Revision 1 Flashcards
Eukaryotic Cells
1 mark
Complex Cells
Examples of a Eukaryotic Cell
2 marks
- Animal
2. Plant
Prokaryotic Cells
1 mark
(Small) Simple Cells
Example of a Prokaryotic Cell
1 mark
- Bacterium
Mitochondria
1 mark
Subcellular structure where most of the reactions for cellular respiration take place
- Powerhouse of the cell; provides energy.
Vacuole
1 mark
Subcellular structure that maintains the internal pressure in a plant cell.
Similarities between a Bacterial Cell and a Plant Cell
4 marks
Both have;
- a Cell Membrane
- a Cell Wall
- Cytoplasm
- Ribosomes
Differences between a Bacterial Cell and a Plant Cell
5 marks
Plant Cells have Chloroplasts + Mitochondria, Bacteria don’t.
Chromosomes of Plant Cells are contained within a Nucleus - Bacteria have a Chromosomal DNA that floats freely in Cytoplasm.
Bacterial Cells may contain small loops of extra DNA called plasmids.
Cell Membrane
2 marks
- Holds cell together
- Controls what enters + leaves.
Nucleus
2 marks
Contains genetic material that controls Cell activities.
Ribosomes
2 marks
Involved in translation of genetic material in the synthesis of proteins.
Structural differences between a Plant Cell and an Animal Cell
(3 marks)
Plant cell has;
- a Cell Wall
- Large Vacuole
- Chloroplasts
Where are ciliates epithelial cells found?
2 marks
On the surface of organs.
2 functions of an egg cell
4 marks
- Carry the female DNA
- Provide nutrients to the embryo in the early stages.
Why do Sperm Cells contain a large number of Mitochondria?
3 marks
To provide the energy (from respiration) needed to swim to the egg.
Why is it important that the Egg + Sperm Cells are Haploid?
4 marks
So when an Egg Cell + a Sperm Cell nucleus combine (at Fertilisation) the resulting Cell will have the right number of Chromosomes.
Cells with only half the number of Chromosomes of a normal body Cell
(1 mark)
Haploid Cells
Cells with the full number of Chromosomes of a normal body Cell
(1 mark)
Diploid Cells
Describe how ciliated Epithelial Cells are adapted for moving substances.
(3 marks)
They have Cilia, which beat to move substances in one direction along the surface.
Why does the structure of an Egg’s Cell Membrane change after Fertilisation?
(2 marks)
To stop more Sperm entering - making sure that the offspring end up with the right amount of DNA.
Parts of the Sperm Cell - Explained
6 marks
Tail - allows the Sperm to swim towards an Egg Cell.
Acromosome - stores the Enzymes the Sperm needs to digest it’s way through the membrane of an Egg Cell.
What is the purpose of the fine adjustment knob on a light microscope?
(2 marks)
To focus the lens until a clear image of what’s on the slide appears.
True or false? Electron microscopes have a smaller magnification, but a higher resolution than light microscopes.
(3 marks)
False. Electron microscopes have both a higher resolution + a higher magnification than light microscopes.
What is resolution?
1 mark
The ability to distinguish between 2 points.
What is magnification?
1 mark
Process of making something look larger.
Describe how you would put a cover slip onto a specimen on a slide so that it’s ready to be viewed under a light microscope.
(6 marks)
The cover slip should be placed at one end of the specimen + held at an angle with a mounted needle.
It should then be carefully lowered onto the slide + pressed down gently so that no air bubbles are trapped under it.
How has Electron Microscopes increased our understanding of Cells?
(7 marks)
Their high magnification + high resolution has allowed biologists to see very small structures in detail, like the internal structure of mitochondria + chloroplasts.
This has allowed biologists to better understand how cells work + has given us a greater understanding of the role of subcellular structures.
What to remember when drawing a scientific drawing of a Cell?
(7 marks)
- Labels of important features
- A scale
- Magnification used
- Make sure lines do not cross over
- Do not shade
- Make lines clear; using a sharp pencil
Is a picometer smaller or larger than a nanometer?
5 marks
Smaller -
a picometer is 10 ^-12m (Small -12)
a nanometer is 10^-9m (Small -9)
Idina knows the eyepiece lens + objective lens magnification of her microscope.
What formula should she use to calculate the microscopes total magnification?
(3 marks)
Total magnification = eyepiece lens magnification x objective lens magnification.
A specimen is 100 μm wide. Calculate the width of the image of the specimen under a magnification of x 200. Give your answer in mm.
Use the equation:
magnification = image size/real size
(10 marks)
Image size = magnification x real size
= 200 x 100 μm = 20 000 μm
To convert micrometers (μm) to millimetres (mm) divide by 1000
= 20 000 μm/1000 = 20mm
Ans: 20mm
How can you Convert Micrometers (μm) to Millimeters (mm)?
3 marks
Divide by 1,000
or x 10^-3.
How can you Convert Millimeters (mm) to Micrometers (μm)?
3 marks
Multiply by 1,000
or x 10^3.
A student uses a calculator to calculate the real size of a protists that has an image size of 214 μm under a microscope with x18 magnification.
Estimate the real size of the protist without a calculator.
(8 marks)
First round the Numbers to one significant figure.
Image size = 200 μm
Magnification = x 20
Real size = 200 / 20 = 10 μm
Ans: 10 μm
Why might the student want to estimate the size of the protist as well as calculate it with a calculator?
(1 mark)
To check the answer they got with the calculator is sensible.
How can you convert Picometers (pm) to Micrometers (μm)?
2 marks
Divide by 100,000,0
or x 10^-6.
How can you convert Micrometers (μm) to Picometers (pm)?
3 marks
Multiply by 100,000,0
or x 10^6.
How can you convert Nanometers (nm) to Millimeters (mm)
3 marks
Multiply by 100, 000,0
or x 10^6.
How can you convert Millimeters (mm) to Nanometers (nm)?
3 marks
Divide by 100, 000,0
or x 10^-6.
How can you convert Millimetres (mm) to Picometers (pm)?
3 marks
Divide by 100,000,000,0
or x 10^-9.
How can you convert Picometers (pm) to Millimetres (mm)?
3 marks
Divide by 100,000,000,0
or x 10^-9.
How can you convert Nanometers (nm) to Picometers (pm)?
3 marks
Divide by 1,000.
or 10^-3.
How can you convert Picometers (pm) to Nanometers (nm)?
3 marks
Multiply by 1,000.
or 10^3.
Standard forms for converting units into Metres (m)
12 marks
Milli (mm)- x 10^-3
Micro (μm)- x 10^-6
Nano (nm)- x 10^-9
Pico (pm)- x 10^-12
How can you convert Micrometers (μm) to Nanometers (nm)?
3 marks
Multiply by 1,000
or x 10^3.
How can you convert Nanometers (nm) to Micrometers (μm)?
2 marks
Divide by 1,000
or x 10^-3.
How do Enzymes affect the rate of a reaction?
2 marks
Enzymes increase the rate of a reaction (they act as Biological catalysts).
What is an active site of an enzyme?
3 marks
The part of the enzyme which joins on to its substrate to catalyse the reaction.
True or false? Enzymes have a high specificity for their substrate.
(2 marks)
True. Enzymes usually only work with one substrate.
A graph shows the effect of substrate concentration on the rate of an enzyme-catalysed reaction.
Why does a further increase in substrate concentration have no effect on the rate of reaction after its peak?
(4 marks)
After it’s peak there are so many substrate molecules that all the active sites of the enzymes are full - adding more substrate makes no difference to the rate of the reaction.
Apart from substrate concentration, give 2 variables that affect the rate of an enzyme-catalysed reaction.
(3 marks)
Temperature + pH
all enzymes have an optimum temp and pH that they work best at
Describe what happens to an enzyme when it is denatured.
4 marks
Some of the bonds holding the enzyme together break + the shape of its active site changes - substrate then won’t fit so the enzyme can’t catalyse reactions any more.
True or false?
pH is the dependent variable in an experiment investigating how pH Affects enzyme activity.
(5 marks)
False.
pH is the independent variable - the variable that you change in order to see what effect it has on another variable. The dependent variable (the variable you measure when you change the independent variable) is enzyme activity.
In an experiment investigating how pH Affects amylase activity, what would you use to test for the presence of starch?
(1 mark)
Iodine Solution
A student is investigating the effect of pH on the rate of amylase activity.
Suggest how the student could control the temperature of the amylase + starch solution during the experiment.
(5 marks)
The student could put a test tube containing the solution in a beaker of Water over a Bunsen burner + use a thermometer to help keep the water at a constant temperature.
Alternatively, the student could use an electric water bath.
The student uses continuous sampling to record how long it takes for the amylase to break down all of the starch.
What is continuous sampling?
(4 marks)
Continuous sampling - when lots of samples are taken at regular intervals over a particular time period.
A scientist carried out an enzyme-controlled reaction. After 100 seconds, 45 cm^3 of the product had been produced.
Calculate the rate of reaction in cm^3/s.
Use the equation:
Rate of reaction = amount of product formed / time
Rate of reaction = amount of product formed / (divided by) time
= 45 / 100
= 0.45cm^3/s
What happens if the temperature is too hot while investigating the effect of pH on enzyme activity?
(2 marks)
The Enzyme will denature
Which type of molecule are proteins broken down into?
1 mark
Proteins are broken down into Amino acids.
What type of Enzyme breaks down Proteins?
1 mark
Proteases
Rice contains a lot of the carbohydrate starch.
Name the type of Enzyme that will break down starch during digestion.
(1 mark)
The starch will be broken down by carbohydrases.
How are carbohydrates synthesised?
3 marks
Simple sugars are joined together to form carbohydrates in a Process catalysed by enzymes.
Why is it important that organisms are able to break down big molecules into smaller molecules?
(7 marks)
E.g. Big molecules are unable to pass through the walls of the digestive system + can’t be absorbed into the bloodstream.
Smaller molecules can pass through + be absorbed, which means they can then pass into cells + be used for growth and other life processes.
Lipase is any enzyme that catalyses the hydrolysis of fats (lipids) breaking it down into fatty acids + ________.
(1 mark)
Glycerol
Lipids are made up of
3 marks
2 fatty acids + Glycerol
Perform essential roles in digestion, transport + processing of dietary lipids (e.g. triglycerides, fats, oils) in most, if not all, living organisms.
(1 mark)
Lipase
Lipids are
2 marks
Fats + oils.
Carbohydrase enzymes break down starch into?
1 mark
Sugars
True or false?
Oxygen entering the Blood from the lungs is an example of Osmosis.
(3 marks)
False.
This happens by diffusion. Osmosis involves the movement of water.
What type of membrane is needed for osmosis to happen?
3 marks
A partially permeable one (it has small holes in it, so only tiny molecules can pass through).
When plants lose water, they start to wilt.
Explain why most plants will wilt if the soil they are growing in is flooded with salty sea water?
(6 marks)
The sea water has a high concentration of salt, so water concentration in the soil will be lower than in the plant.
This means water would move by osmosis from Plant to the soil (from a higher concentration to a lower concentration), causing the plant to lose water + wilt.
Oxygen diffuses from the blood stream into muscles. During exercise, O2 is used up in the muscles faster than when a person is at rest.
Suggest how the rate of O2 diffusion might differ when a person is running vs when they are sitting.
(5 marks)
The diffusion rate will be greater when a person is running vs when they are sitting.
- This is because there will be a lower concentration of O2 in the muscles (as it is used up quicker) meaning there will be a greater concentration gradient + so a faster rate of diffusion.
How does substances travelling (across a cell membrane) via Active Transport move?
(5 marks)
Against the concentration gradient to an area of higher concentration from an area of lower concentration - cellular energy (usually ATP) + carrier proteins are required.
Features of Diffusion
4 marks
Movement of a substance(s) down the concentration gradient from an area of high to an area of low concentration.
Osmosis Features
4 marks
Movement of a water molecules against the concentration gradient from an area of low to an area of high concentration.
Features of Passive Transport
6 marks
Movement of substances down the concentration gradient from an area of high to an area of low concentration - does not require the input of energy.
- Takes place when molecules diffuse across the cell membrane by travelling through specific transport proteins
3 Common types of Passive Transport
3 marks
Simple diffusion, osmosis + facilitated diffusion.
Simple Diffusion vs Facilitated Diffusion
6 marks
Simple Diffusion - movement of molecules through a cell membrane without using the channels formed by integral membrane protein.
Facilitated Diffusion - movement of molecules through those channels.
Protein Channels
8 marks
Special arrangement of amino acids (proteins) which embeds in the cell membrane, providing a hydrophilic passageway for water + small, polar ions - and help them move along.
Transport proteins
3 marks
Size + shape which excludes all but the most specific molecules.
Active transport requires assistance from carrier proteins, which do what?
(2 marks)
Change conformation when ATP hydrolysis occurs.
ATP Hydrolysis
8 marks
When an appreciable amount of energy (found in ATP) is released when a high-energy phosphoanhydride bond is broken in a catabolic hydrolysis (water-mediated breakdown) reaction.
Example of ATP Hydrolysis
3 marks
Found in the muscles, by producing work in the form of mechanical energy.
What does ATP stand for
2 marks
Adenosine Triphosphate
What are examples of carrier proteins within our Cells?
2 marks
Sodium potassium pump + glucose transporters
What is ATP?
3 marks
Small, relatively simple molecule - the main energy currency of cells.
What is the energy released by hydrolysis (breakdown) of ATP is used to do?
(2 marks)
Power many energy-requiring cellular reactions.
Structurally, ATP is what?
2 marks
An RNA nucleotide that bears a chain of three phosphates.
Carrier Proteins
10 marks
Allow chemicals (or Ions/Molecules) to cross the membrane against a concentration gradient or when the phospholipid bilayer of the membrane is impermeable to a chemical.
These proteins are specific to what they allow to cross the membrane depending on the size + shape of the Molecules
ADP stands for
2 marks
Adenosine Diphosphate
Facilitated Diffusion
7 marks
Passive movement of molecules, down the concentration gradient across the cell membrane via the aid of a membrane protein.
- They usually move from an area of high concentration to an area of low concentration but can move freely in and out of a Cell Membrane
Facilitated Transport + Energy
8 marks
Being passive, facilitated transport does not directly require chemical energy from ATP hydrolysis in the transport step itself;
rather, molecules + ions move down their concentration gradient reflecting its diffusive nature.
Active Transport + Carrier Proteins
4 marks
The carrier proteins used in Active Transport are different than the ones seen in facilitated diffusion, as they need ATP in order to change conformation.
Channel proteins are not used in Active Transport because
2 marks
Substances can only move through them along the concentration gradient.
How does water concentration change as solute concentration increases?
(4 marks)
The water concentration of a solution decreases as the solute increases.
How would the mass of a potato cylinder change if you put it in a solution that has the same water concentration as the fluid inside the potato?
(2 marks)
There would be no change in the mass of the potato cylinder.
Yashvi has 2 potato cylinders. The fluid inside the Potato Cells has a concentration of 0.3 mol/dm^3. She weighs the 2 cylinders + places one into a beaker of pure water + the other into a beaker of 1.0 mol/dm^3 Glucose Solution. After 24 hours, she removes the cylinders, dries them, + measures their final mass.
Explain how the mass of each potato cylinder will have changed after 24 hours.
(10 marks)
The mass of the cylinder in pure water will have increased because the water will have moved by Osmosis from an area of higher (pure water) to an area of lower water concentration (the potato). The mass of the cylinder in the Glucose will have decreased, as water will have moved by Osmosis from an area of higher (the potato) to an area of lower water concentration (Glucose solution)
The potato cylinders weren’t dried properly during this experiment, so the excess water added to the mass of the potato.
How could Yashvi reduce the effect of errors like this?
(3 marks)
Repeating the experiment + calculating a mean percentage change in mass.
The mass of a group of potato cylinders has increased from 12g to 15g.
Calculate the percentage change in mass.
(15 marks)
Percentage change in mass =
final mass - initial mass
—————————— x 100
Initial mass
= 15 - 12
_________ x 100 = 0.25 x 100 = 25%
12
When calculating the percentage change in mass of Plant tissue - an increase in mass will give you
(2 marks)
A Positive percentage change.
When calculating the percentage change in mass of Plant tissue - a decrease in mass will give you
(2 marks)
A Negative percentage change.
Calculating a change in mass - percentage
7 marks
Final mass - initial mass
Divide by initial mass
Multiply by 100