Key concepts in biology
What's the difference between prokaryotic and eukaryotic cells?
Prokaryotic cells do not have a nucleus while eukaryotic cells have a nucleus
What is the function of a nucleus?
Contains genetic material which controls the cells activities and it's also enclosed in a nuclear
membrane
What is the function of mitochondria?
Aerobic respiration reactions occur, which provides energy for the cell
What is the function of a cytoplasm?
A gel like substance where most of the cells activities occur, and contains enzymes that control
these
What is the function of a cell membrane?
holds the cell together and controls what goes in and out of the cell
What is the function of ribosomes?
makes new proteins for the cell through protein synthesis
What is the function of a cell wall
made from cellulose and supports and provides strength to the cell
What is the function of a chloroplast
where photosynthesis takes place, providing food for the plant. contains chlorophyll, a green
pigment which traps energy transferred from the sun which is used for photosynthesis
What is the function of a vacuole
stores cell sap and helps keep cell firm and rigid
What is the function of chromosomal DNA
bacterial cells don't have a nucleus so this just floats in the cytoplasm. it controls the cells
activities and replication
What is the function of plasmid DNA
small rings of DNA that contain extra genes to those found in the chromosomal DNA
What is the function of flagellum
helps the cell move
what is the structure of an animal cell
has a nucleus, mitochondria, cytoplasm, cell membrane and ribosomes
,what is the structure of a plant cell
has a cytoplasm, cell wall, cell membrane, chloroplast, nucleus and a vacuole
what is the structure of a bacterial cell
has plasmid DNA, ribosomes, flagellum, a cell wall (made of a different substance),
chromosomal DNA and a cell membrane
How is an egg cell adapted to its function?
● contains nutrients in the cytoplasm to supply the growing embryo
● has a haploid nucleus that can fuse with another from the sperm to form a diploid zygote
● After fertilisation, the membrane changes so that no more sperm cells can enter
How has the sperm cell adapted to its function?
● has a tail for swimming to the egg cell for fertilisation
● lots of mitochondria around the base of the tail to release the energy to propel the sperm
● haploid nucleus that fuses with the egg nucleus to form a diploid zygote
● acrosome contains enzymes to digest a way through the egg cell membrane
how has ciliated epithelial cells adapted to their function
● lines tubes and moves things along the tube, such as mucus
● has a lot of cilia to move mucus, containing dirt and bacteria, away from the lungs
how have electron microscopes enabled scientists to develop their understanding of cells
● allow small sub-cellular structures to be observed in detail
● enable scientists to develop more accurate explanations about how cell structure relates
to function
how to calculate total magnification
eyepiece lens magnification x objective lens magnification
how can the magnification of an image be calculated
magnification = size of image/size of object
investigate biological specimens using microscopes practical method
1. collect a small specimen of the cells
2. add a drop of stein to the centre of the microscope slide
3. place specimen on microscope slide
4. place coverslip on top of specimen
5. examine under microscope, start with the lowest magnification and work your way up
explain the lock and key hypothesis
the shape of the active site matches the shape of the substrate molecules and hold them close
, together, so bonds can form between them and make a product molecule. The product molecule
is a slightly different shape to the substrate molecules, so it no longer fits tightly in the active site
and is released
How can enzymes be denatured due to changes in the shape of the active site?
If the shape of the active site changes too much, the substrate will no longer fit neatly in it. The
enzyme will no longer be able to catalyse a reaction, so the enzyme is denatured
explain the effect of temperature on enzyme activity
As the temperature increases, molecules move faster. Higher speeds increase the chance of
substrate molecules bumping into enzyme molecules and slotting into the active site. However,
when the temperature gets too high, the shape of the enzyme molecule starts to change. The
amount of change increases as the temperature increases. So it becomes more and more
difficult for a substrate molecule to fit into the active site
explain the effect of pH on enzyme activity
Changing the pH can change the shape of the enzyme's active site and so change its ability to
bond with the substrate. The enzyme works fastest at the optimum pH, which is usually seven in
humans
explain the effect of substrate concentration on enzyme activity
At low concentrations, many enzyme molecules have empty active sites, so the rate of reaction
is slow. At high concentrations, most enzyme active sites contain substrate molecules, and the
rate or reaction is as fast as it can be
investigate the effect of pH on enzyme activity practical method
1. place single drops of iodine solution on each well of a spotting tile
2. heat a beaker of water on a Bunsen burner until the temperature is 40°C
3. Measure 2 cm³ of amylase solution into a tube, and add 1 cm³ of a solution with a
particular pH into it
4. Add 2 cm³ of starch solution into the tube, and place it into the beaker of water on the
Bunsen burner and start a stopwatch
5. every 20 seconds, use a pipette to place a drop of the solution into one of the wells. the
mixture should turn blue-black to indicate that starch is still present and hasn't been yet
broken down
6. Continue repeating previous step until the solution remains orange and record the time it
takes
how to calculate rate of reaction
change (change in substance being measured) / time (time taken for change to occur)
function of carbohydrases
convert carbohydrates into simple sugars
What's the difference between prokaryotic and eukaryotic cells?
Prokaryotic cells do not have a nucleus while eukaryotic cells have a nucleus
What is the function of a nucleus?
Contains genetic material which controls the cells activities and it's also enclosed in a nuclear
membrane
What is the function of mitochondria?
Aerobic respiration reactions occur, which provides energy for the cell
What is the function of a cytoplasm?
A gel like substance where most of the cells activities occur, and contains enzymes that control
these
What is the function of a cell membrane?
holds the cell together and controls what goes in and out of the cell
What is the function of ribosomes?
makes new proteins for the cell through protein synthesis
What is the function of a cell wall
made from cellulose and supports and provides strength to the cell
What is the function of a chloroplast
where photosynthesis takes place, providing food for the plant. contains chlorophyll, a green
pigment which traps energy transferred from the sun which is used for photosynthesis
What is the function of a vacuole
stores cell sap and helps keep cell firm and rigid
What is the function of chromosomal DNA
bacterial cells don't have a nucleus so this just floats in the cytoplasm. it controls the cells
activities and replication
What is the function of plasmid DNA
small rings of DNA that contain extra genes to those found in the chromosomal DNA
What is the function of flagellum
helps the cell move
what is the structure of an animal cell
has a nucleus, mitochondria, cytoplasm, cell membrane and ribosomes
,what is the structure of a plant cell
has a cytoplasm, cell wall, cell membrane, chloroplast, nucleus and a vacuole
what is the structure of a bacterial cell
has plasmid DNA, ribosomes, flagellum, a cell wall (made of a different substance),
chromosomal DNA and a cell membrane
How is an egg cell adapted to its function?
● contains nutrients in the cytoplasm to supply the growing embryo
● has a haploid nucleus that can fuse with another from the sperm to form a diploid zygote
● After fertilisation, the membrane changes so that no more sperm cells can enter
How has the sperm cell adapted to its function?
● has a tail for swimming to the egg cell for fertilisation
● lots of mitochondria around the base of the tail to release the energy to propel the sperm
● haploid nucleus that fuses with the egg nucleus to form a diploid zygote
● acrosome contains enzymes to digest a way through the egg cell membrane
how has ciliated epithelial cells adapted to their function
● lines tubes and moves things along the tube, such as mucus
● has a lot of cilia to move mucus, containing dirt and bacteria, away from the lungs
how have electron microscopes enabled scientists to develop their understanding of cells
● allow small sub-cellular structures to be observed in detail
● enable scientists to develop more accurate explanations about how cell structure relates
to function
how to calculate total magnification
eyepiece lens magnification x objective lens magnification
how can the magnification of an image be calculated
magnification = size of image/size of object
investigate biological specimens using microscopes practical method
1. collect a small specimen of the cells
2. add a drop of stein to the centre of the microscope slide
3. place specimen on microscope slide
4. place coverslip on top of specimen
5. examine under microscope, start with the lowest magnification and work your way up
explain the lock and key hypothesis
the shape of the active site matches the shape of the substrate molecules and hold them close
, together, so bonds can form between them and make a product molecule. The product molecule
is a slightly different shape to the substrate molecules, so it no longer fits tightly in the active site
and is released
How can enzymes be denatured due to changes in the shape of the active site?
If the shape of the active site changes too much, the substrate will no longer fit neatly in it. The
enzyme will no longer be able to catalyse a reaction, so the enzyme is denatured
explain the effect of temperature on enzyme activity
As the temperature increases, molecules move faster. Higher speeds increase the chance of
substrate molecules bumping into enzyme molecules and slotting into the active site. However,
when the temperature gets too high, the shape of the enzyme molecule starts to change. The
amount of change increases as the temperature increases. So it becomes more and more
difficult for a substrate molecule to fit into the active site
explain the effect of pH on enzyme activity
Changing the pH can change the shape of the enzyme's active site and so change its ability to
bond with the substrate. The enzyme works fastest at the optimum pH, which is usually seven in
humans
explain the effect of substrate concentration on enzyme activity
At low concentrations, many enzyme molecules have empty active sites, so the rate of reaction
is slow. At high concentrations, most enzyme active sites contain substrate molecules, and the
rate or reaction is as fast as it can be
investigate the effect of pH on enzyme activity practical method
1. place single drops of iodine solution on each well of a spotting tile
2. heat a beaker of water on a Bunsen burner until the temperature is 40°C
3. Measure 2 cm³ of amylase solution into a tube, and add 1 cm³ of a solution with a
particular pH into it
4. Add 2 cm³ of starch solution into the tube, and place it into the beaker of water on the
Bunsen burner and start a stopwatch
5. every 20 seconds, use a pipette to place a drop of the solution into one of the wells. the
mixture should turn blue-black to indicate that starch is still present and hasn't been yet
broken down
6. Continue repeating previous step until the solution remains orange and record the time it
takes
how to calculate rate of reaction
change (change in substance being measured) / time (time taken for change to occur)
function of carbohydrases
convert carbohydrates into simple sugars
