Additional Science (Route 2): Unit 6 Flashcards
What is a gene?
A gene is a section of DNA, coding for one characteristic
What is a gamete and what do they carry?
Gametes are the sex cells (e.g. sperm and egg), which carry genetic information
What is glycogen?
Some glucose is stored as glycogen (in liver / muscle)
During vigorous exercise glycogen is converted back into glucose to provide more energy
What are the sex chromosomes in humans?
X and Y
All men have XY and all women have XX
What is a catalyst?
A catalyst increases the rate of a reaction without being used up
Why are enzymes called biological catalysts?
Biological – from a living organism
Catalyst – increase the rate of reaction without being used up
What are enzymes and how do they work?
Enzymes are biological catalysts – they are protein molecules made up of long chains of amino acids
Enzymes work as a lock and a key – the protein chains have a special shape, which enables other molecules to fit into the enzyme
What happens to enzyme function as the temperature is increased?
At warm temperatures (40ºC) enzymes work faster due to the particles moving faster
At hotter temperatures (>60ºC) the enzymes start to denature (they lose their shape and cannot work any longer)
What pH would you expect enzymes in these areas of the body to work best at?
Mouth
Stomach
Small intestine
Mouth = pH 7
Stomach = pH 2
Small intestine = pH 8/9
What is the difference between aerobic and anaerobic respiration?
Aerobic respiration – uses oxygen
Anaerobic respiration – does not use oxygen
What is the equation for aerobic respiration?
C6H12O6 + 602 → 6CO2 + 6H2O + Energy
Where in a cell does aerobic respiration take place?
Within the mitochondria
What can different organisms use the energy released by respiration for?
- Build up large molecules using smaller ones
- In animals it allows muscles to contract
- In mammals and birds it maintains a steady body temperature
- In plants it allows for the build up of sugars, nitrates and other nutrients into amino acids (which are then built into proteins)
Some enzymes work outside of the body cells – explain how this happens in the digestive system
Digestive system enzymes are produced by specialised cells in the glands and in the lining of the gut – the enzymes pass out of the cell into the gut where they digest larger food molecules into smaller ones
Give 3 examples of processes, which are catalysed by enzymes within living cells
Respiration
Protein synthesis
Photosynthesis
Where is the enzyme amylase produced, and what does it break down?
In the mouth (converting starch to sugars)
Where is the enzyme protease produced, and what does it break down?
In the stomach, pancreas and small intestine (converting proteins into amino acids)
Where is the enzyme lipase produced, and what does it break down?
In the pancreas and the small intestine (converting fats to fatty acids and glycerol)
What is the pH of the stomach?
Why is this?
pH 2 due to the hydrochloric acid produced by the stomach (to kill bacteria)
What is bile?
Where is it produced, and what pH is it?
An alkaline substance which helps with the breakdown of fats – produced in the liver (pH 11)
Why does the small intestine have a low alkaline pH?
Due to the combination of the stomach acid (pH 2) and the bile (pH 11)
How are enzymes used in the home?
Biological washing powder contain protein and fat digesting enzymes (proteases and lipases)
How are enzymes used in industry?
Proteases – used to pre-digest some baby foods
Carbohydrases – used to convert starch to sugar syrup
Isomerase – used to convert glucose syrup to the sweet fructose syrup (which can be used in smaller quantities, useful for slimming foods)
What is isomerase and what is it used for?
Isomerase is an enzyme, which converts glucose syrup into fructose syrup (much sweeter so can be used in smaller quantities) in slimming foods
What is polydactyly?
Polydactyly is a genetic disorder where a baby is born with extra fingers / toes
It is caused by a dominant allele (D)
What are the pros / cons of embryo screening during IVF?
Pros: reduces suffering; laws stop it going too far (e.g. picking of sex); during IVF most embryos are destroyed anyway (just picking a healthy one); treating disorders costs a lot of government money
Cons: designer baby possibility; rejected embryos are destroyed; implies people with genetic disorders are ‘undesirable’; screening is very expensive
What do fossils show?
Fossils are the remains of dead plants and animals providing evidence of organisms that once lived (minerals / casts / impressions / preservation where no decay could take place)
What is extinction and how is it caused?
Extinction is caused when organisms cannot evolve quickly enough due because: -
Environmental change
New predator
New disease
Catastrophic event
New species develops (outcompetes)
What is speciation?
Speciation is the development of a new species (via isolation and then natural selection)
What stages are involved in isolation?
Original population / physical barriers / new adaptations / new species develops
How does natural selection lead to evolution?
Organisms evolved through natural selection: -
One organism has an advantage (mutation / change in environment)
Organism now more likely to survive
Organism more likely to breed and pass on their advantageous genes
What is a mutation and what can it lead to?
A mutation is a change in DNA – this can lead to a negative change / neutral change / positive change (leading to evolution)
What is the theory of evolution?
That all organisms on Earth have evolved from simple single celled organisms millions of years ago
What evidence is there for the theory of evolution?
Fossil records show how animals have changed over time
DNA and physiological similarities
Describe the experiments conducted by Mendel
Mendel investigated inheritance in plants – he used seed shape and colour in pea plants (and height)
He found that some characteristics were stronger (dominant) and some weaker (recessive)
He also provided evidence for the ratio of inheritance of strong and weak characteristics
Complete this genetic cross: -
Hh hh
(H = long stem; h = short stem)
What is the difference between mitosis and meiosis?
Mitosis – production of body cells (cells have full chromosomes number and are exactly the same as the parent cell)
Meiosis – production of gametes (cells have ½ the chromosome number and are genetically different to the parent cell)
How do body cells reproduce and how are the gametes (sex cells) formed?
Body cells = mitosis
Gametes = meiosis
How many chromosomes are found in body cells?
How many chromosomes are found in the gametes (sex cells)?
Body cells = 46 (23 pairs)
Gametes = 23
What is the scientific name for sex cells?
Gametes
What happens during meiosis?
Copies of chromosomes are made – the cell divides twice to form four gametes, each with a single set of chromosomes
What happens at fertilisation?
The gametes fuse – a single body cell with new pairs of chromosomes is formed and the cell reproduces by mitosis to form a new individual
What are stem cells, where are they found and what may they be used to treat?
Stem cells can be made to form into many different types of cells, e.g. nerve cells (they are not restricted to growth and repair)
They are found in embryos and adult bone marrow
They can be used to treat paralysis
What is the difference between sexual and asexual reproduction?
Sexual reproduction: –
2 parents
Offspring genetically different to the parent
Asexual reproduction: -
1 parent (cloning) Offspring genetically identical
What is the difference between the genes of males and females?
Males = XY
Females = XX
What are alleles?
Different forms of the same gene, e.g. brown eyes and blue eyes
What is the difference between a dominant and recessive gene?
Dominant genes are likely to be shown (strong)
Recessive genes are not likely to be shown (weak)
Define the following: -
Chromosome
Gene
DNA
Chromosome – long strands of DNA, containing many genes
Gene – a section of DNA coding for one characteristic
DNA – material which makes up genetic information
What does a gene code for?
A gene tells the body the combination of amino acids needed to make a particular protein
What is a DNA fingerprint?
Each person (apart from identical twins) has unique DNA – the DNA can be identified and used to create a genetic fingerprint, which can be used to solve crimes
Give two examples of inherited disorders
Cystic fibrosis
Huntington’s disease
What is Huntington’s disease?
Is it dominant or recessive?
Affects the nervous system – symptoms develop later in life (about 40 years old)
Caused by a dominant allele, and only one parent needs the disease to pass it on
What is cystic fibrosis?
Is it dominant or recessive?
Affects the cell membranes – mainly affects the lungs and pancreas
It is recessive, with both parents needing to carry the disease to pass it on
What is meant by the term ‘carrier’ of a genetic disease?
A ‘carrier’ of a genetic disease carries the recessive gene, but does not have any symptoms themselves
What is electrolysis used for?
Separating ions in solution
What types of ions do the following form?
Metals
Non-metals
Metals = +ve
Non-metals = -ve
During electrolysis where are these ions attracted to?
Positive
Negative
+ve electrode = negative
-ve electrode = positive
What are the scientific names for the following?
+ve electrode
-ve electrode
+ve electrode = anode
-ve electrode = cathode
What is the gain of electrons called?
What is the loss of electrons called?
Oxidation = loss
Reduction = gain
OIL RIG
During electrolysis where does oxidation occur?
Oxidation occurs at the +ve electrode (electrons are lost)
During electrolysis where does reduction occur?
Reduction occurs at the -ve electrode (electrons are gained)
Write out the half equations which happen during the electrolysis of brine
2Cl- → Cl2 + 2e-
2H+ + 2e- → H2
What are the products of the electrolysis of sodium chloride (brine)?
Hydrogen
(-ve electrode)
Chlorine
(+ve electrode)
Sodium hydroxide
(solution)
What are the products of the electrolysis of sodium chloride, and what are they used for?
Hydrogen – margarine / Haber process
Chlorine – swimming pools / cleaning products
Sodium hydroxide – soap / paper
How can electrolysis be used to obtain pure copper from impure copper?
Impure copper used as the +ve electrode
Pure copper as the –ve electrode
Solution containing copper ions (e.g. copper sulfate)
What is an insoluble salt and how can it be formed?
Insoluble salts will not dissolve in water
They are formed by mixing appropriate solutions and filtering the precipitate
How can precipitation of unwanted salts be used to treat drinking water?
Filter the precipitate (removing unwanted salts)
Give 3 ways in which a soluble salt can be prepared
Metal + acid
Insoluble base + acid
Acid + alkali
How can a solid salt be obtained from a salt solution?
Evaporating to leave the salt crystals
What is a base?
Give some examples
Metal oxides and hydroxides are bases
What is the difference between a base and an alkali?
Give some examples
Metal oxides and hydroxides are bases
Soluble hydroxides are alkalis (e.g. sodium hydroxide)
How are ammonium salts made?
What are they used for?
Ammonia is dissolved in water to produce an alkaline solution
This can then be used to neutralise an acid to produce an ammonium salt
These are important in the production of plant fertilisers
What type of ions are found in the following?
Acids
Alkalis
Acids = H+ (hydrogen)
Alkalis = OH- (hydroxide)
What happens to the H+ ions and the OH- ions during a neutralisation reaction?
Include an equation
H+ reacts with the OH- to produce water (H2O)
H+(aq) + OH-(aq) → H2O(l)
In the following rate of reaction graph: -
Which is the faster reaction?
Which reaction makes the most gas?
X = most gas
Y = fastest
Using the rate of reaction graph: -
Draw a reaction which happened at a lower temp.
Draw a reaction which added a catalyst
Using the rate of reaction graph: -
Draw a reaction which had 2x the reactants
Draw a reaction which had ¼ of the reactants
Why are catalysts used in industry?
Catalysts lower the activation energy reducing the amount of energy needed (and therefore the cost)
They can also be used repeatedly as they are not used up in the reaction
What does a catalyst do to a reaction?
A catalyst lowers the activation energy needed to start the reaction
Iron – Haber process
Magnesium dioxide – decomposition of hydrogen peroxide
What happens to a catalyst at the end of a reaction?
Nothing – the catalyst is not used up and can be used again
How can the rate of a reaction be measured?
Amount of reactant used ÷ time
Or
Product formed ÷ time
Give 4 things which can increase the rate of a reaction?
Temperature
Concentration / pressure
Surface area
Catalyst addition
Why does temperature affect the rate of reaction?
Increasing the temperature gives the particles energy – the particles move faster, colliding more often and with more force
Why does concentration / pressure affect the rate of reaction?
The higher the concentration of a liquid or the higher the pressure of a gas then the higher the chance of a collision = an increased rate of reaction
Why does surface area affect the rate of a reaction?
The larger the surface area the more exposed particles there are to react
How can you increase the surface area of reactants?
The surface area can be increased by cutting the object into smaller pieces – powder has a very large surface area
What must happen for a reaction to take place?
Particles must collide with enough force
What is activation energy?
The energy needed to start a reaction (minimum energy required by the particles to react)
What is an exothermic reaction?
Give an example
A reaction which gives out energy (usually heat), e.g. combustion / respiration
What is an endothermic reaction?
Give an example
A reaction which takes energy in from the surroundings, e.g. photosynthesis uses light energy
How can artificial colours be separated?
Chromatography (colours split based on ability to dissolve / molecular size)
What advantage do machines have at analysing unknown substances?
Very sensitive
Very fast
Very accurate
What is gas chromatography?
Gas chromatography separates out mixtures of compounds allowing the substances present to be identified
What is an indicator and what is pH
An indicator is a dye which changes colour
pH (1-14) is a measure of how acid or alkaline a solution
What is electroplating?
Electroplating uses electrolysis to coat the surface of one metal with another (e.g. silver onto brass to make it look nice)
In electrolysis why is cryolite used?
Aluminium oxide is dissolved in molten cryolite (ore of aluminium) lowering the temperature (and therefore the cost)
Negative electrode: Al3+ + 3e- Al
Positive electrode: 2O2- O2 + 4e
Label the wires of a plug, including their colours
Blue = neutral; brown = live; green / yellow stripes = earth
What is the difference between a.c. and d.c. supplies?
a. c. (alternating current) – current is constantly changing direction
d. c. (direct current) – current does not change direction
What is the frequency and potential difference of the mains supply in the UK
50Hz and 230V
What is an electrical cable made from?
Why is each material used?
Copper for the wire (good electrical conductor) and plastics for the cover (good insulator)
What is the purpose of a fuse, and how does it work?
A fuse is designed to increase the safety of an electrical appliance – if too much electricity flows through the plug the wire melts, breaking the circuit (turning the appliance off)
Why are appliances with a metal case usually ‘earthed’
If the earth wire touches the side of the metal case someone using the appliance could get an electric shock as the electrons flow through them to the Earth
Earth wire provides an easier route for the electrons, preventing electrocution
What happens to the potential difference in the live wire with respect to the neutral wire?
The live terminal of the mains supply alternates between +ve and –ve with respect to the neutral terminal
What happens to the potential in the neutral terminal with respect to the earth?
The neutral terminal stays at a potential close to zero with respect to earth
How should the size of fuse in a plug be determined?
The fuse should allow a slightly higher current than the appliance demands
What is electrical current?
The flow of electrons around a circuit
When a charge flows through a resistor, what form of energy is the electrical energy transformed in to?
Heat (thermal) energy
What 2 equations can be used for working out power?
Power (W) = energy transformed (J) / time (s)
Power (W) = current (A) x potential difference (V)
What is the equation for working out the energy transformed in a circuit?
Energy (J) = potential difference (V) x charge (C)
What is the equation for working out charge?
Charge (C) = current (A) x time (s)
What units are these measured in?
Power
Resistance
Charge
Power = watts (W)
Resistance = ohms
Charge = coulombs (C)
What experiment was carried out by Rutherford and Marsden – what was it used to show?
Rutherford and Marsden’s scattering experiment – an alpha particle (helium nuclei) was fired at a thin sheet of gold (1 atom thick)
They found that some travelled through, some were deflected at different angles and some were reflected back
They used this experiment to establish the modern model of the atomic structure (+ve nucleus with –ve electrons orbiting)
What are the relative charges and masses on these parts of an atom?
Proton
Neutron
Electron
Proton = +ve
(mass of 1)
Neutron = neutral
(mass of 1)
Electron = -ve
(mass of 1/2000th)
Why does an atom have no overall charge?
It has the same amount of protons (+ve) and electrons (-ve), which cancel each other out
What is used to prevent electrical overloads?
Earthing, fuses and RCCBs (residual current circuit breakers which detect a difference in current quickly cutting off the power by opening a switch)
What is potential difference?
The work done per unit charge (energy transferred in Joules per coulomb of charge passing between two points)
Potential difference = work done ÷ charge
V = W ÷ Q
What are the 3 types of radiation?
Alpha
Beta
Gamma
What can happen when radiation is absorbed by a substance?
Radiation may make things hotter, or set up an alternating current with the same frequency as the radiation itself
Why are some atoms radioactive?
Some atoms have unstable nuclei which give out radiation all the time, no matter what is done to them
What are these types of radiation made from: -
Alpha radiation
Beta radiation
Gamma radiation
Alpha: helium nucleus (2 protons and 2 neutrons)
Beta: high energy electron
Gamma: an electromagnetic wave
What is an ion, how are they created?
Give an example
An atom with a charge – created when atoms pick up electrons (become negative) or lose electrons (become positive)
E.g. Cl- and Na+
What part of an atom is always the same for a particular element?
Proton number
What part of an atom is always different for different atoms?
Proton number
What is an isotope?
An atom of the same element with a different amount of neutrons
What do these numbers represent in the atom?
Atomic number
Relative atomic
Atomic number – number of protons (usually the same as the number of electrons)
Relative atomic mass – number of protons and neutrons
What effect does alpha decay have on the nucleus of an atom?
Alpha decay is the loss of a helium nuclei (2 protons + 2 neutrons)
This means that the proton number decreases by 2 (element changes) and the mass decreases by 4
Draw and label and atom
What is an isotope?
An atom with a different number of neutrons
How are the 3 types of radiation affected by electric and magnetic fields?
Alpha & beta are deflected by electric and magnetic fields – gamma is not affected
What does half-life mean?
Are all half-lives the same?
Half-life is the time it takes for a radioactive material to break down to half its original radioactivity – this can occur in seconds, or over millions of years
Which of the 3 types of radiation is the most ionising and why?
Alpha is the most ionising because it is the biggest – causing the most damage to the atoms
Which is the most penetrative type of radiation?
What can each type of radiation be stopped by?
Gamma is the most penetrative radiation
Alpha: stopped by paper
Beta: stopped by aluminum foil
Gamma: stopped by thick lead (or meters of concrete)
Which is the most dangerous type of radiation outside of the body? Explain…
Gamma – it can penetrate to the fragile internal organs
Which is the most dangerous type of radiation inside of the body? Explain…
Alpha – it is the most ionising radiation, causing most damage to the cells
How can radioactive substances such as Tahllium be used for medical ‘tracers’?
Tracers use gamma radiation so it is less dangerous to the patient (they also have a short half life, so they are not radioactive for long)
How are the 3 types of radiation affected by electric and magnetic fields?
Alpha & beta are deflected by electric and magnetic fields – gamma is not affected
Main sequence stars, depending upon size, can develop into what after their hydrogen runs out?
Red giants > white dwarfs
Or
Red super giants > supernova (and leaving neutron stars / black holes)
Draw the life cycle of a star
What effect does beta decay have on the nucleus of an atom?
When beta radiation is emitted a neutron turns to a proton – this means the proton number increases by 1 and the element changes
What is background radiation and where does it come from?
Background radiation is the radiation around us all the time – this may come from space, rocks under-ground, X-rays etc…
What is a chain reaction and how does it occur?
When atoms split they release neutrons – these neutrons can go on to split other atoms, which also release neutrons (a chain reaction)
Draw and label a diagram to show how a chain reaction may occur
What are the two most common substances used in nuclear reactors?
Uranium 235
Plutonium 239
What is nuclear fission?
Nuclear fission is when a nucleus splits into 2 smaller nuclei and 2/3 neutrons are released (+ energy)
What must happen for nuclear fission to occur?
A neutron must be absorbed
What happens to an atom when they undergo nuclear fission?
The nucleus splits and releases 2/3 neutrons
What is nuclear fusion and where does it happen?
2 atomic nuclei join together to create a large one (this is the process by which energy is released in stars)
Where does nuclear fusion happen?
Stars – hydrogen fuses to helium
