All of Biology paper 1 Flashcards
What does a nucleus do?
It contains genetic material and controls the activities of the cell
What does cytoplasm do?
It’s a gel-like substance where most of the chemical reactions happen. It contains enzymes that control these chemical reactions
What does a cell membrane do?
It holds the cell together and controls what goes in and out
What do mitochondria do?
These are where most of the reactions for aerobic respiration occur. Respiration transfers energy that the cell needs to work
What do ribosomes do?
This is where protein synthesis takes place - where proteins are made in the cell
What do cell walls do?
They are made of cellulose and they support and strengthen the cell
What does a vacuole do?
It contains cell sap and helps maintain the shape of the cell
What do chloroplasts do?
This is where photosynthesis occurs, which makes food for the plant. They contain chlorophyll - a green pigment - which absorbs light needed for photosynthesis
What do bacterial cells contain?
Cytoplasm, cell membrane, cell wall, flagella, ribosomes, mitochondria, slime capsule, plasmids (small rings of DNA) and a single circular strand of DNA that floats freely in the cytoplasm
What do bacterial cells NOT contain?
A nucleus
What is the equation for magnification?
Image size divided by actual size
What is differentiation?
The process by which a cell changes to become specialised for its job
What are undifferentiated cells called?
Stem cells
What are sperm cells specialised for and how are they specialised?
Reproduction - they transport the male DNA to the female DNA
-It has a flagella and a streamlined head to help it swim towards the egg
-There are lots of mitochondria in the cell to provide the energy needed
-It carries enzymes in its head to help digest through the egg cell membranes
What are nerve cells specialised for and how are they specialised?
Rapid signalling - they carry electrical signals from one part of the body to another
-They are long to cover more distance
-They have branched connections at their ends to connect to other nerve cells and form a network throughout the body
What are muscle cells specialised for and how are they specialised?
Contraction - they need to contract quickly
-They are long so they have space to contract
-They contain lots of mitochondria to generate the energy needed for contraction
What are root hair cells specialised for and how are they specialised?
Absorbing water and minerals
-They are cells on the surface of plant roots which grow into long hairs that stick out into the soil
-They have a large surface area for absorbing water and mineral ions from the soil
What are chromosomes?
Coiled up lengths of DNA molecules that are found in the nuclei
What do multicellular organisms use mitosis for?
To grow or replace cells that have been damaged
What are stem cells
They are undifferentiated cells that divide to produce lots more undifferentiated cells. They then differentiate into different types of cell
Where are stem cells found?
In early human embryos or the bone marrow of adults
What do embryonic stem cells do?
1) Used to replace faulty cells in sick people - insulin-producing cells for diabetes and nerve cells for paralysed spinal injuries
2) Used to replace faulty blood cells
What is diffusion?
Diffusion is the movement of particles from an area of high concentration to an area of low concentration
Name the substances that can diffuse through cell membranes
Glucose, water, oxygen and amino acids
Name two substances that can’t diffuse through cell membranes
Protein and starch
What is osmosis?
Osmosis is the passive movement of water molecules through a partially permeable cell membrane from an area of high water concentration to an area of low water concentration
What are the two main differences between active transport and diffusion?
Active transport uses energy whereas diffusion doesn’t. Active transport goes against the concentration gradient whereas diffusion goes along it
Adaptations of Exchange Surfaces
1) Large surface area - lots of substances can diffuse at once
2) Lots of blood vessels - to get stuff into and out of the blood quickly
3) Thin membrane - short distance for substances to diffuse
4) Often ventilated - air moves in & out
Give two ways that the villi in the small intestine are adapted for absorbing digested food
1) A single layer of surface cells
2) A very good blood supply to assist quick absorption
Explain how the leaves are adapted to maximise the amount of carbon dioxide that gets into their cells
1) The exchange surface in a leaf is covered in stomata which the carbon dioxide diffuses through
2) The leaf has a flattened shape which increases the area of its exchange surface, therefore it’s more effective
3) The walls of the cells inside the leaf act as another exchange surface
4) The air spaces inside the leaf increase the area of the exchange surface which increases the chance for carbon dioxide to enter the cells
What affects the rate of diffusion?
Concentration gradient - the steeper the gradient, the faster the rate
Temperature - the higher the temperature, the faster the rate (the particles have more energy thus move around faster)
Surface area - the larger it is, the faster the rate
Diffusion distance - the shorter the distance, the faster the rate
Examples of active transport
Plants = Root hairs absorb minerals and water. Each branch of a root will be covered in tiny hairs, therefore increasing the surface area for the absorption of minerals and water. The concentration of minerals is usually higher in the root hair cells than in the soil around them, therefore they can’t use diffusion for this process.
Animals = Glucose is taken in from the gut and from kidney tubules.
How are alveoli in the lungs specialised to maximise the diffusion of oxygen and carbon dioxide?
-an enormous surface area
-a moist lining for dissolving gases
-very thin walls
-a good blood supply
How do fish respire?
-Water enters the fish through the mouth and passes out through the gills
-During this process, oxygen diffuses from the water into the blood in the gills and carbon dioxide diffuses from the blood into the water
How are fish adapted for gas exchange?
-Each gill is made up of lots of gill filaments which create a large surface area for the exchange of gases
-Gill filaments are covered in lamellae which increase the surface even more
-The lamellae have lots of blood capillaries to speed up diffusion
-The lamellae have a thin surface layer of cells to minimise the diffusion distance
-Blood flows through the lamellae one way and water flows over in the opposite direction which maintains a higher concentration gradient between the blood and the water
-The concentration of oxygen in the water is always higher than that in the blood to maximise the amount of oxygen diffusion from the water into the blood
Microscopy Practical - Preparing the Slide
1) Add a drop of water to the middle of a clean slide
2) Cut up an onion & separate it out into layers. Use tweezers to peel off some epidermal tissue from the bottom of one of the layers
3) Using the tweezers, place the epidermal tissue into the water on the slide
4) Add a drop of iodine solution - a stain used to highlight objects in a cell by adding colour to them
5) Place a cover slip on top - stand the cover slip upright on the slide, next to the water droplet. Then, carefully tilt & lower it so it covers the specimen. Try not to get any air bubbles under there - there’ll obstruct your view
Microscopy Practical - Using a Light Microscope
1) Clip the slide you’ve prepared onto the stage
2) Select the lowest-powered objective lens
3) Use the coarse adjustment knob to move the stage up to just below the objective lens
4) Look down the eyepiece. Use the coarse adjustment knob to move the stage downwards until the image is roughly in focus
5) Adjust the focus with the fine adjustment knob, until you get a clear image of what’s on the slide
Microscopy Practical - Drawing Observations
1) Draw what you see under the microscope using a pencil with a sharp point
2) Make sure your drawing takes up at least half of the space available & that it is drawn with clear, unbroken lines
3) Your drawing should not include any colouring or shading
4) If you are drawing cells, the subcellular structures should be drawn in proportion
5) Include a title & write down the magnification that it was observed under
6) Label the important features of your drawing using straight, uncrossed lines
What happens during binary fission?
1) The circular DNA & plasmid(s) replicate
2) The cell gets bigger & the circular DNA strands move to opposite poles of the cell
3) The cytoplasm begins to divide & new cell walls begin to form
4) The cytoplasm divides & two daughter cells are produced. Each daughter cell has one copy of the circular DNA, but can have a variable number of copies of the plasmid(s)
What is binary fission?
A type of simple cell division used by prokaryotic cells to reproduce & split into two
What conditions do bacteria need to divide?
1) Warm environment
2) Lots of nutrients
What is the mean division time?
The average amount of time it takes for one bacterial cell to divide into two
How do you make an agar plate?
Hot agar jelly is poured into shallow Petri dishes. When the jelly’s cooled & set, inoculating loops can be used to transfer the microorganisms to the culture medium. Alternatively, a sterile dropping pipette & spreader can be used to get an even covering of bacteria. The microorganisms then multiply
Investigating the Effect of Antibiotics on Bacterial Growth - Method
1) Place paper discs soaked in different types of antibiotics on an agar plate that has an even covering of bacteria. Leave some space between the discs
2) The antibiotic should diffuse into the agar jelly. Antibiotic-resistant bacteria that aren’t affected by the antibiotic will continue to grow on the agar around the paper discs, but non-resistant strains will die. A clear area will be left where the bacteria have died - an inhibition zone
3) Make sure you use a control - a paper disc that has not been soaked in an antibiotic. Instead, soak it in sterile water so you can be sure that any difference between the growth of bacteria around the control disc & around one of the antibiotic discs is due to the effect of the antibiotic alone
4) Leave the plate for 48 hours at 25°C
5) The more effective the antibiotic is, the large the inhibition zone will be
Avoiding Contamination
1) The Petri dishes & culture medium must be sterilised before use (heating to a high temperature), to kill any unwanted microorganisms
2) If an inoculating loop is used to transfer the bacteria to the culture medium, it should be sterilised first by passing it through a hot flame
3) After transferring the bacteria, the lid of the Petri dish should be lightly taped on - stops any microorganisms from the air getting it
4) The Petri dish should be stored upside down - stops drops of condensation falling onto the agar surface
Investigating the Effect of Sugar Solutions on Plant Tissue - Method
1) Cut up a potato into identical cylinders, and get some beakers with different sugar solutions in them: one should be pure water & another should be a very concentrated sugar solution
2) Measure the mass of the cylinders, then leave one cylinder in each beaker for 24 hours
3) Take them out, dry them with a paper towel & measure their masses again
4) If the cylinders have drawn in water by osmosis, they’ll have increased in mass. If water has been drawn out, they’ll have decreased in mass
5) The dependent variable is the chip mass & the independent variable is the concentration of the sugar solution. All other variables must be kept the same
Possible Errors of the Potato Chip Experiment
1) Some potato cylinders were not fully dried
2) Water evaporated from the beakers
3) The potato chips weren’t identical sizes
4) The volumes of water weren’t identical
Types of eukaryotic cells
Animal cells
Plant cells
What are light microscopes?
They use light & lenses to form an image of a specimen & magnify it
Allow us to see individual cells & large subcellular structures e.g. nuclei
What are electron microscopes?
They use electrons to form an image
They have a higher magnification & a higher resolution
Allow us to see smaller things in more detail e.g. internal structure of mitochondria & chloroplasts & ribosomes & plasmids
Disadvantages of Stem Cells
1) Stem cells grown in the lab may become contaminated with a virus - this will be passed onto the patient & make them sicker
2) Some people think that human embryos shouldn’t be used for experiments - each one is a potential human life
3) Scientists should focus more on finding & developing other sources of stem cells
What is a tissue?
A tissue is a group of similar cells that work together to carry out a particular function
Examples of tissues
Muscular tissue - contracts to move whatever it’s attached to
Glandular tissue - makes and secretes chemicals like enzymes and hormones
Epithelial tissue - covers some parts of the human body e.g. the inside of the gut
What is an organ system?
An organ system is a group of organs working together to carry out a particular function
Example of an organ system
Digestive system - glands (pancreas and salivary glands), stomach, liver, small intestine and large intestine
Why can enzymes be described as biological catalysts?
They speed up useful chemical reactions in the body
Why do enzymes only usually catalyse one reaction?
Their active site is only complimentary to one type of substrate
What does it mean when an enzyme is denatured?
Its active site has changed shape due to intense heat or acidic conditions
Where is amylase found?
It’s made in the salivary gland and the pancreas and it works in the small intestine
What is the role of lipases?
They break down lipids into fatty acids and glycerol
Where is bile made and stored?
It’s made in the liver and stored in the gall bladder
What does bile do?
It emulsifies fats into smaller, more soluble pieces which gives the fat a bigger surface area for lipase to work on. It also neutralises the stomach acid to make the conditions alkaline, therefore the small intestine
What are organs?
Organs are groups of tissues that work together to perform certain functions
What are the tissues in the stomach and what do they do?
Muscular tissue - moves the stomach wall to churn up the food
Glandular tissue - makes digestive juices to digest food
Epithelial tissue - covers the inside and outside of the stomach
What is the name of the substance when a substrate fits into the enzyme’s active site?
Enzyme substrate complex
What is the name of the substance when the enzyme’s active site has turned the substrate into two products?
Enzyme product complex
What is the optimum pH for enzymes?
The pH level that they are most active at. E.g. pepsin has an optimum pH of 2
What does amylase break down?
It catalyses the breakdown of starch to maltose
What do carbohydrases break down?
Carbohydrates into simple sugars
What do proteases break down?
Proteins into amino acids
Where are proteases found?
They’re made in the stomach (called pepsin here) and the pancreas and found in the small intestine
Where are lipases found?
They’re made in the pancreas and work in the small intestine
Name three substances and what they test for
Benedict’s Test - testing for sugars - goes red
Iodine solution - tests for starch - goes blue-black
Biuret Test - tests for proteins - goes purple
What do the salivary glands do?
They produce amylase in the saliva
What does the stomach do?
-It pummels the food with its muscular walls
-It produces pepsin
-It produces hydrochloric acid to kill bacteria and give the right pH for pepsin to work
What does the pancreas do?
It produces amylase, protease and lipase then releases them into the small intestine
What does the small intestine do?
It contains protease, amylase and lipase to complete digestion. Digested food is absorbed into the blood here
What does the rectum do?
It stores faeces
What does the large intestine do?
It’s where excess water is absorbed from the food
What does the gall bladder do?
It stores bile before it’s released into the small intestine
What does the liver do?
It produces bile which neutralises stomach acid and emulsifies fat
Where are the lungs?
The thorax
What are the lungs surrounded by?
Pleural membrane
What protects the lungs?
The ribcage
What goes down the trachea?
The air that you breathe in
What tubes join onto the trachea?
The bronchi
What do the bronchi split off into?
Bronchioles
What are the small bags at the end of bronchioles called?
Alveoli
What happens in an alveolus?
Gas exchange. The blood passing next to the alveoli contains lots of carbon dioxide and little oxygen. The oxygen diffuses out of the alveoli (high concentration) and into the blood (low concentration) and the carbon dioxide diffuses out of the blood (high concentration) and into the alveoli (low concentration) to be breathed out.
What surrounds the alveoli?
Lots of blood capillaries
What happens when blood reaches body cells?
Oxygen is released from the red blood cells and diffuses into the body cells. At the same time, carbon dioxide diffuses out of the body cells and into the blood. It’s then carried back to the heart
What makes up the circulatory system?
The heart, blood vessels and blood
What happens on the right side of the heart?
Deoxygenated blood flows in through the vena cava and into the right atrium. The atrium contracts and pushes the blood through the tricuspid valve, into the right ventricle. The valve closes and the ventricle contracts, to push the blood through the right semi-lunar valve. The valve will close and the blood is pushed out of the pulmonary artery to go up to the lungs
What happens on the left side of the heart?
Oxygenated blood flows in through the pulmonary vein and into the left atrium. The atrium contracts and pushes the blood through the bicuspid valve, into the left ventricle. The valve closes and the ventricle contracts to push the blood through the left semi-lunar valve. The valve will then close and the blood flows out of the aorta to all the cells in the body for gas exchange
How does the heart pump blood around the body?
Blood flows into the two atria from the vena cava (right atrium) and the pulmonary vein (left atrium). The atria contract, pushing the blood into the ventricles through valves. The ventricles contract and force the blood through more valves into the pulmonary artery (right ventricle) and the aorta (left ventricle) and out of the heart
What are the three types of blood vessels?
Arteries, capillaries and veins
Arteries, capillaries and veins
-They carry blood under high amounts of pressure
-Their walls are strong, elastic and thick
-They have the smallest lumens
-They contain thick layers of muscle to make them strong and elastic fibres to allow them to stretch and spring back
What do capillaries do?
-Arteries branch into capillaries
-They are really tiny - too small to see
-They carry blood really close to every cell in the body to exchange substances with them
-They have permeable walls - substances can diffuse in and out
-They supply food and oxygen and take away waste like carbon dioxide
-Their walls are one cell thick - this increases the rate of diffusion
What do veins do?
-Capillaries join up to form veins
-The blood is at low pressure in the veins so the walls aren’t as thick as an artery’s
-They have the biggest lumen to help the blood flow despite the lower pressure
-They have valves to help keep the blood flowing in the right direction
What is the rate of blood flow?
Volume of blood divided by the number of minutes
What are the four components of blood?
Red blood cells, white blood cells, platelets and plasma
What do red blood cells do?
-They carry oxygen from the lungs to all the cells in the body
-They have a biconcave disc shape - creates a large surface area and allows them to fit through capillaries
-They have no nucleus - can store even more oxygen
-They contain haemoglobin - this binds to oxygen to form oxyhaemoglobin
What do white blood cells do?
-They can change shape to ingest microbes - this process is phagocytosis
-Others produce antibodies to fight microbes
-Some produce antitoxins to neutralise any toxins produced by the microbes
-They have a nucleus
What do platelets do?
-They are small fragments of cells that have no nucleus
-They help the blood to clot at a wound - stops blood pouring out and microbes getting into your bloodstream
-Lack of platelets can cause excessive bleeding and bruising
What does plasma do?
Plasma carries:
-red blood cells
-white blood cells
-glucose
-amino acids
-carbon dioxide
-urea
-hormones
-proteins
-antibodies
-antitoxins
What are stents?
-Tubes that are inserted inside arteries to keep them open which allows the blood to pass through to the heart muscles
-They lower the risk of a heart attack in people with coronary heart disease
-They are effective for a long time
-There is a risk of infection from surgery and the patient could develop a blood clot near the stent - thrombosis
What are statins?
-Drugs that reduce the amount of bad cholesterol (LDL) in your bloodstream
-They slow down the rate of fatty deposits forming
-They reduce the risk of strokes, coronary heart disease and heart attacks
-They increase the amount of good cholesterol (HDL) in your bloodstream - HDL removes LDL from the blood
-They are a long-term drug that must be taken regularly - could be forgotten to be taken
-They can have some negative side effects e.g. headaches, kidney failure, liver damage and memory loss
-It takes time for them to kick in
How does coronary heart disease occur?
The coronary arteries are blocked by layers of fatty material building up. It causes the arteries to narrow therefore the blood flow is restricted and there’s a lack of oxygen to the heart - can result in a heart attack
What are artificial hearts used for?
-If heart donor organs aren’t available or suitable, they are used instead
-They are mechanical devices that pump blood around the body if someone’s heart has failed
-They’re usually temporary to allow someone’s heart to rest and heal
-They’re made from metal or plastic, therefore, they’re less likely to be rejected by the body’s immune system
-Surgery to fit one can cause bleeding and infection
-They don’t work as well as healthy natural ones
-Blood doesn’t flow through them smoothly which can cause blood clots which leads to strokes
What are artificial heart valves used for?
-If heart valves become damaged or weakened by heart attacks, infection or old age they can stiffen up or become leaky
-Artificial heart valves replace the natural valves - they can either be mechanical or taken from a cow or a pig
-It’s less drastic than a heart transplant
-It still takes major surgery and there can be a problem with blood clotting
What is artificial blood used for?
-It’s a blood substitute (e.g. a salt solution) which can replace a large lost volume of blood
-It’s safe and can generally keep people alive no matter how big the blood loss
-It gives the patient time to develop new blood cells or time to wait for a blood transfusion
What is health?
The state of physical and mental wellbeing
What are communicable diseases?
Diseases that can be spread from person to person or between animals and people. They can be caused by pathogens and can be described as contagious or infectious. Examples include measles and malaria
What are non-communicable diseases?
Diseases that cannot be spread between people or between animals and people. They generally last for a long time and get worse slowly. Example include asthma, cancer and coronary heart disease
What’s the problem with a weak immune system?
You have an increased chance of suffering from communicable diseases (e.g. the flu) because the body is less likely to be able to defend itself against the pathogen that causes the disease
What can some types of cancer be triggered by?
Infection by certain viruses
E.g. the hepatitis virus can cause long-term infections in the liver which increases the chance of getting liver cancer. Also, infection with HPV can cause cervical cancer
What are asthma sufferers in danger of?
Their symptoms becoming worse - immune system reactions in the body caused by infection by a pathogen can trigger allergic reactions (e.g. skin rashes) or worsen the symptoms of asthma
How can be mental health problems be triggered?
When someone is suffering from severe physical body problems, especially if they have an impact on their ability to do normal activities or affect their life expectancy
What factors can affect you health?
1) Balanced diet - provides your body with everything it needs
2) Stress - being constantly under lots of stress can lead to health issues
3) Life situation - having easy access to medicine or things that can prevent illness e.g. buy healthy food or condoms to prevent catching an STD
What are risk factors?
Things that are linked to an increase in your chance of contracting a disease
E.g. smoking, obesity, drinking, exposure to radiation
Smoking as a risk factor
Causes cardiovascular disease, lung disease and lung cancer. It damages the walls of arteries and the cells in the lining of the lungs
Obesity as a risk factor
Causes Type 2 diabetes - makes the body less sensitive to insulin
Drinking as a risk factor
Drinking too much alcohol causes liver disease, affects brain function and damages the nerve cells in the brain
Exposure to radiation as a risk factor
Cancer can be caused by exposure to ionising radiation, a carcinogen (something that causes cancer)
What are benign tumours?
Tumour grows until there’s no more room
The tumour stays in once place (usually in a membrane)
Isn’t dangerous or cancerous
What are malignant tumours?
Tumours grow and spread to nearby healthy tissues - invading these tissues forms secondary tumours
Cells can break off and spread to other parts of the body via the bloodstream
Is dangerous and cancerous - can be fatal
Risk factors for cancer
Smoking - lung, mouth, bowel, stomach and cervical cancer
Obesity - bowel, liver and kidney cancer
UV exposure - skin cancer
Viral infection - infection with hepatitis B/C can increase the risk of developing liver cancer
Epidermal tissue
Covers the whole plant
Palisade mesophyll tissue
Where most photosynthesis happens
Spongy mesophyll tissue
Contains big air spaces to allow gases to diffuse in and out of cells
Meristem tissue
Found at the growing tips of roots and shoots
Able to differentiate into lots of different types of plant cell - allows the plant to grow - plant stem cell
Waxy cuticle
Reduces water loss via evaporation
Upper epidermis
Transparent so light can pass through it to reach the palisade layer
Palisade layer
Contains chloroplasts - where photosynthesis takes place
Located near the top of the plant to absorb as much sunlight as possible
Large surface area with chloroplasts packed tightly together
Stomata
Little holes in the lower epidermis that allow carbon dioxide to diffuse into the leaf
Guard cells
Control the opening and closing of the stomata
They don’t open up at night as there is no sunlight
Phloem
Made up of elongated living cells
Transports food substances made in the leaves to the rest of the plant for immediate use or storage
Transport food substances in both directions - translocation
Xylem
Made up of dead cells
Transports water and mineral ions from the roots to the stem and the leaves
Transports them one way only
Movement of water from the roots, through the xylem and out of the leaves is called transpiration
What is transpiration?
The loss of water from plants by evaporation Water evaporates from the leaves
Side effect of photosynthesis
How does light intensity affect transpiration?
The brighter the light, the greater the rate
In bright light, the stomata will stay open for longer
How does temperature affect transpiration?
The warmer it is, the faster the rate
The hotter it gets, the more kinetic energy the water molecules gain
How does air flow affect transpiration?
The better the air flow around a leaf, the greater the rate
A good air flow will sweep water vapour away which maintains a low concentration gradient of water in the air outside the leaf
Diffusion happens quicker from an area of high concentration to an area of low concentration
How does humidity affect transpiration?
The drier the air around a leaf, the faster the rate
Humid air contains lots of water, so the lower the humidity, the faster diffusion will take place
How are guard cells adapted to open and close stomata?
When the plant has lots of water, they fill with water and become turgid - opens the stomata
When the plant is short of water, they lose water and become flaccid - closes the stomata
Thin outer walls and thicker inner walls control the opening and closing
Sensitive to light so they close at night
What is a pacemaker?
A group of cells in the right atrium wall that control the resting heart rate
They produce a small electrical impulse which spreads to the surrounding muscle cells, causing them to contract
Artificial pacemakers can be used to control heartbeat if the natural pacemaker cells don’t work well e.g. irregular heartbeat - they are little devices implanted under the skin and have a wire going to the heart - they produce an electric current to keep the heart beating regularly
Investigation into the Effect of pH on Enzyme Activity - Method
1) Put a drop of iodine solution into every well of a spotting tile
2) Place a Bunsen burner on a heatproof mat, & a tripod & gauze over the Bunsen burner. Put a beaker of water on top of the tripod & heat the water until it is 35°C - keep the temperature of water constant throughout the experiment
3) Use a syringe to add 1cm³ of amylase solution and 1cm³ of a buffer solution with a pH of 5 to a boiling tube. Using test tube holders, put the tube into the beaker of water & wait for 5 minutes
4) Next, use a different syringe to add 5cm³ of a starch solution to the boiling tube
5) Immediately mix the contents of the boiling tube & start a stopwatch
6) Use continuous sampling to record how long it takes for the amylase to break down all of the starch - use a dropping pipette to take a fresh sample from the boiling tube every 30 seconds & put a drop into a well. When the iodine solution stays browny-orange, starch is no longer present
7) Repeat the experiment with the buffer solutions of different pH values to see how pH affects the time taken for the starch to be broken down
Benedict’s Test - testing for sugars
1) Prepare a food sample & transfer 5cm³ to a test tube
2) Prepare a water bath so that it’s set to 75°C
3) Add some Benedict’s solution to the test tube (about 10 drops) using a pipette
4) Place the test tube in the water bath using a test tube holder & leave it there for 5 minutes. Ensure the tube is pointing away from you
5) If the food sample contains a reducing sugar, the solution in the test tube will change from the normal blue colour to green, yellow or brick-red - depends how much sugar is in the food
Iodine Solution - testing for starch
1) Make a food sample & transfer 5cm³ of it to a test tube
2) Add a few drops of iodine solution & gently shake the tube to mix the contents - if the sample contains starch, the colour of the solution will change from browny-orange to blue-black
Biuret Test - testing for proteins
1) Prepare a sample of your food & transfer 2cm³ of it to a test tube
2) Add 2cm³ of biuret solution to the sample & mix the contents of the tube by gently shaking it
3) If the food sample contains protein, the solution will change from blue to pink or purple
Sudan III Test - testing for lipids
1) Prepare a sample of the food you’re testing & transfer 5cm³ into a test tube
2) Use a pipette to add 3 drops of Sudan III stain solution to the test tube & gently shake the tube
3) The solution stains lipids, therefore if the mixture contains lipids, it will separate out into two layers - the top layer will be bright red
What is a catalyst?
A substance which increases the speed of a reaction, without being changed or used up in the reaction
Big Molecules
Starch
Proteins
Fats
Small Molecules
Sugar
Amino acids
Glycerol
Fatty acids
What is a double circulatory system?
Two circuits joined together
Humans have one
What are coronary arteries?
Arteries that branch off the aorta & surround the heart, ensuring that it gets all the oxygenated blood it needs
Human Cost of Disease
1) Millions of deaths
2) Lower quality of life
3) Shorter lifespan
4) Effect of disease spreads to family members & relatives
Financial Cost of Disease
1) Cost to the NHS of researching & treating these diseases is huge
2) Families may have to move or adapt their home to help a family member with a disease
3) If a family member has to give up work or dies, the family’s income will be reduced
4) Reduction in the number of people able to work can also affect a country’s economy
Why is the mean rate of water uptake higher on a hot day?
Water molecules will have more kinetic energy, thus they’ll be released from the stomata by transpiration faster
The roots will need to absorb more water to replace the large amounts of water lost from evaporation
How does the movement of potassium ions into the guard cells cause the stoma to open?
1) Ions increase the concentration of the solution
2) Water moves into the guard cells by osmosis
3) The cell swells unevenly due to having a thicker inner wall & a thinner outer wall
How does amylase break down starch?
1) The starch substrate fits into the active site of the amylase to form a complimentary shape
2) The bonds in the substrate are broken to form two smaller substrates
How do viruses make you ill?
They invade healthy cells and replicate inside them. The cells will burst and release all the copies of the virus
What are protists?
Single-celled eukaryotes
What are parasites?
Protists that live in or inside other organisms and cause damage. They are transferred by a vector
How can pathogens be spread?
1) Water - drinking/bathing in dirty water e.g. cholera
2) Air - breathing it in or the spreading of droplets from coughs or sneezes e.g. the flu
3) Direct contact - touching contaminated surfaces e.g. athlete’s foot
Measles
Virus spread by droplets from a sneeze or a cough
Symptoms: red skin rash and a fever
It can sometimes lead to pneumonia or encephalitis (a brain infection)
Can be vaccinated against
HIV
Virus spread by sexual contact or by exchanging bodily fluids e.g. sharing needles when taking drugs
Symptoms: flu-like symptoms for a few weeks
Antiretroviral drugs stop the HIV virus replicating
The virus attacks immune cells
If the immune system is badly damaged, it can’t cope with other infections or cancer - the virus at this stage is known as AIDS
Tobacco Mosaic Virus (TMV)
Virus that affects many species of plants e.g. tomatoes
Symptoms: a mosaic pattern on the leaves - parts of the leaves become discoloured
The discolouration prevents the plant from photosynthesising as well, thus the virus affects growth
Rose Black Spot
Fungus that causes purple/black spots to appear on leaves of rose plants - the leaves then turn yellow and fall off
Inhibits the process of photosynthesis and growth
Spread via the environment e.g. water or wind
Treatment: fungicides and stripping the plant of its affected leaves and then burning the leaves so the virus doesn’t spread
Malaria
Caused by a protist
Mosquitoes are vectors that acquire the malarial protist from feeding on infected animals
Each time a mosquito feeds on another animal, it infects it by inserting the protist into the blood vessels
Symptoms: repeating episodes of fever - can be fatal
Insecticides and mosquito nets help prevent malaria
Salmonella
Bacteria that causes food poisoning by producing toxins
Symptoms: fever, stomach cramps, vomiting and diarrhoea
Caused by eating food contaminated with salmonella e.g. uncooked chicken
In the UK, most chickens are vaccinated against salmonella
Gonorrhoea
Bacterial disease
Sexually transmitted disease (STD) caused by sexual contact e.g. unprotected sex
Symptoms: pain when urinating; thick yellow/green discharge from the vagina/penis
Originally treated with penicillin - now some strains have become resistant to it
Treatment with antibiotics and using barrier methods of contraception (e.g. condoms) help prevent the spread of it
Reducing/Preventing the spread of diseases
1) Being hygienic e.g. washing hands before preparing food or after sneezing
2) Destroying vectors e.g. vectors that are insects are killed by insecticides or destroying their habitats
3) Isolating infected individuals e.g. quarantine for people with communicable diseases
4) Vaccination - vaccinating against communicable diseases stops them from being developed then passed on
What is a vector?
Organisms that spread disease
The skin as a defence
Acts as a barrier to pathogens
Secretes antimicrobial substances which kill pathogens
Hairs and mucus as a defence
In your nose, they trap particles that contain pathogens
The trachea & bronchi as a defence
Secrete mucus which traps pathogens
Cilia as a defence
Hair-like structures which waft the mucus up to the back of your throat where it can be swallowed (and used to trap pathogens)
The stomach as a defence
Produces hydrochloric acid which kills pathogens that make it farther than the mouth
Phagocytes - white blood cells
Engulf foreign cells (microbes etc) and digest them
B-lymphocytes - white blood cells
Recognise foreign antigens on cells and produce antibodies to lock onto the antigens so that the cells can be located and destroyed
The antibodies are specific to that type of antigen - they form a lock and key connection
T-lymphocytes - white blood cells
Produce antitoxins that neutralise any toxins produced by bacteria
What are antibodies?
Y-shaped proteins that are produced by B-lymphocytes
Vaccinations
Injecting small amounts of dead or inactive pathogens into a person’s bloodstream. The pathogens carry antigens which triggers the immune system to produce antibodies to attack them. This helps the immune system to recognise the real pathogen and destroy it quicker and more efficiently
PROS of vaccinations
1) Helped to control many communicable diseases that were once common in the UK e.g. polio, measles, rubella, mumps, tetanus etc
2) Epidemics can be prevented if a large percentage of the population have been vaccinated - therefore, fewer people are likely to spread the disease
CONS of vaccinations
1) Sometimes they don’t give you immunity
2) They can sometimes trigger bad reactions e.g. swelling, fevers, seizures - bad reactions are very rare
What are painkillers?
Drugs that relieve the pain and help reduce the symptoms of a disease
What are antibiotics?
Drugs that kill or prevent the growth of bacteria without killing healthy body cells
What is the problems with antibiotics?
Bacteria can mutate and become resistant to an antibiotic
What is the problem with a resistant strain of bacteria?
It could cause a serious infection that cannot be treated with antibiotics e.g. MRSA causes serious wound infections and is found in people’s noses
Drug testing - Stage 1
Drugs are tested on human cells and tissues
However, human cells and tissue won’t determine a drug’s effectiveness against an entire body system
Drug testing - Stage 2
Drugs are tested on live animals - at least two different mammals
Tests for efficacy (whether it works), toxicity (how harmful it is) and to determine the right dosage
Drug testing - Stage 3
Drugs are tested on human volunteers
1) Drug is tested on healthy volunteers at a low dosage - reveals any harmful side effects
2) Drug is tested on the sick people it is designed to treat - used to find the optimum dosage
3) The patients are randomly sorted into 2 groups - one group gets a placebo, the other gets the actual drug
Why do plants need mineral ions?
If there aren’t enough of them, the plants will suffer from deficiency symptoms
What are nitrates needed for?
To make proteins, which are needed for growth
What are magnesium ions needed for?
To make chlorophyll, which is needed for photosynthesis
A lack of magnesium causes chlorosis and yellow leaves
Common symptoms of plant diseases
1) Stunted growth
2) Abnormal growths e.g. lumps
3) Spots on the leaves
4) Malformed stems or leaves
5) Patches of decay (rot)
6) Discolouration
Physical defences of plants
1) Waxy cuticle - provides a barrier to prevent pathogens from entering
2) Cell walls - form a physical barrier against pathogens that get past the waxy cuticle
3) Layers of dead cells - found around stems that act as a barrier to pathogens
Chemical defences of plants
1) Antibacterial chemicals - these kill bacteria and are found in mint plants and witch hazels
2) Poisons helped to deter herbivores from eating them e.g. tobacco plants, foxgloves and deadly nightshade
Mechanical defences of plants
1) Thorns or hairs - prevent animals from touching or eating them
2) Leaves that droop or curl when something touches them - help to knock insects off the leaves and prevent them from eating the plant
3) Mimicking other organisms e.g. the passion flower has bright yellow spots which resemble butterfly eggs - prevents other butterflies laying their eggs there
How do bacteria make us feel ill?
Producing toxins that damage cells and tissues
Digitalis
Used to treat heart conditions
Developed from a chemical found in foxgloves
Aspirin
Used as a painkiller & to lower fever
Developed from a chemical found in willow
What are monoclonal antibodies?
Produced from lots of clones of a single white blood cell
They’re all identical & will only target one specific protein antigen
What is a hybridoma cell?
The fusion of a mouse B-lymphocyte with a tumour cell
They can be cloned lots to get lots of identical cells - these cells all produce the same (monoclonal) antibodies which can be collected & purified
What is HCG?
Human Chorionic Gonadotropin
A hormone found in the urine of women only when they’re pregnant
Pregnancy Test - Process
1) The bit of the stick you wee on has some antibodies to the HCG hormone, with blue beads attached
2) The test strip has some more antibodies to the hormone stuck onto it
3) If you’re pregnant & you wee on the stick:
-The hormone binds to the antibodies on the blue beads
-The urine moves up the stick, carrying the hormone & the beads
-The beads & hormone bind to the antibodies on the strip
-The blue beads get stuck on the strip, turning it blue
4) If you’re not pregnant & you wee on the stick, the urine still moves up the stick, carrying the blue beads - since there’s nothing to stick the blue beads onto the test strip, it doesn’t go blue
What are tumour markers?
Antigens on the cell membranes of cancer cells that aren’t found on normal body cells
What can an anti-cancer drug be?
1) A radioactive substance
2) A toxic drug
3) A chemical which stops cancer cells growing & dividing
How are monoclonal antibodies used to treat cancer?
They’re attached to an anti-cancer drug which is given to the patient via a drip. The antibodies target the specific cancer cells as they only bind to tumour markers. The cancer cells are killed but the normal body cells are left untouched
What can monoclonal antibodies be used for?
1) Binding to hormones & other chemicals in blood to measure their levels
2) Testing blood samples in laboratories for certain pathogens
3) Locating specific molecules on a cell or in a tissue
How are monoclonal antibodies used to locate specific molecules on a cell or in a tissue?
1) Monoclonal antibodies are made that will bind to the specific molecule
2) The antibodies are then bound to a fluorescent dye
3) If the molecules are present in the sample being analysed, the monoclonal antibodies will attach to them - they can be detected using the dye
Problems of Monoclonal Antibodies
1) They have side effects e.g. fever, vomiting & low blood pressure
2) They’re not as widely used as treatments due to the many side effects they have
Fungi
Some fungi are single-celled
Other fungi have a body which is made up of hyphae - these grow & penetrate human skin & the surface of plants
Hyphae can produce spores - can spread to other plants & animals
How can you identify a plant disease?
1) Looking up the signs in a gardening manual or on a gardening website
2) Taking the infected plant to a laboratory - scientists can identify the pathogen
3) Using testing kits that identify the pathogen using monoclonal antibodies
Why are some patients given a placebo?
It acts as a control - to see if the drug given to the other group was actually effective
Using glucose in plants - respiration
Transfers energy from glucose which enables the plant to convert the rest of the glucose into various other useful substances
Using glucose in plants - making cellulose
Glucose is converted into cellulose for making strong cell walls
Using glucose in plants - making amino acids
Glucose is combined with nitrate ions to make amino acids, which are then made into proteins
Using glucose in plants - stored as oils or fats
Glucose is turned into lipids for storing in seeds
Glucose is turned into lipids for storing in seeds
Glucose is turned into starch and stored in roots, stems and leaves ready for use when photosynthesis isn’t happening, like in the winter. Starch is insoluble, which makes it better for storing than glucose - a cell wall containing lots of glucose would draw in lots of water and swell up
When is light the limiting factor?
Night time
When is temperature the limiting factor?
Winter
When is the carbon dioxide concentration the limiting factor?
When it’s warm and bright enough
Limiting factors - light intensity
As the light intensity increases, the rate of photosynthesis increases steadily
Limiting factors - carbon dioxide concentration
As the concentration of carbon dioxide increases, the rate of photosynthesis increases steadily
Limiting factors - temperature
If the temperature gets too high, the enzymes will denature - 45 degrees
If the temperature is too low, the enzymes will work very slowly
What is light intensity inversely proportional to?
Distance²
Greenhouses - temperature
Help to trap the sun’s heat and ensure the temperature doesn’t become a limiting factor
Heaters are used in winter to maintain a high temperature
Ventilation is used in summer to prevent the temperature increasing too much
Greenhouses - light intensity
Artificial light is used after the sun goes down - gives the plant more quality photosynthesis time
Greenhouses - carbon dioxide concentration
Paraffin heaters help increase the concentration of carbon dioxide - as the paraffin burns, it creates carbon dioxide as a by-product
Other benefits of greenhouses
1) Easier to keep the plants free from pests
2) Fertilisers help provide all the minerals needed for healthy growth
What is respiration?
The process of transferring energy from glucose which goes on in every cell
Is photosynthesis endothermic or exothermic?
Endothermic - energy is transferred from the environment
Is respiration endothermic or exothermic?
Exothermic - transfers energy to the environment
How do organisms use the energy transferred by respiration?
1) To build up larger molecules from smaller ones e.g. proteins from amino acids
2) In animals, it’s used to allow the muscles to contract
3) In mammals and birds, the energy is used to keep their body temperature steady in colder surroundings
Aerobic respiration
Respiration using oxygen
Goes on constantly in plants and animals
Most of the reactions happen inside mitochondria
Aerobic respiration equation
Glucose + oxygen –> carbon dioxide + water
Anaerobic respiration - animals
Respiration without oxygen
Incomplete breakdown of glucose
Happens when your body can’t supply enough oxygen to your muscles during vigorous exercise
Doesn’t transfer as much energy as aerobic respiration - glucose isn’t fully oxidised
Anaerobic respiration equation - animals
Glucose –> lactic acid
Anaerobic respiration - plants & yeasts
In yeasts, it’s called fermentation
Fermentation is used to make bread and alcohol drinks
Anaerobic respiration equation - plants and yeasts
Glucose –> ethanol + carbon dioxide
What three things increase with increased respiration?
1) Breathing rate
2) Breath volume
3) Heart rate
What happens during increased respiration?
More oxygen diffuses into the blood which causes carbon dioxide to be removed more quickly
What does anaerobic respiration lead to?
Oxygen debt - the amount of extra oxygen your body needs to react with the build up of lactic acid and remove it from the cells
What forms when oxygen reacts with lactic acid?
Carbon dioxide and water
How else does the body cope with a high level of lactic acid?
The blood that enters your muscles transports the lactic acid to the liver. Here, the lactic acid is converted back to glucose
Oxygen Production - Method
1) A source of white light is placed at a specific distance from the pondweed
2) The pondweed is left to photosynthesise for a set amount of time. As it photosynthesises, the oxygen released will collect in a capillary tube
3) At the end of the experiment, the syringe is used to draw the gas bubble in the tube up alongside a ruler & the length of the gas bubble is measured. This is proportional to the volume of O2 produced
4) Any variable that could affect the results should be controlled
5) The experiment is repeated twice with the light source at the same distance & the mean volume of O2 produced is calculated
6) Then, the whole experiment is repeated with the light source at different distances from the pondweed
What are lipid molecules made up of?
One molecule of glycerol & three fatty acids
What is metabolism?
The sum of all the reactions that happen in a cell or in the body
What is muscle fatigue?
When over long periods of exercise, the muscles get tired & stop contracting efficiently
5 ways that glucose is used
Produces cellulose
Respiration - energy
Stored as starch
Stored as fats/oils
