B2

• concentration gradient= difference in concentration between two areas.

  high concentration gradient= more steep
• diffusion = movement of particles from an area of high concentration to low concentration.
• factors affecting diffusion

  distance- shorter distance= higher diffusion

  surface area- higher SA = higher diffusion

  concentration gradient- higher concentration gradient= higher diffusion
• osmosis = diffusion of water from an area of high water concentration to low water concentration across a partially permeable membrane
• net movement of water = overall movement either in or out of the cell membrane
• water potential is the chance of water molecules to diffuse out or into a solution (liquid)

  water potential = water concentration
• turgid plant cell= vacuole increases in size

  flaccid plant cell= vacuole decreases in size
• active transport is the movement of molecules from a low concentration to a high concentration across a cell membrane against a concentration gradient using ATP

  opposite of diffusion
• as rate of respiration increases rate of active transport increases because more ATP is produced during respiration

  more ATP from respiration used for active transport
• ATP is an energy source that your body need/uses for active transport and for your muscles to contract (movement)
• simple/small molecules can diffuse through the cell memebrane

  for example- amino acid, glucose, water and oxygen
• large and complex molecules such as proteins starch are transported from outside the cell to inside

  carrier protein are on the cell membrane and they transport large complex molecules in and out of cell.
• image shows carrier protein transporting large complex molecule into cell

  
• mitosis 


  process where cell divide into two identical cell
• mitosis stages

  gap phase 1 = cell grow and new cell structure are made

  synthesis= cell replicates its DNA

  gap phase 2= cell keeps growing and proteins needed from mitosis are made

  mitosis
• Synthesis Part 1. DNA double helix unwinds and splits

  free floating nucleotides pair up with exposed bases

  complementary based pairs = a binds with t , c binds with g
• synthesis part 2:

  cross links formed (g/c or a/t binding) = two DNA double helixes
• mitosis

  stages of mitosis below

  
• cell differentiation

  process where cells becomes specialised for their own job.
• sperm cells has a tail to move to egg , has lots of mitochondria as it needs lots of energy

  Acrosome enzyme used to break down egg membrane
• red blood cells

  Bin-concave shape (dipped down) to increase SA:V ratio so that more diffusion of oxygen and carbon dioxide are in and out of cell

  lots of haemoglobin allow more oxygen to bind to it to form oxyhemoglobin.

  RBC has no nucleus = store more haemoglobin.
• palisade leaf cell

  more chloroplast compared to other parts of plant cells - leaf where photosynthesis occurs so more chloroplasts means more photosynthesis occurs
• ciliated and goblet cells - both found in throat and intestine 


  ciliated cells have cilliar to blow dirt and bacteria away.

  goblet cells produce mucus to trap bacteria
• stem cells= undifferentiated cells that can differentiate to become specialised cells

  two types of stem cells= embryonic and adult stem cells.
• embryonic stem cells= differentiate into any type of cell in the body, found in the embryo

  adult stem cells = differentiate into some type of cell, found in brain and bone marrow
• embryonic stem cells is good because they can be used to treat diseases like diabetes or alzheimer's but unethical - they come from human embryos which is killing them. Adult stem cells is good because they don't kill anyone but bad because they cannot differentiate into all types of cells
• main factors affecting movement of substances- diffusion and active transport


  SA:V ratio higher = higher diffusion and active transport

  temp higher = more diffusion and active transport

  concentration gradient higher= more diffusion
• transpiration is the loss of water from the leaf by DIFFUSION and EVAPORATION the water loss must be replaced - leads to water flowing up the plant through the xylem

  water being lost at leaf reduces water pressure creating a pressure gradient-pressure gradient increases- water pulled up from leaf to root by xylem= the transpiration stream
• stomata opens and closes to allow co2 in and water out. when stomata opens water is lost in form of water vapour/steam EVAPORATION
• Concentration gradient created where there is high water conc in the leaf and low conc in the air

  water is lost by DIFFUSION
• image showing change in stomata shape

  
• factors affecting transpiration

  light intensity increases= ROT increases until it reaches optimum and plateau (evens out)

  temperature increases = ROT increases

  wind speed increases - ROT increases until it reaches optimum and plateau (evens out)

  humidity increases ROT decreases
• osmosis in animal cells

  lots of water taken up untill it swells and burst= lysis

  water lost by osmosis until cell =crenated

  osmosis goes from dilute to concentrated
• light intensity means more stomata open so more water is lost - increase ROT

  temperature- higher temperature = more energy in particles- increase ROT and rate of diffusion and evaporation.

  wind speed-stronger winds=faster water molecules are moved so fewer water molecules in air compared to in plant - conc gradient increases diffusion increases

  humidity- higher humidity=higher water conc in the air- conc gradient decreases - diffusion decreases
• xylem= transport water and minerals from roots to leaves - one way system

  phloem=transport sugars (glucose) from leaf to all other areas of plant (translocation)-two way system
• xylem vessels are made from dead xylem cells

  no cell walls so tubes form that water can pass up through

  
• phloem vessels are made from living cells called sieve tube elements

  end of each element have sieve plates with tiny holes- allow dissolved sugars to pass through (translocation)

  
• high SA:V ratio= higher diffusion

  high conc gradient= higher ROD

  capillary walls very think so short distance for diffusion = higher ROD

  
• artery = thick walls and muscles-can expand and carry blood at high pressure. small lumen

  vein= thin walls and muscles as it is under lower pressure. larger lumen have valves-prevent back flow blood.

  capillary-one cell thick thin membrane, small lumen & single layer of wall diameter= 7 micrometer

  
• circulatory system

  double circulatory system