down the insoluble stain into smaller soluble substances, which are then dissolved in the water.
For example, if your shirt gets stained by egg yolk or blood, there is an enzyme called protease in the washing powder that will break down the insoluble protein into amino acids, which are dissolved in the water and sucked away. Thus the shirt becomes clean.

29
Q

experiment for measuring an Enzyme- controlled reaction ?

A
  1. Amylase catalyses the breakdown of starch, so you can time how long it takes for the starch to disappear.
  2. put drops of amylase and starch mixture into a drop of iodine solution on a spotting tile.
  3. record color change - it will turn blue black if starch is present.
  4. record the time when the iodine solution no longer turns blue black as this is when all the starch has been broken down.
  5. use times to compare reaction rates under different conditions
30
Q

what are the variables for measuring the rate of an enzyme controlled reaction ?

A
  1. temperature : put test tubes in water baths at a range of temperatures
  2. pH : use a range of pH buffers
  3. substrate concentration : vary initial concentrations of starch solution.
31
Q

Describe enzymes / temperature graph ?

A

changing temperature changes rate of enzyme-catalysed reaction. High temp increases rate because the particles have more energy. If it gets too hot , the bonds holding the enzyme together breaks, resulting in the enzyme losing its shape so its active site doesn’t fit the shape of the substrate so the reaction stops. the enzyme is denatured and won’t go back to its original shape. Optimum temp for most enzymes is 37 degrees.

32
Q

Describe enzymes/pH graph ?

A

if it is too high or low , it interferes with the bonds and this changes the shape of the active site and denatures the enzyme. optimum pH is often pH7 but pH of 2 in the stomach.

33
Q

Describe enzyme/ substrate graph ?

A

higher the substrate concentration , the faster the reaction because its more likely the enzyme will meet up and react with a substrate molecule. eventually all the active sites are full and adding more makes no difference.

34
Q

Concept of Human Genome Project ?

A

To find every single human gene through world wide collaboration of scientists , thus resulting in the genes being located in quicker time and the data being made public.

35
Q

advantages of HGP ?

A

predict and prevent disease
develop new and better medicines
accurate diagnoses
improve forensic science

36
Q

disadvantages of HGP ?

A

increased stress
gene-ism
discrimination by employers and insurers

37
Q

How can a plasmid be genetically modified to produce human insulin ?.

A
  1. plasmid is extracted and cut by a restriction enzyme
  2. human insulin gene inserted into plasmid by the ligase enzyme
  3. modified plasmid inserted to new bacteria
  4. bacteria is grown in large fermentation vessels and starts dividing and producing insulin.
  5. once fermentation is completed, the bacteria is harvested, filtered off and broken open to release the insulin they have produced.
38
Q

How do we reduce Vitamin A deficiency ?

A

Lack of vitamin A can result in blindness due to its role in phototransduction. These deficiencies particularly affect children , impairing their immune system and diminishes their ability to fight infections. Many people have vitamin A deficiency are in LEDC’s , they can not combat these deficiencies through a varied diet. Therefore Golden Rice , a variety of GM crops, was designed to produce beta-carotene in the edible part of the rice , the endosperm.

39
Q

How to produce herbicide resistant crops ?

A

Many crops have been GM to be resistant to non-selective herbicides. These crops contain genes that enable them to degrade the active ingredient in an herbicide, Farmers can easily control weeds during the entire growing season , thus increasing crop yeild

40
Q

Disadvantages of Genetic Engineering ?

A

unnatural, people are worried they may develop allergies to the food.
reduces biodiversity , through the decrease in flowers and weeds therefore reducing species in an eco system.
transplanted genes may get out into natural environment which could create a new variety of superweed.

41
Q

What is Mitosis ?

A

mitosis is used for growth and repair. It creates two daughter cells which are genetically identical to original cell. It involves one division and takes place in all body cells.

42
Q

Explain the process of Mitosis (asexual reproduction)

A
  1. The cell replicates itself so there is one copy for each new cell, each chromatid is an exact replicate of the other
  2. the nuclear membrane breaks down and a spindle forms whereby the chromosomes line up at the equator side by side and the cell fibers pull them apart. The chromatids separate and go to the poles of the cell
  3. Nuclear membrane reforms around each set of chromosomes.
  4. cytoplasm pinches in and two new diploid cells which are genetically identical are formed.
43
Q

Define asexual reproduction ?

A

asexual reproduction uses mitosis because there is only one parent and the offspring therefore have exactly the same genes as the parent, therefore are clones. E,g strawberry plants and potatoes.

44
Q

What is Meiosis ?

A

Meiosis is used for producing gametes. It creates 4 daughter cells which are genetically different to original cell because they are haploid. It involves two divisions and takes place in reproductive organs.

45
Q

Explain the process of Meiosis ? (sexual reproduction )

A
  1. The cell replicates so each chromatid is an exact copy of the other.
  2. Nuclear membrane breaks down a spindle forms whereby the chromosomes line up at the equator on top of eachother and the cell fibres pull them apart. The chromosomes separate and go to the poles of the cell.
  3. membrane reforms , cytoplasm pinches in and the 2 new cells have a mixture of both mum and dad’s chromosomes as mixing up the alleles creates variation.
  4. in the second division chromosomes line up at the equator again , then chromatids are pulled apart.
  5. finally , you get four haploid cells each with only a single set of chromosomes in it.
46
Q

Stages of Cloning ?

A
  1. First enucleate an unfertilised egg cell
  2. Take Nucleus out of diploid adult body cell.
  3. insert diploid nucleus into empty egg cell
  4. stimulate egg cell to divide by mitosis by giving it an electric shock.
  5. once embryo is a ball of cells , implant it into a surrogate mother to grow into a genetically identical copy of the original adult body cell.
47
Q

Uses of Cloning ?

A

genetically modified pigs are being bred which could provide suitable organs for humans, this would help meet the demand for organ transplants.
can lead to greater understanding of the development of the embryo and of ageing and age related disorders.
could help preserve endangered species.

48
Q

Disadvantages of cloning ?

A

reduce gene pool as there would be fewer different alleles in a population
a new disease could wipe out a closely related population because they had no allele that gave them resistance to the disease
cloning can take hundreds of attempts to succeed.
clones are often born with genetic defects
cloned mammals immune systems are sometimes unhealthy.

49
Q

What is meant by the ‘differentiation of cells’ ?

A

It is the process of stem cells becoming specialised. It is by this process that the embryo starts to develop a recognisably human body with organs and systems.

50
Q

What is the difference between embryonic stem cells and normal stem cells ?

A

embryonic stem cells can divide into any type of cell whereas stem cells found in places such as in the bone marrow can only differentiate into certain types of cells.

51
Q

Can plants and animals differentiate ?

A

Animals lose the ability to differentiate at an early stage but plant cells never lose this ability.

52
Q

Uses of Stem Cells ?

A

treat diseases like sickle cell anaemia through a bone marrow transplant, containing adult stem cells which produce new blood cells.
create specialised cells to replace those that are damaged by disease or injury e.g new cardiac muscles to help someone with heart disease.
skin graft : grow skin cells

53
Q

Ethical concerns with Stem Cell research ?

A

Embryos are potential human life
playing god
alter natural population
commercially exploited

54
Q

Describe how you transplant a windpipe ?

A
  1. Trachea is removed from dead donor
  2. flushed with chemicals to remove all existing cells
  3. coated with stem cells from the patient’s hip bone marrow. Cells from the airway lining is added.
  4. once cells have grown after about 4 days donor trachea is inserted into patient’s bronchus.

Edexcel Additional Biology (3 decks)

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