Cells, cells, cells
Cells
• Smallest living unit
• Most are microscopic
Review: Cell Theory
• The 3 Basic Components of the Cell Theory are:
• 1. All organisms are composed of one or more cells.
(Schleiden & Schwann)(1838-39)
• 2. The cell is the basic unit of life in all living things.
(Schleiden & Schwann)(1838-39)
• 3. All cells are produced by the division of preexisting
cells. (Virchow)(1858)
Modern Cell Theory
• Modern Cell Theory contains 4 statements, in addition to
the original Cell Theory:
• The cell contains hereditary information(DNA) which is passed
on from cell to cell during cell division.
• All cells are basically the same in chemical composition and
metabolic activities.
• All basic chemical & physiological functions are carried out
inside the cells.(movement, digestion,etc)
• Cell activity depends on the activities of sub-cellular
structures within the cell(organelles, nucleus, plasma
membrane)
Two Basic Cell Types:
Prokaryotic vs. Eukaryotic Cells
Two Basic Types
• Remember….cells are the basic unit of life for
ALL living things.
• There are two basic types of cells:
1. Prokaryotic cells – found in bacteria
2. Eukaryotic cells – found in protists, fungi, plants
and animals
Three Cellular Domains
Bacteria vs. Eukaryotes
Characteristics Shared
• Perform the same basic functions
• Surrounded by plasma membrane to control
what enters and leaves the cell
• “Filled” with cytoplasm
• Contain ribosomes to make protein
• Contain DNA to give the general instructions
for the cell’s life
What Makes Eukaryotic Cells
Different?
Much larger
•
• Much more complex
• Contain a true nucleus to house the genetic
material (DNA)
• Linear DNA packaged into chromatin found inside
the nucleus
• Contains specialized structures in the cytoplasm
called organelles to carry out various functions
• Not all have a cell wall
Bacteria-Like Organelles
(mitochondria and chloroplasts)
• Derived from symbiotic bacteria
• Ancient association
• Endosymbiotic theory
– Evolution of modern cells from cells
& symbiotic bacteria (live together)
Eukaryotic Cells
What Makes Prokaryotic Cells
Different?
• Much smaller
• Less complex
•
•
•
•
No true nucleus
Circular DNA that is found in the cytoplasm
No organelles found in the cytoplasm
Surrounded by a cell wall
Prokaryotic Cell
Prokaryotic Cell
http://www.cellsalive.com/
cells/bactcell.htm#top
What does size have to do with it?
• Prokaryotic cells are much smaller than
eukaryotic cells. Why?
– Smaller surface area- to- volume allows nutrients
to easily and quickly reach inner parts of the cell.
– Eukaryotic cells are larger and can not pass
nutrients as quickly. They require specialized
organelles to:
• carry out metabolism
• provide energy
• transport chemicals throughout the cell
But….back to Eukaryotes
• Eukaryotes are characterized by their
membrane – bound organelles.
• You need to know them!!!!
Organelles are membranebound cell parts
• Mini “organs” that have
unique structures and
functions
• Located in cytoplasm
Cell Structures
• Cell membrane
– delicate lipid and
protein skin
(phospholipids)
around cytoplasm
– found in all cells
Phospholipids
• Polar: has an uneven
distribution of charges
– Hydrophilic head
– Hydrophobic tail
• Interacts with water
Plasma Membrane
Movement Across the Plasma Membrane
• A few molecules move freely
– Water, Carbon dioxide, Ammonia, Oxygen
• Carrier proteins transport some molecules
– Proteins embedded in lipid bilayer
– Fluid mosaic model – describes fluid nature of a
lipid bilayer with proteins
Membrane Proteins
1. Channels or transporters
– Move molecules in one direction
2. Receptors
– Recognize certain chemicals
Membrane Proteins
3. Glycoproteins
– Identify cell type
4. Enzymes
– Catalyze production of substances
Organelles (continued)
• Nucleus
– a membrane-bound sac
evolved to store the
cell’s
chromosomes(DNA)
– has pores: holes
Organelles (continued)
• Nucleolus
– inside nucleus
– location of
ribosome factory
– made of RNA
Organelles (continued)
• Mitochondrion
– makes the cell’s
energy
– the more energy
the cell needs, the
more
mitochondria it
has
Organelles (continued)
• Ribosomes
– build proteins from
amino acids in
cytoplasm
– may be free-floating,
or
– may be attached to ER
– made of RNA
Organelles (continued)
• Endoplasmic
reticulum
– may be smooth:
builds lipids and
carbohydrates
– may be rough:
stores proteins
made by attached
ribosomes
Organelles (continued)
• Golgi Complex
– takes in sacs of
raw material from
ER
– sends out sacs
containing
finished cell
products
Organelles (continued)
• Lysosomes
– sacs filled with
digestive enzymes
– digest worn out cell
parts
– digest food absorbed
by cell
Organelles (continued)
• Centrioles
– pair of bundled tubes
– organize cell division
Cytoskeleton
Cytoskeleton
• made of
microtubules
• found throughout
cytoplasm
• gives shape to cell &
moves organelles
around inside.
Structures found in plant cells
• Cell wall
– very strong
– made of cellulose
– protects cell from
rupturing
– glued to other cells
next door
• Vacuole
– huge water-filled
sac
– keeps cell
pressurized
– stores starch
• Chloroplasts
– filled with
chlorophyll
– turn solar energy
into food energy
How are plant and animal cells different?
Structure
cell membrane
nucleus
nucleolus
ribosomes
ER
Golgi
centrioles
cell wall
mitochondria
choloroplasts
One big vacuole
cytoskeleton
Animal cells
Plant cells
Structure
cell membrane
nucleus
nucleolus
ribosomes
ER
Golgi
centrioles
cell wall
mitochondria
choloroplasts
One big vacuole
cytoskeleton
Animal cells
Yes
Yes
yes
yes
yes
yes
yes
no
yes
no
no
yes
Plant cells
yes
yes
yes
yes
yes
yes
no
yes
yes
yes
yes
Yes
Eukaryote cells can be
multicellular
• The whole cell can be specialized for one job
• cells can work together as tissues
• Tissues can work together as organs
Advantages of each kind of cell
architecture
Prokaryotes
Eukaryotes
simple , grow more quickly
Complex; grow more
slowly
Single-celled organisms
Single celled or
multicellular
all cells the same
Specialized, different cells
Examples of specialized euk. cells
• Liver cell:
specialized to
detoxify blood
and store glucose
as glycogen.
• Sperm cell:
specialized to
deliver DNA to
egg cell
• Mesophyll
cell
– specialized to
capture as
much light as
possible
– inside a leaf