topic 2 - organisation Flashcards
What is a cell?
- Basic building blocks of all living organisms
What is a tissue?
a group of cells with similar structures working together for a specific function
What is an organ?
a group of tissues working together for a specific function e.g. the stomach
What are three examples of tissues?
Muscle tissue - contracts (shortens) to move what it’s attached to. They contain special protein fibres which change their length. They are also packed full of mitochondria, providing the energy needed for contraction. Muscle cells work together to form muscle tissue
Glandular tissue - makes and secretes substances like enzymes and hormones
Epithelial tissue - covers the outside and inside of the stomach
What is an organ system?
A group of organs working together to perform specific functions. e.g. digestive system
What are the three main nutrients food contain?
- Carbohydrates (e.g starch)
- Protein
- Lipids (fats)
What is the main function of the digestive system?
To digest food and absorb the nutrients obtained from digestion
What is the role of the pancreas in the digestive system?
The pancreas releases enzymes which continue the digestion of starch and protein. They also start the digestion of lipids.
What is the role of the stomach in the digestive system?
Produces hydrochloric acid which kills any bacteria present and provides the optimum acidic pH for the protease enzyme to function
What is the role of the small intestine in the digestive system?
- The small intestine is where soluble food molecules are absorbed into the bloodstream by diffusion or active transport.
What is the role of the liver in the digestive system?
- This releases bile which emulsifies lipids and allows the lipase enzyme to work more efficiently.
- Bile also neutralises the acid released from the stomach
What is the role of the large intestine in the digestive system?
Absorbs water from undigested food producing faeces
What is the role of enzymes?
Biological catalysts that speed up the rate of biological reactions without being used up
What is an active site?
The site on an enzyme where the substrate binds
How does the shape of an enzyme affect its function?
Enzymes have a specific active site which is complementary to their substrate
What is metabolism?
The sum of all the reactions in a cell or an organism
What is the lock and key hypothesis of enzyme function?
- Enzymes are specific and will only catalyse particular substrates
- The substrate must fit the active site of the enzyme or it will not catalyse
- After the reaction occurs the enzyme now breaks down the substrate into the products and binds to another substrate
How does temperature affect enzyme action?
- As the temperature increases the enzyme activity also increases. This is because the enzyme and the substrate are moving faster so there are more collisions per second between the substrate and the active site.
- At a certain temperature, the enzyme is working at the fastest possible rate. This is the optimum temperature. At this point, there is the maximum frequency of successful collisions between the substrate and the active site.
- If they go beyond this temperature, the activity of the enzyme rapidly decreases to zero.
- At high temperatures, the enzyme molecule vibrates and the shape of the active site changes.
- Now the substrate no longer fits perfectly into the active site. The active site is denatured
How does pH affect enzyme function?
- The enzyme has an optimum pH where the activity is maximum
- If we make the pH more acidic or more alkaline then the activity drops to zero
- The active site denatures if the conditions are too acidic or too alkaline
What is the role of amylase in the digestive system?
amylase breaks down starch into simple sugars (glucose)
Which organs produce amylase?
salivary glands and pancreas
Where does starch digestion occur?
Mouth + small intestine
What is the role of proteases in the digestive system?
Proteases break down protein into amino acids
Which organs produce proteases?
Pancreas and small intestine
How are the products of digestion used?
They are used to build bigger molecules such as carbohydrates and proteins. Glucose is used as a substrate in respiration
What occurs in the digestive system?
Large food molecules are digested into smaller molecules and then the products of digestion are absorbed into the bloodstream
What is the role of lipase in the digestive system?
Lipases break down lipids into fatty acids and glycerol
Which organs produce lipase?
Pancreas and the small intestine
What is the role of bile?
- Bile converts large lipids droplets into smaller droplets
— > emulsifies lipids - This massively increases the surface area of the lipid droplets.
- This increases the rate of lipid breakdown by lipase.
- Bile is also alkaline. This allows it to neutralise stomach acid, creating alkaline conditions in the small intestine
Describe how the small intestine is adapted for absorbing the products of digestion
- The human small intestine has a length of around 5m. This provides a very large surface area for the absorption of the products of digestion.
- The interior of the small intestine is covered with millions of villi. This massively increases the surface area for the absorption of molecules
- Villi have a very good blood supply so the bloodstream rapidly removes the products of digestion -> this increases the concentration gradient
- The thin membrane ensures a short diffusion path
What is a heart?
an organ that pumps blood around the body in a double circulatory system
How does the double circulatory system work?
- The first circuit pumps deoxygenated blood to the lungs to take in oxygen. The blood then returns to the heart
- The second circuit pumps oxygenated blood around all the other organs of the body.
- The blood gives up its oxygen at the body cells and the deoxygenated blood returns to the heart to be pumped out to the lungs again
What is the purpose of the circulatory system?
To carry oxygen to bodily tissues and remove waste products like carbon dioxide and urea
How does the heart pump blood into the lungs?
- the vena cava brings in deoxygenated blood from the body
- the blood then passes from the heart to the lungs in the pulmonary artery
- Oxygenated blood passes from the lungs to the heart in the pulmonary vein
- Oxygenated blood is pumped from the heart to the body in the aorta
How does blood flow through the heart?
- First blood enters the left atrium and the right atrium
- The atria now contract and the blood is forced into the ventricles
- The ventricles now contract and force blood out of the heart
- The valves stop the blood from flowing backwards into the atria when the ventricles contract
- The blood then flows to the organs through arteries and returns through veins
- The atria fill again and the whole cycle starts over
Why is the wall of the left ventricle thicker?
The left ventricle has to pump blood at a higher pressure around the whole body
What is the purpose of the coronary arteries?
- Coronary arteries provide oxygen to the muscle cells of the heart.
- The oxygen is used in respiration to provide the energy for contraction
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
How can an abnormal heart rhythm be treated?
- Irregular heart rhythms can be treated using an artificial pacemaker, which sends out electrical signals to correct the heart’s rhythm.
What are the three types of blood vessels in the body?
- Arteries
- Veins
- Capillaries
What are arteries?
Arteries are blood vessels which carry high-pressure blood from the heart to the organs in the body
How are arteries adapted for their function?
- Arteries have very thick muscular walls -> which allows them to withstand the very high pressure of the blood
- They contain elastic fibres which stretch when the surge of blood passes through and then recoil in between which keeps the blood moving
What is the function of capillaries?
to enable the transfer of substances between the blood and tissues
How are capillaries adapted for their function?
- Capillaries have very thin walls so their diffusion path is very short.
- This allows substances to diffuse rapidly between the blood and body cells
What is the function of veins?
They carry blood to the heart
How are veins adapted for their function?
- Because blood is at lower pressure in the veins, the walls aren’t as thick as artery walls
- Veins have a bigger lumen to enable low blood pressure
- They also have valves to prevent the backflow of blood
Where does blood pumped by the right ventricle go?
The lungs, where gas exchange takes place
What is blood?
Blood is a tissue consisting of plasma, in which the red blood cells, white blood cells and platelets are suspended
What does blood plasma transport?
- soluble digestion products from the small intestine to other organs
- carbon dioxide from the organs to the lungs to be breathed out
- the waste product urea from the liver to the kidneys to be excreted in urine
What is the function of red blood cells?
- Red blood cells transport oxygen from the lungs to the body cells
How are red blood cells adapted for their function?
- they have a biconcave shape to give them a large surface area for absorbing the oxygen
- they contain a red pigment called haemoglobin which carries the oxygen
- Because red blood cells don’t have a nucleus, there is more room for haemoglobin, which means they can carry more oxygen
How is oxygen transported around the body?
- In the lungs, oxygen diffuses into the blood. The oxygen combines with haemoglobin in the red blood cells to become oxyhaemoglobin
- In body tissues, the reverse happens - oxyhaemoglobin splits up into haemoglobin and oxygen, to release oxygen to the cells
What is the main function of white blood cells?
- defend the body against infections
How are white blood cells adapted for their function?
- White blood cells contain a nucleus.
- This contains DNA which encodes the instructions that the white blood cells need to do their job
What are platelets?
Platelets are small cell fragments which aid the clotting of blood at the site of a wound
What are the problems with donating blood?
- In a blood transfusion, the donated blood must be the same blood type as the patient. Otherwise, the body’s immune system will reject the blood and the patient could die.
- Lots of different diseases can be transmitted via blood. However in the Uk, blood is screened for infections so the risk is extremely low.
What are cardiovascular diseases?
- Cardiovascular diseases are diseases of the heart and blood vessels
- They are non-communicable (not infectious - they cannot be passed from person to person)
What is a coronary heart disease
- Coronary heart disease occurs when layers of fatty material build up inside the coronary arteries. This causes the coronary arteries to narrow. This restricts the blood flow which results in a lack of oxygen for the heart muscle.
- In extreme cases, this can result in a heart attack, where the heart is starved of oxygen
What are treatments for coronary heart disease?
- Statins are drugs which reduce the level of cholesterol in the blood. This slows down the rate that fatty materials build up in the arteries
- A stent is a tube which can be inserted into the coronary artery to keep it open, making sure blood can pass through to the heart muscles
What are the advantages and disadvantages of statins?
- Statins have been proven to reduce the risk of coronary heart disease -
- However, statins have unwanted side effects e.g. liver problems
What are the advantages and disadvantages of a stent?
- Inserting a stent means that the blood can flow normally through the artery
- Quick recovery time
- Lowers the risk of a heart attack
- However, a stent will not prevent other regions of the coronary arteries from narrowing -> it does not treat the underlying causes of the disease
What are the consequences of leaky heart valves?
Blood flows in the wrong direction, causing the heart to become less efficient. Patients may become breathless and die as a result
What types of valves can replace leaky valves?
- mechanical valve
- Biological valve - valve from an animal
What are the pros and cons of mechanical valves?
- Mechanical valves can last a lifetime but they increase the risk of blood clots.
- Patients have to take anticlotting drugs
What are the pros and cons of biological valves?
- Works well - no medication required
- do not last long and may need to be replaced
What is heart failure?
Sometimes, in some patients with cardiovascular disease, the heart cannot pump enough blood around the body.
What are the problems with donated hearts?
- There are not enough donated hearts available to treat every patient.
- The patient must take drugs to stop the donated heart from being rejected by the body’s immune system
What are the problems with donated hearts?
- There are not enough donated hearts available to treat every patient.
- The patient must take drugs to stop the donated heart from being rejected by the body’s immune system
What is the purpose of an artificial heart?
Artificial hearts are intended to support a patient’s heart while they wait for a suitable donor heart
What are the advantages and disadvantages of artificial hearts?
- Artificial hearts increase the risk of blood clotting.
- They are not a long-term solution to heart failure
- However, artificial hearts allows the damaged heart to rest
- Less likely to be rejected by the immune system
What is the function of the lungs?
- To transfer oxygen to the blood and to remove waste carbon dioxide from it
What is the structure of the respiratory system?
- Air passes into the lungs through a tube called the trachea
- Rings of 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 the lungs, the bronchi subdivide into many smaller tubes called bronchioles
- The bronchioles end in tiny air sacs called alveoli
Where is the site of gas exchange?
alveoli
What is plasma in the blood?
A yellow liquid that carries blood cells, proteins and dissolved substances around the body
How are alveoli adapted for their function?
- Alveoli increase the surface area of the lungs
- The alveoli have very thin walls so the diffusion path is very short
- Alveoli have a very good blood supply. Once the oxygen diffuses into the blood, it is rapidly removed. This ensures that the concentration gradient is as steep as possible
What does breathing do?
- breathing brings oxygen into the alveoli and takes away the carbon dioxide
- by breathing, we increase the rate of diffusion
Describe how gas exchange occurs at the alveoli
- oxygen diffuses from the alveoli into the capillary bloodstream down its concentration gradient
- Carbon dioxide diffuses from the capillary into the alveoli down its concentration gradient
How would you calculate the breathing rate
number of breaths/ number of minutes
What is the capillary network?
The alveoli are surrounded by a network of tiny blood vessels known as capillaries. There is a higher concentration of oxygen in the air than in the blood, so oxygen diffuses out of the air in the alveoli and into the blood in the capillaries.
Describe what is meant by a benign tumour
- Benign tumours are growths of abnormal cells which are contained in one location, usually within a membrane
- They are not cancerous and do not invade other parts of the body
- They can grow large very quickly - may cause damage to another organ
What is meant by a malignant tumour?
- Malignant cells invade neighbouring tissues and move into the bloodstream
- Once in the bloodstream, the malignant cells spread to different parts of the body and form new tumours
- Scientists call these new tumours secondary tumours
- Malignant tumour cells are classed as a cancer
What are the risk factors for cancers
- Genetics - certain genes increase the risk of breast and ovarian cancer
- smoking
- obesity
- ionising radiation - UV light and X-rays
- Viral infections - HPV and cervical cancer
What is cancer?
Cancer is the development of a tumour as a result of uncontrolled cell division
How is radon a risk factor for cancer?
Radon is a radioactive gas which increases the risk of developing lung cancer
- This releases ionising radiation which damages the DNA in our cells
- This can cause our cells to undergo uncontrolled cell division, leading to cancer
What is health?
the state of physical and mental wellbeing
What are communicable diseases?
- communicable diseases are diseases that can be spread from person to person e.g. measles
- they are spread by pathogens such as bacteria or viruses
What are non-communicable diseases?
- diseases that cannot be passed from person to person e.g. coronary heart disease
What is ill health caused by?
- Both communicable and non-communicable diseases
- It can also be caused by poor diet, high levels of stress and other life situations e.g. working with harmful chemicals
What is ill health caused by?
- Both communicable and non-communicable diseases
- It can also be caused by poor diet, high levels of stress and other life situations e.g. working with harmful chemicals
Give examples of how health problems can interact
- infection with certain viruses can lead to cancer. For example, HPV can cause cervical cancer
- a compromised immune system e.g. due to cancer or HIV can lead to a higher risk of infection with communicable diseases.
- Immune reactions caused by a pathogen can trigger allergic reactions e.g asthma
- Problems with physical health can lead to mental health issues. For example, people with arthritis can find it very difficult to move and lead a normal life. In certain cases, this can make them feel isolated and depressed
What is epidemiology?
Studying the patterns of a disease to determine risk factors
What is epidemiology?
Studying the patterns of a disease to determine risk factors
What is a causal mechanism?
A mechanism which demonstrates how one factor biologically influences another
How does smoking affect the development of cardiovascular disease?
Nicotine increases heart rate; other chemicals damage the artery lining and increases the blood pressure
How does diet affect the development of cardiovascular disease?
High levels of LDL cholesterol cause arteries to become blocked, increasing the blood pressure and the risk of a heart attack
How does exercise affect the development of cardiovascular disease?
Exercise lowers blood pressure, reducing the strain on the heart
How do alcohol affect liver and brain function?
- Excessive long-term alcohol use may lead to liver cirrhosis
- Increases risk of liver cancer
- Damages brain tissue and nerve cells
How can sampling be used to determine correlation
To avoid bias, scientists must take as large a sample as possible and it must be as random as possible
How can smoking affect the development of lung disease and lung cancer?
Cigarette smoke contains a number of chemicals which can trigger cancer. These are called carcinogens
What are the effects of smoking on an unborn baby?
Smoking when pregnant increases the risk of miscarriage and premature birth
What are the effects of drinking alcohol on an unborn baby?
Drinking alcohol when pregnant can cause fetal alcohol syndrome.
- Children born with fetal alcohol syndrome can have learning difficulties and other mental or physical problems
How does obesity affect the development of type 2 diabetes?
Obese people have a much higher risk of developing type 2 diabetes
What is the function of the epidermis
To protect the surface of the leaf
What is an adaptation of the upper epidermis?
- the upper epidermis is transparent. This allows the light to pass through to photosynthetic cells below
- the upper epidermis is also covered with a thin layer of oily material called the waxy cuticle. The waxy cuticle reduces the evaporation of water from the surface of the leaf which helps to prevent the leaf from drying out.
What is an adaptation of the lower epidermis?
- The lower epidermis has tiny pores called stomata. This allows carbon dioxide to enter the leaf and oxygen to leave.
- Stomata also helps to control the amount of water vapour that can pass out of the leaf
What are palisade mesophylls?
Palisade mesophylls are found at the top of the lead and consist of palisade cells.
How are palisade cells adapted for their function?
Palisade cells are packed full of chloroplasts which allows photosynthesis to progress at a rapid rate
How is spongy mesophyll tissue adapted for its function?
Spongy mesophyll tissue has lots of air spaces which allow carbon dioxide to diffuse from the stomata through the spongy mesophyll to the palisade cells
- Oxygen also diffuses from the palisade cells through the spongy mesophyll to the stomata
What is the function of xylem tissue?
- Xylem tissue transports water from the roots to the stem and leaves. Some of the water is then used in photosynthesis
- the xylem also transports dissolved mineral ions, including magnesium which is used to make chlorophyll
What is the function of phloem
Phloem tissue transports dissolved sugars produced by photosynthesis from the leaves to the rest of the plant.
- the sugars can be used immediately e.g glucose is used in respiration
What tissues does the leaf organ contain?
- Epidermis
- Palisade mesophyll
- Spongy mesophyll
- Xylem
- Phloem
- Guard cells
What tissues does the leaf organ contain?
- Epidermis
- Palisade mesophyll
- Spongy mesophyll
- Xylem
- Phloem
- Guard cells
Where is meristem tissue found
At growing tips
How is meristem tissue adapted for its function?
Made up of stem cells which can differentiate into many different cell types, allowing the plant to grow
What is meant by transpiration?
The evaporation of water vapour from the surface of a plant
What is translocation?
The movement of dissolved sugars from the leaves to other parts of the plant
How does the transpiration stream occur?
- Water evaporates from cells inside the leaf
- The water vapour then diffuses through the air spaces in the spongy mesophyll and out of the leaf through the stomata
- Now, water passes from the xylem into the leaf to replace the water that has been lost
- Finally, water is drawn into the root hair cells and up the xylem vessels to the leaf
What is the transpiration stream in summary?
The movement of water through a plant from the roots to the leaves
How does temperature affect the rate of transpiration?
Transpiration is greater at higher temperatures. That is because evaporation is faster when temperatures are higher.
How does humidity affect the rate of transpiration?
- Increasing humidity slows the rate of transpiration.
- This is because evaporation takes place more quickly under dry conditions
How does wind speed affect the rate of transpiration?
- increasing wind movement increases the rate of transpiration.
- That is because wind removes any water vapour, allowing more water to evaporate
How does light intensity affect the rate of transpiration?
- Increasing the light intensity increases the rate of transpiration.
- That is because high light intensity increases the rate of photosynthesis.
- This allows more stomata to open, and more water vapour to pass out of the leaf
How does light intensity affect stomata?
- When the light intensity is high, the guard cells swell and they change their shape.
- This causes the stomata to open. Now carbon dioxide can diffuse into the leaf and be used in photosynthesis
How does temperature affect the stomata?
- Under hot conditions, the plant closes its stomata to reduce water loss by transpiration.
- This now means that the plant cannot photosynthesise
