Cells that have a nucleus and membrane-bound organelles
Prokaryotes
Cells that lack a nucleus and membrane-bound organelles
Components of animal and plant cells
Cell membrane
Cytoplasm
Nucleus containing DNA
Components of bacterial cells
Cell wall
Cell membrane
Cytoplasm
Single circular strand of DNA and plasmids
Orders of magnitude
Used to understand how much bigger or smaller one object is from another
Prefixes used to show multiples of units
Centi (0.01)
Milli (0.001)
Micro (0.000,001)
Nano (0.000,000,001)
Structures found in animal and plant cells
Nucleus
Cytoplasm
Cell membrane
Mitochondria
Ribosomes
Structures found only in plant cells
Chloroplasts
Permanent vacuole
Cell wall
Structures found in bacterial cells
Cytoplasm
Cell membrane
Cell wall
Single circular strand of DNA
Plasmids
Adaptations of Sperm cells
Streamlinedhead and longtail to aid swimming
Many mitochondria to supplyenergy
Acrosome with digestiveenzymes to breakdowneggcellmembrane
Adaptations of Nerve cells
Longaxon to transmitimpulses
Manydendrites to form branchedconnections
Mitochondria to supply energy for neurotransmitter production
Adaptations of Muscle cells
Specialproteins (myosin and actin) to cause contraction
Many mitochondria to provide energy
Can storeglycogen for respiration
Adaptations of Root hair cells
Large surfacearea for water and mineralion uptake
Large vacuole to affect watermovement
Mitochondria to provide energy for activetransport
Adaptations of Xylem cells
Lignin deposition to form hollow tubes for water transport
Lignin spirals to withstand water pressure
Phloem cells
Sieve plates to allow movement of substances
Rely on mitochondria in companion cells for energy
Cell differentiation
Process where stem cells switch on/off genes to become specialised cells
In animals, most cells differentiate early and lose ability to differentiate further
In plants, many cells retain ability to differentiate throughout life
Light microscope
Has two lenses, objective and eyepiece, to magnify and view tissues, cells and largesub-cellular structures
Electron microscope
Uses electrons instead of light to form high magnification (up to 2,000,000x) and highresolution (0.2nm) images of sub-cellular structures
Calculating magnification of light microscope
Magnification of eyepiece lens x magnification of objective lens
Calculating size of object
Size of image / magnification = size of object
Standard form
Expressing very large or small numbers as a number between 1 and 10 multiplied by a power of 10
Components of culture medium
Carbohydrates
Minerals
Proteins
Vitamins
Growing microorganisms in nutrient broth
1. Make suspension of bacteria and mix with sterilenutrient broth
2. Stopper flask with cotton wool to prevent contamination
3. Shake regularly to provide oxygen
Growing microorganisms on agar plates
1. Spread bacteria suspension on agar surface
2. Seal plates to prevent contamination
3. Incubate at optimum temperature for growth
Culturing microorganisms
Microorganisms are very small, so scientists need to grow many of them in the lab using nutrients
Components of culture medium
Carbohydrates for energy
Minerals
Proteins
Vitamins
Growing microorganisms in the lab
1. In nutrient broth solution
2. On an agar gel plate
Making an agar gel plate involves pouring hot sterilised agar jelly into a sterilised Petridish, letting it cool and set, then inoculating with a microorganism and incubating
Sterilisation
Petri dishes and culture media must be sterilised before use, often by autoclave or UV light, to prevent contamination
Inoculating loops
Wire loops used to spread microorganisms over the agar, which must be sterilised by passing through a flame
Sealing Petri dish
The lid should be sealed but not completely, to prevent airbornecontamination while allowing oxygen entry
Storing Petri dish
Upsidedown to prevent condensation from the lid disrupting growth
Incubation temperature
25 degrees, to prevent growth of bacteria harmful to humans
Testing antibiotic effectiveness
Soak paper discs in antibiotics, place on agar plate with bacteria, measure inhibition zone after incubation
The formula to calculate cross-sectional area is πr^2, where r is the radius
Chromosomes
Contain coils of DNA, with each chromosome carrying many genes
There are 23 pairs of chromosomes in each body cell, and 23 chromosomes in each sex cell
Cell cycle and mitosis
1. Interphase: cell growth, organelle increase, DNA replication