Cell biology

• Eukaryotic cells

  -genetic material enclosed in nucelus

  -have cell membrance + cytoplasm
• Eukarytoic cells examples

  Plant and animal cells
• prokaryotic cell

  -much smaller than eukaryotic cells

  -have a cell wall, cytoplasm and cell membrane

  -genetic material not enclosed in nucleus

  -has a single DNA loop and could also have smaller rings of DNA called plasmids
• Prokrayotic Cell example

  Bacterial cells
• Cytoplasm

  -chemical reactions occur here

  -contains enzymes
• cell membrane

  -holds cell together

  -controls what goes in and out
• Nucelus

  -contains genetic material

  -controls cells activities
• Mitochondria


  -aerobic respiration occurs here
• Ribosomes

  -proteins synthesis
• Cell wall


  -made of cellulose

  -supports the cell
• Permenant vacuole


  -contains cell sap

  -weak solution of salts and sugars
• Chloroplasts


  -contain chlorophyll

  -do photosynthesis
• Magnification equation

  magnification = image size/actual size

  (M = I/A )
• nm —> um


  divide by 1000
• Um->mm

  divide by 1000
• Mm -> cm

  divide by 10
• microscope practical - prepare the slide

  1-firstly add a drop of water to the middle of clean slide

  2-use tweezers to peel off some epidermis tissue

  3-using tweezers to place the tissue onto the water on the slide

  4-add a drop of iodine solution - its a stain so it highlights objects in cell

  5-place cover slip over, get rid of bubbles otherwise they will obstruct specimen
• Electron microscope


  -higher magnification + resolving power then light microscope

  -cells can be seen in much finer detail - can see sub-cellular structures
• Sperm function


  Carry male DNA to female DNA
• Sperm features

  -long tail + steamlined head to help it swim

  -lots of mitochondria to provide energy
• Nerve cell function


  To carry nerve impulses to different parts of the body
• Nerve cell features

  -electrical impulses

  -long to travel greater distance

  -branched connection to connect to other nerve cells
• Muscle cell function


  to contract quickly to allow movement
• Muscle cell features

  -long to have space to contract

  -lots of mitochondria to generate energy needed for contraction
• Root hair cell function

  Absorbs water + mineral ions
• Root hair cell features

  -have long hairs which gives the plant a larger surface area for absorbing water and mineral ions from soil
• Phloem tubes function

  Transport sugar
• Phloem tubes features

  -made of columns of elongates cells with small pores in end walls to allow cell sap through

  -transport food substances made in leaves to the rest of the plant for immediate use/ storage

  -transports both directions

  -translocation
• Xylem Tube Function

  Takes water and mineral ions
• Xylem Tube Features

  - made of dead cells joined end to end with no end walls

  - strengthened by lignin

  - carry water + mineral ion from roots to the stem and leaves through transpiration

  - one direction
• cell differentiation

  the process by which a cell becomes specialized for a specific structure or function
• Most animal differentiate at:

  An early stage

  -restricted to repair and replacement
• Most plants ...

  Retain the ability to differentiate through life
• Binary fission

  Division of bacteria
• Binary fission process

  1- circular DNA + plasmids replicate

  2- cells get bigger and DNA moves to opposite ends

  3- cytoplasm begins to divide and new cell walls begin to form

  4- cytoplasm divides resulting in 2 daughter cells produced

  
  

  (Number of plasmids normally not evenly distributed)
• Bacteria can multiple once every...

  20 mins if they have enough nutrients and a suitable temperature
• Culturing Microorganisms before

  - petri dishes and culture mediums must be sterilised to kill unwanted microorganisms

  - inoculating loop must be sterilised by passing through a hot flame

  - lid of petri sieh and should be lightly taped on to stop microorganism getting air

  - stored upside down to stop condensation droplets falling on surface
• Practical - effect of antibiotics on bacterial growth

  1- place paper disks soaked in different concentrations of antibiotics on an agar plate that has been evenly covered with bacteria

  2- antibiotic should diffuse into agar jelly, antibiotic resistant bacteria will continue to grow around disks, non-resistant strains will die, clear area all be left where bacteria have died called the inhibition zone

  3- use a control-a paper disk not soaked in antibiotic

  4- leave for 48 hours at 25 degrees

  5- more effective=larger zone of inhibition
• Nucleus contains...

  Chromosomes made of DNA molecules

  - each chromosome carries a large number of genes
• cell cyle

  1- before cell divides it grows + increase number of sub cellular structures such as ribosomes and mitochondria. DNA replicates to form two copies of each chromosome

  2- in mitosis one set of chromosomes is pulled to each end of the cell and the nucleus divides

  3- cytoplasm and cell membranes divide to form two identical daughter cells