BIO206H5 Chapter Notes - Chapter 1: Exocytosis, Sexual Reproduction, Scanning Electron Microscope
ProfessorGeorge S Espie
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Chapter 1: Introduction to cells
Cells: small, membrane in closed units filled with a concentrated aqueous solution of chemicals
and endowed with the ability to create copy of them.
Cells: fundamental units of life
Main question: what life is and how it works?
Unity and diversity of cells
Cells vary in appearance and function.
Size: in micrometers.
Paramecium: single celled, moves by beating cilia.
Branched nerve cell, receives thousands of signals
Human white blood cells: approach and engulf red blood cells
Living cells have a similar basic chemistry
Cells are living things in the sense that they can grow reproduce and convert energy
from one form to another.
In all living things, genetic instructions-genes- are stored in DNA molecules.
Written in same chemical code
Constructed out of same chemical building blocks
Interpreted by same chemical machinery
Duplicated in the same way
DNA polymer chain is made out of 4
DNA instructions are transcribed into set of
polymers called RNA.
Serves as mRNA: messages carried by this
polymer chain are translated into protein.
Protein: structural support, catalysts and
Made from same set of 20 amino acids but
different sequences giving diff 3-D shape or
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Contain genetic info in the form of DNA or RNA
Have no ability to reproduce on its own
Copied by parasitizing the reproductive machinery of the host cell.
Inert and inactive outside their host cells
All cells evolved from the same ancestor
DNA replication 2 daughter cells
Copying is not always perfect, may cause mutations
Mutations can create offspring that are changed for worse, better or neutral
Survivor genes : genes of next generations
Sexual reproduction: 2 cells fuse, DNA mixed and then new combination is presented
in next generation
Evolution: the process by which, living species become gradually modified and adapted to
their environment in more and more sophisticated ways.
Genes provide the instruction for cellular form, function and complex behavior.
Cell’s genome: the entire set of genetic info in its DNA.
It’s a genetic program that instructs cell how to function.
Diff types of cells: fat, skin, bone
^ All contain identical copies of DNA.
They vary in terms of their use of the genetic instruction.
Diff cells express diff genes
Cells under microscope
Light microscope (17th century) vs electron microscope(1930s)
Electron microscope transmits beam of electron instead of light
The invention on light microscope led to the discovery of cells
1. The cell is the smallest unit of life
2. All living things are made up of cells
3. New cells arise only from pre-existing cells
Cells, organelles and even molecules can be seen under light microscope
Cells separated by extracellular matrix: dense material made of protein fibers
embedded in polysaccharide gel.
Cell components differ in terms of refractive index.
General cell anatomy
5 nm thick enclosing membrane surrounding cell
Internal membranes : membrane surrounding organelles
Plasma membrane: external membrane
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