CAS BI 105 Lecture Notes - Lecture 3: Lipid Bilayer, Plant Cell, Phospholipid
14 Dec 2017
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CELLS
We are made of 50-75 trillion human cells and 100 trillion bacteria and fungal cells.
A cell is the smallest unit of life that can function independently (functional unit).
It contain the genetic information for the entire organism. It is composed of molecules. It can
make new macro moles and it can also reproduce itself. It has some organization to its
contents.
All cells contain genetic information (DNA) and can utilize energy and make new macro moles.
Cells vary in their level of organization. The central division is the presence or absence of a
nucleus, which is a membrane sack to hold DNA.
Cells are:
-Eukaryotic — have a true nucleus. All their DNA is housed within the nucleus.
-Prokaryotic — have no nucleus, their DNA is gathered in a clump in the center of the cell.
Almost all cells live in a watery (aqueous) environment. All cells have an aqueous interior. They
must create a barrier for autonomy (must have a membrane — phospholipid bilayer).
The plasma membrane is the site of communication with external environment. It separates the
cell’s internal environment from the external. It is selectively permeable. It controls entrance and
exit from the cell. It is formed of non-polar lipids between two aqueous environments.
The plasma membrane surrounds all cells (specifically, it surrounds the cytoplasm). The
functional unit of the plasma membrane is a single phospholipids molecule. Each molecule is
formed by:
-a polar glycerol head, which is hydrophilic
-two non polar tails, which are hydrophobic fatty acid tails
These molecules are in fact amphipathic. In a watery environment, the phospholipids arrange
themselves tails together and heads facing out.
Cells have an aqueous interior: cytosol (the aqueous environment inside the cell which occupies
20-50% of its volume). The cytosol is central to many metabolic activities.
Eukaryotic cells use membranes for internal organization, have a nucleus and other structures
inside called organelles.
Some cells have cell walls which provide shape and prevent overfilling (only in prokaryotic cells,
eukaryotic plant and fungal cells). Bacteria have cell walls which are made of peptidoglycan
(protein and sugar). All plant cell have cells walls made of cellulose, which is a starch
indigestible to humans and makes up the bulk of human and animal feces. Plant cell walls
provide rigidity so that plants can stand up without a skeleton.
Glycocalyces can aid in protection from the environment as well as identifying certain cells.
Flagella can assist in cell movement for eukaryotic or prokaryotic cells.
All cells are capable of reproducing themselves. Cell copies genetic material and then splits in
two, dividing cellular contents. Each daughter cells should be an approximate copy of the parent
cell. This process is known as Mitosis.
Moreover, all cells are capable of manufacturing molecules: proteins are made in ribosomes
(which both prokaryotic and eukaryotic cells have).
Prokaryotic cells are unicellular organisms. They have a relatively simple structure and they are
quite small. They lack a membrane enclosed nucleus. Key features are:
-plasma membrane — double layer of phospholipids; a barrier for autonomy.
-cytoplasm — the region of the cell contained within the plasma membrane
-nucleoid region — location where the genetic material is found
find more resources at oneclass.com
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Document Summary
We are made of 50-75 trillion human cells and 100 trillion bacteria and fungal cells. A cell is the smallest unit of life that can function independently (functional unit). It contain the genetic information for the entire organism. It can make new macro moles and it can also reproduce itself. All cells contain genetic information (dna) and can utilize energy and make new macro moles. The central division is the presence or absence of a nucleus, which is a membrane sack to hold dna. All their dna is housed within the nucleus. Prokaryotic have no nucleus, their dna is gathered in a clump in the center of the cell. Almost all cells live in a watery (aqueous) environment. They must create a barrier for autonomy (must have a membrane phospholipid bilayer). The plasma membrane is the site of communication with external environment. It separates the cell"s internal environment from the external. It controls entrance and exit from the cell.
