b1 - cell biology Flashcards
where are stem cells found in the human body
in the bone marrow
where are chromosomes housed in eukaryotic cells
nucleus
how many micrometres in an egg cell
200
how big are eukaryotic cells
10 - 100 micrometres
how do you perform a light microscope experiment
- put thin sample of tissue on microscope slide
- add a few drops of stain e.g. iodine
- place coverslip on tissue and place slide on microscope stage
- use objective lens with lowest magnification and focus on the sample
- increase magnification and refocus
which microscope allows scientists to understand the functions of sub-cellular structures
electron microscope
which microscope was first used in 1933
electron microscope
equation for magnification
size of image / size of real object
why do animal cells mostly divide for
to replace cells and repair tissues
what sub-cellular structures do animal cells not have
vacuole
chloroplasts
cell wall
what are ribosomes for
making proteins
what process is chlorophyll needed for
photosynthesis
where do most of the cell’s chemical reactions take place
cytoplasm
what are the uses of stem cells
plant cloning
therapeutic cloning
stem cell treatments
what is therapeutic cloning
a process that produces an embryo that has the same genome as patient
where are plant stem cells found
meristem tissue
what happens when the cell divides
2 identical cells are created by the division of the cytoplasm and cell membrane
what happens during mitosis
the 2 sets of chromosomes are pulled to opposite ends of the cell then the nucleus divides into 2
what happens during the initial growth stage
extra ribosomes and mitochondria produced and the cell’s chromosomes are replicated
what do chromosomes contain
different genes that produce different proteins
what are the stages of the cell cycle
mitosis
initial growth
cell divides
what is the cell cycle
the series of events involved in cell growth and division
what do acrosomes contain
digestive enzymes
what is resolution
the ability to tell apart 2 or more objects that are close
what 2 variables matter when using microscopes
magnification and resolution
what are the adaptations of muscle cells
lots of mitochondria and protein fibres that contact
what happens when a cell differentiates
it becomes a different type of body cell
differentiation occurs when cells…
acquire different sub-cellular structures
what cells can keep their ability to differentiate and create new tissues
plant cells
which sub-cellular structures can be found in prokaryotic cells
single dna loop
plasmids
cell membrane
what is active transport
the net movement of particles against a concentration gradient
what does active transport allow
sugar absorption in human gut
mineral absorption in plants
what is an independent variable
something that is controlled and changed in the experiment
what are the features of osmosis
partially permeable membrane
net movement of water
why does water move by osmosis
so that the concentration is the same on both sides of the membrane
what is osmosis
where water moves from an area of high water concentration to low water concentration
why can’t multicellular organisms rely on diffusion
their cells are too far from the external environment
what is the formula for surface area to volume ratio
surface area / volume
how does the cell membrane affect diffusion
the larger the surface area the faster the rate of diffusion
how does the concentration gradient affect diffusion
the bigger the difference in concentration in 2 areas the faster the diffusion
how does temperature affect diffusion
higher = faster
what is diffusion
net movement of particles from an area of high concentration to an area of low concentration
disadvantage of stem cells
they can transfer viral infections
how is a sperm cell specialised for its function
the acrosome in the head contains enzymes so it can penetrate an egg. the middle piece has lots of mitochondria as it needs energy to swim
how are nerve cells specialised for their function
thin so can carry messages quickly. branched connections at each end so can connect to other nerve cells to pass messages around the body
how are muscle cells specialised for their function
contain mitochondria to provide the energy for muscle contraction. they store glycogen which can be sued for respiration
how are root hair cells specialised for their function
large surface area to increase the rate of absorption. lots of mitochondria to provide energy for active transport
how are xylem cells specialised for their function
they lose their end wall to form a continuous hollow tube. strengthened by lignin
how are phloem cells specialised for their function
sieve tubes - its cytoplasm connects one cell to another
companion cells - attached to each sieve tube to provide energy
stem cells from meristems in plants can be used to…
clone rare species of plants to protect them from extinction
