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Cell Bio Final All Lectures.docx

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All Cell Bio Lecture Up To Midterm 1
Cell Bio Lecture 2
It’s important to read beyond the lecture material
Objectives for the lecture:
- Cell theory
- Basic properties of cells
- Cell diversity: prokaryotes vs. eukaryotes
- Model organisms
- Ch. 2 (not 2.5)
- Ch. 3.5
- Purple pages F-52-F-56
- Website
What is a cell?
- Fundamental unit of life – every organism either consists of cells or a single cell
Key characteristics of a cell
- Contains unique genetic material
- Ability to divide
- Living
- Smallest unit of life/functional unit of life
- Smallest structural and functional unit of life
- Surrounded by a cell membrane
- Inside the membrane is the control center/genetic information
- Cytoplasm inside the cell – a semi-fluid liquid made up of water, sugars, salts,
organic molecules
- Contains structures within the cell that enable it to synthesize proteins
- Responds to external stimuli
- Wide variety of cells
- All cells come from another cells
- Eukaryotic or Prokaryotic
- They have metabolisms – conversion of energy from one form to another
- It can evolve – primarily only over long periods of time
These key points are part of the Cell Theory which states:
1. All organisms consist of one or more cells
2. The cell is the basic unit of structure for all organisms
3. All cells arise only from pre-existing cells (i.e. the cell is the basic unit of
There is enormous diversity in form, function and size of cells
- simple to complex shapes
- 200nm to about 13cm in diameter
- shape often reflects function
- jack-of-all-trades to extreme specialization
- we can usually derive the cells function from its structure
Similar to basic chemistry (unity)
- similar chemical composition
- Metabolism; use of ATP as the cellular energy currency
- Use of DNA for genetic information
Some cells are massive, such as an ostrich egg or any egg really
- Although much of what’s found in the egg is energy reserves for the embryo
Some cells can be up to a meter in length, such as a neuron in a giraffe
- most cells are small, but not all of them, there is a lot of diversity
We can usually make some generalizations from on cell to another
Generally made up of proteins, lipids, carbohydrates and nucleic acids
We see the same building blocks being used in all cells generally
All cell types use DNA for genetic information – common structural unit/genetic coding
Cells can be quite diverse in the type of metabolism they have but they all use ATP as the
cellular energy currency – allows for generalization across all cell types. Also tells us that
cells have a single common ancestor
1 micrometer = 10^-6 m
1 nanometer = 10^-9 m
Sizes of cells:
- Typical prokaryote 1-5 microns
- Typical Eukaryote 10-30 microns
Why are cells small?
1. Surface area to volume ratio – surface area determines how much can be
exchanged and the volume determines how much nutrients is needed and how
much waste needs to be excreted
- Ex. How many people can sit in a room is determined by the volume, but the
ability of people to come in is determined by the number of entrances/exits
2. Rates of diffusion
- Time required for diffusion increases with distance
- For example, it takes 0.067 seconds for O2 to diffuse across 0.1mm but take 78
days for 1m
3. Adequate concentrations or synthetic capacity
Significantly more substrates are needed for the biochemical reactions of life to
proceed if a cell is large
So the cells sizes have to be small so adequate concentrations for the biochemical
reactions of life to proceed
Typical prokaryotic cells is 1-5 microns
Simple cytoplasm – consists of the cytosol and within it is ribosomes and genetic material
Genetic material is in the form of a single circular chromosome
Area in with the genetic material is found is called the nucleoid
They have flagellum for movement
Within a capsule, then a cell wall and finally a plasma membrane
Two broad groups of prokaryotic cells
Archaens – they are the extremophiles; live in love pH, high heat, halophiles (salt lovers),
methanogens (love methane)
True bacteria/bacteria – Generally cause disease; E. coli, Clostridium butyricum
Understanding of prokaryotic diversity is very limited, we know about 5000 and there’s
estimated to be millions
E. Coli is the model organism
A model organism is one that is very popular in research; in this case, E.coli
- Anaerobe, can live without oxygen
- Most strains are harmless but some are very bad
- It lives in your gut
- Extremely easy to grow in a lab, all you need is culture and a 37 degree Celsius
- They divide about every 20 minutes
- Easy to use in a lab setting
- Avg. cell size; 10-30 microns, significantly bigger than prokaryotes
- Interior of the cell is subdivided into small compartments to make membrane
bound organelles
- Overcomes the limitations of adequate concentrations
- Few molecules are needed because they’re in their own compartments thus
reducing the concentrations needed
- Not reliant on diffusion – they have transport systems to rapidly move things
around the cell
- This allows eukaryotes to overcome the limitations of cell size
- Often have elaborate cell membranes to increase the surface area without
impacting the volume
- Inside the cytoplasm is much more complex than in the prokaryotes
- This complexity allows the cells to overcome limitations on cell size
- However this comes at an energy cost – however they are much better at
generating ATP thanks to their mitochondria

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