Tour of A Cell
A. Introduction
1.
Robert Hooke - 1665
a. Sliced a wine bottle cork
b. Looked at it under the
microscope - The microscope had just been invented
c. Found that the cork was made up
of little “cells”
2.
Cell theory
a. All living things made up of
cells
1. Some are just one cell
b. All cells come from previous
cells
3.
Simple parts of cell
a. Plasma membrane - forms outside
border
b. Cytoplasm - semi-fluid medium
inside cell
c. Organelle - “little organ”
structures inside cell
B. How to see cells
1.
Light microscope
a. Limited magnification - about
1,000X
b. To get more magnification you
need radiation with a shorter wavelength
2.
Electron Microscope
a. Electrons behave like waves -
really short wavelength
1. Result is high magnification
2. An electron microscope can
magnify 100,000 x
b. Great to look at cell organelles
C. Cell sizes
a.
Many are very tiny - 100 microns (1 millionth of a meter)
b.
Some cells are very large - some nerve cells are as long as you are tall
1. A chicken egg starts out as 1
gigantic cell
D. Why are there cells?
a.
Surface to volume problem
1. If you have to quickly
get stuff into the cell you need to put it through the cell membrane
2. Mostly the speed at which
you can get stuff into the cell is limited by the surface area
3. For a cell, as you
increase the size you increase the volume faster than you increase the surface
area
a. For a big cell, you have
a smaller ratio of surface/Volume than for a small
cell
b. Thus cells need to be small to
keep the surface/volume large
E. The cell as a factory
1.
The cell is really a little factory
a. Some cells manufacture things -
secretory cells
b. Some cells make things happen -
nerve cells and muscle cells
F. Cell Structures
1. Nucleus
a. If the cell is a factory - the
nucleus is the shop foreman’s office
b. It contains the genetic material
in the form of DNA
1. This genetic material is
in the form of chromosomes and chromatin
c. The nucleus is surrounded by a
plasma membrane
d. We classify cells by the presence
or absence of a nucleus
1. Prokaryotes - Bacteria
a.
They have no membrane-bound nucleus
b. They do have a single
circular chromosome - circular DNA
c.
These were probably the first organisms on earth
2.
Eukaryotes
a.
Have a membrane bound nucleus
b.
Chromosomes are linear arrangements of DNA
2.
Membranes
a. Lipid bilayer
3.
Ribosomes
a. Locations were proteins are
assembled from amino acids
4.
Endoplasmic reticulum
a. Rough Endoplasmic Reticulum
1. A lipid bilayer covered with
ribosomes
2. Makes secretory proteins
a.
Hair
b.
Fingernails
c.
Digestive enzymes
b. Smooth Endoplasmic Reticulum
1. Synthesis of lipids
2. In liver
a.
Smooth ER detoxifies chemicals
1. Detoxifies drugs
2. Reduces efficacy of drugs
c. Golgi Apparatus
1. Molecular warehouse and finishing
location for proteins
5.
Lysosomes
a. digestion - safe storage of
digestive enzymes
b. Digestive enzymes used to
digest particulate food in single-celled organisms
c. Used to reconstruct the
body during metamorphosis in tadpoles and insects
6.
Vacuoles
a. Membrane-bound sacs
1. Central vacuole in plant cells
2. Contractile vacuole in
single-celled animals
7.Energy-producing
organelles
a. Mitochondria (plural) - the
singular is mitochondrion
1. Organelle for energy transfer
2. The cell takes in sugar,
but that is not the way energy is used in the cell
a. The cell uses ATP -
Adenosine tri-phosphate to provide energy for
chemical reactions
3. The mitochondrion is the
site of respiration - it takes in oxygen and “burns” sugar to produce ATP
4. Intermediary metabolism
5. Some cells have lots of
mitochondria - these are cells with high metabolism
and lots of work to do
a.
Muscle cells - contraction
b.
Sperm cells - need lots of
energy to swim
1. Mitochondria are arranged
in a ring around the location where the flagella joins the rest of the cell
2. This is where the energy is needed
b. Chloroplasts - only in plants
1. Contain Chlorophyl - a
green colored chemical that captures the energy of light for the plant
2. The chloroplast takes in
carbon dioxide and light to make oxygen and sugars
a. The energy from the light
is captured as chemical bonds in the sugar
b. This process is called
photosynthesis - it is the source of all food on earth
3. Plants cannot live where there is
no light
a. The bottom of the sea -
below 100m is absolutely dark so there can be no photosynthesis so there are
not plants
1. Animals in the deep sea
get their food from particles that fall from the upper 100 m of the ocean
2. A few bacteria at
hydrothermal vents can get their energy from
chemical compounds
b.
The bottom of Cougar Lake is just like the deep sea
1. All light is gone by 2m
in the lake - I have measured it
2. It is a lot more turbid than the ocean
3. There are no plants in
the deep water of Tower Lake
4. What about where there is
light?
a.
The upper 100 m of the ocean
1. Plants do fine here
2. There are plants called
phytoplankton that live floating in the water
a.
Phytoplankton are algae
3. There are two types of algae
a.
Eukaryotes
1. Just like land plants but
they are one celled
2. Have chloroplasts, nuclei
& chromosomes
3.
They do standard photosynthesis
a. Take in carbon dioxide
b. Give off oxygen
b.
Prokaryotes - blue-green algae
1.
Really photosynthetic bacteria
2.
Take in carbon dioxide
3.
Give off oxygen
4.
No nuclei - circular chromosome
8.
Organelles of Movement - flagellae and cilia
a. Flagellae - long and whip-like
1. On Euglena - flagellates
2. Sperm cells - organelle of motion
- allows sperm to swim
b. Cilia - short and hair-like
1. On the surface of Paramecia
2. Line air passages of human lungs
a.
Keep passages clean - remove soot and particles
b. Move particles to top of
airway and into mouth for disposal
c. Anatomy of cilia and flagellae
1. Really the same thing - only
difference is the number
2. 9+2 pattern of microtubules
a.
Contractile proteins that allow cilia and flagellae to move
3. Seem to be controled by a
structure called a basal body
G. Materials Transport in Cells
1.
Cells need to get materials in and out
a. There are a group of different
methods to get stuff into cells
2.
Passive Transport - these require no input of energy
a.
Diffusion
1. Perfume in a room
2. Random motion of
molecules distributes them acroos cell membrane
3. Gases diffuse into or out of
cells
1.
Oxygen
b. Osmosis
1. Transfer of water
a. The cell membrane is
semipermeable - most solutes can’t pass through
1. Membrane allows water
through but not solutes like salt
b.
Hypertonic Solution
1. Less salt than cell contents - water moves into cell
c.
Hypotonic
1. Saltier than cell contents - water moves out of cell
d.
Osmosis presents a problem for animals and plants
a. Water diffuses into cell from freshwater
1. Problem for freshwater
organism - water will dilute its cell contents
a. Contractile vacuole - in
one celled animals
b.
Turgor pressure in plants c.
Constantly working kidneys in fish
b. Water diffuses out of organisms in salt water
1.
Problem for salt water organisms
a. Sea is hypotonic to some
organisms
1. They need to get rid of salt
2. Salt glands
3. Sea turtles, fish
b. Some organisms adjust
body fluids to match seawater
1. Shark - has a circulating
protein in blood
3. Active Transport - takes energy
a. This system is used to get
materials into the cell that it needs
1. Transport proteins that
capture material on the outside of the cell membrane and put it inside
2.
Nutrients in plants - transport mechanisms in roots
4. Endocytosis
a. Phagocytosis
b. Pinocytosis