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
a student draws a cheek cell. the cell in their drawing is 50mm wide. in real life the cell is 0.025mm. what is the magnification of their drawing?
500.025 = 2,000
=2,000
what are three structures that are found in plant cells but not in animal cells
- cell wall
- chloroplasts
- permanent vacuole
what are all living things made of?
cells
what are the differences between a prokaryotic and eukaryotic cell?
- size (eukaryotic cells are bigger)
- prokaryotic cells have no nucleus
- eukaryotic cells have no cell wall
what is the function if the nucleus?
to contain genetic material and controlling the activities of the cell
what is the function of the cytoplasm?
the site where most chemical reactions take place
what is the function of the cell membrane?
to control what goes in and out of the cell
what is the function of mitochondria?
to help with aerobic respiration
why are some people concerned about using stem cells from cloned embryos
- there may be risks, such as the transfer of viral infection
- they may have ethical or religious objections
what is the function of ribosomes?
to make proteins via protein synthasis
what type of cell is bacteria?
prokaryotes
what is the formula for magnification?
image size/real size
does a bacterial cell have a nucleus?
no
what is a plasmid?
a circular strand of DNA that floats freely in the cytoplasm
do bacteria have mitochondria or chloroplasts?
no
what are chloroplasts?
absorb light to make food (glucose) by photosynethsis
what is cell differentiation?
a process where cells become specialised
what are sperm cells specialised for?
reproduction
what are nerve cells specialised for?
signalling
what are muscle cells specialised for?
contraction
what are root hair cells specialised for?
absorbing water and minerals
what are phloem and xylem cells specialised for?
transporting substances
what do chromosomes do?
contain genetic information
why do we have 23 pairs of chromosomes?
because we have one from the father and one from the mother
what is the function of the cell cycle?
make new cells for growth, development and repair
what is mitosis?
the stage in the cell cycle where the cell divides
how many stages are there in the cell cycle?
4
what happens in the growth and DNA replication stage?
cell grows and duplicates its DNA increases sub cellular structures like mitochondria and ribosommes
what are the stages of mitosis?
interphase
prophase
metaphase
anaphase
telophase
cytokinesis
how do prokaryotic cells divide?
by binary fission
what occurs in binary fission?
asexual reproduction by a separation of the body into two new bodies
what temperature do we culture microorganisms at?
35
where do we find stem cells?
human embryos
can adult stem cells turn into any type of cell?
no
what is the difference between embryonic and adult stem cells?
embryonic can turn into any type of cell
adult can’t
how could adult stem cells be used in medicine?
bone marrow cells can replace faulty blood cells
how could embryonic stem cells be used in medicine?
to make insulin producing cells for. diabetics
why are some people against stem cell research?
because they feel human embryos are potential human life and shouldn’t be used for experiments
What is the function of the cell wall?
To provide structure and support to a plant cell
Name 3 organelles found in a plant cell but not in an animal cell
-cell wall -chloroplasts -permanent vacuole
What is a specialised cell?
A specialised cell is a cell that is adapted to its function
Describe and explain 3 ways in which a sperm cell is specialised.
A sperm cell is specialised because it has: - a tail so that it can swim towards the egg for fertilisation - many mitochondria so they can produce energy for movement - an acrosome containing digestive enzymes to penetrate the egg
describe and explain how a muscle cell is specialised
muscle cells are adapted to contract and relax. striated muscle cells have three main adaptions:
- they contain special proteins that slide over each other making the fibres contract
- they contain many mitochondria to produce the energy needed to contract and relax
- they can store glycogen which is used to produce energy.
describe and explain the adaptions of root hair cells
root hair cells have 3 main adaptions:
- they have a projection which increases the surface area available for water to move in to the cell
- they have a large permanent vacuole which speeds up the movement of water in to the cell
- they have many mitochondria to produce the energy needed to move ions and minerals in to the cell
compare the magnification and resolution of a light microscope and an electron microscope
an electron microscope has a much higher magnification and resolving power than a light microscope. this means that it can be used to study cells in a. much finer detail.
describe the stages in the cell cycle
- before the cell can divide it grows and increases the number of sub-cellular structures
- the DNA replicates to form 2 copies of each chromosome.
- one set of chromosome is pulled to each end of the cell and the nucleus divides
- the cytoplasm and cell membranes divide to form two identical daughter cells
Describe and explain how a nerve cell is specialised.
Nerve cells are specialised to carry electrical impulses around the body. They have several adaptations including: - dendrites to make connections to other nerve cells. - long axons that carry the impulse from one place to another - a myelin sheath for insulation. - synapses that contain many mitochondria to produce the energy needed to make neutrotransmitter
Explain why cell division by mitosis is important in multicellular organisms
Cell division is important so the organisms can grow and repair damaged cells
What is a stem cell?
A stem cell is an undifferentiated cell that can differentiate in to a specialised cell
Where are stem cells found in plants?
Stems cells are found in the meristem tissue
describe the stages in mitosis
- parent cell with two pairs of chromosomes
- each chromosome replicates itself.
- chromosomes line up along the centre of the cell, divide and copies move to opposite poles.
- each ‘daughter’ cell has the same number of chromosomes, and contains the same genes as the parent cell
what are the factors that affect diffusion
- the difference in concentration, known as the concentration gradient
- the temperature
- the surface area of the membrane
why does a plant have a meristem at the tip of the shoot and the tip of each root?
allow plants to make new cells for growth
What is the equation for photosynthesis?
Carbon dioxide + water ——> glucose + oxygen
What structures could be found in a eukaryotic cell but are NOT found in prokaryotic cells
-nucleus -plasmids -mitochondria
What sub-cellular structures are found in ALL eukaryotic cells
-cytoplasm -cell membrane -nucleus
Where is the genetic material stored in a prokaryotic cells
The genetic material of prokaryotes is stored in a single DNA loop in the cytoplasm
what is a tissue
a tissue is a group of cells, with a similar structures turn and function which all work together to do a job.
