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!!!