Studied by 6 people
Light microscope
use a beam of light to form an image
Electron microscope
use a beam of electrons to form an image
Features of the light microscope [4]:
magnify up to 2000x
relatively cheap
portable
can magnify live specimens
Features of the electron microscope [4]:
magnify up to 2000000x
very expensive
immovable
need special temperature, pressure and humidity
What electron microscope creates high quality 2D images?
Transmission electron microscope
What electron microscope creates low quality 3D images?
Scanning electron microscope
Image size =
Magnification x Real size
Resolving power
the capacity of a microscope to distinguish between two separate points
Organelles in an animal cell [5]:
nucleus
cytoplasm
cell membrane
mitochondria
ribosome
Nucleus
controls activities in the cell and contains genetic information
Cytoplasm
organelles are suspended and chemical reactions take place
Cell membrane
controls the movement of substances in and out of the cell
Mitochondria
where aerobic respiration takes place
Ribosome
where protein synthesis takes place
What organelles are unique to plants and algae? [3]
cell wall
chloroplast
permanent vacuole
Cell wall
a cellulose casing which strengthens and supports the cell
Chloroplast
organelles containing chlorophyll to absorb sunlight for photosynthesis
Permanent vacuole
space in cytoplasm filled with cell sap - keeps cells rigid
Eukaryotic cell
cell with a nucleus
What organisms are eukaryotes? [4]
animals
plants
fungi
protista
Prokaryotic cell
cell without a nucleus
What do bacteria have instead of a nucleus?
a ring of genetic material and individual plasmids
Plasmid
extra small rings of DNA for very specific features
Adaptations of the neurone [3]:
many dendrites to connect to other cells
long axon to carry the nerve impulse
myelin sheath to insulate
Adaptations of striated muscle cells [3]:
special proteins that slide over each other
many mitochondria to transfer energy for contraction
store glycogen, insoluble chain of carbohydrates
Adaptations of sperm cells [4]:
flagella for moving withing the female reproductive system
many mitochondria to transfer energy for the flagella
acrosome stores digestive enzymes to break down the egg
large nucleus for genetic information
Adaptations of root hair cells [3]:
increased surface area for osmosis
large permanent vacuole to speed up osmosis
many mitochondria to transfer energy for active transport
Adaptations of photosynthetic cells [3]:
contain chloroplasts containing chlorophyll to absord energy
positioned in continuous layers in leaves and stem to absorb energy
large permanent vacuole to keep cell rigid for stem and leaf support
Adaptations of xylem cells [2]:
build up lignin spirals then die to form long, hollow tubes
spirals and rings of lignin make cells strong to withstand pressure of water moving up the plant
Adaptations of phloem cells [2]:
cell walls between cells break down into sieve plates
lose internal structures but are supported by companion cells
What does the xylem carry?
water and mineral ions
What does the phloem carry?
nutrients from photosynthesis
Diffusion
the spreading out of particles in a fluid
What is the net movement in diffusion?
from an area of high concentration to an area of low concentration
What increases the rate of diffusion? [2]
a large concentration gradient
higher temperature
net movement =
particles in - particles out
How do cells speed up diffusion?
higher surface area (microvilli, protrusions)
Osmosis
water moves across a partially permeable membrane from an area of high concentration to an area of low concentration
Partially permeable membrane
a membrane that only lets some types of particles through
Isotonic
concentrations are the same in and out
Hypertonic
water concentration is higher in than out
Hypotonic
water concentration is higher out than in
What happens to an animal cell in a hypertonic solution?
it becomes shrivelled
What happens to an animal cell in a hypotonic solution
it may burst
Turgor
water pressure in a plant cell
What condition must plant cells be kept in?
hypotonic solutions (keep turgid)
What happens to a plant cell in a hypertonic solution?
plasmolysed
What happens to a plant cell in a hypotonic solution?
turgid
What happens to a plant cell in an isotonic solution?
flaccid
What happens to plants if their cells are not turgid?
They wilt
How to investigate osmosis:
Put chips of plant tissue into solutions with different concentrations of salt or sugar, then find the difference in mass from start to finish.
Active transport
the movement of substances across a partially permeable membrane, against the concentration gradient
What is needed for active trasport?
mitochondria, which respire, which releases energy
Active transport in plants:
the root hair cells take nitrate and other ions out of dilute solutions in the soil
Active transport in animals:
glucose sometimes must be actively transported from the gut to the blood
Surface area to volume ration (SA:V)
the ratio of an organism’s surface area to its volume
What SA:V ratio is ideal for diffusion and why?
a small one, as it gives short diffusion distances
How does a large SA:V affect diffusion?
simple diffusion is no longer enough for the organism, as the distance from the centre and the surface increases
Downsides of a large SA:V [2]:
gas and food molecules cannot reach every cell
metabolic waste cannot be removed fast enough
Adaptations for exchanging materials [4]:
large surface area for exchange
thin membrane for a short diffusion path
efficient blood supply to maintain a steep concentration gradient
being ventilated to maintain a steep concentration gradient
How are the lungs adapted for gas exchange? [4]
ventilated
large surface area
rich blood supply
short diffusion path
How are gills adapted for material exchange? [4]
ventilated by operculum
large surface area from filaments
rich blood supply
short diffusion path
How are plant roots adapted for material exchange? [2]
large surface area
transpiration stream moves water away, keeping steep concentration gradient
How are plant leaves adapted for material exchange? [2]
large surface area (thin,flat leaves; air spaces in leaf tissues, stomata)
steep concentration gradient maintained
Cell division
the formation of two genetically identical daughter cells
Where are the chromosomes?
in the nucleus
What are chromosomes?
long, thin strings of genes that contain instructions for making new cells
What are genes?
Genes are sections of DNA that control a single genetic trait.
How many chromosomes are in the nucleus of a body cell?
46 chromosomes
How are chromosomes arranged in cells?
23 pairs - one from mother and one from father
How many chromosomes do gametes have?
23 chromosomes
Cell cycle
series of events that cells go through as they grow and divide
Mitosis
asexual reproduction by splitting the nucleus
How long is the cell cycle?
24 hours to several years
When is the cell cycle rapid?
as a baby develops and throughout childhood
When does the cell cycle slow?
after puberty
What areas continue rapid cell division in adults? [4]
the hair follicles, the skin, the blood, the lining of the digestive system
Cell cycle: stage 1 [4]
longest stage
cells grow bigger and increase mass
replicate DNA to form two copies of each chromosome
replicate organelles
Cell cycle: stage 2 [3]
mitosis
one set of chromosomes is pulled to each side
nucleus divides
Cell cycle: stage 3 [1]
cytoplasm and cell membranes divide to form daughter cells
Diploid
46 chromosomes
Interphase [3]
cell grows
cell replicates chromosomes
organelles replicated
Prophase [3]
chromosomes condense
nuclear membrane dissolves
spindle fibres form
Metaphase [2]
nucleus dissolves
chromosomes align in centre
Anaphase [1]
chromosomes moved to opposite poles of cell
Telophase [3]
just before cells split
nuclear membranes reform
spindle fibres dissolve
Cell cycle order
interphase
prophase
metaphase
anaphase
telophase
Differentiation
process in which cells become specialised in structure and function
Stem cells
cells that can differentiate into specialised cells
Embryonic stem cells
can differentiate into any kind of cell
Adult stem cells
can only differentiate to a limited set of cells
What organism can differentiate all through life?
plants
Where are undifferentiated cells found in plants?
meristem (stem and roots)
What is special about plant cells?
they can redifferentiate
Cloning in plants
You take cuttings from good parent plants and then planting them in moist conditions to produce clones of the parent plant.
Zygote
fertilized egg
Where are embryonic stem cells found?
inner cells of early embryo
Where can adult stem cells be found?
bone marrow
When might adult stem cells be used?
after injury
How could we use stem cells in medicine? [6]
body parts for transplant
replacing nerves (paralysis)
curing blindness
treat type 1 diabetes
treat infertility
treat dementia
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Flashcard (102)