Biology Flashcards
cells
cell
the basic building blocks of all living organisms. Plants and animals are formed of millions of cells, but a bacterium is formed of only one cell
cell membrane
controls what comes in and out of cells
lets food materials and o2 in
lets waste products like carbon dioxide
only allows certain things through, partially permeable
nucleus
control centre of cell, contains DNA, genetic material
organised into units of info called genes just before cell division, DNA is organised into neat bundles called chromosomes
nuclear membrane
surrounds nucleus
ensures chromosomes are kept inside
cytoplasm
complex mix of chemicals and enzymes
chemical reactions are the base of life
mitochondria
found in cytoplasm within, where cell respiration takes place
cellulose cell wall
firm rigid wall of cellulose
strands of cellulose Criss cross over each other to form a strong outer barrier around the cell
supports cell and whole plant
when fibres of cellulose cross over each other, spaces are formed
large molecules pass easily in and out of the cells
semi permeable
chloroplast
chloroplast contains chlorophyll, green pigment which absorbs energy from the sunlight .Used in photosynthesis
Vacuole
one large permanent vacuole which is in the centre of cell, filled with cell sap which makes cell rigid and provides support
Differences between Plant cells and animal cells
Plant cell Animal cell
nucleus nucleus
cell membrane cell membrane
chloroplast no chloroplasts
vacuole no vacuole
cell wall no cell wall
Main features of bacterial cells
cell wall contains murein instead of cellulose
DNA is not arranged in chromosomes butt instead arranged in circular structures called plasmids
They have no nucleus
they have a cell membrane
Making a slide of plant cells
Forceps used to peel a layer of thin, transparent layers of epidermal cells and place onto a glass slide
Add a few drops of water or chemical stain
is added to slide( iodine or methylene blue)
A stain may be used to make some parts of the cell, such as the nucleus more visible
A coverslip is then lowered over the epidermis using a mounted needle, helping to prevent air bubbles, helps protect microscope lens and prevent cells from drying out
tissues
cells with the same specialised structure and function are grouped to form tissues
organs
An organ is a structure made of several types of tissue that carry out a particular function
organ system
organs that operate together to carry out a particular function belong to an organ system
Human cheek cells method
Rub a clean cotton bud gently over inside of your cheek
Smear end of cotton bud on the surface of a clean microscope slide. Dispose of the cotton bud safely.
Add on drop of methylene blue stain to smear and slowly lower the coverslip over cells
View and draw cells you see using microscope
What are the two properties embryonic stem cells contain
they continue to divide by cell division to produce more stem cells
they differentiate into a wide variety of specialized cell types
Ways embryonic stem cells can be collected
they can be collected from embryos now used in treatment (fertility treatment ,umbilical cord or placenta
electron microscopes
electron microscopes are special microscopes that pass electrons through a specimen and allow much higher magnification and resolution.
very large and expensive microscopes which require special rooms in a lab and use of this microscope will cause death of tissue.
allows us to see very small cell structures in high detail with magnification up to *500 000 and resolution of 1/1000 apart
difference between magnification and resolution
resolution is the ability to see separate points as distinct objects( how clear the image is) magnification is how much larger we can make an object
movement of substances into and out of cells
cells need oxygen, food and mineral ions and get rid of waste products such as carbon dioxide and nitrogenous waste.
cell membrane allows these substances to pass through but block others so it is said to be selectively permeable
surface area to volume ratio
the rate at which substances diffuse in and out of cells depends on the surface area and volume of the cell
As the size increases the surface area : volume ratio decreases
the larger the cell volume, the greater amount of oxygen is required. At the same time, the larger the surface area, the greater the amount of oxygen can diffuse into the cell
eventually a cell will be so large there is not enough surface area to allow the oxygen that the cell needs to diffuse in, so it will die
as previously stated, for many organisms to increase in size they evolved to become multi celled. Organisms still need to have a large SA/V ratio to allow efficient exchange of materials with their environment and being multicell does not solve this problem.
adult stem cells
in adult animals, most stem cells have changed permanently into specialized cells and lost their ability to divide and specialize further
however it is possible to collect stem cells from some adult tissues like bone marrow but these can only differentiate into different types of blood types
plant cells
found in the apical growing pints or meristems at ends of shoots or roots
these cells divide until they are in their final position in the root, stem or leaf and in certain circumstances the specialization can be reversed.
means scientists can clone large numbers of genetically identical plants in a short time
stem cell use in treating leukemia
cancer where the white blood cells in the bone marrow abnormally function and cant fight disease
- chemotherapy and radiotherapy which destroy white blood cells and stop the bone marrow producing more blood cells
give a bone marrow transplant containing stem cells matching healthy doner. These multiply and produce healthy blood cells in patient
Risks
chemo and radiotherapy will leave patient with no immune system and in danger of infections from outside world
stem cells divide uncontrollably and produce tumors or unwanted cells
Ethical issues
some people may have ethical issues with stem cell research as embryos will be destroyed. best stem cells come from aborted embryos, people believe they have a right to live and may be against their religion
