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.
