Paper 3 Higher Flashcards
Base
Nitrogenous base found in DNA - adenine, thymine, guanine or cytosine
Nucleotide
A nucleotide is made up of a sugar, phosphate group and a nitrogenous base
Gene
A small section of DNA on a chromosome, that codes for a particular sequence of amino acids, to make a specific protein
Allele
A different version of the same gene
What a sticky end?
A length of DNA which is single stranded
Phylogenetics
The study of evolutionary relationships based on molecular studies
Translocation
The movement of sugar produced in photosynthesis to all other parts of the plant for respiration
Transpiration
When the plant opens its stomata to let in carbon dioxide, water on the surface of the cells of the spongy mesophyll and palisade mesophyll evaporates and diffuses out of the leaf.
Why is surface run off water important to organisms living in a lake?
- It prevents the lake from drying out
- Washes minerals into the lake
Petri dish lake experiment
- Water from each lake is added to a separate Petri dish using a sterile Pipette
- Filter paper is placed in the centre of each dish with the sterile forceps
- Petri dishes are incubated
- The inhibition zone with no bacteria growth around the discs is measured
Is a plant cell prokaryotic or eukaryotic?
A eukaryotic cell
Nanometer (nm)
x10 ^-9
Micrometer (um)
x10 ^-6
Compare genetic material between eukaryotic and prokaryotic cells.
Eukaryotic cell- DNA is found in a nucleus
Prokaryotic cells- DNA is a single molecule, found free in a cytoplasm, additional DNA is found on one or more rings called plasmids
Difference in size between eukaryotic and prokaryotic cells
Eukaryotic- 10um to 100um
Prokaryotic- 1um to 10um
Type of cell division between prokaryotic and eukaryotic cells
Eukaryotic- mitosis
Prokaryotic- binary fission
What is the purpose of a fine adjustment knob on a microscope?
It’s used to focus the lens until a clear image of what’s on the slide appears.
Describe how you would put a cover slip onto a specimen on a slide so that it’s ready to be viewed under a light microscope.
The cover slip should be placed at one end of the specimen and held at an angle with a mounted needle. It should then be carefully lowered onto the slide and pressed down gently so that no air bubbles are trapped under it.
Why should you add methylene blue when viewed onion cells under a light microscope?
To highlight structures in an onion cell, making them easier to see.
Total magnification formula
Total magnification= eyepiece lens magnification x objective lens magnification
Magnification formula
Magnification = image size/real size
What is a polymer?
A large, complex molecule. It is made up of long chains of smaller molecules, called monomers, that are joined together.
Structure of nucleotide
Consists of a sugar, a phosphate group and one of the four different bases. The base is attached to the sugar.
How is the sequence of amino acids in proteins decided?
The amino acid sequence of a protein depends on the order of bases in the gene that codes for it, and each gene contains a different sequence of bases.
Where does transcription take place?
In the nucleus
Where in the cell does translation take place? What is it?
In the cytoplasm. Translation is where amino acids are joined together to make a protein based on the code in mRNA.
Why is it important for DNA to unzip around a gene during protein synthesis?
So that the DNA can be used as a template to make mRNA during transcription.
Describe how the code for a gene is transferred to the cytoplasm.
A molecule of mRNA is made by copying the code from the DNA in the gene. Base pairing ensured that the mRNA molecule is complementary. The mRNA molecule carries the code of the nucleus to the cytoplasm.
How is a protein produced once the code from its gene is present in the cytoplasm?
The amino acids that match the triplet codes on the mRNA are joined together in the correct order. This makes the protein.
What is the Independent variable?
The variable that you change in order to see what effect it has on another variable.
What is the dependent variable?
The variable you measure when you change the independent variable.
What do lipids get broken down to?
Glycerol and fatty acids
What type of biological molecule can be identified using the Benedict’s test?
Sugars
What does the iodine test check for?
Starch, solution turns blue-black
How would you test if a food sample contains protein?
Add biuret solution. If the food sample contains protein, the solution will change from blue to purple. If protein isn’t present, it will stay blue.
What is the emulsion test used for? Describe how it’s performed.
It’s used to test if there any lipids in a sample. It’s performed by shaking the test sample with ethanol until it dissolves. The solution is then poured into water. If there are any lipids present, a milky emulsion will be visible.
Two stages of photosynthesis
First stage- energy transferred by light is used to split water into oxygen gas and hydrogen ions
Second stage- carbon dioxide combines with the hydrogen ions to make glucose
Formula for light intensity and distance
Light intensity = 1/distance squared
Mitosis
The stage of the cell cycle when the cell divides. A cell reproduces itself by splitting to form two identical offspring.
What is mitosis used for?
To grow or replace cells that have been damaged
How many times is DNA replicated in each cell cycle?
Once
What type of plant tissue contains stem cells?
Meristem tissue (this is where growth occurs)
Difference in ability to differentiate between embryonic and adult stem cells
Embryonic stem cells can differentiate into any kind of cell, but adult stem cells can only turn into certain types of cell from the tissue they originally came from.
Why is cell differentiation important?
It allows cells to become specialised for a specific job. Having specialised cells allows organisms to work more efficiently.
How are sperm cells specialised?
Flagellum- whips from side to side to propel the sperm to the ovum
Lots of mitochondria- respiration occurs in mitochondria, and the reactions of respiration transfer energy from chemical stores so that the flagellum can move
Acrosome- stores digestive enzymes, which break down the outer layers of the ovum to allow the sperm to transfer and incorporate its genetic material
Examples of molecules that can’t fit through a cell membrane
Starch and proteins
Why is the rate of diffusion of oxygen higher when a person is taking part in exercise?
Because there will be a lower concentration of oxygen in the muscles as it is used up quicker. This means there will be a greater concentration gradient and so a faster rate of diffusion.
Type of membrane for osmosis
Partially permeable membrane
Two gases that diffuse out of a leaf
Oxygen and water vapour
Function of alveoli
To allow the efficient transfer of oxygen into the blood and the remove of waste CO2 from the blood
How are alveoli adapted for their function?
They have a large surface area due to spherical shape, a moist lining for dissolving gases, very thin walls, and a good blood supply
Coeliac disease is a condition that can cause villi in the small intestine to flatten. Suggest how coeliac disease could affect the absorption of digested food into the blood.
Fewer digested food molecules would be absorbed into the blood because the flattened villi would have a much lower surface area.
Explain how the structure of a leaf allows gases to diffuse in and out of cells.
The underneath of a leaf is covered in lots of stomata, through which carbon dioxide diffuses into the leaf, and oxygen and water vapour diffuse out. The leaf has a broad, flattened shape to increase the area of the exchange surface. Air spaces inside the leaf increase the area of this surface, increasing the chance of carbon dioxide getting into cells.
Which side of the heart pumps deoxygenated blood to the lungs?
The right side
Name of blood vessel which carries blood into the right atrium of the heart
Vena cava
Function of valves
Prevent back flow of blood
Describe the route that blood from the lungs take through the heart
Pulmonary vein, left atrium, left ventricle, leaves the heart via the aorta
Adaptation of cardiac muscle for its function
They contain lots of mitochondria to provide the cells with ATP so the cardiac muscle can contract
Describe the structure of the double circulatory system
It is two circuits joined together. In one circuit, the heart pumps deoxygenated blood to the lungs to take in oxygen. The oxygenated blood then returns to the heart. In the other circuit, the heart pumps oxygenated blood around all the other organs in the body. The blood gives us it’s oxygen at the body cells and deoxygenated blood returns to the heart to be pumped out to the lungs again
Advantage of double circulatory system
Returning the blood to the heart after it’s picked up oxygen at the lungs means it can be pumped around the body at a much higher pressure. This increases the rate of blood flow to the tissues, so more oxygen can be delivered to the cells.
Veins structure
Large lumen, thin outer wall, thin layer of elastic muscle fibres
Advantage of capillaries being one cell thick
The distance over which materials are exchanged is very small, so the rate of diffusion between capillaries and cells is high.
Artery structure
Thick outer wall, small lumen, thick layer of muscle and elastic fibres
What is plasma
The liquid that carries everything in blood
Waste products that are carried in plasma
Carbon dioxide and urea
Explain the importance of haemoglobin in red blood cells
Haemoglobin enables red blood cells carry oxygen around the body. In the lungs, haemoglobin binds to oxygen to become oxyhaemoglobin. In body tissues, oxyhaeomoglobin splits up to release oxygen to the cells.
What is translocation? In which tissue does it take place in a plant?
It is the movement of food molecules around the plant. It takes place in the phloem tissue.
Transpiration and where it occurs most
It is the loss of water from the plant. It mostly happens at the leaves.
Main type of food molecule transported around the phloem tubes
Sugar
Role of xylem tubes
To carry water and mineral ions from the roots up the stem to the leaves
Explain why the transpiration stream is constant in a plant
Evaporation and diffusion of water from the leaves create a slight shortage of water in the leaves. This means more water is drawn up from the rest of the plant through the xylem vessels to replace it so more water is drawn up from the roots.
Benefits of transpiration stream
Constant stream of water helps keep the plant cool
It provides a constant supply of water for photosynthesis
Structures of xylem tubes and phloem tubes
Xylem tubes- made of dead cells joined end to end with a lumen down the middle. The side walls are made of cellulose to give support, and the cell walls are strengthened with lignin.
Phloem tubes- made of columns of living cell, which have perforated end-plates to allow the flow of substances. Each sieve tube element has a companion cell.
What do guard cells do?
Control the opening and closing of the stomata
How does increase in temperature increase the rate of transpiration?
Water molecules have more energy to evaporate and diffuse out of stomata
Shrubs live in a dry desert. It’s stomata are small and located on the lower surface of its leaves. How does this help the shrug survive in the desert?
Lower surface- it is cooler and protected from wind, slowing diffusion of water out the leaf
Smaller stomata- reduces water loss
Benefits of an axon having a myelin sheath
A myelin sheath acts as an electrical insulator, which speeds up the movement of electrical impulses along the axon
How are nerve signals transferred across a synapse?
The electrical impulse triggers the release of transmitter chemicals. These diffuse across a synapse and bind to receptor molecules in the membrane of the next neurone. This sets off a new electrical impulse.
Change in eye muscles when going from nearby to distant object
Ciliary muscles relax, allowing the suspensory ligaments to pull tight. This pulls the lens into a less rounded shape, so it refracts light by a smaller amount.
Two things the medulla controls
Breathing and heart rate
Why is it hard to repair nervous system damage?
Neurones in the CNS dont repair themselves and scientists havent yet developed a way to repair nervous tissue in the CNS.
What is a target organ?
Contains target cells, and is the organ that a particular hormone effects.
Explain the body’s reaction when it thinks you’re in danger
- The brains detects fear and sends nervous impulses to her adrenal glands which respond by secreting adrenaline
- The adrenaline binds to specific receptors in the heart, causing an increase in heart rate, which means the blood flow to muscles increase
- This helps to increase the supply of oxygen and glucose to the muscles for increased respiration, to prepare for flight or fight response
What is ovulation?
The release of an egg from an ovary
Describe how the lining of the uterus changes over the stages of the menstrual cycle
Stage one- the uterus lining breaks down
Stage 2- builds up again into a thick spongy layer full of blood vessels
Stage 3/4- lining is maintained
- if no fertilised egg implants in the uterus by day 28, the uterus lining starts to break down, and a new cycle begins at stage 1
Describe how hormones control the development and release of an egg.
FSH causes an egg to mature in one of the ovaries
LH then stimulates the release of a matured egg at day 14 (ovulation)
Role of oestrogen in the menstrual cycle
It causes the lining of the uterus to thicken and grow between days 4 and 14. Towards day 14, it stimulates LH release (which stimulates the release of an egg) and inhibits FSH production (which stops another egg from maturing in that months cycle).
What effect do hormonal contraceptives have on the lining of the uterus?
They thin the lining of the uterus
Differences between the mini and combined pill
- Mini pill contains progesterone but the combined pill contains oestrogen
- Mini pill has to be taken every day but the combined pill is taken every 21 days
Explain how the combined pill uses hormones to reduce fertility
Oestrogen- inhibits FSH so prevents ovulation
Progesterone- stimulates production of thick cervical mucus, also thins uterus lining to reduce chance of a fertilised egg implanting
When are FSH and LH given during an IVF and why?
Before the egg collection because they stimulate egg production so that more than one egg can be collected.
What is sterilisation?
A surgical procedure to cut or tie tubes in the reproductive system
Long term method of non hormonal contraception
Intrauterine device (IUD)
Explain how the shoots are negatively gravitrophic
Gravity causes an unequal distribution of auxin in the tip of the shoot, with more auxin on the lower side. This causes the lower side of the shoot to grow faster, so the shoot bends upwards.
Give a reason as to why someone would want to control seed germination
To make seeds germinate at times of the year that they wouldn’t normally or to make sure all the seeds in a batch germinate at the same time.
What do gibberellins stimulate?
Seed germination, stem growth and flowering
How is blood glucose concentration reduced in a normal person?
Insulin is secreted by the pancreas. This causes glucose to move from the blood into the cells of the liver and muscles, where it is stored as glycogen.
How is blood glucose concentration increased in a normal person?
Glucagon is secreted by the pancreas. This causes the liver to convert glycogen into glucose, which is then released into the blood.
How does decreasing blood flow to the skin effect the body’s temperature?
If less blood flows to the skin near the body’s surface, less energy is transferred to the surroundings.
Why does shivering occur when you are cold?
Receptors in the skin and hypothalamus detect the decrease in temperature and cause the muscles to start contracting. This needs respiration, which transfers some energy to warm the body.
If too much water moves into a cell
Lysis could happen/cell may burst
Which blood vessel brings blood to the kidney and which one takes blood away from it?
Renal artery brings blood to the kidney. The renal vein takes blood away from it.
As blood flows through the glomerulus in the kidney, small molecules such as water, sugar and salt move into the Bowmans capsule. Describe what happens to these molecules after this.
The molecules flow from the capsule along the tubule. Useful molecules are selectively reabsorbed from the tubule. Anything not reabsorbed forms urine and is stored in the bladder.
Releases ADH into the bloodstream
Pituitary gland
What does ADH do?
It makes the kidneys reabsorb more water
Bodys response to high conc of water in the blood
The brain detects a high level of water in the blood. It responds by releasing less ADH from the pituitary gland. Less ADH means that less water is reabsorbed by the kidney tubules, so level of water in blood decreases.
Why does the brain trigger thirst?
It is used as a signal for a person to drink more water.
What hormone peaks at around day 28?
Progesterone
Which hormones peak immediately before ovulation?
Oestrogen, LH and FSH
Lens too thick leads to…
Short-sightedness
What happens to lens when you change from looking at distant to nearby object?
It thickens
Good conditions for bacteria replication
Keeping the temperature constant, controlling the humidity, keeping it well ventilated
Give two reasons why scientists publish their research
- So their work can be peer reviewed
- To allow recognition for their work
How does lower brain diffusion speed account for Alzheimers?
Reactions are slower
Describe the role of tRNA
It brings the correct amino acids into place and reads the triplets on the mRNA
Advantages of light microscopes
- relatively cheap
- can be used in the field
- does not require specialist training
- can look at living specimens
Disadvantages of light microscopes
- low resolution (200nm)
- low magnification strength
- staining is required for some organelles to present
Cytoplasm
Liquid substance in which chemical reactions occur
Contains enzymes (biological catalysts) which speed up the rates of reactions
Ribosomes
Site of protein synthesis
Structures which are specific to plant cells
Chloroplasts, vacuole, cell wall
Chloroplasts
Site of photosynthesis
Contains chlorophyll
Permanent vacuole
Contains cell sap
Found within the cytoplasm
Improves cells rigidity
Plant oxygen production photosynthesis experiment
- Pondweed is paced in a test tube full with water. The top is sealed with a bung. A capillary tube also containing water leads into the test tube, and is attached to a syringe.
- A lamp is placed at a measured distance from the test tube
- As it photosynthesises, oxygen is produced, forming a gas bubble in the capillary tube
- The distance the bubble has moved is measured using a ruler to calculate the volume of oxygen produced
- Many variables can be changed to observe the effect on photosynthesis: the temperature, time the pondweed is left, light intensity
Hypertonic solution
The concentration of sugar in external solution is higher than the internal, water moves out
Hypotonic
Conc of sugar in external solution is lower than the internal, water moves in
Active transport in plants (root hair cells)
- They take up water and mineral ions from the soil as they are usually in higher concentrations in the cells
- Requires energy from respiration to work
Active transport in the gut
- Substances such as glucose from food have to move from your gut into your bloodstream
- Active transport may be required to move sugars to the blood from the gut against conc gradient
4 differences between plant and bacterial cell
- bacterial cells do not have a nucleus
- bacterial cells are smaller
- bacterial cells do not have a chloroplast
- bacterial cells have plasmids
How to test for a protein
Food needs to be grinded up and a biuret agent needs to be added. The solution would turn purple if a protein is present
How to test for starch
Add iodine solution to the sample. It would turn blue-black in the presence of starch.
How to test for sugar
Mix the grinded up food sample with water. Benedict’s solution will then be added. Solution should turn red, orange or brown.
Function of receptor in the skin
Detect stimuli, so it can convert that information into an impulse
Function of mitochondrion
To release energy
