1
Q
What are all living things made up of?
A
Cells
2
Q
What are organisms always?
A
- Eukaryotes(made up of eukaryotic cells)
- Prokaryotes(made up of a prokaryotic cells also known as a one cell organism)
3
Q
State examples of eukaryotic cells
A
- Plant cells
- Animal cells
4
Q
State examples of prokaryotic cells
A
Bacterial cells
5
Q
What are the characteristics of the a eukaryotic cell?
A
Contains:
- A cell membrane
- Cytoplasm
- Genetic material enclosed in a nucleus
6
Q
What are the characteristics of the a prokaryotic cell?
A
- Bacterial cells (prokaryotic cells) are much smaller than eukaryotic cells.
- Cytoplasm of a cell membrane surrounded by a cell wall.
- Genetic material not included in the nucleus.
- Single DNA loop
- Possibly one or more small rings of DNA called plasmids.
7
Q
State the equation to calculate magnification
A
Magnification = Image size/Real size
8
Q
What do microscopes allow us to do?
A
- Lets us see things we can’t see with the naked eye.
The microscopy techniques we can use have developed over the years as technology and knowledge have improved.
9
Q
What are light microscopes and what do they use and what do they let us see?
A
- Use light and lenses to form an image of a specimen and magnify it (make it look bigger).
- Lets us see individual cells and large subcellular structures, like nuclei.
10
Q
What is resolution?
A
- The ability to distinguish between two points in an image
- So a higher resolution gives a sharper image
11
Q
What are electron microscopes and what do they use and why is it better than light microscopes?
A
- Electron microscopes use electrons to form an image.
- Better as it has a much higher magnification and resolution than light microscopes
12
Q
What do electron microscopes allow us to see?
A
Lets us see organelles(smaller things) in more detail such as:
- Internal structure of mitochondria
- Chloroplasts
They even let us see tinier things like:
- ribosomes
- plasmids
13
Q
What is the size of a cell?
A
Cells can vary between 1 micrometer (μm) and hundreds of micrometers in diameter.
(This is why microscopes are needed to see these small organisms)
14
Q
How do we write a cells size?
A
In standard form (e.g 5 x 10^-6)
15
Q
What do most animal cells contain?
A
- Nucleus
- Cytoplasm
- Cell membrane
- Mitochondria
- Ribosomes
16
Q
What do most plants cells contain?
A
- Nucleus
- Cytoplasm
- Cell membrane
- Mitochondria
- Ribosomes
- Chloroplasts
- Permanent vacuole filled with cell sap
17
Q
What is the function of a nucleus?
A
Contains genetic material that controls the activities of the cell.
18
Q
What is the function of the cytoplasm?
A
- A gel-like substance where most of the chemical reactions happen
- It contains enzymes that control these chemical reactions.
19
Q
What is the function of a cell membrane?
A
- Holds the cell together
- Controls what goes in and out.
20
Q
What is the function of the mitochondria?
A
- Where most of the reactions for aerobic respiration take place.
- Respiration transfers energy that the cell needs to work.
21
Q
What is respiration able to transfer?
A
Energy that the cell needs to work
22
Q
What is the function of ribosomes?
A
These are where proteins are made in the cell
23
Q
What is the function of the rigid cell wall?
A
Made of cellulose to support the cell and strengthen it
24
Q
What is the function of the permanent vacuole?
A
contains cell sap, a weak solution of sugar and salts.
25
What is the function of chloroplasts?
- Where photosynthesis occurs, which makes food for the plant.
- Contains chlorophyll(green substance),which absorbs the cells of algae (eg. seaweed) also the light needed for photosynthesis.
26
What is the function of plasmids?
Small rings of DNA which act as delivery vehicles, or vectors, to introduce foreign DNA into bacteria.
27
What do plant and algal cells have?
A cell wall made of cellulose, which strengthens the cell
28
Note:
AQA says that students should be able to use estimations and explain when they should be used to judge the relative size or area of sub- cellular structures
29
Practical 1
Aaaa
30
What is differentiation?
- The process by which a cell changes to become specialised for its job.
- As cells change, they develop different subcellular structures and turn into different types of cells.
- This allows them to carry out specific functions.
31
State examples of cells that are specialised
Sperm cells - specialised for reproduction
Nerve cells - specialised for rapid signalling
Muscle cells - specialised for contraction
Root hair cells - specialised for absorbing water and minerals
Phloem and xylem cells - specialised for transporting substances
32
State the function of a sperm cell
The function of a sperm is basically to get the male DNA to the female DNA.
33
State the specialisation of a sperm cell
- Long tail and a streamlined head to help it swim to the egg
- Lots of mitochondria in the cell to provide the energy needed
- Carries enzymes in its head to digest through the egg cell membrane
34
State the function of a nerve cell
To carry electrical signals from one part of the body to another
35
State the specialisation of a nerve cell
- Cells are long (to cover more distance)
- Have branched connections at their ends to connect to other nerve cells and form a network throughout the body
36
State the function of muscle cells
To contract quickly
37
State the specialisation of muscle cells
- Cells are long (so that they have space to contract)
- Contain lots of mitochondria to generate the energy needed for contraction
38
State the function of root hair cells
Absorbing water and mineral ions
39
State the specialisation of root hair cells
- Lots of root hairs which gives the plant a big surface area for absorbing water and mineral ions from the soils
- Contain lots of mitochondria in order to provide the energy needed for active transport
40
State the function of xylem cells
To transport water and some soluble mineral ions
41
State the adaptations of xylem cells
- Lose their end walls so the xylem forms a continuous, hollow tube.
- Strengthened by a substance called lignin.
- Lignin gives strength and support to the plant. We call lignified cells wood.
42
State the function of phloem cells
Transport food substances
43
State the adaptations of phloem cells
SIEVE TUBES
- specialised for transport and have no nuclei
- Each sieve tube has a perforated end so its cytoplasm connects one cell to the next
- Sucrose and amino acids are translocated within the living cytoplasm of the sieve tubes
COMPANION CELLS
- transport of substances in the phloem requires energy
- One or more companion cells attached to each sieve tube provide this energy
- A sieve tube is completely dependent on its companion cells
44
When does most differentiation occur?
As an organism develops
45
When do animal cells and plant cells lose the ability to differentiate?
- In most animal cells, the ability to differentiate is then lost at an early stage, after they become specialised.
- However, lots of plant cells don't ever lose this ability.
46
Why is cell differentiation important?
- Allows cells to specialize and perform specific functions in an organism.
- Allows for the formation of tissues and organs, and is necessary for the proper functioning of the body.
47
Why is it in mature animals that cell division is restricted?
Due to repair and replacement.
48
When a cell differentiates what happens to a cell and what does it become known as?
It acquires a different subcellular structure to enable it to carry out a certain function.It has become a specialised cell.
49
How have microscopy techniques developed over time?
- Not much changed in basic microscope design over the next 200 years
- But improvements in lens manufacture (such as the use of purer glass) solving problems like colour distortion and poor image resolution.
- Mirrors were added to compound microscopes to add more light and improve the image
50
How has electron microscopy increased the understanding of sub-cellular structures?
- An electron microscope has a much higher magnification and resolving power than a light microscope.
- This means that it can be used to study cells in a much finer detail.
- This has enabled biologists to see and understand many more sub-cellular structures.
51
What do chromosomes contain?
- The nucleus of a cell contains chromosomes made of DNA molecules.
- Each chromosome carries a large number of genes.
52
What are the stages of growth and DNA replication?
1) In a cell that's not dividing the DNA is a spread out in Long strings.
2) Before it divides, the cell has to grow and increase the amount of sub cellular structures such as mitochondria and ribosomes.
3) It then duplicates its DNA – so there is one copy for each new cell. The DNA is copied and forms X-shaped chromosomes. Each "arm" of the chromosone is an exact duplicate of the other.
53
What are the stages of mitosis?
Once its contents and DNA has been copied, the cell is ready for mitosis.
4) The chromosomes line up at the centre of the cell and to sell fibres pull them apart. The two arms of each chromosome go to the opposite ends of the cell.
5) Membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells – the nucleus has divided.
6) Lastly, the cytoplasm and cell membrane divide.
The cell has no produce two new daughter cells. The daughter cells contain exactly the same DNA – they're identical. The DNA is also identical to the parent cell.
54
What is cell division in mitosis important for?
The growth and development of multicellular organisms
55
What is a stem cell?
A stem cell is an undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type, and from which certain other cells can arise from differentiation.
56
What is the function of stemcells in embryos?
They are used to clone and made to differentiate into most different types of human cells
57
What is the function of stem cells in adult animals?
Stem cells from adult bone marrow can form many types of cells including blood cells.
58
What is the function of stem cells in the meristems in plants?
Meristem tissue in plants can differentiate into any type of plant cell, throughout the life of the plant.
59
What are examples of what treatment of stem cells help with?
Treatment with stem cells may be able to help conditions such as diabetes and paralysis.
60
What happens in therapeutic cloning?
In therapeutic cloning an embryo is produced with the same genes as the patient. Stem cells from the embryo are not rejected by the patient's body so they may be used for medical treatment.
61
What are the drawbacks of stem cells?
The use of stem cells has potential risks such as transfer of viral infection, and some people have ethical or religious objections.
62
Benefits of stem cells from meristems in plants
Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers.
63
What is diffusion?
The net of random movement of particles from an area of high concentration to an area of low concentration.
Substances move into and out of cells across the cell membrane, via diffusion
64
State examples of diffusion occuring?
Some of the substances transported in and out of cells by diffusion of oxygen and carbon dioxide, a gas exchange and of the waste of product area from cells into the blood plasma for excretion in the kidney
65
What are factors which affect the rate of diffusion?
- The difference in concentrations ( concentration gradient )
- The temperature
- The surface area of the membrane
66
What are the benefits of single-celled organisms?
A single-celled organism has a relatively large surface area to volume ratio. This allow sufficient transport of molecules into and out of the cell to meet the needs of the organism.
67
Note:
AQA says that students should be able to calculate and compare surface area to volume ratios
68
What is the problem with multi-cellular surfaces?
Multicellular organisms have a smaller surface area compared to their volume - not enough substances can diffuse from their outside surface to supply their entire volume. This means they need some sort of exchange surface for efficient diffusion.The exchange surface structures have to allow enough of the necessary substances to pass through.
69
How have multicellular organisms adapted to maximise effectiveness?
- They have a thin membrane, so substances only have a short distance to diffuse.
- They have a large surface area so lots of a substance can diffuse at once.
- Exchange surfaces in animals have lots of blood vessels, to get stuff into and out of the blood quickly.
- Gas exchange surfaces in animals (e.e. alveoli) are often ventilated too - air moves in and out.
70
How is the small intestine adapted for exchanging materials in a fish?
- Adapted by having a large surface area
- A thin membrane to provide a short diffusion path
71
How is the lungs adapted for exchanging materials in a fish?
- Lungs have alveoli, to increase their surface area for diffusion
- The alveoli also have a rich blood supply, thus keeping the concentration gradient going
72
How is the gills adapted for exchanging materials in a fish?
- Large surface area of the gills.
- Large surface area of the blood capillaries in each gill filament.
- The short distance required for diffusion – the outer layer of the
gill filaments and the capillary walls are just one cell thick.
- Fish have gills for transport
73
How do plants absorb water from the soil?
By osmosis. They absorb mineral ions by active transport, against the concentration gradient.
74
How is the roots adapted for exchanging materials in plants?
Adapted for taking up water and mineral ions by having a large surface area to increase the rate of absorption.
75
How is the leaves adapted for exchanging materials in plants?
Leaves are adapted for photosynthesis and gaseous exchange. They are adapted for photosynthesis by having a large surface area, and contain openings, called stomata to allow carbon dioxide into the leaf and oxygen out
76
What is osmosis?
The net of random movement of water particles from a dilute solution to a concentrated solution for a partially permeable membrane
77
Note:
AQA says that students should be able to
- Use simple compound measure of rate of water uptake
- Use percentages
- Calculate percentage gain and loss of mass of plant tissue
78
Note:
AQA says that students should be able to plot draw and interpret appropriate graphs
79
Practical 2:
AAA
80
What is active transport?
Sometimes substances need to be absorbed against a concentration gradient, i.e. from a lower to a higher concentration. This requires energy from respiration
81
What does active transport allow for mineral ions?
Active transport allows the plant to absorb minerals from a very dilute solution, against a concentration gradient. This is essential for its growth. But active transport needs ENERGY from respiration to make it work.
82
What does active transport allow for sugar molecules?
It allows sugar molecules to be absorbed from lower concentration in the gut into the blood which has a higher sugar concentration. Sugar molecules are used for cell respiration.
