Studied by 5 people
explain how changes in microscope technology have enabled cell structures and organelles with more clarity and detail
modern light microscopes have an increased magnification and resolution, allowing images to be seen in greater detail
electron microscopes have been created which allow images to be seen in a higher magnification and resolution than light microscopes
explain how changes in microscope technology have increased understanding of the role of sub-cellular structures
being able to see sub-cellular structures in more detail shows the structure of the organelle
which allows for the role of the sub-cellular structure to be understood
state what the quantitative unit is for milli
x 10⁻³
state what the quantitative unit is for micro
x 10⁻⁶
state what the quantitative unit is for nano
x 10⁻⁹
state what the quantitative unit is for pico
x 10⁻¹²
state the function of the nucleus in eukaryotic cells
contains genetic material
which controls cell activities
state the function of the cell membrane in eukaryotic cells
controls substances moving in and out of the cell
provides structural support for the cell
state the function of the mitochondria in eukaryotic cells
releases energy through aerobic respiration for cell activities
state the function of the ribosomes in eukaryotic cells
site of protein synthesis
state the function of the cell wall in plant cells
made of cellulose
provides structure for the cell
state the function of chloroplasts in plant cells
absorbs sunlight rays to produce energy for photosynthesis
state the function of the vacuole in plant cells
supports shape of cell
can be used to store certain substances
explain how to investigate biological specimens using microscopes
place a very thin layer of the biological specimen on a slide
put a few drops of suitable indicator on it
gently lower a cover slip on top of the specimen
press down on the cover slip to remove any bubbles
place on stage and focus the microscope
start on lowest magnification and work your way up to a higher magnification
describe the function of acrosomes in sperm cells
contains enzymes
which digest the jelly coat of the egg cell
allowing the sperm to fertilise the egg cell
describe the function of the haploid nucleus in sperm cells
contains 23 chromosomes
which come together with the egg’s 23 chromosomes during fertilisation
to create a diploid zygote
describe the function of mitochondria in sperm cells
release lots of energy from aerobic respiration
to allow the sperm to swim to the egg cell in the oviducts
describe the function of the tail in sperm cells
allows the sperm to move and swim to the egg cell in the oviducts
describe the function of nutrients in the cytoplasm in egg cells
cytoplasm is nutrient-dense
to provide energy for the development of the zygote
describe the function of the haploid nucleus in egg cells
contains 23 chromosomes
which come together with the sperm’s 23 chromosomes during fertilisation
to create a diploid zygote
describe the function of the change in cell surface membrane after fertilisation in egg cells
the cell surface membrane hardens after fertilisation
to stop other sperm from fertilising the egg cell
describe how ciliated epithelial cells are adapted to their function
cilia are hair-like structures
that beat and waft
and are capable of moving egg cells from the ovaries to the uterus
or wafting mucus to the oesophagus
explain the function of chromosomal DNA in prokaryotic cells
contains genetic material for the cell
explain the function of plasmid DNA in prokaryotic cells
contains a small amount of non-essential genetic material for the cell
explain the function of the cell membrane in prokaryotic cells
controls what substances enter and leave the cell
explain the function of ribosomes in prokaryotic cells
site of protein synthesis
explain the function of the flagellum in prokaryotic cells
used for cell movement
explain how energy in food can be calculated using calorimetry (method)
measure out 25 cm³ of water into a boiling tube using a measuring cylinder
record the starting temperature of the water using a thermometer
record the starting mass of the food sample
set fire to the food sample using a bunsen burner
hold the burning sample 2 cm below the boiling tube until it has completely burned
record the final temperature of the water
explain how energy in food can be calculated using calorimetry (results)
larger increase in water temperature
means more energy contained within the food sample
calculation of energy content of a food sample EQUATION
energy content = (water mass x temp increase x 4.2) / food mass
explain how to investigate the use of chemical reagents to identify starch
add iodine to the unknown sample
a positive result will turn the iodine blue-black
a negative result will keep the iodine yellow
explain how to investigate the use of chemical reagents to identify reducing sugars
add benedict’s solution to the unknown sample
heat in a water bath for 5 minutes
a positive result will turn the benedict’s solution brick red
a negative result will keep the benedict’s solution blue
explain how to investigate the use of chemical reagents to identify proteins
add biuret solution to the unknown sample
a positive result will turn the biuret solution purple
a negative result will keep the biuret solution blue
explain how to investigate the use of chemical reagents to identify fats
mix the unknown sample with 4 cm³ of ethanol
allow the sample to dissolve in the ethanol
strain the solution into another test tube
add the solution to an equal volume of distilled water
a positive result will produce a cloudy emulsion
a negative results will keep the solution colourless
explain the importance of enzymes
they are biological catalysts
in the synthesis of
carbohydrates, proteins and lipids
and their breakdown into
sugars, amino acids, fatty acids and glycerol
explain the mechanism of enzyme action
enzymes are specific to one substrate as the active site of the enzymes is complementary to the substrate
when the substrate moves into the active site, the enzyme-substrate complex is created
after the reaction has been catalysed by the enzyme, the products leave the active site
explain how enzymes can be denatured due to change in the shape of the active site
once the temperature is past its optimum temperature, it denatures
as the bonds that hold the amino acid chain of the enzyme together have been disrupted
causing the shape of the active site to change
meaning the complementary substrate is unable to fit into the active site and complete the enzyme substrate complex
explain the effect of temperature on enzyme activity
as temperature increases, enzyme activity increase
due to increased kinetic energy of the particles leading to them moving faster and creating more successful collisions of substrate with enzyme
which leads to a faster rate of reaction
after the optimum temperature, the enzyme denatures
as the bonds holding together amino acid chain of the enzyme have been disrupted
changing the shape of the active site
making it no longer complementary to the specific substrate (no enzyme substrate complex)
explain the effect of substrate concentration on enzyme activity
substrate concentration increases, enzyme activity increases
increases the rate of reaction
when enzyme concentration remains fixed whilst substrate concentration increases
enzyme’s active site becomes saturated
and the rate of the reaction will not increase any further
explain the effect of pH on enzyme action
most human enzymes have a pH of 7
at optimum pH, the rate of the reaction will be quickest
when the pH is too far above or below the optimum pH, the bonds that hold together the amino acid chain creating the enzyme are disrupted
leading to the shape of the active site to change and no longer be able to complete the enzyme-substrate complex
state how to calculate the rate of enzyme activity
rate = change / time
explain how to investigate the effects of pH on enzyme activity (method)
add a drop of iodine to each well in a spotting tile
use a syringe to place 2 cm³ of amylase into a test tube
add 1 cm³ of buffer solution at pH 2 to the test tube using a syringe
add 2 cm³ of starch solution to the test tube
using a stopwatch, every 10 seconds, add a drop of the solution into one of the wells
repeat this process until the iodine stops turning blue-black
record the time taken for the reaction to have completed (iodine to have stopped turning blue-black)
repeat the experiment with buffer solutions at different pHs
explain how to investigate the effects of pH on enzyme activity (results)
amylase (enzyme) breaks starch down into glucose
when iodine solution stops turning blue-black, all the starch has been digested
at optimum pH of amylase, iodine will have stopped turning blue-black the fastest
as enzyme is catalysing the reaction at the fastest rate and digesting all the starch
below or above the optimum pH, the iodine will take longer to stop turning blue-black or will remain blue-black the entire investigation
due to the enzyme starting to denature and being unable to bind with the starch and digest it
explain how substances are moved in and out of cells by diffusion
movement of molecules
from a high concentration gradient
to a low concentration gradient
state examples of diffusion in leaves
diffusion of oxygen from air spaces between mesophyll cells to mitochondria in plant cells
diffusion of carbon dioxide from air spaces between mesophyll cells to chloroplasts in mesophyll cells
state examples of diffusion in lungs
diffusion of oxygen from the alveolar air space to blood in capillaries around alveoli
diffusion of carbon dioxide from blood in capillaries around alveoli to the alveolar air space
state a factor that influences diffusion
surface area to volume ratio
a bigger cell has a smaller surface area to volume ratio
which slows down the rate of diffusion
osmosis definition
osmosis is the movement of water molecules from a high water concentration to a low water concentration across a partially-permeable membrane
explain how substances are moved in and out of cells by active transport
movement of molecules through a membrane
from a low concentration gradient
to a high concentration gradient
explain how active transport works
molecules from a low concentration gradient
are transported through the membrane
by a carrier molecule
to a high concentration gradient
state how to calculate percentage gain/loss of mass in potatoes
(final mass - initial mass / initial mass) x 100
explain how to investigate osmosis in potatoes (method)
prepare a range of sucrose solutions in different labelled beakers from 0 mol/dm³ (distilled water) to 1 mol/dm³
use a knife, cork borer and ruler to cut 6 equal-sized potato cylinder
blot each cylinder with a paper towel and weigh their initial masses
put 1 cylinder into each sucrose solution
after 4 hours, remove the potato cylinders and weigh their final masses
use the equation (final mass - initial mass)/initial mass x 100 to find the percentage gain/loss of mass in the potato
explain how to investigate osmosis in potatoes (results)
the potato in the distilled water will have gained the most mass, lower water concentration in potato than in water, causes molecules to move across the partially-permeable membrane
as the sucrose concentration in the solutions increases, mass gain will decrease and eventually lead to mass loss as, water concentration in the potato is becoming higher than the water concentration in the sucrose solutions
