Cell Biology
Cell Structure
Specialisation + Differentiation
Plants
Many cell types can differentiate throughout a plant's life
Xylem cells
Phloem cells
Animals
Most differentiate at an early stage
Sperm cells
Nerve cells
Microscopy
Electron Microscope
Higher...
Resolution
Smallest distance between 2 points where they are seen as separate
Magnification
Number of times large the image appears compared to the size of the object
Size of image/ Size of object
Observes greater detail
Uses electron beam
Light Microscope
Limited by...
Resolution
Smallest distance between 2 points where they are seen as separate
Uses light to create an image
Domains
Eukaryotes
Plants
Nucleus
Cellulose cell wall
Permanent vacuole
Stores cell sap and pigments
Cell membrane
Controls movement of substances in and out of cells
Mitochondria
ATP synthesis
Ribosomes
Involved in protein synthesis
Endoplasmic reticulum
Rough
Protein synthesis
Smooth
Lipid synthesis
Golgi apparatus
Packaging and modification for transport
Nuclear envelope present
Animals
Nucleus
Cell membrane
Controls movement of substances in and out of cells
Mitochondria
ATP synthesis
Ribosomes
Involved in protein synthesis
Endoplasmic reticulum
Rough
Smooth
Protein synthesis
Lipid synthesis
Golgi apparatus
Packaging and modification for transport
Prokaryotes
Plasmids
Cell wall
No membrane bound organelles
Circular DNA
Binary fission
No nucleus
To test the effectiveness of antibiotics, measure area of zone of inhibition
Aseptic techniques
Sterilise equipment by flaming
Incubate at 25C to prevent growth of bacteria pathogenic to humans
Petri dish lid should be taped and placed upside-down
Upside down to prevent condensation disrupting culture
Cell Division
Cell Cycle
Mitosis
2 sets of chromosomes
Separated to opposite poles of the cell
DNA replicates
For growth and repair
Produces two genetically identical cells
Cytoplasm division
Interphase
Cell grows in size, synthesises new organelles
DNA replicates
2 sets of chromosomes
Separated to opposite poles of the cell
Stem Cells
An unspecialised cell that is capable of differentiating into other cell types and of self-renewal
Plant cells
Meristem cells
Can differentiate into any kind of plant cell during the plant's life
Animal cells
Embryonic stem cells
Can differentiate into most types of human cells
Bone marrow stem cells
Can differentiate into some types of cell e.g. blood cells
Treatment
e.g. diabetes, paralysis
Therapeutic Cloning
Embryo cloned with the same genetic makeup as the patient - no rejection
Protection of rare species from extinction
Plant meristem cloning
Enables production of large numbers of disease - resistant plants
Chromosomes
Carry genes
A section of DNA which codes for protein
DNA molecules combined with proteins
Humans have 46 chromosomes (23 pairs)
Transport In Cells
Active transport
e.g. absorption of sugar in the small intestine
Requires energy from respiration
e.g. absorption of ions in plant roots
Movement of molecules from a low concentration to a high concentration against their concentration gradient
Transport in organisms
Diffusion
Osmosis
Movement of water molecules from a region of high water potential to a region of low water potential down their water potential gradient
Factors affecting the rate of osmosis
Surface area
Concentration gradient
Temperature
Passive
Plant Tissue
Placed in hypotonic solution: mass increases
Placed in hypertonic solution: mass decreases
Diffusion
Need for mass transport systems
Surface area: volume ratio too small
Adaptations
Thin cell walls of root cells giving a short diffusion distance
Alveoli and cells of the small intestine have a large surface area
Good ventilation and blood supply
Thin membrane giving a short diffusion path
Substances
Carbon dioxide
Urea
Oxygen
Movement of molecules from a region of high concentration to a region of low concentration down their concentration gradient
Factors affecting the rate of diffusion
Surface area
Temperature
Concentration gradient
Passive
Diffusion is important for transport of materials in organisms e.g. Oxygen diffuses into RBCs