BIOLOGY

CELL BIOLOGY

Animal and plant cells

• Eukaryotic cells have a nucleus

  • Animal, plant or fungi…

  • Have ‘you’ in them

• Prokaryotic cells have no nucleus and their DNA is free

  • Bacterial cells…

• Animal cells

  

  • The cell membrane controls what enters and leaves the cell

  • The nucleus contains the cell’s genetic material (DNA)

  • Cytoplasm is where chemical reactions reactions take place

  • Mitochondria provide cells with energy needed to function, from cellular respiration

  • Ribosomes are the site of protein synthesis

• Plant cells

• Plant cells have all the same organelles as animal cells, as well as a vacuole, cell wall and chloroplasts

  • The vacuole is permanent and contains cell sap - sugars, salts and water

  • The cell wall keeps the cell’s shape and is made of cellulose

  • Chloroplasts are where photosynthesis occurs - green because of chlorophyll

Mitosis

• Multicellular eukaryotic organisms continuously need a supply of new cells for growth, development and repair

  • Especially in young organisms

• The cell cycle is the process of the generation of new cells, and is a cell’s ‘life cycle’

  • It is from when the cell is formed to when it divides

  • The mains stages are growth, DNA replication and mitosis, and finally division

• Growth - The cell grows in size, and increases it’s number of sub-cellular structures

• DNA replication and mitosis - The DNA is duplicated so that the new cell formed can have a full set

  • Mitosis is where the cell divides

• Division is where the cytoplasm and cell membranes fully divide

  • Also called cytokinesis

Chromosomes

• Chromosomes carry genetic information in DNA

  • ‘Codes’ for characteristics

  • They are a singular molecule of DNA

• Each human cell contains 46 chromosomes

  • 23 pairs

Osmosis

• Osmosis is the diffusion of water molecules across a partially permeable membrane

  • The net movement of water molecules across a partially permeable membrane from a higher water concentration to a lower concentration

  • Only the movement of WATER particles

  • No energy is required as with the concentration gradient

Diffusion

• Diffusion is the net movement of particles from an area of high concentration to an area of high concentration

  • It can happen in gases and in liquids

  • It is a passive process, so no energy is required - with the concentration gradient

• Factors that affect diffusion are:

  • The concentration gradient - the higher the difference, the faster the rate of diffusion will be

  • Temperature - the higher the energy, the more energy particles have and therefore a faster rate of diffusion

  • Surface area - the large the surface area, the faster the rate of diffusion as more particles can move at one time

Active transport

• Active transport is the movement of particles against a concentration gradient across a membrane

  • It requires energy

    • Energy used comes from cellular respiration in the mitochondria (break down of bonds in glucose releases energy)

    • This energy is stored in APT molecules - they take energy to the parts of the cell that need it

• Root hair cells used active transport to absorb mineral ions and water molecules

  • They are adapted to use active transport so they can have a higher concentration inside, lots of mitochondria for energy release and a large surface area to increase rate of active transport

Stem cells

• Cells divide by mitosis to form more cells

  • These cells are able to differentiate into specialised cells

• Sperm and egg cells merge to form a zygote, and using mitosis this grows to form an embryo with embryonic stem cells

• Embryotic stem cells can differentiate into any type of cell

• When embryos grow into babies, and later an adult, there are no embryonic stem cells left

• As adults, there are no longer stem cells that can differentiate into absolutely anything

  • Instead, there are adult stem cells, found in bone marrow, that can divide by mitosis but only into different types of blood cell

  • They can replace damaged cells to keep us alive, but don’t produce any new tissues, unlike embryonic stem cells

• Plant stem cells are found in plant tissues called ‘meristems’, and they are found in areas of the plant that are continuously growing

  • Roots and shoots

  • They will differentiate into any of the cells needed in the plant

    • Palisade cells, phloem, xylem, root hair, etc.

    • They exist for the entire life of the plant

Stem cells in medicine

• Lots of conditions are caused by faulty/damaged cells 

  • Type 1 diabetes, paralysis, sickle cell anaemia

• These faulty cells can be replaced to treat conditions

• We can extract embryonic stem cells for early embryos, which can be grown in a laboratory

  • These can be stimulated to differentiate into specialised cells that are needed, and then given to patients to replace faulty cells

    • This can be used to produce healthy pancreas cells, nerve cells, red blood cells, etc. 

• Drawbacks:

  • It requires embryonic stem cells, that are in limited supply and there are ethical issues around it

  • Rejection as there are different genomes so patients body may reject or destroy

    • This risk can be reduced by giving medication to suppress an immune system

• Alternatives:

  • Adult stem cells can be taken from a patient, which avoids rejection, and are easily accessible

    • They can only differentiate into different types of blood cells, so can only treat diseases such as sickle cell anaemia  

  • New research is exploring how adult stem cells could produce any type of cell 

• Risks:

  • Virus transmission - if donor cells are infected (before taken or in a lab), the patient will be infected and that could cause more problems

  • Tumour development - stem cells divide so quickly that there’s a chance they’ll become uncontrollable and develop into a tumour/cancer 

• Ethical objections include issues with embryo’s being potential human life, so shouldn’t be used in research

  • However, do benefits of curing existing people outweigh rights of embryos?

Cell specialisation and differentiation 

• Animal and plants are complex organisms with lots of different cells to perform certain functions

  • Specialised cells

  • Sperm, nerve, muscle cells, etc.

  • Root hair, phloem, xylem cells, etc. 

• Sperm cells

  • Their role is to deliver genetic material to the egg in order to fertilise

  • Adaptations include:

    • They are streamline so they can swim faster

    • They have digestive enzymes in their heads, to break the egg

    • Their nucleus’ only have half of the amount of genetic material - half comes from egg

    • They have lots of mitochondria for energy

    • They have flagellum to allow them to swim quickly to reach the egg

• Root hair cells

  • They are found in the roots of plant, and take in nutrients and water from the soil

  • Adaptations include:

    • Lots of mitochondria for energy, for active transport

    • They have thin walls to decrease distance of active transport

    • They have a large surface area to provide more contact with soil - increased rate of active transport

• Nerve cells

  • They carry electrical signals from and to the brain

  • Adaptations include:

    • Lots of branches to increase efficiency of communication

    • They have a fatty sheath (myelin) around the axon, which insulates them and speeds up electrical impulses

    • They are extended so can run to and from different parts of the body to the central nervous system easier

• Differentiation is the process of which cells become specialised

  • Zygote (before embryo), is made of lots of non-specialised cells, then they undergo differentiation, where they change shape, number of organelles and structure and become specialised 

Microscopy

• Microscopy is the use of microscopes

• Light microscopes - 

• An object is the real sample that you are looking at, and it’s size

• The image is what we see when we look down the microscope, and it’s size

• Light microscopes work as light from the light source reflects through the sample and passes through the objective and eye piece lenses

  • These lenses spread out light so the image we see is far larger than the object

• Magnification is how many times larger the image is than the object

  • Magnification = image size / object size

• Resolution is the shortest distance between two points on an object that can be distinguished as two separate entities

  • How detailed an image is

• PROS - They are easy to use

  • They are relatively cheap

• CONS - They rely on light

  • Resolution is limited to 0.2 μm (the wavelength of light)

    • You can see cells, but no smaller

• PROS of electron microscopes

  • They use electrons instead of light

  • The maximum resolution is 0.1 nm (the wavelength of electrons)

    • You can see subcellular structures - 2000x better

• CONS - They are very expensive

  • They are hard to use

Binary fission

• Binary fission is the process of which prokaryotic organisms, like bacteria, divide and reproduce

  • Bacteria’s genetic information is found in plasmids (non-essential) and a large circular strand - no nucleus

• First, the cells grow, then they replicate their genetic material 

  • The cell wall and membrane grows, and the cell splits

• This process can happen up to every 20 mins

  • Depends on temperature, moisture and nutrients

  • In 5 hours, a bacteria could grow from 1 to more than 250000 if it divided every 20 minutes

DONE!!!

ORGANISATION

Principles of organisation

• Organelles - subcellular structures

  • Nucleus, ribosome, mitochondria…

• Cells - different organelles, become specialised

  • Muscle, red blood cells…

• Tissues - a group of similar cells that work together to carry out a function

  • Muscle, epithelial…

• Organ - a group of different tissues that work together to perform a function

  • Stomach, pancreas, liver…

• Organ system - a group of organs that work together

  • Digestive system, cardiovascular system…

• Organism!!! - a group of organs

  • Humans

Cancer

• Cancer is a disease caused by cells growing abnormally and uncontrollably which can spread through the body

• Tumours are an abnormal mass of cells that form when a group of cells undergo uncontrolled growth and division

  • Benign - Cells are contained in one area, usually in a membrane

  • Malignant - Cells aren’t contained in membrane, so can enter the bloodstream and travel through the body.

                            - Can invade other tissues and form secondary tumours when cells detach                                   (metastasis)

                            - Process causes damage and is dangerous, so is seen as cancer

• Risk factors - Lifestyle

  • Smoking - Lung, mouth, stomach and cervical cancers

  • Obesity - Bowel, liver and kidney cancers

  • UV light exposure - Skin cancers

  • Alcohol - Liver cancers

• Risk factors - Genetics

  • Genes inherited from our parents can make you more susceptible to certain cancers

  • ‘BRCA’ genes are linked to breast and ovarian cancers

• Risk factors - Environmental

  • Increased exposure to ionising radiation

  • Exposure to chemical carcinogens (an agent that causes cancer)

The human digestive system

• Digestive enzymes break down food in the pancreas and small intestine

• Carbohydrates are usually found as starch (a polymer of glucose) and are broken down by amylase to maltose and then from maltose to glucose by maltase, which can be absorbed

• Proteins are broken down by proteins (pepsin and trypsin, etc.) into amino acids

• Lipids (fats) are broken down by lipase into glycerol and fatty acids

  • Bile helps this process by emulsifying lipids, which increases the surface area to allow lipase to further break down

• All enzymes are broken down by the pancreas and small intestine 

• The digestive system has two main roles - digestion and absorption - and breaks down food so nutrients are absorbed and waste is excreted

• The mouth

  • Teeth - physically break down food, increases surface area and improves ease of swallowing

  • Salivary glands - releases saliva, which contains amylase (to digest starch) and wettens food

• Oesophagus - food is passed through

• Stomach - contracts muscular walls, produces pepsin (type of protease) and produces HCl to kill bacteria and provide the right pH for pepsin

• Pancreas - when food enters the stomach, it releases pancreatic juices to the small intestine, which contains enzymes for digestion

• Gallbladder - neutralises acid from the stomach and releases bile to emulsify lipids (made in the pancreas, stored in the gallbladder)

• Small intestine - Where most of digestion happens

  • Digestive enzymes are released to break nutrients down

  • Nutrients are absorbed - the small intestine has lots of villi (and microvilli), with a large surface area, good blood supply and a single layer of cells for increased rate of diffusion

• Large intestine - Absorbs excess water

• Rectum - Where waste is stored before excretion

The heart

• The heart is part of a double circulatory system - pulmonary circuit (with the lungs) and systemic circuit (with the body)

• The heart has 4 chambers

  • The left ventricle, right ventricle, left atrium and right atrium

  • The left ventricle has a thick muscular wall than the right as it needs to generate high pressure to pump blood to the rest of the body

• The Vena Cava pumps DEOXYGENATED blood FROM the body to the heart

• The Pulmonary Artery pumps DEOXYGENATED blood TO the lungs from the heart

• The Aorta pumps OXYGENATED blood TO the body from the heart

• The Pulmonary Vein pumps OXYGENATED blood FROM  the lungs to the heart

Blood vessels

• Arteries - Carry blood AWAY from the heart

  • Carries at high pressure 

    • Strong and thick elastic and muscle tissue

    • Small lumen

• Capillaries - Really small (single cell thick)

  • Are permeable - allows for gas exchange to blood and nutrients

  • Exchange substances with cells - oxygen and nutrients

  • Remove waste - carbon dioxide

  • Low pressure

• Veins - Carry blood TOWARDS the heart

  • At a low pressure

    • Thin walls

    • Largest lumen

  • Have valves - stop blood flowing wrong way

Blood

• Blood is made up of red blood cells, white blood cells, plasma and platelets

• Red blood cells - Make up around half of our blood by volume

  • Carry oxygen from lungs to cells

  • Contain haemoglobin

    • Become oxyhaemoglobin when oxygen is present, and separates so oxygen is free to diffuse into tissues

  • Adaptations - no nucleus so there is more space for haemoglobin

    • biconcave disk shape to increase surface area for diffusion

• White blood cells - less than 1% of blood

  • Defend against infections and pathogens :( 

  • They produce 

    • Antibodies - bind onto pathogens and help to destroy them

    • Antitoxins - neutralise toxins

    • Perform phagocytosis - engulf pathogens so they can be destroyed by antibodies

• Platelets - small fragments of cells (no nucleus)

  • Float about in blood until we get a cut and they act as a ‘glue’ and help us patch up

    • Clotting prevents blood loss and stops more pathogens entering

• Plasma - around 50% of blood volume

  • Watery so blood can flow

  • Carries RBC, WBC, platelets, nutrients (glucose and amino acids), waste products (carbon dioxide and urea), antibodies and antitoxins

• In a human, there is around 5 litres of blood

  • If blood loss is severe, the blood may not be able to efficiently supply oxygen to the tissues

  • New blood can be given!

• New blood (ooooh…)     

  • Artificial blood - adds volume, is mainly salt water, and contains no red blood cells so can’t transport oxygen

    • Can only replace 1/3 of blood

  • Blood transfusions - has RBC, but needs to be donated and there are certain types for different people

Coronary heart disease

• A cardiovascular disease are any diseases linked to the cardiovascular system (heart and blood vessels)

• Coronary heat disease is when the coronary arteries become blocked and can prevent blood supply to the heart

  • Is caused by a build up of fatty material (cholesterol)

• Treatments - Stents

  • Stents are placed into the coronary arteries and are an expandable tube that ensures blood can keep flowing

  • A balloon is inflated in the artery and is later removes - stent is left in

  • Benefits - they are quick and long lasting

  • Drawbacks - there are risks of infection or heart attack and clots

• Statins - Medication that lowers the production of fatty material and cholesterol, taken to prevent coronary heart disease 

  • When too much CDL is made, it causes blocked arteries, which is bad :( 

    • HDL is good fatty material

  • Benefits - they lower the risks of coronary heart disease, strokes and heart attacks

  • Drawbacks - have to be taken regularly, can cause kidney failure and headaches

• Valves can be damaged over time or become infected 

  • They can be replaced in surgery with either biological or mechanical valves

• Heart failure happens when the heart can’t pump blood

  • This can be treated with a new heart  - artificial is temporary and biological is from a donor

    • Risks of rejection and there is a long wait list

Health issues

• Health is a state of physical and mental wellbeing

  • It is effected by exercise, sleep, diet and medical care

• Disease is a condition that causes ill health

  • Communicable - infectious diseases, like colds or malaria

    • Viruses, bacterial, parasites and fungi

  • Non-communicable - can’t spread, like asthma or diabetes

  • Physical diseases can lead to mental health issues

  • Immune systems are linked to communicable diseases and our health

Effect of lifestyle on some non-communicable diseases

• Risk factors are anything that increases the chance that someone will develop a disease

• Lifestyle factors - Diet

  • Alcohol (liver disease)

  • Stress (mental and physical health)

  • Lack of exercise

  • Obesity from these factors can lead to diabetes, heart attacks and coronary heart disease

• Environmental factors - Smoking (lung disease and cancers)

  • Air pollution

  • Radiation exposure

Plant cell organisation

• Leaves are the main site of photosynthesis in a plant - requires carbon dioxide, water and sunlight

  

• The waxy cuticle protects the surface of the leaf and prevents water loss - is transparent to allow sunlight through

• The upper epidermis is almost transparent to allow sunlight through

• The palisade mesophyll is where most photosynthesis occurs and therefore has lots of chloroplasts (chlorophyll absorbs sunlight)

• Air space is necessary to allow carbon dioxide to easily diffuse

• The spongy mesophyll has lots of air space which increases surface area and allows for efficient gas exchange

• The lower epidermis allows for gas exchange via the stomata

• The stomate allow carbon dioxide to enter and oxygen to leave the leaf

• The guard cells control the movement of gases

  • Xylem transport water from the roots continuously to the palisade cells, which can be lost through the leaf (stomata and surface)

  • The waxy cuticle prevent water loss from the top side

  • Guard cells control whether the stomata are open or closed to prevent water loss    

    • If they are well hydrated, the cells are turgid which increases the gap and allows carbon dioxide in

    • If they are dehydrated, they become flaccid and prevent carbon dioxide from entering

    • When they are open, water is able to diffuse out of the leaf, which is bad :( if the cell is dehydrated, so they close the gap to decrease this water loss

    • Guard cells are light sensitive, and close when there is no sunlight - water loss is prevented and no carbon dioxide is needed as photosynthesis can’t occur without light

    • They are on the underside of the leaf which is shaded and cooler to decrease water evaporation

Transpiration and translocation

• Translocation is used to transport sugars in the plant

• Transpiration transports water up the plant

• Translocation is used to ensure the rest of the plant has sugars made through photosynthesis in the leaf, and transports it

• Phloem are used for this translocation and allow movement in both directions

  • There are pores throughout the structure

  • They enable the movement of cell sap - sugar and water - which can be used directly for energy or stored for later

  • Companion cells supply phloem with the energy required to transport cell sap and nutrients - necessary for translocation

• Transpiration transports water and minerals up the plant to be used in photosynthesis

  • Done via xylem tubes

    • Made of dead cells

    • Have no ends

    • Long and hollow

    • Strengthened by lignin

•  The water stream is constant as it evaporates through the stomate in the leaves when not used for photosynthesis

  • This stream of water molecules is called the transpiration stream

• The rate of transpiration depends on:

  • Light intensity - more light means a higher rate of photosynthesis so the stomata are open more for carbon dioxide

    • Means more water is required for photosynthesis and evaporation through stomata

  • Temperature - the warmer it is the easier water will evaporate as it has more energy so transpiration rate is higher

  • Air flow - the higher the air flow is, the easier water gets ‘blown away’ so concentration gradient needs to be kept high so the transpiration rate increases

  • Humidity - the more humid it is, means the air has more water already, so less evaporates from the leaf, so the concentration gradient can be decreased and transpiration rate decreases

DONE!!!

BIOENERGETICS

Photosynthesis

• Occurs in plants in the chloroplasts in the leaves

  • The leaves contain chloroplasts with lots of chlorophyll (green pigment) that absorbs sunlight - needed for photosynthesis

• Carbon dioxide + water $\rightarrow$ glucose + oxygen (using sunlight)

  • 6CO₂ + 6H₂O $\rightarrow$ C₆H₁₂O₆ + 6O₂

  • Is an endothermic reaction

• Carbon dioxide diffuses through the leaf through the stomata, and water is transported up the stem from the roots by the xylem

Uses of glucose

• Glucose from photosynthesis is used for:

  • Cellular respiration - breaks apart glucose to release energy

  • Makes cellulose - strengthens walls

  • Makes starch - long term storage of glucose

  • Makes oils and fats - future energy sources

Rate of photosynthesis

• The rate of photosynthesis depends on light intensity, temperature, carbon dioxide concentration and chlorophyll levels

• Chlorophyll levels - Is found in chloroplasts

  • If there is less chlorophyll, less photosynthesis will be able to carry out

  • Can decrease due to diseases, like tobacco mosaic virus, environmental stress and a lack of nutrients

• Light intensity - The higher the light intensity, the higher the rate of photosynthesis

  • It will reach a point where it levels out, as either CO₂ or temperature becomes a limiting factor instead

• Carbon dioxide concentration - When CO₂ is in excess, the rate of photosynthesis increases as it is a reactant

• When it is plentiful and easily available, carbon dioxide stops becoming a limiting factor and instead light or temperature becomes limiting

• Temperature - As temperature increases, so does the rate of photosynthesis as the particles have more energy so can therefore move and work faster - molecules work faster

  • As the temperature increases, the rate will start to drop as the enzymes begin to die and become denatured - limiting factor

  • At 45°, the enzymes will be fully denatured and the rate of photosynthesis will be 0.

• Artificially created conditions can be created for increased rate of photosynthesis

  • In colder climates - crops in greenhouses to trap sun’s heat

  • Artificial light for photosynthesis at night

  • Pump for CO₂

  • Paraffin heater for CO₂ and heat

  • Enclosed greenhouses to prevent bugs

  • Fertiliser for essential minerals

  • Pesticides to kill unwanted bugs

Aerobic and anaerobic respiration

• Respiration is the process of transferring energy from glucose and it continuously occurs in living cells   

  • Cellular respiration is exothermic (photosynthesis is endo)

• Organisms use energy for:

  • To build larger molecules from smaller ones - amino acids to proteins

  • For muscle contraction

  • Maintaining body temperature

• Aerobic respiration takes place when there is enough oxygen as is the most efficient in animals and plants

  • It takes place in the mitochondria

  • Glucose + oxygen $\rightarrow$ carbon dioxide + water

    • C₆H₁₂O₆ + 6O₂ $\rightarrow$ 6CO₂ + 6H₂O

• Anaerobic respiration takes place when there is no oxygen (or limited) and only occurs when necessary

  • It doesn’t fully break down glucose

  • Lactic acid is toxic and has to be removed

  • Glucose $\rightarrow$ lactic acid

• In plants and yeast, anaerobic respiration is called fermentation and is used in bread/alcohol…

  • Glucose $\rightarrow$ ethanol + yeast

Response to exercise

• During exercise, our muscles move more, and contract more so need more energy

  • Therefore need more oxygen and GLUCOSE

  • Our rate of breathing and volume of breath increases

  • Our heart rate increases - both also need more energy

• If there is not enough oxygen present, we anaerobically respire

  • Is used only in intense exercise

  • Produces lactic acid, which builds up in tissues

    • Creates a burning sensation

    • Is remove by reacting with oxygen - creates oxygen debt

  • Lactic acid is transported to the liver via the blood stream, where it reacts with oxygen to produce either

    • Glucose (often stored as glycogen after)

    • OR carbon dioxide + water

• Investigating effects of exercise

  • Heart rate - count pulse for 60 seconds before, directly after and a while after exercise

  • Breathing rate - count the number of breathes per minute

Metabolism

• Metabolism is all the chemical reactions in an organism’s body

  • Changes between person

DONE!!!

INFECTION AND RESPONSE

Communicable diseases

• Microorganisms - bacteria, viruses, protists and fungi, and some can cause issues in the body

• Pathogens are microorganisms that cause disease

• Pathogens spread by:   

  • Air - influenza and measles, tiny droplets that we cough or sneeze

  • Contaminated food - salmonella

  • Contaminated water - Cholera and bacteria diseases

  • Direct contact - athlete’s foot (fungal), through contaminated surfaces

• We can stop the spread of pathogens by:

  • Hygiene - washing hands, clean cooking items

  • Killing the vectors🗡 - mosquitoes carrying malaria can be killed by insecticides

  • Isolation - for serious diseases

  • Vaccination - Can’t catch, so therefore can’t pass on

Viral diseases

• Viruses aren’t cells and are not living and can’t reproduce, they are considered organisms

  • They go inside other cells and use them to reproduce - can burst cell and move to other cells which is damaging and dangerous

• Measles

  • Spread by droplets in the air - from sneezes and coughs

  • Causes a red rash and a fever

  • Can be fatal

  • Most people are vaccinated

• HIV

  • Spread through sexual contact and exchanging of bodily fluids (needles)

  • Causes an inadequate immune system

  • Can cause flu like symptoms (fevers, tiredness and aches), and then start to fell better though still infected

  • Virus damages immune system and catches unusual infections - can develop into cancers

  • Person can develop AIDS - a system/syndrome when an immune system can’t cope

  • Treated by antiretroviral drugs, which prevent the virus replicating

• Tobacco mosaic virus

  • Affects plants (tomato and tobacco)

  • Causes a mosaic pattern on leaves, so photosynthesis is slowed can’t occur - a lack of sugars for growth                    

Bacterial diseases

• Bacteria is mainly good, but there are a few bad ones that cause diseases :(

• Bacteria are single celled organisms

• They can reproduce by themselves

  • They are often in our bodies as good food supply, and they can produce toxins - cause illness

• Salmonella

  • Causes food poisoning

  • Mainly from chicken (who had disease when alive)

    • In the UK, most are vaccinated against it

  • Causes fever, stomach cramps, vomiting and diarrhoea ( as it affects the intestines)

  • Passes in about a week and hydration is important

• Gonorrhoea

  • Sexually transmitted disease

  • Causes pain when urinating and thick discharge

  • Prevented by barrier contraception

  • Treated by penicillin - however many stains are resistant to it

    • Instead, rarer and more expensive antibiotics are used

Fungal diseases

• Fungi are eukaryotic cells, and can be unicellular (yeast) or multicellular

• Multicellular can be mushrooms, often have long thread-like structures (hyphae), can penetrate skins and produce spores

• Rose black spot

  • Causes purple/black spots on leaves

  • Can cause leaves to turn yellow and drop off, which causes reduced photosynthesis, leading to less growth

  • It spreads in the water and air

  • Treated by cutting of infected leaves and destroying them, or spraying with fungicide

• Athlete’s foot

  • Causes a rash - dry red and flaky or white, wet and cracked skin

  • Transmitted by touching infected skin or contaminated surfaces

  • Treated by antifungal medication

Protist diseases

• Protists are eukaryotic cells that can be multicellular or unicellular (majority)

• Some are parasites and live in/on another organism

• They are often transmitted by vectors (malaria and mosquitos)

• Malaria

  • Caused by a parasitic protist and needs a host to survive

  • Transported by mosquitos, who feed on an animal with malaria , the mosquito ‘sucks up’ the parasite, and then feeds on another animal and spreads it to a new most

  • Causes fever, headaches in recurrent episodes and can be fatal in humans

  • Prevented by destroying mosquito breeding sites, killing with insecticides and stopped with mosquito nets and repellent

Human defence systems

• Physical and chemical barriers

  • Skin - a physical barrier that secretes oil and antimicrobial structures that kill pathogens

  • Nose/mouth - The nose has lots of hairs and mucus to trap pathogens

    • The trachea/oesophagus has a mucus layer and cilia to waft pathogen back up to nose

    • Stomach kills pathogens with acid

• Immune systems

  • White blood cells

    • Phagocytosis - Wbc can engulf some pathogens, so we can track the pathogens to later bind and engulf

    • Anti-toxins - Wbc produce and they can bind and counteract pathogens and toxins

    • Antibodies - Small proteins that act as a signal and bind onto pathogens so Wbc’s can come and destroy them

      • They are specific to certain antigens

Vaccinations

• Once our bodies and immune systems have been exposed to a pathogen, they become immune to it and it’s diseases

  • This is why we can only catch some diseases once, like measles

• To protect ourselves from pathogens, we need to be exposed to the disease without actually catching it, as it could be lethal if caught

• Vaccines are a weakened or dead version of a pathogen that still contains the antigens needed to produce antibodies that lead to immunity

• They can work bacterial and viral diseases

• PROS - Protection against pathogens

  • Control over common diseases

  • It can prevent outbreaks and epidemics, which kill a lot of people

  • Herd immunity - when enough people in a community are vaccinated, the pathogen won’t have anyone to spread to, so when the host overcomes the disease or dies, the pathogen disappears

• CONS - Vaccines don’t always work and don’t necessarily grant full immunity

  • Can cause bad reactions, like swelling or seizures, although rare

Antibiotics and painkillers

• Antibiotics treat the disease by preventing growth or killing the bacteria

  • They can only treat bacterial diseases

  • They are specific to each type of bacteria and each target a different type of bacteria

• Antibiotic resistance is when strains of bacteria adapt to become resistant to the antibiotic and no longer work

• Painkillers only relieve symptoms and don’t help cure the problem

Discovery and development of drugs

• New drugs are constantly being developed, often from plants and microorganisms

• The first antibiotic made was penicillin and discovered by Alexander Fleming

  • He went on holiday, and when he came back there was mould growing in his petri dish that killed of bacteria that was already growing

    • Penicillium mould became penicillin antibiotic

• Aspirin - made from willow bark and it lowers fevers

• Digitalis - a heart drug that is extracted from foxgloves

• Drugs can be made from plants and microorganisms - can be directly used or modified in a lab

• Testing

  • We test for efficacy, toxicity and dosage

• Stage 1 testing - pre-clinical

  • Testing on human cells and tissues 

  • Cheaply test lots of possible substances

  • Doesn’t show effect on whole organisms or organs

• Stage 2 - pre-clinical

  • Testing on live animals

  • In UK, you have to test on at least 2 mammals

  • Shows effects and ideas around efficacy and toxicity

• Stage 3 - clinical

  • Testing on healthy volunteers with a low dosage, which is slowly increased to find the maximum without side effects

  • Testing on patients with the illness

    • A low dosage which is very slowly increased to find the optimum dosage (max efficacy, min toxicity)

• Blind testing is when both placebo and real drugs are used and the volunteers don’t know which they are getting

• Double-blind testing uses placebo and real drugs and the doctors also don’t know which is which

  • Both are used to avoid biases

    • The volunteers knowing they took the drug might report more side effects

    • Doctors might notice or expect more side effects, so question more

• Peer reviews are where results are analysed by other scientists, to prevent false results or claims

Producing monoclonal antibodies

• Monoclonal antibodies are a single clone of a specific cell made to produce antibodies

• Antibodies are small proteins produced by white blood cells (lymphocytes)to help fight disease

  • They bind onto foreign material - antigens

  • They are specific to certain bacteria

• They are made in a laboratory

  • This requires lots of B-lymphocyte clones (they don’t duplicate very quickly, so need something to increase rate)

  • We can combine B-lymphocyte clones with fast-dividing tumour cells - forms a hybridoma

• Hybridomas - produce lots of antibodies

  • Divide rapidly, in a petri dish, and are them collected and purified

• We collect these white blood cells and inject an animal with them with the antigen we want our antibody to bind to 

  • This produces the lymphocytes that we can isolate and fuse

• They always bind to one specific thing ,and with the right B-lymphocyte we can create antibodies that bind to anything we want

  • For example, protein or cells in the body, a pathogen or chemical 

• We can attach things to the antibody, likes to drugs, fluorescent proteins or radioactive materials, to deliver it to certain areas

Uses of monoclonal antibodies

• Pregnancy tests 

  • Pregnant women produce a hormone called HCG, which is excreted in urine

  • They are cheap, reliable and quick

  • In the test strip, there are blue beads covered in antibodies (specific to HCG) that are free to move at one end

  • In the middle, there are the same antibodies fixed to the test strip

  • If the women is not pregnant, the urine washes the blue beads down the strips and over the fixed antibodies, so it doesn’t go blue

  • If the women is pregnant, the urine will contain HCG, which binds to the blue beads and antibodies on them

    • When the urine washes over the fixed antibodies, it binds to them as well and the beads stay, so the strip appears blue

• Cancer diagnosis and treatment

  • If a person with cancer is injected with monoclonal antibodies, they will bind to the tumour and cancerous cells and will ‘clump’ together

    • This makes it easier to identify tumours

    • We can carry drugs (attached to the antibodies) directly to the tumour

    • We can encourage the immune system to directly attack cancerous cells

Detection and identification of plant diseases

• Plants can catch diseases from fungi, bacteria, viruses, insects and have deficiency diseases (stunted growth)

• Symptoms of plant diseases could be abnormal growth or lumps, patches of decay, discolouration on leaves, malformed stem or leaves and aphids or spider mites

• We can diagnose plant diseases by

  • Basic observation - match a gardening manual or website with findings

  • Take a tissue sample and send to a plant pathologist, who look at unique antigens and take DNA tests

  • Trial and error to treat

Plant defence systems

• Physical defences 

  • Waxy cuticle

  • Cellulose (cell walls)

  • Dead cell layers (bark)

• Chemical defences

  • Antimicrobial

  • Poisons

• Mechanical defences

  • Thorns

  • Hairs

  • Leaves dropping off or curling if insects land on them to prevent infection

DONE!!