Why Study Cell
Biology?
The key to every
biological problem must
finally be sought in the
cell, for every living
organism is, or at some
time has been, a cell. E.B.
Wilson, 1925
Cells are Us
Cells are Us
Cilia on a protozoan
Sperm meets egg
Cells are Us
A person contains about 100 trillion cells.
That’s 100,000,000,000,000 or 1 x 1014
cells.
There are about 200 different cell types in
mammals (one of us).
Red and
white blood
cells above
vesselforming cells.
nerve cell
CELL SIZE
• Smallest cell in the human body is the
sperm cell
• Largest cell in the human body is the egg
cell
Most cells are small
1. Surface to volume
ratio: cell has to be
small enough to get
– Waste out
– Nutrients in
2. The nucleus can only
control a certain size
cell
Robert Hooke
• Used a microscope to look at small object and coined the
term “cells”
• They looked like little boxes that monks lived in called
“cells”
Anton von
Leewenhoek
• FIRST person to
OBSERVE and
DESCRIBE
MICROSCOPIC
ORGANISMS and
LIVING CELLS.
• Matthias Schleiden : “plants
are made of cells”
Schleiden
• Theodor Schwann : “Animals
are made of cells”
Schwann
The Cell Theory
The cell theory (proposed independently in 1838 and
1839) is a cornerstone of biology. Proposed by
Rudolph Virchow
1. All living things are made of cells.
2. Cells are the basic unit of structure and function
3. New cells come from preexisting cells.
*cells are different shapes and sizes based on their function
A Sense of Scale and Abundance – Bacteria on the Head of a Pin
Two Fundamentally Different Types of Cells
Us vs. Them Eukaryotes and
Prokaryotes
• Organisms whose cell contain a nucleus and
other membrane bound organelles are called
EUKARYOTES
• Organisms whose cells never contain (or
lack) a nucleus and other membrane bound
organelles are called PROKARYOTES
Major Divisions of the Eukaryotic Cell
1. NUCLEUS
2. CYTOPLASM
3. CELL MEMBRANE
A rat liver cell (with color enhancement to show organelles)
It’s Crowded In There
An artist’s conception of the cytoplasm - the region of a cell
that’s not in the nucleus or within an organelle.
It’s Crowded In There
A micrograph showing
cytoskeleton (red),
ribosomes (green), and
membrane (blue)
Animal and Plant Cells Have More
Similarities Than Differences
Cellular Anatomy
We’ll start by seeing what role these parts play in making
and moving proteins.
The Nucleus
•Control center
of the cell
•Surrounded by a
nuclear envelope
with pores
•DNA is in the
form of
chromatin which
condenses down
into
chromosomes
Ribosomes and the Endoplasmic Reticulum
Ribosome
• Ribosomes Are Not Surrounded by a
membrane. They are the site of
PROTEIN SYNTHESIS (Production or
Construction) in a cell.
The Rough Endoplasmic Reticulum
Studded with ribosomes
Protein synthesis (about
half the cell’s proteins are
made here).
Protein movement
(transport)
Smooth ER
• SMOOTH ER IS NOT Covered with
RIBOSOMES and processes LIPIDS and
CARBOHYDRATES. The Smooth ER is
involved in the synthesis of steroids in
gland cells, the regulation of calcium levels
in muscle cells, and the breakdown of toxic
substances by liver cells.
Cystic Fibrosis
Click here to see the article.
Golgi Apparatus
• Processing, Packaging and Secreting
Organelle of the Cell that is made of
flattened SAC
The Lysosome
Functions:
Digesting food or cellular invaders
Recycling cellular components
The
Lysosome
This bacterium
about to be
eaten by an
immune system
cell will spend
the last minutes
of its existence
within a
lysosome.
Many Diseases are Caused by Lysosome Malfunction
Cellular Anatomy
The Mitochondrion
Think of the mitochondrion as the
powerhouse of the cell.
Both plant and animal cells contain
many mitochondria.
Mitochondrial Diseases
Mitochondria and Health
Animal vs. Plant Cells – Chloroplasts Are a Big Part of
the Difference
Cells In a Leaf
The Chloroplast
Think of the chloroplast as the solar panel of the plant cell.
Only plants have chloroplasts; they perform photosynthesis
Two Other Unique Features of Plant Cells
The central
vacuole may
occupy 90%
of a plant
cell.
A Consequence of Cell Walls –
the Great Strength of Woody
Plants
The Central Vacuole Controls Turgor Pressure
Flaccid – no water
Turgid – full of water
Cellular Anatomy
The Cytoskeleton
The name is misleading. The
cytoskeleton is the skeleton
of the cell, but it’s also like
the muscular system, able to
change the shape of cells in a
flash.
Maintains the shape of the
cell
Aids in movement
An animal cell cytoskeleton
A Cytoskeleton Gallery
The
Cytoskeleton
in Action
A white
blood cell
using the
cytoskeleton
to “reach
out” for a
hapless
bacterium.
The Cytoskeleton in Action
Cilia on a protozoan
Beating sperm tail at fertilization
Smoker’s cough is due to destruction of cilia linking the airways.
Cell membrane
• The Cell Membrane is a complex barrier
separating the cell from it's external
environment. The "Selectively
Permeable" Membrane regulates what
passes into and out of the cell.
Cell Wall
• Plant cells have a cell wall. A Cell Wall
DOES NOT REPLACE the Cell
Membrane; Cells with WALLS also have a
CELL MEMBRANE. Plant Cells are
covered by a Rigid Cell Wall that lies
Outside the Cell Membrane.