I took IB HL Biology and received a score of 7. This is a full chapter note for those of you who take HL or SL Biology. The notes are short and concise, and they have been revised multiple times during my high school years.
,UNIT 1: CELL BIOLOGY
1/2 INTRODUCTION + ULTRASTRUCTURE OF CELLS
Statistical Analysis
Sig-figs Graphs
- Non-zero digits are always significant - Error bars: variability of data = uncertainty (shows
- Between 2 significant digits range/standard deviation)
- Leading zeros = x significant - Standard deviation: spread of data (mostly,
- Final zero is only significant if it has decimal 68% in 1 SD, 95% 2, 99% 3)
Microscopes
Light microscope Electron microscope
- does not kill organisms - kills organisms
- portable - can differentiate organelles = detailed study
- wide range of magnification - higher resolution
- 400X - 10000x
Difference between:
Magnification Resolution
Seeing a small cell larger = zooming in Seeing 2 close points at separate
Basic conversions Calculating Magnification:
I = Image size
M = magnification
A = actual size
*remember to convert values to same unit
Basics
All cells have the following features: organelle
- Surrounded by cell membrane (=plasma membrane)
- Genetic material storing instructions for activities Evidence can be demonstrated as:
- Activities are chemical reactions catalyzed by enzymes - Can be visualized
- Individual energy releasing system - Carry out all functions of life
- Spontaneous growth does not occur
Membrane does not count because it could be a membrane of an
There are exceptions:
1. Fungi (Hyphae): have multiple nuclei in their long threads → (discrete cells make up living structures x)
2. Giant Algae: can be bigger than 100mm despite being a single cell (cells are microscopic x)
3. Striated Muscle cells (skeletal muscle): fibres can be bigger than 300 mm and multiple nuclei can be in a single plasma membrane →
(autonomous units x)
1
,Cell Theory:
1) All living things are composed of cells (unicellular/multicellular (say organism))
2) Cells are the smallest unit in life
3) All cells come from preexisting cells through cell division (asexual, sexual)
Surface Area to Volume
In all cells, surface area to volume ratio limits the abilities of a cell as it is not a linear correlation;
- Larger surface area, larger volume, smaller ratio
- Smaller surface area, smaller volume, larger ratio (more efficient)
- Volume: rate of production of heat, waste, CO2/O2 consumption
- Surface: rate of exchange of heat, waste, nutrients
- Smaller the better because:
- Faster diffusion, absorption, waste removal
- Less distance to travel
- More efficient energy production
Types of Cells
1. Unicellular: single cell carries out all functions of life
- For example,
Paramecium (aquatic organism) Chlamydomonas
- Food vacuoles: digests smaller organisms in vesicles → - Chloroplast: produces own food by photosynthesis → growth
accumulates organic matter/minerals from food through absorption of light
- Cilia: reverses movement when touched by object - Flagella: wwims to brightest light using eyespot
- CO2 diffuses out of cell - O2 diffuses out of cell
- Cell Membrane: controls exit and entry - Cell wall: controls exit and entry
- Cell membrane: regulates cell entrance/exit - Nucleus: asexually (mitosis) & sexually (meiosis)
- Cytoplasm: enzymes catalyze chemical reaction - Contractile vacuoles: keep cell’s water content with tolerable limits
2. Multicellular
- Volvox aureus: can live in colonies = because daughter colonies independently form, it is not fusion
- Caenorhabditis elegans: single mass cells fuse together
- 1mm, 959 cells = seen as decomposing matter
- 30% = nerve cells, but still have mouth, pharynx, intestine, anus
Advantages:
- Emergence property: cells with different functions but same objective, where they form new properties
- Division of labour: Different cells do different functions
3. Specialised Cells
Tissue: specialised group of cells (humans have 220)
- Specialised tissue develops by: cell differentiation
- Division of labour: different cells have different functions
- Gene expression: genes are expressed different depending on cell
- Difference between ‘cell differentiation’ and ‘gene expression’: Gene expression is what makes a cell differentiation
Stem cells: cells that result from an early division of zygote = embryonic; important because:
1) Unspecialised
2
, 2) Can differentiate into different pathways
3) Produce copious quantities (some in bone marrow, liver, skin etc.)
- Can be used for therapeutic purposes (regeneration tissues) like:
- Stargardt’s Disease (retinitis degenerating): stem cells generate to retinal cells which improve vision (embryonic)
- Leukemia (too many white blood cells): chemotherapy (kill dividing cells), injects cells so blood can be produced → adult
stem
Types of stem cells:
Embryonic Cord blood Adult
Pros - unlimited growth → used for - easily obtained - less chance of tumour growth
research of medication/cures - storage service available - x rejection problem
- less chance of genetic damage - x rejection problems - removal does not kill the adult
Cons - tumour cells - limited extraction since it is naturally - difficult to obtain
- removal kills embryo made - less growth potential
- umbilical cord is discarded
Ultrastructures of Cells
Prokaryotes: any group of organisms simple WITHOUT compartmentalization (membrane bound organelles) (E.coli; pili, flagella)
- Go through binary fission: division of pre-existing cells into identical daughter cells
- Organelle: cell structures that have their own specific functions
CCCRPNMPF
1) Capsule: protection
2) Cell wall: protects from bursting, containing peptidoglycan
3) Cytoplasm: reactions take place and genetic material is found
4) Naked Nucleoid: DNA is not enclosed in a membrane
5) Plasmid: carries genes like antibiotic resistance and pili production
6) 70S Ribosome: protein making
7) Mesosomes (foldings of plasma membrane): helps transport materials in and out of cell
8) Pili: attract to other bacteria for exchange of genetic material
9) Flagella: movement
Eukaryotes: any of the single-celled or multicellular organisms whose cell contains distinct, membrane-bound nucleus w/
compartmentalized cell structure
Animal cell = flexible and rounded Plant cell = fixed and angular
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