Part 1: The Cell
I. Function of the cell
A. Serves as the structural building
block to form tissues and organs
B. Each cell is functionally
independent- it can live on its own under the right
conditions
1. it
can define its boundaries and protect itself from external changes causing
internal
changes
2. it
can use sugars to derive energy for different processes which keep it alive
3. it
contains all the information required for replicating itself and interacting
with other cells
in order
to produce a multicellular organism
4. It
is even possible to reproduce the entire plant from almost any single cell
of the plant
II.
Types of
cells
A. Prokaryotic cells- eg. bacteria
1. very
simple-there are no organelles and most everything functions in the cytoplasm
B. Eukaryotic cells
1. all
contain the organelles that subcompartmentalize the cell
2. includes
unicellular algae and protists (e.g. ameba) that live alone or in colonies
3. includes
multicellular organisms - animals, plants, fungi - where cells work together
a. plant cells are unlike animal cells in that plant cells have chloroplasts
and cell walls.
Animal cells have neither of these. Plant cells also have relatively large
vacuoles.
III.
Parts
of the eukaryotic cell and their function- See this
fully
annotated and useful diagram of a
plant cell.
dissect a cell
online
A. Outside (boundary) of the cell
1. cell
wall
a. protects and supports cell
b. made from carbohydrates- cellulose and pectin- polysaccharides
c. strong but leaky- lets water and chemicals pass through- analogous to
a cardboard
box
2. cell
membrane
a. membrane is made up from lipids - made from fatty acids
b. water-repelling nature of fatty acids makes the diglycerides form a sheet
or film which
keeps water from moving past sheet (think of a film of oil on water)
c. membrane is analogous to a balloon- the spherical sheet wraps around the
cell and
prevents water from the outside from mixing with water on the inside
d. membrane is not strong, but is water-tight- lets things happen inside
the cell that are
different than what is happening outside the cell and so defines its boundaries.
Certain
gatekeeping proteins in the cell membrane will let things in and out.
B. Inside the cell
1. cytosol
- watery inside of cell composed of salts, proteins which act as enzymes
2.
microtubules and microfilaments - cables made out of protein which stretch
around the
cell
a. provide structure to the cell, like cables and posts on a suspension bridge
b. provide a structure for moving cell components around the cell -sort of
like a moving
conveyer belt.- see also this
site
3. organelles
- sub-compartments within the cell which provide different functions. Each
organelle
is surrounded by a membrane that makes it separate from the cytosol
a. nucleus- contains the genetic information which tells the cell machinery
which proteins,
carbohydrates and lipids to make and how they are assembled.
i. this genetic information is coded in DNA (deoxyribonucleic acid)
ii. the
DNA is
seen packaged up into
Chromatin/chromosomes
b.
mitochondrion
- Cell powerhouse. Converts sugars into energy through aerobic
respiration. (up to 100 per cell)
c. chloroplast (50-100 per cell) - site of photosynthesis.
i. allows production of sugars from sunlight and carbon dioxide
ii. only found in plants and algae- other cells have to find sugar from outside
the cell
d. vacuole or tonoplast- stores compounds that may interfere with other things
in the cell.
Dominates the inside of a plant cell.
i. sugars, salts, pigments (e.g. red pigment in beets and purple onions,
acids (lemon
acids)
e. ribosomes - site of protein synthesis- see also
this site
i. many different proteins have to be made by the cell- the proteins that
a cell makes
directs the cell's function and identity
ii. ribosomes use the information coded in the DNA of the nucleus to produce
proteins
f.
endoplasmic
reticulum (ER) - a network of folded membranes throughout the cytoplasm
i. rough ER has attached ribosomes, active in protein synthesis
ii. smooth ER lacks ribosomes and functions in the transport and packaging
of proteins
as well as the synthesis of lipids
g. golgi apparatus - membranous hollow sacs arranged in a stack
i. modifies proteins, lipids, and other substances from the ER
ii. packets of these materials move to the edge of the golgi where the golgi
membrane
is pinched off to make vesicle (package); this new vesicle moves to the plasma
membrane where it leaves the cell, or it goes to other sites within the cell
iii. builds primary cell walls between newly divided nuclei
Four groups of biologically important molecules: lipids, carbohydrates, nucleic acids, proteins
I. Lipids
A. Composed of Carbon, Oxygen,
Hydrogen atoms (COH) in building blocks of Fatty acids
(see different
fatty acids here)
B. Fats (solid) and oils (liquid
at room temperature)
1. fats
associated with animals - butter, lard
2. oils
associated with plants - corn oil, olive oil
C. Main characteristic of lipids
- won't dissolve in water and is repelled from water (e.g. Corn
oil in water- the oil droplets
separate from the water and float to the top to try and avoid the
water) and form
self-associating
packages to exclude water.
A
membrane is one such
self-associating structure.
D. Roles of lipids
1. food-
high energy (many C-H bonds), has more energy than any other molecule
2. part
of cell membranes
3. also-
waxes (cutin, suberin), hormones (testosterone, estrogen), certain vitamins,
certain
pigments
(chlorophyll)
4. basic
form for energy storage- monoglycerides, diglycerides, triglycerides
a. glycerol + 1 fatty acid -> monoglyceride + water (ex- butyric acid
w/4C; 14-20 C
most common)
b. monoglyceride + 2nd fatty acid -> diglyceride
c. diglyceride + 3rd fatty acid -> triglyceride
II.
Carbohydrates
A. Composed of COH
-makes
building blocks of monosaccharides
(see different
structures here)
B. Roles
1. energy
storage (many C-H bonds) - sugar/starch energy source
2. structural
(especially in plants- cellulose)
Note: most important structural component in animals - protein
3. carbon
sources for making other building blocks (such as ribose and deoxyribose
for
nucleic
acids, amino acids)
C. 3 main types
1.
monosaccharides
a. simple sugars
i. example- glucose C6H12O6, energy storage
- blood sugar very different structure
ii. example- fructose C6H12O6, energy storage
- fruit sugar
iii. example- ribose C5H10O5, nucleic acids
2.
disaccharides
a. example- sucrose
(transport form for plants)
Glucose + Fructose -> Sucrose + Water
b. C12H22O11
c. sugar cane, sugar beet --> sucrose (table sugar)
3.
polysaccharides (poly = many)
a. polymers- composed of repeating subunits of monosaccharides -
b. eg. all these are repeating units of glucose
i. starch-energy storage (plants store glucose in a compact, insoluble form)
ii. cellulose- cell walls in plants- component of cardboard
iii. glycogen- energy storage in animals
III.
Nucleic
acids- DNA (deoxyribonucleic acid; master information carrying
molecule for the
cell), RNA (ribonucleic acid; Copy of DNA molecule)
A. Function- Contains the information
for entire cell-expressed through protein
synthesis
B. Polymers
of
nucleotides- composed of:
1. base-
organic molecule with nitrogen- cytosine, guanine, thymine, adenine, and
uracil
(uracil
is in RNA only)
2. sugar-
ribose, deoxyribose
3. phosphate
C. Shape of DNA molecule-
double helix (DNA
D. Other important nucleotide
compounds- example- ATP (universal in organisms; role-
energy transfer or exchange)
1. Recall
ATP <->ADP + P + energy
IV. Proteins
A. Composed of COH and Nitrogen
(four main elements) -building block is
amino acids
(20 different)
(see
structures here)
B. Large molecular weight (10,000
- 1,000,000) - note: hydrogen atom = 1
C. Roles
1. basic
building blocks of cell - much of cell structure
2. part
of cell membranes (help control entrance and exit of materials through
membranes)
3. important
in animal structure: hair, nails, connective tissue (tendons, cartilage),
muscles
4. enzymes-
facilitate chemical reactions -see this avi file
ftp://ftp.bionet.leeds.ac.uk/bionet/biochem/4pfk.avi
of enzyme (thin lines) and substrates (thick spheres)
D. Composed of
amino
acids
1. repeating
amino acids joined by the
peptide
bond forms a protein
2. 20
of them in proteins
3. 2
functional groups:-NH2 (amino group) & -COOH (acid group)
4. order
of amino acids is important- order determines the 3-dimensional shape of
the
molecule.
This is significant because the function follows form: the biological activity
of a
protein
depends largely on its
3-dimensional
structure.
Click
here to see a folded protein move.
Link to other sites
A beginner's
guide to molecular biology: A scary title but really filled with wonderful
stuff on cells!
Facts
about cells: And other neat stuff
Another summary:
But with all of the serious stuff
A
solid discussion of organelles, great diagrams
The Cell: Excellent
review
An
imaginary trip through a piece of a cell: In wonderful color as well!
A review of
basic chemistry
Introduction
to lipids and carbohydrates
Introduction
to nucleic acid
CyberDiet (Commercial site)-
shows the nutritional content of specific foods