Cell bio

• what’s the difference between eukaryotic cells and prokaryotic cells?


  eukaryotic cells have genetic material (DNA) contained within a nucleus (eukaryotic cells are ANIMAL and PLANT cells )

  Whereas

  prokaryotic cells are single-celled and have no nucleus - only a single loop of DNA. (prokaryotic cells are bacteria)
• Animal cell


  • Cell membrane controls the movement of substances in and out of a cell
  • Nucleus contains DNA
  • Mitochondria where energy is released through respiration
  • Ribosomes for protein synthesis
  • Cytoplasm is a jelly-like substance where chemical reactions happen
• Plant cell


  • Permanent vacuole contains cell sap
  • Chloroplasts contain chlorophyll to absorb light energy for photosynthesis
  • Cell wall made of cellulose which strengthens the cell
• what characteristics do animal cells have?

  1. cell membrane - CONTROLS MOVEMENT OF SUBSTANCES IN AND OUT THE CELL
  2. nucleus - CONTAINS DNA
  3. mitochondria - WHERE ENERGY IS RELEASED THROUGH RESPIRATION
  4. ribosomes - SITE OF PROTEIN SYNTHESIS
  5. cytoplasm - JELLY LIKE SUBSTANCE, WHERE CHEMICAL REACTIONS TAKE PLACE

  (plant cells also contain a cell membrane, nucleus, mitochondria, ribosomes and cytoplasm)
• what characteristics do prokaryotic cells have?


  bacteria have the following:

  • single-celled
  • no nucleus - have a single loop of DNA
  • have small rings of DNA called plasmids
  • smaller than eukaryotic cells
• Characteristics of a light microscope

  • uses light to form images
  • living samples can be viewed
  • relatively cheap
  • low magnification
  • low resolution
• characteristics of an electron microscope

  • uses a beam of electrons to form images
  • samples cannot be living
  • expensive
  • high magnification
  • high resolution

  electron microscopes allow you to see sub-cellular structures such as ribosomes that are too small to see with a light microscope
• diffusion


  the net movement of particles from an area of higher concentration to an area of lower concentration

  • particles move down the gradient
• Diffusion in humans

  • Nutrients in the small intestine diffuse into the blood in the capillaries through the villi
  • Oxygen diffuses from the air in the alveoli into the blood in the capillaries. Carbon dioxide diffuses from the blood in the capillaries into the air in the alveoli
  • Urea diffuses from the cells into the blood for excretion by the kidney
• Diffusion in fish

  • Oxygen from water passing over the gills diffuses into the blood in the gill filaments
  • Carbon dioxide diffuses from the blood in the gill filaments into the water
• Diffusion in plants

  • Carbon dioxide used for photosynthesis diffuses into the leaves through the stomata
  • Oxygen produced during photosynthesis out the leaves through the stomata
• factors that effect the rate of diffusion

  1. difference in concentration - steeper gradient = faster rate of diffusion
  2. temperature - higher temperature = faster rate of diffusion
  3. surface area of the membrane- the larger the me surface = faster rate of diffusion
• osmosis

  the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane

  • low concentration to high concentration
• examples of osmosis

  in plants

  • water moves by osmosis from a dilute solution in the soil to the a concentrated solution in the root hair cell
• active transport 


  the movement of particles from a dilute solution to a more concentrated solution using energy from respiration

  • moves against the concentration gradient

  • uses energy released from respiration
• examples of active transport


  in humans :

  • allows sugar molecules to be absorbed from the small intestine when the sugar concentration is higher in the blood than in the small intestine

  in plants :

  • used to absorb mineral ions into the root hair cells from more dilute solutions in the soil
• adaptations for exchanging substances

  multicellular organisms have a small surface area to volume ratio . this means they need specialised organ systems and cells to allow enough molecules to be transported in and out their cells

  • exchanging surfaces work most efficiently when they have a large surface area . thin membrane and a good blood supply
• villi in the small intestine


  • FOR ABSORBING NUTRIENTS

  characteristics :

  • network of capillaries
  • large surface area due to folding
  • thin wall ( only one cell think)
  • good blood supply
• alveoli in the lungs

  FOR GAS EXCHANGE

  • network of capillaries provide a good blood supply
  • the rate of diffusion is increased because the membrane of the alveoli — is moist, has a large surface area, is one cell thick ( short diffusion pathway)
• fish gills 


  FOR GAS EXCHANGE

  fish gills are made up of stacks of thin filaments with

  • a large surface area to increase diffusion
  • a network of capillaries
• root hair cells


  FOR UPTAKE OF WATER AND MINERALS

  • lots of mitochondria to take in mineral ions by active transport
  • large surface area helps efficient absorption of water and mineral ions