Biology: cell organisation

• In most organisms, cells arranged into tissues
• tissue is a group of cells with similar structure and function which all work together to do a job                                                                                                                                                          e.g: muscular tissue contracts to produce movement                                                                           glandular tissue produces substances such as enzymes and hormones                                           epithelial tissue covers organs 
• organs are groups of different tissues, all work together to perform a similiar job 
• each organ may contain several tissues
• For example: the stomach is an organ that contains:                                                                             muscle tissue, contracts and churns contents                                                                                  glandular tissues to produce digestive juices                                                                                                         epithelial tissue to cover the outside and inside of the stomach
  
• organs organised into organ systems, which are groups of organs working together to do a particular job 
• the digestive system is an example of an organ system,                                                                   several organs work together to digest and absorb food                                               
• lots of organ systems work together to make an organism

specialised cells

• cells are the basic building blocks of life
• as an organism developes, cells differentiate to form different types of cells, become specialised
• most types of animal cell diffrentiate at the early stages but plant cells differentiate throughout their life                                 
• as a cell diffrentiates:                                                                                                                   it may change shape                                                                                                                                                         different sub cellular structures develope to let it to carry specific function 
• specialised animal cells include: 
• sperm 
• nerve and muscle cells
• in plants: root hair, xylem and ploem cells 

Enzymes 

• enzymes are biological catalysts, speeding reactions in all living organisms
• enzymes have a number of properties:                                                                                                      all large proteins                                                                                                                           space within protein molecule - actice site                                                                                        each enzyme cataylists a specific reaction                                                                                        works best at a specific temperature                                                                                          
• the lock and key theory - explains how enzymes work, chemical that reacts call sustrate, fits into enzymes active site (lock)
• high temp and extremes of ph make enzymes change shape - denaturing
• enzyme cannot work work once it has been denatured becuase substance cannot fit into active site- lock and key can no longer fit together 

• digestive enzymes are produced by specialised cells in glands and in lining of the gut: 

1. the enzymes pass out of the cells into the digestive system                                                              2. come into contact with food molecules                                                                                                             3. they catalyse the breakdown of large insoluble molecules into smaller soluble molecules

• the digestive enzymes, protease, lipase and carbohydrase, digestproteins, lipids and carbohydrates to produce smaller molecules that can be easily absorbed into the bloodestream
• amylase                                                                                                                                                 produced in the salivary glands and the pancreas                                                                                      carbohydrase breaks down starch into sugar  
• protease:                                                                                                                                                   produced in the stomach, pancreas and small intestine                                                                  breaks down proteins and amino acid            
• lipase:                                                                                                                                                  Produced in pancreas and small intestine                                                                                        breaks down lipids into fatty acids and glycerol                                                                           

• bile is a liquid made in liver and stored in he gall baldder 
• alkaline to neutralise hydrochloric acid from the stomach 
• it also emulsfies fat to form small droplets, increasing the surface area for enzymes to act on 
• the alkaline conditions and large surface area inreacese the rate at which fat is broken by lipase

• blood is a tissue
• made of liquid called plasma, three different components suspended in it:                               red blood cells                                                                                                                             white blood cells                                                                                                                                  platelets                                                                                                                                                            
• plasma transports various chemical substances around body like products of digestion, hormones antibodies, urea and carbon dioxide
• red blood cells:                                                                                                                                   contain haemoglobin binds to oxygen transport it from lungs to tissues and cells, needs for respiration
• do not contain nucleus there is more room for haemoglobin
• very small, fit through tiny capillaries, large surface area that oxgen can quickly diffuse across
• white blood cells:                                                                                                                         help protect body against infection                                                                                             can change shape, squeeze out of blood vessels into tissues or engulf organisms
• platelets fragment of cells, collect at wounds, trigger blood clotting 

• Blood passes around body in blood vessels 
• Body contains three different types of blood vessel
• Arteries:                                                                                                                                              take blood from heart to organs                                                                                                       thick walls made from muscles and elastic fibres                                                                      
• Veins:                                                                                                                                                   take blood from your organs to heart                                                                                                 thin walls and valves prevent backflow                                                    
• Capillaries:                                                                                                                                             allow substances needed by cells to pass out blood                                                                        allow substances produced by cell pass into blood                                                                         narrow thin walled blood vessels  

• Heart pumps blood around body in double circulatory system 
• blood passes through heart twice on each circuit            
• Four chambers in heart:                                                                                                                                   left and right atria, recieve blood from veins                                                                                       left and right ventricles, pump blood our of arteries 
• Blood enters heart through atria 
• Atria contracts and forces blood into ventricals 
• Ventricals contract force blood out heart
• Valves make blood flow correct direction
• Natural resting heart rate contolled by group cells located in right atrium, act as pacemaker
• Artificial pacemakers electrical devices used to correct irregularities in heart rate

• heart send blood to lungs via pulmonary atery 
• air obtained by breathing reaches the lungs through trachea, has rings of cartilage to prevent collapsing 
• trachea divides into two tubes- the bronchi
• bronchi divides to form bronchioles
• bronchioles divide until end in tiny air sacs - alveoli
• millions of alveoli, adapted to be efficient at exchanging oxygen and carbon dioxide:                                                 have large moist surface area                                                                                                                            have rich blood supply                                                                                                                 close to blood capillaries, distance for gases to diffuse - small
• blood taken back to heart through pulmonary vein

• good health - state of physical and mental wellbeing
• disease causes by part of body not working properly, can affect physical and or mental health
• diseses can be divided into 2 main types:                                                                                   communicable diseases and non- communicable diseases 
• non communicable diseases cannot be spread between organisms, communicable can
• example of how diseases can interact with each other:                                                                   viruses infecting cells can be the trigger for cancers , cervical cancers                                     disease of immune system mean that individual more likely to catch infectious disease           immune reactions triggered by pathogen can cause allergies: skin rashes and asthma 
• non communicable disease: diabetes, can change persons life and cost countries large sums of money

• non communicable diseases often caused by interaction of number factors
• factors called risk factors, make more likely person going to get disease
• risk factors:                                                                                                                                                                                       aspects persons lifestyle                                                                                                                    substances in persons body or enviroment                                  
• sometimes clear risk factor and chance of getting disease 
• this does not mean that risk factor causes disease

cardiovascular disease =lack of excersise/smoking                                                                 Type 2 diabities =obesity                                                                                                                 Liver and brain damage =excessive alcohol intake                                                                                Lung disease, lung cancer =smoking                                                                                       Skin cancer= ionising radiation                                                                                                 Low birth weight in babies = smoking during pregnancy                                                         Brain damage in babies =excessive alcohol intake during pregancy 

• coronary heart disease- layers of fatty material build up inside coronary ateries and narrow them 
• Treatments for coronary heart disease include:                                                                           stents to keep coronary arteries open                                                                                         statins to reduce blood cholesterol levels and slow down the rate at which fatty materials build up     
• heart valves may become faulty, developing leak pr preventing valve opening properly 
• faulty valves can be replaced using biological or mechanical valves
• for cases of heart failure:                                                                                                             donor heart or heart and lungs - transplanted                                                                             artifiicial hearts - used to keep patients alive while waiting for heart transplant to to allow heart recover

• cancer - non communicable disease 
• genetic risk factors for some cancers may run in families 
• cancer- caused by uncontrolled cell division  - form masses of cell = tumours 
• 2 main types of tumours:                                                                                                             Benign tumours = do not spread around body                                                                                     Malignant tumours spread = blood to different parts of body, form secondary tumours 

Plant tissues

• epidermis = covers other surfaces of plant for protection        
• palisade mesophyll = main site of photosynthesis in the leaf
• spongy mesophyll = air spaces betwwen cells allow gases to diffuse through leaf
• xylem vessels =Transport water and minerals through plant , from roots to leaves, supports plant 
• phloem vessels = transports dissolved food materials through plant 
• meristem tissue = found mainly at tips of roots and shoots, where produces new cells for growth
• plant tissues gathered together to form organs 
• leaf is plant organ
• structures of tissues in leaf related to functions

• water enters plant from soil- through root hair cells by osmosis
• root hair, xylem and phloem cells specialisd to transport water, minerals and sugars around plant
• water contains dissolved minerals
• water and mineral transported up xylem vessels from roots to stems and leaves
• at leaves, most water evaporates + diffuses out of stomata 
• loss of water from leave = transpiration
• helps draw water up xylem vessels from roots
• many factors affect rate of transpiration:                                                                                     increase in temp - increase rate, more energy transfered to water allow evaporate                   faster air flow- increase rate, blow away water vapour alowing to evaporate                             increased light intensity - increase rate , cause stomata to open                                               increase - humidity decrease rate, air contains more water vapour
• in leaf, role of guard cell =to open and close stomata 
• at night stomata close - carbon dioxide not needed - photosynthesis, closing stomata reduces water loss
• when water plentiful - guard cells take water+bend , causes stomata to open, gases for photosynthesis free to move in and out stomata along with water 
• when water scarce-loosing water, stomata change shape and close

• phloem tissues transports dissolves sugars from leaves to rest of plant 
• movement of food through ploem tissues called translocation 
• phloem cells adapted for this function