b1 - cell biology

Created by

Lissy

Cards (41)

problems with light microscope
have a limited magnification - cannot view inside nucleus
limited resolution- image is blurry even with increased magnification- cannot see fine details
advantages of electron microscope  
greater magnification and resolution
can see detail in nucleus
formula for magnification
magnification = size of image/size of real object
size of image = magnification x size of object
size of object = size of image/magnification
features of a light microscope
eye piece
objective lens
stage
slide
lamp
fine focus
coarse focus
animal cell features
nucleus- enclose genetic material
cytoplasm- watery solution where chemical reactions and respiration occur
cell membrane- controls molecules that leave and enter the cell
mitochondria- site of aerobic respiration
ribosomes- site of protein synthesis
plant cell features
have a regular shape
nucleus - contains genetic material
cytoplasm- chemical reactions and respiration
cell membrane- controls molecules leaving and entering
mitochondria- aerobic respiration take place
ribosomes- site of protein synthesis
chloroplasts - contain chlorophyll for photosynthesis
cell wall- made from cellulose to strengthen cell
vacuole- cell sap to give a plant its shape
eukaryotic
contain their genetic material enclosed in a nucleus have a cell membrane and cytoplasm
prokaryotic
not enclosed in a nucleus but in a single loop of dna and small dna plasmids
have a cell membrane and cell wall and cytoplasm
animal cell specialisation
most animal cells are specialised
they have adaptations that carry out a particular function
when cells become specialised they differentiate
sperm cell adaptations
to join with ovum in fertilisation
contain genetic material in haploid nucleus
have a long, streamlined tail to swim to ovum easily
contain enzymes in the tip to digest through outer layer of the ovum
Nerve cell adaptations
carries eletrical impulses around body
Axon to carry impulses
Myelin insulates the axon and speeds up the transmission of nerve impulses
End of the axon has synapses which are junctions for impulses to pass from one nerve cell to another
Dendrites increase the surface area so other nerve cells can connect easier
muscle cell adaptation s
can contract
contain protein fibres which change their length
packed with mitochondria to provide energy for muscle contraction
work together to form muscle tissue
Specialisation of root hair cell
hairs increase surface area of the root, so it can absorb water and dissolved minerals effectively
Do not contain chloroplasts because they are underground
specialisation of xylem cells
found in stem of a plant and form long tubes Which carry water and dissolved minerals from the roots to the leaves
Have very thick walls which contain chemical lignin and provide support
Because cell walls are sealed with lignin they die
No nucleus, cytoplasm, vacuole or chloroplast to make it easier for water and minerals to flow
specialisation of phloem
phloem tubes carry dissolved sugars up and down the plant
Phloem vessels have No nucleus and limited cytoplasm
End walls of the vessel have pores called sieve plates
Both allow dissolved sugars and minerals through cell interior
Each phloem vessel has a companion cell connected by pores
Mitochondria increase companion cell provide energy to phloem vessel cell
Diffusion definition
The spreading out of particles resulting in a net movement from an area of higher concentration to an area of lower concentration
oxygen - diffusion
cells need oxygen for respiration carried out by mitochondria
cells are surrounded by a high concentration of oxygen which is transported in the bloodstream from the lungs
the oxygen molecules move into the cell by diffusion from an area of higher concentration to low
carbon dioxide diffusion
oxygen produces energy in respiration which produces waste carbon dioxide
We then have a higher concentration of carbon dioxide inside the cell than outside
The carbon dioxide moves out of the cell by diffusion
urea diffusion
urea is a waste product produced inside cells
it diffuses out of the cells into the blood plasma and is excreted by the kidneys
what are the factors that affect the rate of diffusion
concentration
temperature
surface area
What is concentration gradient 
The difference in concentration inside and outside the cell
the greater the concentration gradient, the faster diffusion takes place
The smaller the concentration gradient, the slower the rate of diffusion
temperature effecting diffusion
higher the temp the greater the rate of diffusion as particles have more kinetic energy and are moving faster
how does surface area effect rate of diffusion
the larger the surface area the greater the rate of diffusion
Osmosis definition
The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
Dilute vs concentrated solutions
dilute solutions have a high concentration of water
Concentrated solutions contain a low concentration of water
what do partially permeable membranes do
separate dilute and concentrated solutions but allow some molecules to pass through (water but not sugar)
How does water diffuse (osmosis)
From the side with higher water concentration to the lower concentration
osmosis in animal cells
cytoplasm is a concentrated solution
if the cell is placed in water, osmosis will take place
water will move from outside the cell into the cytoplasm
the water moving into the cell will cause it to expand, and even burst
if we then place the cell in a very concentrated solution, water will move out of the cell through osmosis and it will shrink
plant cell osmosis
if a plant cell is placed in water, the water will move into the cell through osmosis and it wilL expand
in plant walls the cell wall prevents the cell from bursting
it becomes turgid
If we place the plant cell in a concentrated solution water moves out of the cell through osmosis causing the cell to shrink and become flaccid
Equation to calculate percentage change of osmosis
Change in value/ original value x 100
Active transport definition
Net movement of substances from a more dilute solution to a more concentrated solution against the concentration gradient and requires energy from respiration
how is active transport and diffusion different
diffusion- particles move down concentration gradient, does not require energy from respiration
active transport- against concentration gradient, requires energy from respiration
active transport - small intestine
the concentration of substances (sugar) in the lumen id lower than the concentration of sugars in the cell
sugars cannot diffuse into the cell they are carried in by active transport
once inside the cell they are transported into the bloodstream and carried around the body
the cells have lots of mitochondria which carry out respiration providing the energy needed for active transport
Active transport In root hair cell
transport ions from soil into cell
The concentration of ions in the soil is lower than the concentration in the cell
Active transport move the ions into the cell
The ions are then transported into the xylem vessels and moved to the leaf
Root hair cell has lots of mitochondria to provide energy for active transport
Surface area to volume ratio
as organisms get bigger, the surface area to volume ratio falls sharply
problems with large surface area to volume ratio
huge problem for multi-cellular organisms
Surface area is not large enough for volume
cells on the surface can get enough oxygen through diffusion
not enough oxygen can diffuse into the cells in the centre as they are too far away from the surface
metabolic waste cannot be removed fast enough to avoid poisoning larger cells
Adaptations fr exchanging materials
Having a large surface area
Having a thin membrane/ being thin to provide short diffusion path
Animals having an efficient blood supply to move diffusing substances away from exchange surfaces and to maintain a steel concentration gradient
Being ventilated to make gas exchange more efficient
Adaptations for exchanging material
Alveoli in lungs, tiny ventilated air sacs, that have a huge surface area and a very rich blood supply for gas exchange.
Villi of small intestine - large surface area, short diffusion path and rich blood supply to make exchange of materials more effective
Gills to exchange carbon dioxide between blood and water - stacks of thin filaments with thin blood supply
Plant roots have a large surface area to make uptake of water and mineral ions more efficient
Stomata - big surface area to maintain steep concentration gradient for diffusion (water,ions,co2)
units for cells
1 millimetre = 1000 micrometers
1 micrometer = 1000 nanometers
microscopy practical
aim to measure length of cells under a microscope
peel a one cell thick layer of onion skin using a scalpel and tweezers
place this on a microscope slide
add a drop of iodine to stain cell
place cover slip over slide and put on stage
turn on light or position mirror
use lowest magnification objective lens
use coarse focus and fine focus knobs
increase magnification and refocus if needed
add a graticule to slide to measure length in micrometer