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

Biology Topic 1 - Genes and Enzymes Flashcards

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1
Q

What four things are there in both an animal and a plant cell?

A
  • Nucleus
  • Cytoplasm
  • Cell Membrane
  • Mitochondria
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2
Q

What three things are only found in plant cells?

A
  • Rigid Cell Wall
  • Large Vacuole
  • Chloroplasts
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3
Q

What is the role of the nucleus in plant and animal cells?

A

Contain the cell’s DNA, and it is the DNA (and therefore the nucleus) that controls what the cell does.

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4
Q

What is the role of cytoplasm in plant and animal cells?

A

It’s a gel-like substance where the chemical reactions of the cell occur.

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5
Q

What is the role of the cell membrane in plant and animal cells?

A

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

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6
Q

What is the role of the mitochondria in plant and animal cells?

A

Where the reactions for respiration takes place. It therefore releases energy to make the cell work.

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7
Q

What is the role of the cell wall in plant cells?

A

Gives support to the cell. Made of cellulose.

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8
Q

What is the role of the vacuole in plant cells?

A

Contains cell sap - the weak solution of sugars and salts. [Store of plant’s glucose for respiration.]

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9
Q

What is the role of the chloroplast in plant cells?

A

Where photosynthesis occurs, as it contains a green substance called chlorophyll.

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10
Q

What are the four features of a bacterial cell?

A
  • Chromosomal DNA
  • Plasmids
  • Flagella (sing. flagellum)
  • Cell Wall
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11
Q

What is the role of the chromosomal DNA in a bacterial cell?

A

It’s one long circular chromosome, which controls activities and replications of the cell. It floats free in the cytoplasm (and not in a nucleus).

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12
Q

What is the role of the plasmids in a bacterial cell?

A

They’re small loops of extra DNA that aren’t part of the chromosome. They contain genes for things like drug resistance, and can be passed between the bacteria.

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13
Q

What is the role of the flagella in a bacterial cell?

A

Long, hair like structure [out the back of the cell] which rotates to make the bacteria move.

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14
Q

What is the role of the cell wall in a bacterial cell?

A

To support the cell.

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15
Q

What is the word equation for magnification?

A

length of image/length of specimen

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16
Q

What is the use of a microscope?

A

To let us see things we can not see with the naked eye.

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17
Q

Describe the use of a light microscope.

A

Invented in 1590s. Let us see things like nuclei chloroplasts, mitochondria.

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18
Q

Describe the use of an electron microscope.

A

Invented in 1930s. Let us see much smaller things in more detail like internal structure of mitochondria and chloroplasts, and tinier things like plasmids.

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19
Q

Describe the structure of DNA.

A
  • DNA molecule has two strands coiled together in a double helix.
  • Two strands are held together by chemicals called bases: adenine (A), cytosine (C), guanine (G), and thymine (T).
  • Always paired A-T and G-C.
  • Base pairs are joined together by weak hydrogen bonds.
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20
Q

What is a gene?

A

A gene is a section of DNA. The sequences of bases in a specific gene code for a specific protein.

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21
Q

What is a set of three bases called and what does it do?

A

Triplet. Codes for a specific amino acid.

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22
Q

How many different amino acids are there?

A

20

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23
Q

What determines whether genes are switched on or off?

A

DNA (therefore which protein the cell produces, and which type of cell is produced)

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24
Q

What organelle makes protein?

A

Ribosomes

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25
Q

Why can the DNA in the nucleus not be used in the ribosome?

A

It is too big to get out of the nucleus.

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26
Q

What is a mutation?

A
  • A change in an organism’s DNA base sequence.
  • Could affect sequence of amino acids in the protein, changing the protein’s function.
  • Could affect an organism’s characteristics.
  • Can be harmful, beneficial or neutral.
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27
Q

Explain how a mutation could be harmful.

A

Could cause a genetic disorder, like cystic fibrosis.

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28
Q

Explain how a mutation could be beneficial.

A

Could produce new characteristics which is beneficial for the organism, eg. mutations in genes on bacterial plasmids can make them resistant to antibiotics.

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29
Q

Explain how a mutation could be neutral.

A

Can be neither harmful nor beneficial, do not affect a protein’s function.

30
Q

What is a catalyst?

A

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

31
Q

Give an example of a biological catalyst.

A

Enzymes, reduce need for high temperatures as they speed up reaction. Only enzymes speed up chemical reactions in the body.

32
Q

How are enzymes used in DNA replication?

A

Help copy a cell’s DNA before it divides by mitosis or meiosis.

33
Q

How are enzymes used in protein synthesis?

A

Hold amino acids in place and form bonds between them.

34
Q

How are enzymes used in digestion?

A

Various enzymes are secreted into the gut to digest different food molecules.

35
Q

Describe how enzymes speed up reactions through the lock and key method.

A
  • Every enzyme has an active site; area which joins on to a substrate to catalyse the reaction.
  • Usually only work with one substrate; have high specificity for their substrate.
  • For enzyme to work, substrate has to fit into the active site.
  • Substrate forms products after catalyzed.
  • Called lock and key as substrate fits into active site like key into lock.
36
Q

Explain how changing temperature changes the rate of an enzyme-catlysed reaction.

A
  • Higher temperature increases rate at first, as more heat = enzymes + substrate particles have more energy; move more so more likely to interact + react.
  • If gets too hot, bonds holding enzyme together break, making it lose shape so that the substrate can’t fit in active site + reaction stops meaning enzyme is denatured.
  • Each enzyme has optimum temperature at which reaction goes fastest, just before the enzymes get too hot and denature.
37
Q

What does it mean for an enzyme when it becomes denatured?

A

The enzyme won’t go back to its original shape even when the temperature cools.

38
Q

Describe the graph showing the relationship between the temperature and the rate of reaction

A
  • x axis = temperature; y axis = rate of reaction.
  • The graph climbs at a steady rate until it reaches the optimum temperature (37ᵒC) and then falls steeply if the temperature continues to rise.
39
Q

Explain how changing pH changes the rate of an enzyme-catlysed reaction.

A

If pH is too high or to low it interferes with the bonds that hold the enzymes together. This changes the shape of the active site thus denaturing the enzyme. All enzymes have an optimum pH, often pH 7 (neutral)

40
Q

Describe the graph showing the relationship between the pH and the rate of reaction

A
  • x axis = pH; y axis = rate of reaction.
  • Graph follows pattern similar to normal distribution curve with the peak at optimum (often pH 7).
  • e.g. pepsin (in stomach for breaking down proteins) works best at pH2 so well suited to the acidic conditions in the stomach. Graph for pepsin would peak at pH2.
41
Q

Explain how changing substrate concentration changes the rate of an enzyme-catlysed reaction.

A
  • Higher substrate concentration = faster reaction as more likely enzyme will encounter a substrate molecule.
  • Only true up to point when every active site is full - more substrates after this make no difference.
42
Q

Describe the graph showing the relationship between the substrate concentration and the rate of reaction

A
  • x axis = substrate concentration; y axis = rate of reaction.
  • Graph climbs at steady rate until it reaches optimum substrate concentration when all active sites full + then levels out at that point.
43
Q

Describe the human genome project.

A
  • Thousands of scientists worldwide collaborated to find every single human gene.
  • Human DNA is made up of around 25000 genes curled up into 23 chromosomes.
  • The collaboration meant the genes were found more quickly.
44
Q

List the pros of the human genome project.

A
  • Predict and prevent diseases
  • Develop new and better medicines
  • Accurate diagnoses
  • Improve forensic science
45
Q

Explain how the human genome project helped predict and prevent diseases.

A
  • Individually tailored advice on diet/lifestyle to avoid likely problems.
  • Doctors could check regularly for diseases we are susceptible to.
  • Cures could also be found for genetic disorders like cystic fibrosis and sickle cell anaemia.
46
Q

Explain how the human genome project helped develop new and better medicines.

A
  • Could help to make medicines designed for us, based on the way we would react to the disease and possible treatments.
  • Could help design more effective treatments.
47
Q

Explain how the human genome project helped accurate diagnoses.

A

Some diseases are difficult to test for (eg Alzheimer’s), but if we know genetic cause, accurate testing would be easier.

48
Q

Explain how the human genome project helped improve forensic science.

A

Can produce a DNA fingerprint from biological material found at a crime scene. If matches person’s DNA, they were almost certainly there.

49
Q

List the cons of the human genome project.

A
  • Increased stress
  • Pressures towards people with certain genes
  • Discrimination by employers and insurers
50
Q

Explain how the human genome project could cause increased stress.

A

For example, if a person know they’re susceptible to a brain disease, they could panic every time they get a headache.

51
Q

Explain how the human genome project could cause pressures towards people with certain genes.

A

People with genetic problems could have pressures like not having children.

52
Q

Explain how the human genome project could cause discrimination by employers and insurers.

A
  • Life insurance could be difficult to get if have genetic likelihood of getting a serious disease.
  • Employers may not want someone who could get a serious disease [unemployed because of potential time off].
53
Q

Explain how genetic engineering takes place.

A
  • Useful gene is ‘cut’ from an organism’s chromosomes using (restriction) enzymes.
  • Enzymes then used to cut another organism’s chromosomes + insert useful gene.
  • Produces genetically modified organisms (GMOs).
54
Q

Explain how genetic engineering can be used to reduce vitamin A deficiency.

A
  • Beta-carotene used by our bodies to make vitamin A.
  • Deficiency in it can cause blindness.
  • Golden rice is a variety of GM rice.
  • Contains two genes from other organisms so it can produce beta-carotene.
  • So reduces deficiency as more people get the necessary vitamin A.
55
Q

Explain how genetic engineering can be used to produce human insulin.

A

The human insulin gene can be inserted into bacteria to produce human insulin, meaning lots of human insulin can be produced quickly and cheaply.

56
Q

Explain how genetic engineering can be used to increase crop yield.

A
  • GM crops have their genes modified, like to become resistant to herbicides.
  • Fields of these crops can be sprayed with herbicide and only the GM crops will survive, therefore increasing the crop yield.
57
Q

Why is genetic engineering controversial?

A
  • Some say can affect number of weeds + flowers (wildlife) in areas around crops, so reducing farmland biodiversity (no. of species in an ecosystem).
  • Some believe GM crops not safe + could develop allergies to the food (although no more dangerous than ordinary foods).
  • Transplanted genes may get out into natural environment e.g. herbicide resistant gene picked up by weeds so not killed by herbicide.
58
Q

What is a diploid? Give an example.

A

(A cell having) Two versions of each chromosome - one from each parent - forming 23 PAIRS of chromosomes.

59
Q

When is mitosis used?

A

Growing and replacing damaged cells, and for asexual reproduction. It creates two diploid cells with the same DNA - they are genetically identical.

60
Q

Explain the process of mitosis.

A
  • When DNA not dividing, spread out in long strings.
  • When cell gets signal to divide, duplicates DNA, + forms ‘X’ shaped chromosomes. Each side is exact duplicate of other.
  • Chromosomes line up in centre of cell + cell fibres pull them apart. Each side of chromosome go to opposite ends of the cell.
  • Membranes form around each set of chromosomes, becoming nuclei of two new cells.
  • Lastly, the cytoplasm divides.
61
Q

Explain what asexual reproduction is.

A

Organisms reproducing through mitosis e.g. strawberry plants from runners. The offspring have the same gene as the parent, so there’s no genetic variation.

62
Q

What does haploid mean and give examples?

A

A haploid is a cell with only one copy of each chromosome (e.g. gametes; sperm and egg cells (ova) so that when the gametes combine in ferilisation the resulting cell has the diploid number of chromosomes (zygote).

63
Q

What is the difference between zygote and gametes?

A

Zygotes are diploid, gametes are haploid. All cells are zygote apart from sex cells.

64
Q

Explain the process of meiosis.

A
  • Like mitosis, before division, DNA duplicated
  • Then, in 1st division, chromosomes line up in centre of cell.
  • Then pulled apart so each new cell has only one copy of each new chromosome; some of the father’s + some of the mother’s so into each new cell.
  • Mixes up the alleles causing variation in the different offspring.
  • ^Advantage of sexual reproduction over asexual reproduction.
  • In 2nd division, chromosomes again line up in centre.
  • Arms of each of the chromosomes pulled apart creating 4 haploid gametes each with only a single set of chromosomes.
65
Q

What is cloning?

A

Cloning is a type of asexual reproduction producing cells genetically identical to the original cell.

66
Q

Explain the process of cloning

A
  • Adult cell cloning involves taking unfertilised egg cell + removing its nucleus (enucleated).
  • Nucleus taken from adult body cell (e.g. skin); diploid nucleus with the standard number of chromosomes.
  • Inserted into the ‘empty’ egg cell.
  • Egg is stimulated by electric shock making it divide by mitosis like a normal embryo.
  • When embryo is a ball of cells it’s then implanted into female surrogate to grow a genetically identical copy of original adult body cell.
  • This is how dolly the sheep was cloned.
67
Q

Uses of cloning

A

Good:

  • Cloning mammals could help with the shortage of organs for transplants
  • Studying animal clones could lead to a greater understanding of the development of the embryo and of ageing and age related disorders
  • Preserve endangered species

Issues:

  • Reduced gene pool leading to fewer alleles in the population. e.g. a disease could wipe out a species.
  • Cloned mammals may not live as long (Dolly only lived for 6 years).
  • Other risks include repeated failure of the cloning exercise; cloned mammal often born with genetic defects; immune systems are sometimes unhealthy so suffer more diseases
68
Q

What is an embryonic stem cell?

A
  • A fertilised egg can divide by mitosis to produce a bundle of cells the embryo of a new organism
  • Firstly, the cells in the embryo are identical (undifferentiated) - embryonic stem cells
  • Stem cells can divide to produce more stem cells or different types of specialised cells, e.g. blood cells
  • The process of a stem cell becoming specialised is called differentiation. It is by this process the embryo starts developing recognisable human body organs and systems.
  • In most animal cells the ability to differentiate is lost at an early stage but lots of plants don’t ever lose this ability.
  • Adult humans only have stem cells in certain places like bone marrow. These aren’t as versatile as embryonic stem cells and can only differentiate into certain types of cells.
69
Q

What is an adult stem cell?

A
  • Doctors already use adult stem cells to cure some diseases, e.g. sickle cell anemia can sometimes be cured by bone marrow transplant
  • Scientists have experimented extracting embryonic stem cells and growing them, under certain conditions they will differentiate into specialised cells.
  • Stem cells may be used to create specialised cells to replace damaged ones, e.g. new cardiac muscle in heart attack patients
70
Q

What are the ethical concerns with stem cell research?

A
  • Embryos shouldn’t be used for experiments as each one is a potential for new life.
  • Some think curing patients is more important than the potential life of the embryos, the embryos are often unwanted ones from fertility clinics so would often be destroyed.
  • In some countries stem cell research is banned. It is allowed in the UK under strict guidelines.
71
Q

What colour does iodine solution go if starch is present?

A

blue-black

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