biology paper 1 finisher

• eukaryotes and prokaryotes


  Eukaryotic cells contain their genetic material enclosed in a nucleus. eg plant cells and animal cells Prokaryotic cells - genetic material is not enclosed in a nucleus. they are found in a strand and a plasmid(rings of DNA)
• What subcellular structures are in animal cells

  Animal cells

  cytoplasm - watery solution where chemical reactions take place

  cell membrane - controls the molecule that enters and leaves

  mitochondria - where aerobic respiration takes place to release energy

  Ribosomes - the sites of proteinsynthesis
• Plant cell organelles 


  they have all the organelles an animal cell has but they also have:

  chloroplasts - contain chlorophyll - sites of photosynthesis

  cell wall - made from cellulose - strengthens the cell

  permanent vacuole - contains cell sap - helps the plant give its shape
• Sperm cells


  -Their role is to join with an ovum and fertilise

  • both ovum + sperm genetic information combine
  • lots of mitochondria - provides energy needed for swimming
  • contain enzyme(acrosome) - which allow them to digest their way through the outer layer of ovum
  • only contain half the genetic info of a normal adult cell
• nerve cell

  • send electrical impulse around the body
  • axon carries electrical impulse from one part of the body to another
  • myelin insulates the axon and speeds up transmission
  • synapse - junction between two nerve cells
  • dendrites - increased surface area - allow other nerve cells to connect easily
• muscle cells

  • muscle cells can contract
  • they contain protein fibres which can change their length
  • when muscles cells contract - protein fibres shorten - decreasing the length of the cell
  • lots of mitochondria to provide energy to contract
  • work together to form muscle tissues
• Root hair cells

  • hairs increase the surface area of the root so it can absorb water and dissolved minerals more effectively
  • Do not contain chloroplast as they are underground
• xylem cells

  • are found in the plant stem. They form long tubes
  • tubes carry water and dissolved mineral from the roots to the leaves
  • have very thick walls - containing lignin - provides support to the plant
  • cell walls sealed with lignin causes the xylem cells to die
  • end walls between cells have been broken down - cells now form a long tube which allow the water and dissolved minerals to go up
  • no nucleus, cytoplasm, vacuole or chloroplast
• phloem cells

  • tubes carry dissolved sugars
  • end walls of the vessel cells have pores called sieve plates
  • allow dissolved sugars to move through the cell interior
  • phloem vessel cells - no nucleus and limited cytoplasm
  • each vessel cell has a companion cell
  • mitochondria in companion cell provides energy to the phloem vessel cell
• microscopy 


  allow us to magnify
• light microscope 


  have a limited magnification and limited resolution
• electron microscope 


  have a much greater resolution and magnification than light microscopes
• equation for magnification 


  magnification = size of image/size of object x100
• mitosis


  stage one:

  • DNA replicates to form two copies of each chromosome
  • the cell grows and copies its internal structure
  • stage two:
  • mitosis takes place
  • one set of chromosomes is pulled to each end of the cell. the nucleus also divides
  • stage three:
  • the cell membrane and cytoplasm divide to form two identical daughter cells
• functions of mitosis

  • mitosis is essential for growth and development of multicellular organisms
  • mitosis takes place when an organism repairs it self
  • mitosis happens during asexual reproduction
• What are stem cells and why are they important

  stem cells are able to divide by mitosis to form new cells

  stem cells are able to divide and differentiate in to specialised cells
• adult stem cells


  jelly like substance - bone marrow - contains adult stem cell

  • can divide by mitosis
  • can only differentiate into different types of blood cells
• plant stem cells 'meristems' 


  Areas of the plant that are continually growing eg roots and shoots

  as the plant grows, all the unspecialised stem cells will differentiate into all the cells they need
• diffusion


  the net movement of particles from an area of high concentration to an area of low concentration. no energy required
• osmosis


  diffusion of water from a dilute solution to a more concentrated solution. through a partially permeable membrane.
• Active transport 


  the net movement of particles from an area of low concentration to an area of high concentration - goes against the concentration gradient and is not passive like diffusion and therefore requires energy from respiration, which is why it is called active
• What is a tissue


  a group of cells within a smaller structure or function
• what is an organ?


  an organ is a group of tissues working together for a specific function
• how are organisms formed?


  organs are grouped in to organ systems which work together to form organisms
• What are the three main nutrients a food contains:

  carbohydrates, protein and lipids - they are large molecules which are too large to be absorbed by the bloodstream and therefore digested
• how are the large food molecules absorbed?

  During digestion, large food molecules are broken down into small molecules by enzymes which can be absorbed into the blood stream
• The process of digestion


  1. Food is chewed in mouth

  2. Enzymes in saliva begin to digest starch into smaller sugar molecules

  3. Food passes down oesophagus into the stomach (contains hydrochloric acid)

  4. Enzymes begin to digest proteins

  5. Churning action of the stomach muscles turns the food into a fluid which increases the surface area for enzymes to digest

  6. Fluid passes down to small intestine

  7. Pancreas releases enzymes to continue the digestion of proteins and starch, they also start the digestion of lipids

  8. Liver releases bile (neutralises the acid from the stomach) - speeds up the digestion of lipids

  9. In small intestine, smaller food molecules produced by digestion is absorbed into the bloodstream by diffusion or active transport

  10. Fluid makes its way to the large intestine where water is absorbed into the bloodstream

  11. Faeces is released from the body
• enzymes


  enzymes catalyse chemical reactions

  they are large protein molecules and they have a groove on their surface called the active site

  the active site is where the substrate attaches to

  enzymes are specific -substrate must fit perfectly in the active site
• what enzymes are proteins broken down by?


  proteins are broken down by enzymes called proteases

  proteins are long chains of chemicals called amino acids

  protease converts proteins in to individual amino acids which is absorbed in to the blood stream

  they are joined together into a different order to make human proteins
• what enzyme is starch broken down by?


  starch consists a chain of glucose molecules

  starch is broken down by the enzyme called amylase

  produces simple sugars

  Amylase is found in the saliva and pancreatic fluid
• what enzymes are lipids broken down by 


  a lipid molecule consists of a molecule of glycerol attached to three molecules of fatty acid

  digested by enzyme called lipase

  produces glycerol and fatty acids

  lipase is found in the pancreatic fluid and the small intestine
• what is the benefit of the heart having a double circulatory system

  can travel rapidly better to the body cells as the blood passes the heart twice
• how the heart works

  • oxygenated blood passes from the lungs into the heart by the pulmonary vein
  • oxygenated blood is pumped from the heart to the body by the aorta
  • deoxygenated blood is passed from the body to heart by the vena cava
  • deoxygenated blood is pumped from the heart to the lungs by the pulmonary artery

  
• pattern of blood flow

  blood enters the left atrium and right atrium

  atria now contracts and blood goes down to ventricles

  ventricles contract and forces blood out of the heart

  valves stop the blood from flowing backwards
• arteries?

  • carry very high pressure blood from the heart to the organs in the body
  • thick muscular walls - to withstand the very high pressure of the blood
  • blood travels through the arteries in surges every time the heart beats
  • contain elastic fibres - stretch when the surges of blood passes and then recoil in between surges so the blood keeps moving
• capillaries

  when the blood passes through capillaries, substances such as glucose and oxygen diffuse from the blood to the cells

  carbon dioxide diffuses from cells back in to the blood

  very thin walls - diffusion path is very short

  allows the substances to diffuse rapidly between the blood and body cells

  it makes its way to the heart by veins
• veins

  blood is now travelling slowly at low pressure - blood could go backwards

  contain a thin wall - blood pressure is low

  valves open to allow the blood to flow through

  valves close to prevent blood from flowing backwards
• what does blood plasma transport(the liquid part of the blood)

  transports soluble digestion products(such as glucose) from the small intestine to organs

  transport carbon dioxide(produced by aerobic respiration) from the organs to the lungs to be breathed out

  transports the urea products from the liver to the kidney to be executed in urine
• Red blood cells


  transport oxygen from the lungs to the body cells

  biconcave discs - gives a larger surface area - so that oxygen can diffuse in and out rapidly

  contain the red pigment haemoglobin - which binds to oxygen which makes it oxyhaemoglobin

  no nucleus - more room to carry oxygen
• White blood cells 


  form part of the immune system eg by making antibodies

  contain a nucleus - contains a DNA which encodes the instruction that a white blood cell need to do their job