BIOLOGY YEAR 10

• diffusion: the net movement of particles from a region of higher concentration to a region of lower concentration
• diffusion is a passive process as energy is not transferred
• in diffusion the particles move down a concentration gradient. (the difference in concentration between two places)
• diffusion in the body:

  • out cells need oxygen and glucose for respiration. the blood carries these around the body.

  •they then diffuse out of the blood and into the cell that need them
• waste products diffuse out of the respiring cells into the blood to be removed
• in diffusion, particles enter and leave the cells through the cell membrane from high to low concentration
• limiting factors of diffusion

  •distance

  •concentration gradient

  •surface area

  •temperature
• increasing rate of diffusion

  • decrease distance particles that the particles need to move

  • steeper the concentration gradient

  • increasing surface area- allowing more space for diffusion

  •increasing temperature (up to a certain point)
• osmosis: the net movement of water molecules from an area of high water potential to a low water potential through a partially permeable membrane
• solution= solute+ solvent (water)
• calculating the rate of photosynthesis:

  counting bubbles of oxygen produced in a set time

  rate=1/time
• how the structure of the leaf is specialised for photosynthesis:

  stomata- lets in Co2

  root hair cell- osmosis

  chlorophyll- absorbs sunlight

  large surface area
• a limiting factor: the one factor that there is a lack of

  eg. sunlight, Co2, temp, water
• osmosis practical: measuring the weight of visking tubing after osmosis
• active transport is the movement of molecules from an area of low concentration to an area of high concentration using energy
• as particles are moving against the concentration gradient in active transport, energy must be transferred from an energy store
• three key features of active transport:

  1. particles are pumped from an area of low concentration to an area of high concentration.
  2. ATP from respiration is required as it releases energy
  3. it uses carrier proteins that span the cell membrane
• cells that carry out a lot of active transport contain many mitochondria. this means that they can carry out respiration to produce ATP molecules
• The rate at which active transport can occur will depend on the rate of respiration to produce the required ATP
• what are carrier proteins?

  special proteins that span the width of the cell membrane.
• a particular molecule that the cell requires binds to a specific carrier protein receptor is released from an energy store to the protein so that it can change shape or rotate. the carrier protein transports the molecule into or out of the cell.
• active transport occurs whenever a substance needs to be moved against a concentration gradient
• examples of active transport :

  1. digestion- carbohydrates are broken down into glucose in the small intestine which is actively transported through the villi. the blood takes the glucose to wherever it is needed.
  2. nerve impulse- a carrier protein actively pumps sodium ions out and potassium ions in to create a nerve impulse
  3. plant absorption of minerals: plants need mineral ions to make nitrates for growth, but this is normally at a lower concentration in the soil water than in the plant
• what is mitosis?


  the process by which the body cells divide
• in mitosis each cell divides to produce genetically identical (not the same) daughter cells. these are genetically identical to the parent cell.
• mitosis increases the number of cells in a multicellular organism
• uses of mitosis:

  1. body cells divide to replace worn out cells
  2. repair damaged tissue due to injury or disease
  3. to allow the organism to increase in size in growth by one body cell dividing into two
• the process of cell growth and division is called the cell cycle
• the fist stage of the cell cycle involves a cell replicating its chromosomes (each new cell produced will include a complete whole set of genetic material)
• each chromosome is made from one molecule of DNA so in order to copy a chromosome, it’s DNA must be replicated to make two DNA molecules
• how DNA is replicated

  1. DNA molecule unzips forming two separate strands
  2. the DNA bases on each strand are exposed
  3. free nucleotides in the nucleus line up against each of the original strands following the rule of complementary base pairs (A-T and C-G)
  4. this forms DNA base pairs
  5. the new nucleotides join up to form new strands. when the whole strand is complete, there are two identical molecules of DNA.
• how do chromosomes move?

  chromosomes move in the second stage of the cell cycle. this is called mitosis.
• stages of mitosis

  1. the nucleus breaks down
  2. the DNA is replicated
  3. the chromosomes line up across the middle of the cell
  4. the two identical copies of each chromosome, now seen as X (double strand) formed during DNA replication are pulled apart by spindle fibres
  5. the separated sister chromosome copied move to opposite ends of the cell.
  6. each end now contains a full ser of identical chromosomes
  7. two nuclei then form around these groups
  8. the cell is now ready to divide my cytokinesis
• after the movement of chromosomes in replication, the cell membrane pinches to separate and enclose the two nuclei, then pinched off to split the original cell into two genetically identical daughter cells
• red blood cells are specialised to transport oxygen around the body
• red blood cells have four main adaptations:

  1. biconcave shape, increasing surface area to volume ratio
  2. contains haemoglobin which binds to oxygen to form oxyhaemoglobin
  3. no nucleus, more space for more haemoglobin, for more oxygen
  4. flexible wall, so they can squeeze through narrow capillaries
• ciliated cells

  1. in the trachea (bronchi and bronchioles)
  2. between these are goblet cells which secrete a sticky mucus, trapping dirt and bacteria
  3. the cilia (tiny hairs) waft the mucus away from your lungs and into your throat
  4. you then swallow the mucus
  5. any bacteria present are then killed in your stomach acid
• palisade cells are specialised for carrying out photosynthesis. they are found near the top of the leaf and are packed full of chloroplast to absorb more light. they have a regular shape to allow close packing within the leaf, maximising the absorption of light
• root hair cell

  designed to absorb water and mineral ions from the soil. they have a stretched out piece of cytoplasm to increase surface area to absorb maximum water and minerals. they have a thin cell wall for short diffusion pathways for fast diffusion and absorption. they have many mitochondria to release lots of energy to absorb many minerals by active transport.
• differentiation is when cells become specialised by differentiation to perform a particular function