cell biology (T1) Flashcards
what are eukaryotic cells? give examples.
a more complex cell that has a nucleus. e.g. animal and plant cell
what are prokaryotic cells? give examples.
a simple cell without a nucleus. e.g. bacteria
where is the genetic material in eukaryotic and prokaryotic cells?
in eukaryotes it is enclosed in the nucleus, in prokaryotes it is a small loop of DNA and in plasmids.
what is the prokaryotic cell wall composed of?
Peptidoglycan
what are plasmids
small circular loops of dna found free in the cytoplasm and seperate from main dna. they carry genes that provide genetic advantages e.g. antibiotic resistance.
what is order of magnitude?
a power to the base of 10 used to quantify and compare size e.g. 10^2 is 1 order of magnitude bigger than 10^1.
what is a cm, mm, µm, nm
1 x 10 ^-2m, 1 x 10^-3 m, 1 x 10^-6, 1 x 10^-9
list the components of both plant and animal cells
cell membrane, mitochondria, cytoplasm, ribosomes, nucleus
list the additional components found in plant cells
permanent vacuole, chloroplast, cell wall
other than storing genetic information, what is the function of the nucleus
controls cellular activities
describe the structure of cytoplasm
- fluid component of cell
- contains organelles, enzymes and dissolved ions and nutrients
what is the function of cytoplasm
site of cellular reactions
what is the function of the cell membrane
controls what goes in and out of the cell
what is the function of mitochondria
site of aerobic respiration
what is the function of the ribosome
site of protein synthesis
what is the plant cell wall made of
cellulose
what is the function of the plant cell wall
provides strength
what does the permanent vacuole contain
cell sap
what is the function of the permanent vacuole
supports the cell
what is the function of chloroplasts
site of photosynthesis
describe how sperm cells in animals are adapted to their function
- (haploid) nucleus contains genetic information of father
- tail enables movement
- mitochondria provides energy for the cell
- acrosome contains enzymes that digest the egg cell membrane
describe how nerve cells are adapted to their function
- long axon allows electrical impulses to be transmitted all over the body
- dendrites from the cell body connect to and receive impulses from other nerve cells, muscles and glands
- myelin sheath insulates the axon and speeds up the transmission of impulses along the nerve cell
describe how muscle cells are adapted to their function
- arrangement of protein filaments allow them to slide over each other to produce muscle contraction
- mitochondria to provide energy for muscle contraction
describe how root hair cells are adapted to their function
- large surface area to absorb nutrients and water from surrounding soil
- thin walls that do not restrict water absorption
describe how xylem cells are adapted to their function
- no end walls to provide a continuous route for water to flow
describe how phloem cells are adapted to their functions
- sieve plates let dissolved amino acids and sugar to be transported up and down the stem
- companion cells provide energy needed for active transport of substances along the phloem
what is cell differentiation
the process by which cells become specialised
why is differentiation important
allows production of different tissues and organs that perform various vital functions in the human body
at what point in their life cycle to most animal cells differentiate
early in their life cycle
for how long do plant cells retain their ability to differentiate
throughout their life
what is the purpose of cell division in mature animals
repair and replacement of cells
what changes does a cell go through as it differentiates
becomes specialised by developing different sub-cellular structures to enable it to perform a specific function
define magnification
the number of times bigger an image appears compared to the actual size of the real object
define resolution
the smallest distance between two objects that can still be distinguished
how does a light microscope work
passes a beam of light through a specimen which travels through the eyepiece lens allowing the specimen to be observed
what are advantages of light microscopes (4)
- inexpensive
- easy to use
- portable
-can observe both live and dead specimens
what are disadvantages of light microscopes
- limited resolution
- lower magnification than electron microscopes
how does an electron microscope work
uses electron beams which are focused by magnets the electrons hit a fluorescent screen which emit visible light producing an image
what are advantages of electron microscopes
- greater magnification
- greater resolution
why do electron microscopes have a higher magnification and resolution
they use a beam of electrons with a shorter wavelength than light
what are disadvantages of electron microscopes
- expensive
- hard to use
- not portable
-can only see dead specimens
magnification equation
magnification= image size ÷ real size
how many chromosome are found in human body cells
46
how many chromosomes are found in gametes
23
how are chromosomes arranged in the nucleus of a human body cells
46 chromosomes form 23 pairs
what are the three main stages of the cell cycle
- chromosomes duplicate
- mitosis
-cell divides
why is mitosis important
- produces identical cells that all have the same genetic information
- produces additional cells for growth and repair
describe the first stage of the cell cycle
cells grow, replicate dna and synthesise more organelles
describe the second stage of the cell cycle
each chromosome in a pair is pulled to opposite poles of the cell then the nucleus divides
describe the third stage of the cell cycle
the cytoplasm and cell membrane split, two daughter cells are provided
what is a stem cell
unspecialised cell capable of differentiating into other cell types
what is the function of stem cells in embryos
embryonic stem cells can differentiate into any type of cell and they can be used to treat conditions such as paralysis and diabetes
what is the function of the stem cells in bone marrow
adult stem cells can differentiate into several cell types to replace dead or damaged tissues, bone marrow turns into many types of blood cell
what is the function of stem cells in plant meristems
to differentiate into any type of cell required by the plant
what is therapeutic cloning
cloning method where an embryo is produced with the same genetic makeup as the patient. the stem cells which originate from the embryo will not be rejected by the patients immune system so can be used to treat certain medical conditions
what are advantages of cloning plants using meristem stem cells
- can prevent rare plants from becoming extinct
- can produce large number of plants with a favourable characteristic
- can produce identical plants for research
what are issues associated with the use of stem cells
- many embryonic stem cells are sourced from aborted embryos -> some people have an ethical/ religious objection
- development of stem cell therapies is slow, difficult and expensive.
- adult stem cells with viruses could transfer infections to the patient
- if donor cells do not have a similar genetic makeup to the patient, an immune response could be triggered
what is diffusion
the net movement of particles from an area of high concentration to an area of low concentration
what three main factors affect the rate of diffusion
- surface area
- concentration gradient
- temperature
give examples of substances transported by diffusion in the lungs and kidney
- lungs: oxygen diffuses into the blood from the lungs and carbon dioxide diffuses into the lungs from the blood
- kidney: urea diffuses from the cells into blood plasma so it can be excreted in urine
how are single-celled organisms adapted for diffusion
large surface area:volume ratio - maximises the rate of diffusion
what four factors increase the effectiveness of a gas exchange surface
- good blood supply
- large surface area
- thin walls
- ventilation
what is osmosis
the movement of water molecules from an area with a high concentration of water to an area of low water concentration through a partially permeable membrane
what is meant when a solution is isotonic to a cell
the water concentration of the solution and the cell is the same
what is meant when a solution is hypertonic to a cell
the water concentration of the solution is lower (higher solute concentration) than the cell
what is meant when a solution is hypotonic to a cell
the water concentration of the solution is higher (lower solute concentration)
what will happen to an animal cell in a very hypotonic solution
water will move into the cell until it bursts
what will happen to an animal cell in a very hypertonic solution
water will leave the cell causing it to shrivel up
how do plant leaves and stems remain rigid
water moves in by osmosis causing the vacuole to swell and the cytoplasm to press against the cell wall
what may happen when a plant cell is places in a very hypertonic solution
water moves out of the cell by osmosis causing the vacuole and cytoplasm to decrease in size. the cell membrane may pull away from the cell wall.
what is active transport
the movement of molecules from an area of low concentration to an area of high concentration against the concentration gradient, using energy from respiration
how do root hair cells use active transport
take up mineral ions from a lower concentration in soil, ions such as magnesium and nitrate are needed for healthy growth
how is active transport used to absorb the products of digestion
active transport is used to transport glucose from a low concentration to a higher concentration in the blood - glucose is then transported into tissues to be used in respiration.
