cell biology

• prokaryotic or eukaryotic

  • eukaryotic are complex cells e.g. plant and animal cells
  • prokaryotic are smaller and simpler we.g. bacteria
  • eukaryotes are organisms made up of eukaryotic cells
  • prokaryote is a prokaryotic cell (single -celled organism)
• animal cells

  • nucleus = contains genetic material - controls activities of the cell
  • cytoplasm = gel-like substance where chemical reactions take place - contains enzymes
  • cell membrane = hold cell together - controls what goes in or out
  • mitochondria = aerobic respiration takes place which transfers energy
  • ribosomes = where proteins made
• plant cells

  • contains all things animal cells contain
  • cell wall = made of cellulose - supports and strengthens cell
  • permanent vacuole = contains cell sap
  • chloroplasts = where photosynthesis occurs - contain green substance called chlorophyl that absorbs light
• bacteria cells

  • dont have true nucleus - has single circular strand of dna that floats freely in cytoplasm
  • no chloroplasts or mitochondria
  • may contain plasmids
• microscopes

  • light microscopes = use light and lenses to form and magnify an image - let us see individual cells and large sub-cellular structures
  • electron microscope = use electrons to from and image - higher magnification and resolution . let us see internal structure of mitochondria and chloroplasts
  • magnification = image size / real size
• preparing slides

  • drop of water to slide
  • place specimen on water
  • add drop of iodine solution - stain which highlights objects
  • place coverslip on top
• looking at slide

  • clip slide onto stage
  • select lowest powered objective lens
  • use coarse adjustment to move stage to just below lens
  • look down eyepiece use coarse adjustment knob until roughly in focus
  • adjust focus with fine adjustment knob for clear image
• differentiation

  • cell changes to become specialised
  • develop different sub-cellular structures and turn into different types of cells
  • most occurs as organism develops for animals this ability lost at early age , plant cells never lose it
  • cells that differentiate into mature animals are used for repairing and replacing skin or blood cells
• sperm cells

  • specialised for reproduction
  • get male dna to female dna
  • long tail and streamlined head to help swim
  • lots of mitochondria to provide energy needed
  • carries enzymes in head to digest egg cell membrane
• nerve cells

  • specialised for rapid signalling
  • carry electrical signals from one part of body to another
  • longer and have branched connections at ends to connect to other nerve cells and form network in body
• muscle cells

  • specialised for contraction
  • long so have space to contract
  • lots of mitochondria to generate energy needed
• root hair cells

  specialised to absorb water and minerals

  on surface of plants roots , grow into long hairs that give plant big surface area for absorbing water and mineral ions
• xylem and phloem

  • specialised for transporting substance
  • tubes which transport food and water around plant
  • cells are long and joined end to end
  • xylem are hollow and phloem have very few sub-cellular structures , substances can flow through them
• chromosomes

  • nucleus contains genetic material in from of chromosomes
  • normally have 2 copies of each chromosome - one from mother and one from father
• growth and dna replication

  • before it divides , cell has to grow and increase amount of sub-cellular structures
  • then duplicates its dna
• mitosis

  • chromosomes line up at centre of the cell fibres pull them apart, chromosomes go to opposite ends
  • membranes from each set of chromosomes , become nuclei - nucleus has divided
  • cytoplasm and cell membrane divides
  • cell produced two new daughter cells , they contain exactly the same dna and is identical to parent cell
• binary fission

  • prokaryotic cell replicate by binary fission
  • circular dna and plasmids replicate
  • cell gets bigger and dna move to opposite poles of cell
  • cytoplasm begins to divide
  • daughter cells produced , one copy of dna and variable number of plasmids
  • bacteria can divide quickly in warm and moist conditions
• culturing microorganisms

  • bacteria cultured in a culture medium which contains carbs , minerals , proteins and vitamins
  • medium can be nutrient broth solution or solid agar jelly
• testing action of antibiotics or antiseptics

  • paper discs soaked in different types of antibiotics on agar plate
  • clear area will be left where bacteria have died - inhibition zone
  • control disc to compare difference
  • leave plate for 48 hours at 25 degrees
  • more effective antibiotic = larger inhibition zone
• contamination by unwanted microorgansims will affect you results

  • petri dishes sterilised
  • inoculating loop passed through flame too sterile
  • lid taped on - stop airborne microorganisms
  • dish stored upside down- stops condensation
• stem cells

  • undifferentiated cells , can divide to produce other cells
  • found in early human embryos , have the potential to be any type of cell
  • adult stem cells found in bone marrow and cant turn into any cell
• use of stem cells

  • can be grown to produce clones and differentiate into specialised cells to use in medicine and reattach
  • embryonic stem cells can replace faulty cells
  • therapeutic cloning of an embryo could be made to have same genetic information as patient - no rejection
• risks

  • contaminated with virus which could make them sicker
  • ethical problems with embryonic stem cells
• stem cells in plants

  • found in meristems , throughout plants entire life , can differentiate into any type of plant cell
  • produce clones of plants quickly and cheaply
  • grow more plants of rare species
  • grow cops of identical plants with desired features for farmers
• diffusion

  • spreading out of particles from an area of higher concentration to lower concentration
  • larger gradient = faster diffusion
  • higher temp = faster diffusion because particles have more energy to move faster
• cell membranes

  • dissolved substances can move in and out of the cells by diffusion
  • molecules like oxygen , glucose , amino acids and water
  • moving randomly so go both ways
  • larger surface area of membrane = faster diffusion rate
• osmosis

  • movement of water molecules across a partially permeable membrane from a region of higher concentration to a region of lower concentration
• osmosis experiment

  • piece of potato placed into identical cylinders with different sugar solutions
  • measure mass of potato before putting i breaker
  • take out and dry them , measure masses again
  • mass increased = drawn in water
  • dependent variable = potato mass
  • independent variable = concentration of sugar solution
• active transport

  • substances move against concentration gradient
  • root hair cells absorb minerals from soil using active transport
  • used in gut when lower concentration of nutrients in gut to blood
• exchange surfaces

  • cells diffuse to take in substances they need to get ride of waste products - o2 and co2 , urea
  • bigger surface area to volume ratio = faster exchange
  • single celled organisms can diffuse directly in or out of cells large surface area to volume ration = enough substance can exchange
  • multi cellular organisms not enough substances can exchange
  • exchange surfaces in animal have lots of blood = get stuff in and out of cell quickly
  • gas exchange surfaces are ventilated
• adaptations for exchange surfaces

  • thin membrane = substances only short distance to diffuse
  • large surface area = lots of substances ca diffuse
• alveoli

  • specialised to maximise the diffusion
  • enormous surface area
  • moist lining for dissolving gases
  • thin walls
  • good blood supply
• villi

  • provide a larger surface area
  • inside small intestine is covered in millions of villi
  • help food to be absorbed much more quickly into the blood
  • have a single layer of surface cells and very good blood supply to assist quick absorption
• leaf

  • cos diffuses into air spaces within the leaf
  • co2 diffuses into stomata
  • o2 + water vapour diffuse out via the stomata
  • controlled by guard cells close if loosing too much water
  • flattened shape of leaf increase area of exchange
  • walls of cell from another exchange surface
  • water vapour evaporates from cells inside leaf
• gills

  • water enters through mouth and passes out gills, oxygen diffuses from water into blood and carbon dioxide diffuse from blood to water
  • made of thin plates called gill filaments , big surface area
  • covered in lamellae , increase surface ares
  • lamea have blood capillaries to speed up diffusion
  • thin surface area to minimise distance
  • blood flows through them in one direction water in another maintain large concentration gradient
  • concentration always higher than in blood