Cell biology

• Cell structure (eukaryotic)

  -plant & animal (multicellular)

  -both: nucleus, cell membrane, cytoplasm, mitochondria, ribosome,

  -plant: permanent vacuole, chloroplast (chlorophyll), cell wall,
• Cell structure (prokaryotic)

  -bacteria are unicellular

  -no nucleus only plasmids and nucleoid

  -cell wall + membrane, cytoplasm, ribosomes

  -flagella allow movement
• Animals

  -multi cellular

  -heterotrophs, get energy from other organisms

  -reproduce sexually
• Plants

  -multi cellular

  -autotrophs, energy from sun via photosynthesis
• Fungi

  -can be both multi cellular and uni cellular (yeast)

  -can’t photosynthesis

  -heterotrophs, saprophytic nutrition where digestive enzyme outside body break down food and absorb into there body

  -mycellium made of hyphae

  -can be pathogens e.g athletes foot
• Protists

  -nearly all uni cellular

  -some photosynthesis and some consume organisms to get energy

  -some are pathogens e.g plasmodium = malaria
• Bacteria

  -uni cellular

  -live everywhere

  -some can photosynthesis but most consume other organisms for energy

  -can cause disease e.g salmonella = food poisoning

  -most aren’t harmful and many are useful in the body
• Viruses

  -non living tiny particles

  -protein coat and genetic material

  -only reproduce in living cells so must infect them to replicate = parasites

  -all are pathogens, always cause harm to organisms when replicating

  -e.g influenza, tobacco mosaic, HIV etc.
• Microscopes (light)

  -base and arm = support

  -light source e.g lamp or mirror with stage above

  -microscope slide secured on stage

  -lenses, 3x objective lens with different magnifications

  -eyepiece lens has fixed magnification

  -coarse focus knob, help focus

  -fine focus knob, help focus
• Object and image

  Object = real sample you are looking at on slide

  image = what you see through the microscope
• Light microscope

  -light shone or reflected up through object

  -pass through a objective lens

  -then can be seen through eyepiece lens

  -lenses spread light rays to magnify image
• Magnification

  -how many times larger image is to object

  -magnification = image size divided by object size
• Resolution

  -the shortest distance between two points on an object that can still be distinguished As two separate entities ( how detailed the image is )
• Microscope (light)

  +easy to use

  +cheap

  -rely on light

  -resolution limited to 0.2um therefore can’t study sub-cellular structures
• Microscope (electron)

  -very expensive

  -hard to use, only by scientists

  +use electrons

  +max resolution 0.1nm can see sub cellular structures (x2000 better resolution)
• Units of length (microscopy)

  Nm = nanometers

  um = micrometers

  mm = millimetres

  m = meters

  km = kilometres

  -all 1000x bigger/smaller than the one next e.g nm 1000x smaller than um

  e.g 6x10⁶ nm , is 6x10³ um, is 6mm, is 6x10‐³ m, is 6x10‐⁶ km
• cell cycle

  -growth, increase in size + number of sub cellular structures it contains

  -DNA replication + mitosis, chromosomes duplicate (92) and line up, then are pulled by fibres to opposite sides of cell( poles )

  -cell division (cytokinesis), cell splits forming 2 identical daughter cells each with same DNA
• Binary fission

  -prokaryotic cells divide and reproduce

  -asexual reproduction

  -first it grows , secondly replicate all genetic material

  -then genetic material moves to opposite sides of cell

  -new cell wall grows down middle so two sides pull apart = new bacteria cells
• Binary fission calc

  -e.g bacterias mean division time is 30 mins how many will there be after 3 hrs ?

  3hrs = 180mins

  180 divided by 30 = 6 divisions

  1x2⁶ = 64

  -mean division time depends on bacteria type and conditions
• Culturing bacteria

  -done in agar dishes to test antibiotics and disinfectants

  Factors affecting growth:

  -temp, warm = faster

  -nutrients, more = faster, nutrient broth has carbohydrate (energy), nitrogen (proteins), vitamins + minerals

  -moisture, moist = faster

  -oxygen= more = faster
• aseptic techniques

  prevent contamination by:

  -clean surface w disinfectant -wash hands with antiseptic

  -sterilise instrument, solutions and mediums

  -create sterile field w Bunsen burner

  -incubators at 25 degrees to avoid harmful pathogens
• Growing bacteria colonies

  Inoculation = transfer of bacteria from broth to agar plate

  -sterile inoculating loop dipped into bacteria broth

  -top Of broth held near Bunsen burner to prevent other organisms entering and contamination

  -petri Dish lid lifted slightly and bacteria zig-zagged on w inoculating loop the lid quickly closed

  -lid secured with tape then stored upside down in incubator at 25 degrees

  -steriles all equipment used and surfaces
• Investigating antiseptics + antibodies

  -in prepped agar plate add disks of filter paper soaked in different antibiotic /antiseptic solutions

  -zones of inhibition = larger the area around disc the better it works against the bacteria

  -area = pie x radius squared
• Stem cells (animals)

  -a cell not yet undergone differentiation (undifferentiated)

  -embryo in early stages of development is a stem cell

  -if cells removed from early embryo they are embryonic stem cells = can differentiate into any cell type

  -adult stem cells can be found in eyes, blood, bone marrow and muscles etc.

  -can only differentiate into related cell types e.g bone marrow cells -> blood or immune system cells but no others
• Stem cells (plants)

  -found in meristems (shoots and roots)

  -can differentiate into all types of plant cells
• Red blood cells

  • Contain haemoglobin to carry oxygen molecules
  • No nucleus for more space for oxygen
  • Biconcave for larger surface area
• Sperm cells

  • Tail for movement
  • Lots of mitochondria for energy
  • Acrosome (head) releases enzymes to digest eggs membrane
  • Haploid nucleus holds genetic material
• Egg cell

  • Cytoplasm has nutrients for growth
  • Haploid nucleus holds genetic material
  • Membrane changes after fertilisation
• Nerve cell

  • Thin and very long so can carry signals very quickly
  • Branch connections
  • Myelin sheath increases speed messages travel
• Cilia cells

  • Beat with a rhythm
  • Move mucus etc out of airways
  • Move eggs down oviducts
• Villi

  • Small intestine, have large surface area
  • Thin walls one cell thick
  • Tiny hairs absorb food and water
• Stem cells (medicine)

  -can treat type 1 diabetes, replace failing cells with ones that can produce insulin

  -can treat multiple sclerosis

  -can treat some spine or brain injury

  -can treat blood cancers, bone marrow cells differentiate into blood cells and transplanted
• Diffusion

  -net movement of particles from a high to low concentration

  -leaves, oxygen diffuses from high in leave to low in air + carbon dioxide diffuses from high in air to low in leaf

  -lungs, in alveoli the oxygen diffuses from high concentration to low in the blood + carbon dioxide diffuses from high in blood to low in alveoli

  -liver, urea diffuses from high in liver cells to low in the blood to travel to the kidney
• Osmosis

  -Diffusion of water through a semi-permeable membrane from an area of high to and area in low concentration

  -occurs in root hair cells

  -cells can lose water and shrink or gain water and burst

  -hypertonic = high solute concentration

  -hypotonic = low solute concentration

  -isotonic = rate of osmosis is equal both ways
• Osmosis RP

  -in test tubes prepare a range of sucrose solution varying in concentration and one containing distilled water (control)

  -cut equal length potato cylinders and weigh the mass

  -place sample in each solution and leave for 5-10mins

  -after weigh the new mass and compare to determine the effect of different concentration on the mass + concentration of cell sap of potato cell
• Active transport

  -against concentration gradient

  -substance move from area of low to high concentration

  -requires energy
• Active transport (plants)

  -root hair cells

  -mineral ions move into root cell where there is a high concentration than in the soil
• Active transport (animals)

  -in gut when glucose concentration is lower in intestine than in blood it moves via active transport

  -requires energy from respiration
• Specialised exchange surfaces

  -large surface area = alveoli, villi, leaves

  -one cell thick = cell membrane, leaves, capillaries, alveoli, villi

  -around villi and alveoli there are lots of capillaries = good blood supply