2 - Organisation

• • A tissue is a group of cells with a similar structure and function 
  • An organ is a group of tissues working together for a specific

   function (eg: the stomach- contains muscle tissue and glandular 

  tissue which releases enzymes) 

  • Organs are grouped into organ systems which work together to

   from organisms 
• Food contains 3 main nutrients: carbohydrates, protein and lipids

  (fats- these are molecules, too large to be absorbed into the bloodstream so they have to be digested) 

  1. During digestion, large food molecules are broken down into small molecules by enzymes. They can then be absorbed into the bloodstream 
  2. The products of digestion are then used by the body to build new carbohydrates, lipids, and proteins - Some of the glucose produced is used in respiration
• 1. Mouth 
  2. Oesophagus 
  3. Stomach 
  4. Small Intestine 
  5. Pancreas
  6. Liver
  7. Small Intestine 
  8. Large Intestine 
  9. Leave the body through rectum

  
• 1. Mouth: Food is chewed in the mouth. Enzymes in the saliva begin to digest the starch into smaller sugar molecules 
  2. Oesophagus: Food passes down the oesophagus and into the stomach. In the stomach, enzymes begin the digestion of proteins 
  3. Stomach: churning actions of the stomach muscles turns the food into a fluid increasing the surface area for enzymes to digest 
  4. Small Intestine: Fluid passes into small intestine- at this point chemicals are released into the small intestine from the liver and pancreas
• 5- Pancreas: Releases enzymes that continue the digestion of starch and protein. They also start the digestion of lipids

  6- Liver: Releases bile which helps speed up digestion of lipids. Also neutralizes the acid released from the stomach 

  7- Small Intestine: The walls of the small intestine releases enzymes to continue the digestion of protein and lipids, the small food molecules producer by digestion are absorbed into the bloodstream (diffusion or active transport) 

  8- Large Intestine: Water is absorbed into the bloodstream 

  9- Leaves the body through rectum: Faeces
• enzymes catalyse (speeds up) chemical reactions

  • They Are large protein molecules and they have a groove on their surface called the active site- this where the substrate (molecule the enzyme breaks down) attaches to

  Enzymes are specific- the substrate must fit perfectly into the active site (lock and key theory)

  
• Protease 

  Proteins are broken down by enzymes called proteases they’re found in the stomach, pancreas, and small intestine 

  1. Proteins are long chains of chemicals called amino acids 
  2. When we digest proteins, the protease enzymes convert the protein  back to the individual amino acids, which are then absorbed into the bloodstream 
  3. When the amino acids are absorbed by the body cells, they are joined together in a different order to make human proteins 
• Starch- carbohydrase 

  • Starch consists of a chain of glucose molecules 

  1. Carbohydrates are broken down by enzymes called carbohydrases - if starch this called amylase
  2. When carbohydrates like starch are digested, it produces simple sugars
  3. Amylase are found in the saliva and the pancreatic fluid
• Lipids (fats)

  1. A lipid molecule consists of a molecule of glycerol attached to three molecules of fatty acid
  2. Lipid molecules are digested by the enzyme lipase. This  produces glycerol and fatty acids
  3. lipase is found in the pancreatic fluid and also in the small Intestine
• Bile

  • Bile is made in the liver and is stored in the gallbladder- helps to speed up the digestion of lipids but its not an enzyme 
  • Converts large lipid droplets into smaller droplets  
  • Bile emulsifies the lipids- this increases the surface area of the lipid Droplets and this increase the rate of lipid breakdown 
  • Is also alkaline- allows it to neutralise stomach acid, increase the rate of lipid digestion 
• Affect of Temperature on Enzymes:

  • temperature increases, the activity of the enzyme increases (reaction goes faster)- this is bc the enzyme and substrate are moving faster = more collisions per second
  • Reaches optimum temperature (37 for humans)- enzymes are working at fastest rate possible- there's a max frequency of successful collisions between active site and substrate
  • past optimum, activity of enzyme rapidly decreases to 0- due to high temperatures the molecule vibrates and shape of active site changes- substrate no longer fits it is denatured, enzyme can no longer catalyse reaction

  
• Affect of Temperature on Enzymes:

  If pH is too acidic or alkaline the activity drops to 0- this is because it will denature if conditions are too neutral or too acidic

  
• Required Practical: Food Tests

  1. Take the food sample and grind it with distilled water using a mortar and pestle to make a paste 
  2. Transfer the paste to a beaker and add more distilled water. Stier so the chemicals in the food dissolve in the water
  3. Filter the solution to remove suspended food particles 
  4. Place 2cm3 of food sample into a test tube and then use the solution of your choice
• Required Practical: Food Tests

  
  

  Carbohydrates/Starch - Iodine: (orange) - If present: Black - Not present: Stays Orange

  
  

  Glucose/Sugar 10 drops of Benedict (blue) Present:

  • Green - Small amount, Yellow - More sugar, Red - Less sugar - Not: stays same

  Protein - Biuret - present: Purple/Lilac - not present: Stays blue

  
  

  Lipids/Fats - Ethanol - White Cloudy Emulsion - no emulsion will form
• Required Practical: Food Tests

  
  

  Glucose Test

  •  Place the test tube (containing Benedict's solution and  2cm3 of food sample) into a beaker. Half fill the beaker with hot water and leave it for around 5 minutes
  • If sugar; it will change colour- this gives an approximate idea of amount of sugar present   
  • Only works on glucose (reducing sugars)- benedicts will not work on anything thats not this (eg: sucrose)  
• Required Practical: Food Tests

  Lipids Test

  1. Take a small sample of food and place in test tube
  2. Add in a few drops of distilled water and ethanol, gently shake the solution, if present there will be a white cloudy emulsion
• • Human small intestine : 5m, provides a very large surface area for absorption 
  • The interior is covered with millions of villi- they increase the surface area for absorption of molecules  
  • On the surface of villi, there are microvilli which further increase surface area 
  • Villi have a very good blood supply- so bloodstream rapidly removes the product of digestion (increases concentration gradient) 
  • Thin membrane ensures a short diffusion path 

  Any molecules that cannot be absorbed by diffusion are absorbed by active transport 
• Fish have a single circulatory system: heart → gills → organs (repeat) - problem: blood loses a lot of pressure when it passes through the gills, this means the blood travels slow so it cannot deliver lots of oxygen 

  
  

  Humans: double circulatory system: heart → lungs (to collect oxygen) → oxygenated blood to hearts → pumps blood to organs (transfers oxygen to body cells) → blood returns back to hearts

  • Because the blood passes through the heart twice it can travel rapidly through the body cells delivering the oxygen cell needs
• The heart: an organ consisting of muscle tissue- pumps blood around the body 

  • 4 Chambers- right atrium, left atrium, right ventricle and left ventricle, the atria are separated from the ventricles by valves  
• pattern of blood flow from heart

  1. first blood enters left atrium then right atrium

  2. atria contracts and blood is forced into the ventricles

  3. ventricles contract and force blood out of the heart

  4. valves stops the blood from flowing backwards when ventricles contract

  5. left side of heart has thick muscular wall- left ventricle pump blood around whole body so it needs to provide greater force

  right ventricle- only pumps to lungs
• Arteries carry very high pressure blood from the heart to the organs 

  • They have thick muscular walls; allows them to withstands the very high pressure of blood 
  • blood travels in surges every time the heart beats; theft have elastic fibres with stretch when the surges pass and then recoils in between surges which keeps blood moving 
• Capillaries: blood passes through capillaries, substances such as glucose and oxygen diffuse from the blood to the cells, carbon dioxide diffuses from the cells back to the blood 

  • Have thin walls; allows substances to diffuse rapidly between blood and body cells
• Veins 

  • have a thin wall- this is because blood pressure is low
  • Contain valves: to stop blood flowing backwards; when blood is flowing in correct direction the valves open to allow to flow through and when blood flows backwards it shuts 
• Blood Plasma

  Transports:

  • Soluble digestion products (eg glucose) from small intestine to other organs 
  • Carbon dioxide (produced by aerobic respiration) from the organs to the lungs to be breathed out
  • Waste product urea from liver to kidneys to be excreted in urine
• Red Blood Cells 

  Transports oxygen from lungs to body cells ; 3 adaptations 

  • Contain oxygen-carrying molecule: haemoglobin

  Haemoglobin  + oxygen → (lungs → oxyhaemoglobin) → (organs) → haemoglobin + oxygen 

  •  No nucleus = more space for haemoglobin 
  • In the centre of the cell there are dimples, their shape is called biconcave disc- this gives a greater surface area so oxygen can diffuse in and out rapidly 

  
• White blood cells  Part of the immune system 

  • Contain nucleus (DNA): encodes the instructions that wbc needs to do their job 
• Platelets- tiny fragments of cell: to help blood clot 

  Blood donors: 

  1. To replace blood loss during injuries 
  2. Some people are given platelets extracted from blood to help in clotting
  3. Protein extracted from blood can also be useful eg antibodies 

  Problems: 

  1. Blood transfusion- must make sure blood type is the same between patient and doner or it will be reject by the immune system and patient could die 
  2. Disease cann be transmitted via blood- the blood is scanned for infections so risk is low
• Cardiovascular disease are of the heart and blood vessels, they are non-communicable, not infectious 

  Coronary heart disease- coronary arteries branch out of the aorta and spread out into the heart muscle, purpose- provides oxygen to muscle cells of the heart, then sued in respiration to provide energy for concentration  

  • In coronary disease, layers of fatty material build up inside the coronary arteries, this causes them to narrow. : The effect of this reduces the flow of the blood   
  • This results in a lack of oxygen, extreme cases in a heart attack (heart is starved of oxygen)
• Treatment [CHD]:

  • Satins: drugs that reduce the level of cholesterol; slows down the rate that fatty materials built up.
  • Advantages: proven to reduce risk of the disease 
  • Disadvantage: unwanted side effects (eg liver problems)

  In some people, there can be a total blockage of coronary artery 

  • Stent: a tube that's inserted in the artery to keep it open 
  • Advantage: blood can flow through normally 
  • Disadvantage: will not prevent other regions from narrowing, does not treat underlying causes of disease  
• Treatment [CHD]:

  Sometimes heart valves do not fully open, so it needs to pump extra hard to get blood through this causes the heart to enlarge 

  Valves are leaky = patient feels weak and tired 

  • Replace with a  mechanical valve of animal valve: can last a lifetime but they increase risk of blood clots (will have to take anti clotting drugs)   
  • Animal valves: need to be replace but do not ned to take drugs 
• Treatment [CHD]:

  The heart cannot pump enough blood

  • Sometimes given a donated heart (and/or lungs): not enough donated hearts, patient must take drugs to stop rejection  
  • Artificial hearts increase risk of blood clotting (not a long term solution) 
• Gas Exchange in lungs

  1. Air passes through the lungs through trachea- contains ring cartilage; prevents trachea from collapsing during inhalation 
  2. Bronchi- two tubes that pass into each lung 
  3. Bronchi subdivide into smaller tubes called bronchioles and they end in tiny air sacs called alveoli (gases diffuse in and out the bloodstream)
• Alveoli- oxygen in the air diffuses into the bloodstream and carbon dioxide diffuses out the bloodstream back into the air 

  Adaptations:

  1. Huge surface area 
  2. Very thin walls 
  3. Good blood supply - once oxygen diffuses it is rapidly movies, ensures  that the concentration gradient is as steep as possible 

  Breathing

  • Breathing increases the rate of diffusion; brings in fresh diffusion into the alveoli and takes away the carbon dioxide 
  • This makes the concentration gradients high for these gases
• Benigns Tumours 

  • Growths of abnormal cells found in one area, usually constrained within a membrane  
  • Do not invade other parts of the body- stay in one place 

  Malignant Cells 

  • Invade neighbouring tissues and move into the bloodstreams- classed as a cancer 
  • Once in the bloodstream, the malignant cells spread to different parts of the body and form new tumours (secondary tumours)
• Risk Factors // Cancer:

  • Some cancers are genetics; breast cancer, prostate and cancer of the large intestine  
  • Lifestyle: smoking- lung cancer, ultraviolet- skin cancer, alcohol- mouth and throat 
  • Substances of the environment: radon is a radioactive gas, increases chance of lung cancer, releases ionising radiation and damaged the DNA which causes uncontrolled cell division
• Communicable- spread from one person to another spread my pathogens (eg: bacteria or viruses)

  Non-Communicable- cannot be passed on (eg: coronary heart disease) 

  Health: the state of physical and mental well-being

  Ill health- can be caused by communicable and non communicable diseases, can also be caused by poor diet, stress and other life-situations (working with harmful chemicals) 
• Tuberculosis: communicable lung disease and can be fatal

  • Defective immune system (due to HIV)  are more likely to suffer from infectious diseases  

  Human papillomavirus (HPV): extremely common and usually harmless 

  • In some it can cause cervical cancer, HPV infects cells of the cervix  

  Some diseases can be triggered by the immune system, eg: asthma or dermatitis, the body is infected with a pathogen which the immune system fights off but the body is left with an allergy 

  Mental illness can be triggered by a physical illness- can lead to isolation and depression 
• Epidemiology: studying patterns of disease to determine risk factor correlation (link)- through a scatter graph 

  Correlation doesn’t always prove cause, it may just suggest they’re linked 

  Causal mechanism: looking at how the correlation causes the disease 

  Problems: 

  • Sampling; impossible to sample everyone in the population- lacks representativeness, one town isn’t everyone, it’s biassed (please in that town may not exercise, or are exposed to a specific pollution)  - to avoid; random, big sample
• • High salt diet = increase in blood pressure - cardiovascular diseases (and smokers) but decreased in those who exercise regularly 
  • Smoking increases lung cancer- contains chemicals that trigger cancers: carcinogens , smoking increase the risk of other lung diseases eg: emphysema
  • Alcohol- risk of liver cirrhosis and liver cancer, affect brain- addiction and memory loss   
• When pregnant

  Smoking - risk of miscarriage and premature birth

  Fetal Alcohol Syndrome- learning disabilities, mental or physical problems    

  Type 2 diabetes- struggle to control blood glucose levels - obese people have higher risk 

  • Can lead to blindness and amputation of limbs 
  • Risk factors can interact: excess alcohol = obesity = increase chance of type 2 diabetes