| Define eukaryotic cells | Eukaryotic (animal and plant) cells contain their genetic material - DNA enclosed in a nucleus |
| Define prokaryotic cells | Prokaryotic cells are much smaller than eukaryotic cells and they do not have a nucleus, their genetic material consists of a single loop of DNA, (some prokaryotic cells- bacteria, has small rings of DNA called plasmids) |
| Express 1cm as an equation | 1cm = 1 x 10^-2m
Meaning 1cm = 1/100th a meter |
| Express 1mm as an equation | 1mm = 1 x 10^-3m
Meaning 1mm = 1/1000th a meter |
| Express 1 micrometer as an equation
And draw the measurement for micrometers | 1 micrometer = 1 x 10^-6m
Meaning 1 micrometer = 1/1,000,000th a meter |
| Express 1nm as an equation | 1nm = 1 x 10^-9m
Meaning 1nm = 1/1,000,000,000th a meter |
| State a measurement using the measurement manometers | Proteins are measured using nanometers such as the haemoglobin molecule which is 5nm |
| When is order of magnitude used? | Order of magnitude is used when the someone wants to compare the approximate size of different objects |
| Define order of magnitude | Every order of magnitude is 10x greater than the one before
1 order of magnitude is 10x (1 is 10^-1)
and 2 orders of magnitude is 100x (2 is 10^-2)
The equation to calculate the order of magnitude
N = a x 10^b
Where a is an integer and N is the order of magnitude number |
| List the five structures of an an animals cell and describe their functions | Cytoplasm - execute chemical reactions, such as the first stage in respiration
Cell membrane - control molecules that enter and leave the cell
Mitochondria - execute aerobic respiration
Ribosomes - execute protein synthesis (when cells make proteins)
Nucleus - enclose DNA |
| List the three additional structures of a plant cell and describe their functions | The cytoplasm, cell membrane, mitochondria, ribosomes and nucleus have the same function in plant cells as animal cells
Chloroplasts - contains chlorophyll which helps execute photosynthesis
Cell wall - contains cellulose to help strengthen the cell
Vacuole - filled with cell Sao which allows it to maintain the plants shape |
| Describe the function of sperm cells | The function of a sperm cell is to join wit an ovum (egg cell) in fertilisation and during this process the DNA of the sperm and ovum combine |
| Describe how sperm cells are specialised for fertilisation | Soren cells are specialised for fertilisation as they have a long tail which helps them to swim to the ovum, they are packed full of mitochondria giving them energy for swimming and sperm cells contain enzymes allowing them to digest through the outer layer of the ovum |
| Describe the function of a never cell | The function of a nerve cell is to send electrical impulses around the body |
| Describe how nerve cells are specialised for their function | nerve cells are specialised to carry electrical impulse around the body as the axon carries impulses from one part of the body to another, the axons are covered with myelin which insulted the axon and speeds up the transmission of nerve impulses, at the end of the nerve cells are synapses which are junctions that allow impulses to pass from one nerve cell to another and the dendrites - head has a large surface area allowing never cells to easily connect |
| Describe the function of a muscle cell | The function of a muscle cell is to contract |
| Describe how muscle cells are adapted for their function | Muscle cells are adapted for contraction as they contain protein fibres which can shorten in contraction and their contain mitochondria which produces energy for muscle contraction |
| Describe the function of root hair cells and stater how their are specialised for their function | The function of a root hair cell is to absorb water and minerals.
Root hair cells are specialised for absorption as they contain hairs which increase the roots surface area |
| Describe the function of xylem cells and state how they are specialised for their function | The function of xylem cells it does carry water and dissolved minerals from a plants root to its leaves through the stem.
Xylem cells are specialised for their function as they have cell walls sealed with lignin which provides support for the plant, the end walls between the cells have been broken down forming a long tube, and xylem cells have no internal structure both of which factors allow for a easier flow of water/minerals |
| Describe the function of phloem cells and state how they are specialised for their function | The function of phloem cells is to carry dissolved sugars up and down the plant.
Phloem cells are specialised for their function as their contain phloem vessel cells and sieve plates which allow dissolved sugars to move through the cell interior, and phloem cells contain mitochondria priding energy for the phloem vessel cells |
| List the seven components of an optical microscope | The seven components of an optical microscope are:
- A stage where the microscope slide is placed
- clips to hold the slide in place
- a Light below the stage providing light that passes through the stages slide
- above the stage are 3 objective lenses usually with magnifications of 4x, 10x and 40x
- at the top of the microscope is the eyepiece used to look at the slide through
- the eyepiece contains the eyepiece lens which usually has a magnification of 10x
- an optical microscope contains a coarse focussing lens and a fine focussing lens |
| Explain how to use an optical microscope to view a prepared slide in four practical steps and two data collecting steps | 1. Firstly place the slide onto the stage and use the clips to hold it in place
2. Then select the lowest-power objective lens (usually 4x) and turn the coarse focussing lens so the objective lens is almost touching the slide
3. Now look down the eyepiece and adjust the coarse focussing lens until the cell comes into focus, then turn the fine focussing lens so the cell comes into a clear-focus
4. Calculate the total magnification using the equation:
Magnification (of the cell) =
magnification of eyepiece lens x magnification of objective lens
(Usually 10x x 4x ) = 40x
5. Lastly select a high power objective lens and adjust the fine focussing lens to bring the cells back into focus and record new results
6. After the practical you will be required to draw the cell sample with a magnification scale
How to draw a magnification scale - place a ruler over the stage and measure the diameter of the field view in millimetres and present this measurement as a scale bar on your drawing and write down the magnification (eg. 100x) |
| State the problems of a light microscope | Light microscopes have limited magnification making it diffuser to view details in cell structures such as the nucleus
They also have limited resolution so fine detail isn’t visible
So electron microscopes where created to see in better magnification and resolution |
| What is the equation to calculate magnification | Magnification = size of image / size of real object |
| What features of prokaryotic and eukaryotic cells are visible and which are not visible under an optical microscope | Visible feature prokaryotic and eukaryotic cells: nucleus, cytoplasm, cell membrane
Eukaryotic only - cell wall
Possibly visible features of prokaryotic and eukaryotic cells include mitochondria and chloroplasts and vacuole
Non visible features: ribosomes |
| State four key features of chromosomes | Four key features of chromosomes:
- chromosomes are made of DNA and they are located in the nucleus
- body cells contain two pairs of long and short chromosomes
- the main body contains 23 pairs of chromosomes
- chromosomes contain a large number of genes which determine many of our features |
| Describe the three main stages of the cell cycle by mitosis | In the first stage of the cell cycle by mitosis, the DNA replicates to form two copies of each chromosome it grows and also copies its internal structures such as mitochondria and ribosomes
In the second stage of the cell cycle, mitosis takes place and one set of chromosomes are pulled to each end of the cell while the nucleus divides
In the third stage of the cell cycle, the cytoplasm and cell membrane divide to form two identical cells |
| What are three of the functions of mitosis | Functions of mitosis
The function of mitosis include it’s essential for the growth and development of multicellular organisms, such as plants and animals
a second function of mitosis is it takes place when an organism repairs themselves such as a broken bone healing
Mitosis also happens during asexual reproduction |
| Briefly describe the development of an ovum to specialised cells | Human growth begins in fertilisation after the ovum is fertilised it goes through mitosis and forms a ball of cells called an embryo. The embryo continues to undergo mitosis and then begins to form specialised cells such as nerve and muscle cells - this specialisation is known as differentiation |
| Give the scientific name for early-stage embryo cells and define what a stem cell is | The scientific name for early-stage embryo cells are embryonic stem cells
A stem cell is an undifferentiated cell which can give rise to more cells of the same type and differentiate to form other types of cells |
| What three specialised cells can be found in bone marrow? | Stem cells in bone marrow differentiate to form specialised cells found in blood, including red blood cells, white blood cells and platelets |
| Describe the use of stem cells in the treatment of the bone marrow cancer: leukaemia | Firstly the patients existing bone marrow is destroyed using radiation then the patient receives a transplant of bone marrow from a donor.
The stem cells in the bone marrow now divide to form new bone marrow.
And the stem cells also differentiate and form blood cells |
| What are two common issues with bone marrow transplants? | Two common issues with bone marrow transplants
The donor has to be compatible with the patient or the white blood cells produced by the donated bone marrow could attack the patients body
There is also a risk of the patient adopting doners transmissible viruses |
| Describe the use of stem cells in therapeutic cloning and state the uses of therapeutic cloning | In therapeutic cloning a stem cell formed embryo is created with the patients genes
The stem cells forming the embryo are transplanted into the patient without the chance of rejection of their immune system
So they can differentiate to replace damaged or unstable cells
therapeutic cloning is used to treat diabetes and paralysis |
| What is an example of the medical use of stem cells in plant cells? | An example of the medical use of stem cells in plant cells is in roots and buds. Roots and buds contain meristem tissue - a type of stem cell that can differentiate into any type of plant tissue at any point of the plants life. Meristem tissue can be used to clone crop plant that are resistant to diseases |
| Define diffusion | Diffusion is the random movement of a substance from a high concentration to a low concentration |
| What is the objective of diffusion | The objective of diffusion is to gain useful substances required to gain energy, grow and remove waste products |
| Define a concentration gradient | A concentration gradient is the difference in concentration between two solutions, or two different cells and a surrounding solution |
| Give molecules which enter and exit cells using diffusion | Molecules which use diffusion to enter cells include oxygen molecule
Molecules which use diffusion to exit cells include carbon dioxide and urea |
| What are three factors that affect the rate of diffusin? | Three factors that affect the rate of diffusion:
If the concentration gradient is higher diffusion will happen faster
If the temperature is higher diffusion will happen faster because particles have more kinetic entry and are therefore moving faster
If the surface area of the cell membrane is larger diffusion will happen faster |
| Why is an organisms surface area getting larger and therefore it’s volume decreasing an issue? | The problem with an object having a large surface area an a small volume is cells in the surface get enough oxygen with diffusion while cells inside the organism don’t revive enough oxygen with diffusion alone |
| How do filaments in fish hill allow for oxygen to enter the blood? | Fishes gills are covered in filaments which deoxygenated blood passes into and oxygen diffuses from the water into the blood so oxygenated blood returns to the body |
| Give three adaptations of filaments that increase the rate of diffusion | Three adaptations of filaments that increased the rate of diffusion
Filaments increase the surface area of fish gills
filaments have a thin membrane to produces a short diffusion pathway
Filaments have an efficient blood supply to take oxygenated blood away which ensures the concentration gradient is always high |
| Define osmosis
And state what partially permeable means | Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
Partially permeable membranes allow only some molecules to pass through |
| State the contraction of dilute and concentrated solutios | Dilute solutions contain a high contraction of water while concentrated solutions contain a low concentration of water |
| What happens to an animal cell when placed in a dilute and concentrated solution? | Cytoplasm in animals cells has a low concentration of water and when animals cells are placed in water, a dilute solution, osmosis takes place: water moves from outside the cell to inside the cell which causes expansion and possible bursting
While if animal cells are placed in a very concentrated solution water will move out of the cell and it will shrink |
| What happens to a plant cell when placed in a dilute solution?
And what happens to a plant cell when placed in a concentrated solution? | When a plant cell is placed in a dilute solution such as water the water will move into the cell by osmosis and just like an animal cell it will expand, the cell walls in plant cell prevent it from bursting, instead the cell becomes turgid (swollen)
When a plant cell is placed in a concentrated solution water moves out of the plant cell and the cell becomes flaccid (it shrinks) |
| Describe the practical which investigate the effects of osmosis on plant tissue in six steps | Firstly the potato is peeled because the skin can affect osmosis and three cylinders are cut out of it using a cork borer which ensures all the cylinders are equal in diameter
Then a scalpel is used to cut the cylinders to an equal length (usually around 3cm)
Next the length is mesusrrecusung a ruler and the weight is measured using a balance
Now the cylinders are placed into test tubes and 10^3cm of 0.5 molar sugar solution is adde to the first test tube, 10^3cm of 0.25 molar sugar solution is added to the second test tube and distilled water is added to the third
Then the potato is left overnight to let osmosis take place
The potato is rolled in tissue kaisee to remove surface moisture
Lastly the length and the mass of the clingers are measured again and the percentage change from the original values is calculated - equation to calculate percentage change =( change in value / original value ) x 100 |
| What is should be drawn up after the osmosis practical | A graph should be drawn showing the percentage changes of mass/length against the con concentration of the sugar solution |
| What are the conclusions of the osmosis practical? | The conclusions of the osmosis practical are that the potato gains mass because water has moved in by osmosis. In concentrated solutions, the potato loses mass because water exits by osmosis. Then where the line crosses the x-axis there is no change in mass which means the concentration outside and inside the cell are the same so osmosis does not take place. Therefore this is also the approximate concentration inside the cell. |
| State what happens in active transport | Active transport requires energy from respiration as substances move from a more dilute solution to a more concentration solution - against the conversation gradient |
| Give an example of active transports in animal cells | In animal cells active transport is used to carry the sugar glucose into the cell of the cavity in the small intestine, the lumen. This is where food is digested and molecules such as the digested sugar glucose are produced.
Active transport is use to carry glucose because the concentration of sugars in the lumen is lower than the concentration of sugars outside the cell therefore they are unable to diffuse into the cell.
Lumen also contains many mitochondria which perform respiration, providing the energy needed for active transport |
| Give an example of active transport in plant cells | In plant cells active transport is used to move the ion magnesium, by root hair cells that transport magnesium from the soil to the leaves to make chlorophyll in the leaves.
As the concentration of ions in the soil is lower than the contraction of ions inside the root hair cell, active transport is used to move the ions into the cell. Now the ions are transported to the xylem cells and ions move into the leaf
Root hair cells contain lots of mitochondria to provide energy for active transport |
