paper 1 topics
what are the organelles in an animal and plant cell [functions]?
- nucleus: contains DNA [a polymer of 2 strands that form a double helix]
- cytoplasm: a jelly like substance where chemical reactions occur
- mitochondria: where energy is released for respiration
- ribosomes: site of proteinsynthesis
- cell membrane: controls what substances goes in and out of the cell
plant only:
- cell wall: contains cell cellulose and strengthens the cell
- vacuole: contains cell sap and gives support to the cell
- chloroplasts: contains chlorophyll which absorbs light energy for photosynthesis
what are the properties of a eukaryotic cell?
- DNA is found in the nucleus
- eukaryotic cells are plant/animal/fungi cells
- larger
- divide by mitosis
what are the properties of a prokaryotic cell?
- DNA is a single loop or a plasmid
- smaller
- have a cell wall
- bacteria cells
- divide by binary fission
what are the properties of a light microscope?
- relatively cheap
- low magnification
- low resolution
- sample can be living
- use light beams
what are the properties of an electron microscope?
- expensive
- high magnification
- high resolution
- sample cannot be living
- use electron beams
what is magnification?
the number of times larger a specimen appears to be
what is resolution?
the smallest change in quality measured
what is the IAM triangle ?
I = image size
A = actual size
M = magnification
what are the unit conversions?
mm to micrometer = x1000
micrometer to nanometer = x1000
what does the coarse adjustment knob do on a microscope?
moves the stage up or down
what does the fine adjustment knob do on a microscope?
it is for focus
what is the high power objective lense for?
for high magnification
what is the low power objective lense for?
for low magnification
when do animal and plant cells differentiate?
- animal: at early development
- plant: throughout their lifetime
what is the function of a sperm cell and its structure?
- fertillises an egg cell
- flagellum: to swim to the egg
- mitochondria: to release energy for respiration so it can swim
- enzymes: to break past the white blood cells
what is the funcrion of a red blood cell and its structure?
- carries oxygen around the body
- flat bi concave disk shape: increases the surface area to volume ratio
- no nucleus: to carry more blood
- haemoglobin: red pigment that binds onto oxygen molecules
what is the function of a muscle cell and its structure?
- contracts and relaxes for movement
- protein fibres: contract to make the cell shorter
- mirochondria: energy is released for respiration so the cell can contract
what is the function of a nerve cell and its structure?
- carries electrical impulses around the body
- dendrites: connects with other neurones
- myelin sheath: increases transmition speeds
what is the function of a root hair cell and its structure?
- absorbs water and mineral ions
- long projection: increases surface area which speeds up absorbtion
- mitochondria: for active transport
what is the function of a palisade cell and its structure?
- enables photosynthesis
- chloroplasts: contains chlorophyll which absorb light energy gor photosynthesis
- located at the top of the leaf: absorbs the most light energy
what is osmosis?
- the net movement of water molecules from an area of high water concentration to an area of low water concentration down the concentration gradient and through a partially permeable membrane
- passive process [no energy]
- plants: water moves via osmosis from the soil into the root hair cells
what is diffusion?
- the net movement of particles from an area of high concentration to an area of low concentration down the concentration gradient
- passive process
- humans: nutrients in the small intestine diffuse into the blood in the capillaries through the villi / oxygen diffuses from the air into the alveolu into the blood and in the capillaries / carbon dioxide diffuses from the blood in the capillaries into the air in the alveoli / urea diffuses from cells into the blood for excretion by the kidney
- plants: carbon dioxide diffuses into the leaves through the stomata / oxygen diffuses into the air through the stomata
what is active transport?
- the movement of particles from an area of low concentration to an area of high concentration against the concentration gradient
- energy is released through respiration
- humans: sugar molecules are absorbed from the small intestine when the sugar concentration is higher in the blood
- plants: absorbs mineral ions into the
root hair cells
what factors affect the rate of diffusion?
- difference in concentration [the steeper the concentration gradient the faster the rate]
- temperature [the higher the temperature the faster the rate]
- surface area of the membrane [the larger the surface area the faster the rate]
What are the adaptations of the villi for gas exchange?
the villi absorbs nutrients
- good blood supply
- thin wall [only one cell thick]
- network of capillaries
- large surface area [due to folding]
what are the adaptations of thhe alveoli for gas exhange?
the alveoli are in the lungs and are for gas exhange
- network of capillaries [good blood supply]
- rate of diffusion is fast because the membrane is moist/only one cell thick [short diffusion distance]/large surface area
what is mitosis?
- produces two genetically identical daughter cells
- for growth and repair of cells
- asexual reproduction [clone]
what is stage 1 of the cell cycle?
- celk grows bigger
- dna is replicated [chromosomes duplicate]
- number of sub cellular structures increases
what is stage 2 of the cell cycle ?
- complete set of chromosomes is pulled to either side of the cell
- nucleus divides to form two nuclei
what is stage 3 of the cell cycle?
- cytoplasm and cell membrane divide; forming two genetically identical daughter cells
what is a stem cell?
an undifferentiated cell that can specialise into one or more different stem cells
what are the two types of stem cells in mammals
- embryonic stem cells
- adult stem cells