Biology Paper 1 Flashcards
what is denaturing?
denaturing is when high temperature and extremes of pH make enzymes change shape
what is the ‘lock and key theory’
a model used to explain how enzymes work: the chemical that reacts is called the substrate (key) and it fits into the enzymes active site (lock)
what are the properties of an enzyme:
- they are all large proteins
- there is a space within the protein molecule called the active site
- each enzyme catalyses a specific reaction
- they work best at a specific temperature and pH called the optimum
what are enzymes
enzymes are biological catalysts - they speed up chemical reactions in living organisms
what is the main function of the digestive system?
to digest food and absorb the nutrients obtained from digestion
what is the process called that allows water out of the leaf
diffusion
how do plants move water
transportation / evaporation from the leaf
why is the structure of a root hair cell important for its function
- the long projection to increase surface area to absorb water and minerals
- lots of mitochondria for active transport of minerals
what is the function of epithelia?
to cover organs/all parts of the body
what is a group of cells with a similar structure and function called?
tissue
why do sperm cells contain lots of mitochondria?
to provide energy for its journey to the egg. also the. major site of respiration
why do cells differentiate?
cells change to a more specialised type
what is an organ system?
a group of organs working together together to do a particular job. for example the digestive system contains organs such as the stomach, the small intestine and the large intestine
what is an organ?
a group of different tissues working together to perform a specific function. for example the stomach contains glandular, muscular and epithelial tissues
in addition to a large surface area, name one other feature that makes an exchange surface more efficient
thin barriers to minimise the diffusion distance
what is required for substances to be absorbed against a concentration gradient
energy
examples of specialised animal cells
- sperm cell
- nerve cell
- muscle cell
examples of specialised cells in plants
- xylem
- phloem
- root hair
give example of tissues
- muscle tissue contracts to produce movement
- glandular tissue produces substances such as enzymes and hormones
- epithelial tissue covers organs
what do cells use diffusion for?
to take in and remove waste products
what is osmosis?
the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
the effect of osmosis on plant tissue practical method?
- cut some cylinders of potato tissue and measure their mass
- place the cylinders in different concentration of sugar solution
- after about 3o minutes remove the cylinders and measure their mass again.
what are the independent,dependent and one control variables in the osmosis practical?
independent variable - the concentration of sugar solution
dependent variable - the change in mass of the potato
control variable- the temperature, the length of time the cylinders were left in the solution and the volume of the solution
what is the independent variable?
the one deliberately changed
what is the dependent variable?
the one that is measured
what is the control variable?
the ones that are kept the same
the considerations, mistakes and errors in the effect of osmosis on plant tissue
- the cylinders need to be left in the solution long enough for a significant change in mass to occur
- before the mass of the cylinders is measured again, they should be rolled on tissue paper to remove any excess solution
- if the cylinders change in mass, they have gained or lost water by osmosis
what is active transport?
active transport move substances against a concentration gradient, from an area of low concentration to high concentration
starch test?
iodine solution
protein test?
biuret solution
glucose test?
Benedict solution
what is diffusion?
movement of particles from an area of higher concentration to an area of lower concentration
what is the function of cell sap?
to support the plant
where is the DNA found in a bacterium?
cytoplasm
what is flagella?
a tail-like structure that rotate to help some bacteria move
a student looks at a plant cell under a microscope using a magnification of x120
the image go the cell is 1.5m in height .
calculate the height of the actual cell.
1.5 x 10= 15mm
120= 15/actual height
actual height= 15/120
=0.123mm
required practical microscopy.
method:
- place a tissue sample on a microscope slide.
- add a few drops of a suitable stain.
- lower a coverslip onto the tissue.
- place the slide on the microscope stage and focus on the cells using low power.
- change to high power and refocus.
- draw any types of cells that can be seen.
- add a scale line to the diagram
a nucleus is measured as 0.005mm in diameter. how many micrometers is this?
0.000005