Studied by 46 people
Light microscope
Two lense, an objective and eyepiece
The objective lense produces a magnified image, which is then magnified an directed into the eye by the eyepiece lens
Usually illuminated from underneath
Maximum magnification of a light microscope
They have approximately, a maximum magnification of x2000 and a resolving power (this affects resolution) of 200nm
What is a light microscope used to view
Tissues, cells and large sub-cellular structures
When was the light microscope first used
In 1665 by Robert Hooke who observed the first cells of cork
Electron microscope
Electron are used to form an image because the electrons have a much smaller wavelength than that of light waves
There are two types: a scanning electron microscope that creates 3d images and a transmission electron microscope which creates 2d images detailing organelles
Magnification of electron microscopes
They have a magnification of up to x2,000,000 and resolving power of 10nm (SEM) and 0.2nm(TEM)
When was the Electron microscope invented
It was developed in the 1930s and enables scientists to view deep inside sub-cellular structures, such as mitochondria, ribosomes, chloroplasts and plasmids
Magnification of a light microscope formula
Magnification of the eyepiece lens x magnification of the objective lens
Size of an object formula
Size of the image / Magnification = size of object
Differences between eukaryotic and prokaryotic cells
Prokaryotic cells are much smaller and do not contain membrane bound organelles and a nucleus containing genetic material
What is the prokaryotic cell wall composed of?
Peptidoglycan
How is genetic information stored in a prokaryotic cell?
Found free within the cytoplasm as: Chromosomal Dna (single large loop of circular DNA) or plasmid DNA
What are plasmids
Small circular loops of DNA found free in the cytoplasm and separate from the main DNA
Carry genes that provide genetic advantages eg antibiotic resistance
List all the components of both animal and plant cells
Nucleus
Cytoplasm
Cell Membrane
Mitochondria
Ribosomes
What cell components are just found in plant cells
Chloroplasts
Permanent Vacuole
cell wall
Other than storing genetic information, what is the function of the nucleus?
Controls cellular activities
Describe the structure of the cytoplasm
Fluid component of the cell
Contains organelles, enzymes and dissolved ions and nutrients
What is the function of the cytoplasm
Site of cellular reactions eg first stage of respiration
Transport medium
What is the function of the cell membrane
Controls the entry and exit of materials into and out the cell
What is the function of the mitochondria
Site of later stages of aerobic respiration in which ATP is produced
What is the function of ribosomes
Joins amino acids in a specific order during translation for the synthesis of proteins
What is the plant cell wall made of
Cellulose
What is the function of the plant cell wall
Provides strength
Prevents the cell bursting when water enters by osmosis
What does the permanent vacuole contain?
Cell sap (a solution of salts, sugars and organic acids)
What is the function of the permanent vacuole
Supports the cell, maintaining its turgidity
What is the function of chloroplasts
site of photosynthesis
Describe how sperm cells in animals are adapted to their function
Haploid nucleus which contains genetic information
Tail enables movement
Mitochondria provides energy for tail movement
Acrosome contains enzymes that digest the egg cell membrane
Describe how nerve cells in animals are adapted to their function
Long axon allows electric impulses to be transmitted all over the body from the central nervous system
Dendrites from the cell body connect to and receive impulses from other nerve cells, muscles and glands
Myelin sheath insulates the axon and specs up the transmission of impulses along the nerve cell
Describe how muscle cells in animals are adapted to their function
Arrangement of protein filaments allows them to slide over each other to produce muscle contraction
Mitochondria to provide energy for muscle contraction
Merged cells in skeletal muscle allows muscle fibre contraction in unison
Describe how root hair cells in plants are adapted to their function
Large surface area to absorb nutrients and water from surrounding soil
Thin walls that do not restrict absorption
Describe how xylem cells in plants are adapted to their function.
No upper or lower margins between cells to provide a continuous route for water to flow
Thick, woody side walls strengthen their structure and prevent collapse
Describe how Phloem cells in plants are adapted to their function
Sieve plates let dissolved amino acids and sugars be transported up and down the stem
Companion cells provide energy needed for active transport of substances along the phloem
What is cell differentiation
The process by which cells become specialised
Why is cell differentiation important?
Allows production of different tissues and organs that perform various vital functions in the human body
At what point in their life cycle do most animal cells differentiate
Early in their life cycle
For how long do plant cells retain the ability to differentiate
Throughout their entire life cycle
What is the purpose of cell division in mature animals?
Repair and replacement of cells
What changes does a cell go through as it differentiates
Becomes specialised through acquisition of a different sub-cellular structures to enable a specific function to be performed by the cell
Disadvantages of electron microscopes
Expensive
large so less portable
require training to use
only dead specimens can be observed
How do bacteria multiply
Binary fission
How often do bacteria multiply
Once every 20 minutes if enough nutrients are available and the temperature is suitable
2 ways Bacteria can be grown
Nutrient broth solution
Colonies on agar gel plate
Name the two types of electron microscope
Transmission electron microscope (TEM)
Scanning electron microscope (SEM)
Disadvantage of light microscopes
limited resolution
How does an electron microscope work?
It uses a beam of electrons which are focused using magnets. The electrons hit a fluorescent screen which emits visible light, producing an image.
Viruses
communicable disease
very small
move into cells and use the biochemistry of it to make copies of itself
This leads to the cell bursting and releasing all the copies of it into the bloodstream
The damage and destruction of the cell make the individual feel ill
Bacteria
Communicable diseases
They multiply very quickly through dividing by a process called binary fission
small
They produce toxins that can damage cells
Protists
Communicable
Some are parasitic which means they can use humans and animals as their hosts
Fungi
communicable
They can either be single celled or have a body made of hyphae
They can produce spores which can be spread to other organisms
Anaerobic respiration in plants and yeast
This is called fermentation and is used to make bread and alcoholic drinks
Glucose → ethanol + co2
The trachea and bronchi
secret mucus in other to trap pathogens
Cilia best to waft mucus upwards so it can be swallowed
The stomach
Produces hydrochloric acid that kills any pathogens in your mucus, food or drink
Tobacco mosaic virus symptoms
discolouration of the leaves, the affected part of the leaf cannot photosynthesise
Good field hygiene and pest control can help prevent it
Diffusion
Diffusion is the spreading of particles resulting in a net movement from an area of higher concentration to an area of lower concentration
The higher the temperature the greater the rate of diffusion because the particles have more kinetic energy
The larger the surface area of the cell membrane, the greater the rate of diffusion
Osmosis
Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
Active transport
Active transport moves substances from a more dilute solution to a more concentrated solution which requires energy from respiration
What is the difference between diffusion and active transport?
Diffusion: particles move down the concentrated gradient and don’t require energy from respiration
Active transport: Particles are moved against the concentrated gradient and this requires energy from respiration
What three ways do the white blood cells destroy pathogens
Phagocytosis
Producing antibodies
producing antitoxins
Phagocytosis
Engulfing and consuming pathogens which destroys them meaning they can no longer make you feel ill
Antibodies
Each pathogen has an antigen on their surface, which is structure which a specific complementary antibody can bind to. Once antibodies begin to bind to the pathogen, the pathogens start to clump together, resulting in it being easier for white blood cells to find them.
If you become infected again with the same pathogen, the specific complementary antibodies will be produced at a faster rate.
Anti toxins
They neutralise the toxins released by the pathogen by binding
Three stages of the cell cycle
In the first stage of the cell cycle the DNA replicates to form two copies of each chromosome. The cell also grows and copies it’s internal structures such as mitochondria and ribosomes.
I’m the second stage, mitosis takes place. One set of each chromosome is pulled to each end of the cell and the nucleus also divides
In the final stage the cell membrane and the cytoplasm divide to form two identical cells
Functions of mitosis
Essential for growth and development of multicellular organisms
Mitosis takes place when an organism repairs itself (eg when a broken bone heals)
Mitosis happens during asexual reproduction
Blood plasma
Blood plasma transports soluble digestion products from the small intestine to other organs, Carbon dioxide from the organs to the lungs to be breathed out and the waste urea from the liver to the kidneys to be extracted in urine
Red blood cells
Red blood cells transport Oxygen from the lungs to the body cells, they contain the oxygen carrying molecule haemoglobin. Red blood cells have no nucleus and in the centre of the cell there are dimples.
White blood cells
White blood cells form part of the immune system, they contain a nucleus which contains Dna that encodes the instructions that the white blood cell needs to do their job.
Platelets
These are tiny fragments of cells and their job is to help the blood clot
Gas exchange in lungs
Air passes into the lungs through a tube called the trachea. Rings of the cartilage prevent the trachea from collapsing during inhalation. The trachea now splits into two smaller tubes called bronchi with one passing to each lung further into into the lungs, the bronchi subdivide into many smaller tubes called bronchioles which end in tiny air sacs called Alveoli. Alveoli are where gases diffuse in and out of the blood stream
Breathing
Breathing increases the rate of diffusion
Millions of alveoli mean that the lungs have a huge surface area
Cancer
Cell division by mitosis occurs all over the body, especially during growth and repair. It’s extremely lightly controlled genes in the nucleus tell cells when to divide and when not. Sometimes changes take place in these genes and that leads to uncontrolled growth and mitosis which produces a tumour
Benign tumours
These are growths of abnormal cells which are found in one area and are usually contained within a membrane.
Benign tumours do not invade other parts of the body
Malignant tumours
Their cells invade neighbouring tissues and move into the bloodstream, these cells are classed as a cancer as they spread and from secondary tumours
Cancers linked to genetic s
Certain types of breast cancer, prostate cancer and cancer of the large intestine
Cancer linked to lifestyle
Smoking causes lung cancer
Ultraviolet light causes skin cancer
Alcohol can cause mouth and throat cancer
Radon
This is a radioactive gas that increases your risk of developing lung cancer because it releases ionising radiation which damages the DNA in our cells
Risk factors for cardiovascular disease
A diet high in fat and low in vegetables as this increases the rate that fatty materials build up in the arteries
A diet high in salt can increase blood pressure
Risks involved with smoking
Smokers risk cardiovascular diseases
Smoking when pregnant increases the risk of miscarriages and premature birth or a baby being born with a low body mass
Risks of drinking alcohol
Adults who drink increase their risk of liver cirrhosis and liver cancer
Alcohol can also effect the brain leading to addiction and memory loss
uses of monoclonal antibodies
In pregnancy testing they are used to detect a specific hormone. (Hormone produced by the placenta of the developing fetus)
We can use them to measure the levels of hormones in blood and to detect pathogens in the blood
The can be used to locate or identify specific molecules in a cell or tissue
Sometimes they can stop cancer cells from dividing
Give one reason that cell division by mitosis is important in fully grown animals
Repair of tissues/regrowth of cells
Stems, roots and leaves
All plant organs which are made of tissue and work together to carry substances around the plant
Epidermal tissue
Covers the whole plant
Palisade mesophyll tissue
The part of the leave where the most photosynthesis happens
Why are the leaves of the rose yellow
Chlorophyll has been broken down and they grow slowly as they aren’t going through photosynthesis
Food tests
Sugar - Benedict’s solution
Starch - Iodine solution
Protein - Blurent reagent
Why is starch not absorbed into the blood
Starch is insoluble
Spongy mesophyll tissue
Part of the leaf that has big air spaces. this allows gas to move in and out of cells
Xylem and phloem
Transport water, mineral ions and food around the roots, stems and leaves
Meristem tissue
Found at the growing tip of shoots and roots
Food tests colours
Biuret solution (proteins) - Purple
Iodine test (starch) Blue black
Benedict’s solution (sugars) Red, orange, yellow green depending on how much glucose
Sudan III (fats) - stains red
What are the four main blood vessels associated with the heart
Aorta (left) - carries oxygenated blood from the heart to the body
Pulmonary vein (left) carries oxygenated blood from the lungs to the heart
Vena cava (right) Carries deoxygenated blood from the body to the heart
Pulmonary artery (right) carries deoxygenated blood from the heart to the lungs
What is the purpose of valves in the heart
Prevent the back flow of blood
What is the purpose of coronary arteries
Supple the heart muscle with oxygenated blood
How is the heart rate controlled
Heart rate is controlled by a group of cells in the right atrium which act as a pacemaker. They release waves of electrical activity which cause the heart muscle to contract
What are the three types of blood vessel in the body?
Arteries
Veins
Capillaries
How are arteries adapted for their function
Function: carry blood away from the heart
Thick muscle layer which adds strength to resist high pressure
Thick elastic layer which allows arteries to stretch and recoil in order to withstand high pressure
How are veins adapted for their function
Function:carry blood towards the heart
Wide lumen - enables lows blood pressure
Valves prevent the back flow of blood
How are capillaries adapted for their function
Function: enable transfer of substances between the blood and the tissue
Walls are one cell thick - short diffusion path
Permeable walls - substances can diffuse across
Narrow lumen - blood moves slowly so there’s more time for diffusion
How to calculate the rate of blood flow
Volume of blood/number of minutes
What tissues and organs make up the gas exchange system
Trachea
Intercostal muscles
Bronchi
Bronchioles
Alveoli
Diaphragm
Note 
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