Biology topic 1

• animal vs plant cells

  -both are Eukaryotic cells

  -both have cell membranes, cytoplasm, vacuoles, and other structures

  -PLANTS have a cell wall made of cellulose, have chloroplasts

  -Plants usually have one LARGE vacuole while animals have many SMALL vacuoles

  
• bacteria cells


  - Prokaryotic

  - free DNA

  - cell wall and membrane

  - plasmids

  - cytoplasm

  
• Microscopes (practical)


  - get a slide

  - add a drop of water to the middle of the slide

  - cut onion and separate its layers (peel of epidermal tissue)

  - place tissue onto the (water) on slide using tweezers

  - add a drop of iodine solution for a stain

  - place a cover slip on top
• using a light microscope

  1. Clip slide onto stage

  2. Select lowest-powered objective lens

  3. Move stage up to just below objective lens with coarse knob

  4. Looking into eyepiece, move stage down until roughly focused

  5. Adjust focus with other knob (fine), until clear

  
• cell differentiation


  the process by which a cell becomes specialized for a specific structure or function.
• sperm cells


  Sperm cells are produced by the testes when they are stimulated by testosterone. It has a lot of mitochondria to provide energy and a long tail to swim to the egg. The head also carries enzymes

  
• Nerve Cells


  fast cell communication, sends electrical impulses through nervous system. They are long and have branched connections at the ends to connect to others.

  
• Muscle cells


  Function is to contract quickly. They are long and contain a lot of mitochondria for energy.
• Root Hair Cells


  they stick off of roots into the soil this gives the plant a bigger surface area for absorbing water and mineral ions.

  
• Phloem/Xylem cells


  they form the Phloem and xylem cells in the plant. They join together to form a long tube.

  
• Mitosis


  PMAT

  1) cell replicates the DNA

  2) chromosomes line up at the centre of cell

  3) fibres pull them apart to opposite ends

  4) membranes form around each set of chromosomes

  5) cytoplasm and cell membrane now divide to make 2 identical daughter cells

  
• Binary Fission


  1) plasmids replicate

  2) cell bigger, strands move to opposite sides

  3) Cytoplasm begins to divide, new cell walls form

  4) cytoplasm divides, 2 new daughter cells formed

  This all happens in 20 minutes.

  
• Growing Bacteria


  Use Petri dish, and Agar jelly.

  
  

  Sterilise the inoculating loop, by heating it in the Bunsen burner flame.

  Dip the inoculation loop into the microorganism solution and make streaks on the surface of the agar plate.

  Replace the lid as soon as possible, secure with tape. Label and invert the plate, and store upside down.

  Do not fully seal the lid, as this will stop oxygen reaching the bacterium, and this may encourage harmful anaerobic bacteria to grow.

  Labels are important, as this identifies the growing bacterium.

  Incubate at a maximum temperature of 25°C in schools and colleges because this reduces the chance of growing harmful pathogens.

  Hospital laboratories would incubate plates at 37°C (body temperature) to allow quick growth and identification.

  
• testing effects of antibiotics on bacteria

  1) put paper disks soaked in different antibiotics on an agar plate with an even covering of bacteria.

  2) antibiotic should diffuse into the agar jelly

  3) ensure u do a CONTROL paper to compare

  4)leave the plate for 48hrs at 25 degrees

  5) more effective = largest inhibition zone
• Stem Cells


  undifferentiated cells that are able to differentiate into something.
• Embryonic stem cells


  Found in early human embryos.

  Can turn into any type of cell.

  Divide to produce lots more undifferentiated cells.

  Can be grown in a lab to create clones
• Bone Marrow stem cells.


  Found in adults as well as children. Can't turn into any cell, only certain ones, e.g blood.

  Can be grown in a lab to produce clones
• Stem cell uses - cures

  Bone marrow stem cells are used to replace faulty blood cells.

  Embryonic stem cells can be used to make: insulin-producing cells for diabetics or nerve cells for people with a spinal injury.
• pros of stem cells

  - treatment of diseases such as diabetes, dementia and paralysis.

  - May be used to treat untreatable diseases

  - Most embryos used are unwanted ones from fertility clinics which would otherwise be destroyed
• against stem cells in humans


  - feel embryos shouldn't be used as their a potential human life.

  - feel scientists should find other sources of stem cells.

  - some places stem cells are banned.
• stem cells in plants

  MERISTEM CELLS

  can differentiate into any type of plant cell.
• Diffusion


  The net movement of particles from an area of high concentration to low concentration
• Osmosis


  The net movement of WATER MOLECULES across a PARTIALLY PERMEABLE MEMBRANE from an area of high concentration to low concentration
• Osmosis practical


  1. Use a cork borer to cut 3 potato cylinders

  2. Trim to make them the same length

  3. Measure and record the mass of the potato cylinder

  4. Measure 10cm3 of water into a boing tube and label it

  5. Do the same with a concentrated sugar solution

  6. Add one potato to each tube

  7. After 24hrs remove each potato and excess water

  8. Measure the new length and mass

  9. Calculate percentage change
• Active Transport


  a substance that is absorbed against a concentration gradient.

  e.g absorbing mineral ions through root hair cells cell
• Active Transport in root hair cells

  The root hair cells have carrier proteins in their cell membranes. These pick up the mineral ions and move them across the membrane into the cell against the concentration gradient. Because active transport moves ions against the concentration gradient into the root hair cells, energy is needed from respiration.
• Active Transport in the gut

  ● Substances such as glucose and amino acids from your food have to move from your gut

  into your bloodstream

  ● Sometimes there can be a lower concentration of sugar molecules in the gut than the

  blood, meaning diffusion cannot take place

  ● Active transport is required to move the sugar to the blood against its concentration

  gradient
• Exchange surface in lungs

  ALVEOLI

  - large surface area

  - moist lining

  - thin walls

  - good blood supply
• Gills


  - large surface area

  - lamallae to increase surface area

  - lots of capillaries

  - thin surface layer