bio paper 1

• Nucleus


  Contains genetic material
• Mitochondria


  Powerhouse of cell, site of aerobic respiration
• Cytoplasm


  Where chemical reactions happen, contains enzymes
• Cell membrane


  Holds the cell together and controls what goes in and out
• Ribosomes


  Site of protein synthesis
• Plant cell


  • Cell wall> made of cellulose which supports and strengthens the cell
  • Chloroplast> where photosynthesis occurs, contains chlorophyll
  • Permanent vacuole> contains cell sap to support the plant
• Bacteria cells


  • Prokaryotic
  • Singular strand of DNA
  • Plasmids
  • No mitochondria or chloroplast
• Sperm cells


  • Specialised for reproduction
  • Long tail and streamlined head
  • Mitochondria for energy
  • Enzymes help digest through egg cell membrane
• Nerve cells


  • Specialised for rapid signalling
  • Carry electrical signals
  • Long and have branched connections
• Muscle cells


  • Specialised for contraction
  • Long for space to contract
  • Mitochondria for energy
• Root hair cells


  • Specialised for absorbing water and minerals
  • Give plant big surface area
• Phloem cells


  • Transport food down stem to all parts of plant
  • Few subcellular structures
• Xylem cells


  • Transport water up plant's stem to all parts of plant
  • Hollow in centre
• Stem cells


  • Found in early human embryos and adult bone marrow
  • Can be grown in a lab to produce clones
  • Can cure diseases and be used to replace faulty cells in sick people
• Stem cells in plants

  • Found in the meristems of plants throughout life
  • Can make disease resistant crops
• Diffusion


  Movement of molecules from an area of higher concentration to an area of lower concentration (the bigger the concentration gradient, the faster the diffusion rate)
• Osmosis


  Diffusion of water through a partially permeable membrane
• Partially permeable membrane


  Membrane with very small holes so only tiny molecules like water can pass through
• Active transport


  • Movement of substances from more dilute solution to a more concentrated solution
  • Allows plant root hair cells to absorb mineral ions
• Cell cycle


  1. Growth and DNA replication, forms two copies of each chromosome

  2. Mitosis> nucleus divides

  3. Cell divides in two
• Human digestive system


  • Mouth
  • Oesophagus
  • Stomach
  • Small intestine
  • Large intestine
  • Gall bladder
  • Liver
• Liver


  Produces bile
• Stomach


  Breaks down large insoluble molecules into smaller soluble molecules
• Small intestine


  Breaks down food and passes the nutrients into the blood
• Large intestine


  Absorbs water and forms feces
• Carbohydrates


  The starches and sugars present in foods
• Simple carbohydrates


  • Simple sugars that are easily digestible and readily available
  • Turn blue benedict's solution brick red on heating
• Complex carbohydrates


  • Long chains of simple sugar units> starches found in grains, potatoes, and vegetables
  • Starch turns yellow red iodine solution blue black
• Lipids


  Consist of three molecules of fatty acids bonded to a molecule of glycerol
• Protein


  Molecules are made up of long chains of amino acids
• How do root hair cells take in minerals

  Active transport
• How does active transport stop us from starving

  • It allows nutrients to be taken into the blood despite the concentration gradient being the wrong way
  • Also means glucose can be taken into the bloodstream when it's concentration in the blood is higher than in the gut
• Exchanging substances


  How easily stuff moves between an organism and it's environment> depends on its surface area to volume ratio
• Gas exchange


  • Takes place in lung tissue between the alveoli and lung capillaries
  • Alveoli are surrounded by lung capillaries
  • Numerous small alveoli share common walls making a large surface area for gas exchange
• Properties of alveoli


  • Large surface area
  • Moist lining for dissolving gases
  • Very thin walls
  • A good blood supply
• Villi in the small intestine

  Increase surface area so that digested food is absorbed much faster into the blood
• Properties of villi


  • A single layer of surface cells
  • A very good blood supply to assist quick absorption
• Stomata


  Controlled by guard cells> close the stomata if plant is losing water faster than it's being replaced
• Air spaces in the spongy mesophyll

  Increase the rate of diffusion for gases
• Gill filaments


  • Lots of thin plates
  • Give a big surface area for exchange of gases