Download No Slide Title

CELLS: UNITS OF LIFE
Chapter 4
Cells- basic units of life.
•Cell membrane separates living matter from
the environment.
•Complex cells house specialized structures,
called organelles.
•Interior of cells consists of cytoplasm.
•Cell biologists use a variety of microscopes to
magnify different types of images of cell
contents.
Lens reveal the world of cell
The study of cells (cell biology) – began in 1660,
when Robert Hooke found out remnants of cells
that were once alive in abark from a type of oak
tree.
Called these units “cells” as they looked like
cubicles.
In 1673, Antonie van Leeuwenhoek- used lens.
“To my great surprise, I found that it contained many very small
animalcules, the motions of which were very pleasing to behold. The
motion of these little creatures, one among another, may be likened
to that of a great number of flies disporting in the air”.
A. The Early Years
•
•
•
Robert Hooke (1660)
• 1st person to see the outlines of cells
Antonie van Leeuwenhoek (1673)
• developed high magnification lenses
• 1st record of microorganisms
Matthias Schleiden & Theodore
Schwann (1839) & Rudolph Virchow (1855)
• contributed to the cell theory
1.
Cell Theory
All living things are composed of
cells. [Schleiden & Schwann].
Cells “elementary particles of organisms,
the unit of structure and function”
2. All cells come from preexisting cells.
[Virchow]
Range of Light, Electron and Scanning Probe
Microscopes
B. Cell Size
•
•
•
•
Most are 1-100m in diameter
Smallest?
Largest?
Why can’t cells grow to be as large as
a car?
• - surface area/volume ratio
• - as cell grows, its volume increases
more rapidly than its surface area
C. Types of Cells
3 basic types:
• Bacterial
• Archaean
Prokaryotic
•
Eukaryotic
Cells of the Three Domains of Life
1. Bacterial cells
•
•
•
•
•
•
1-10 m in diameter
NO membrane-bound organelles
1 circular DNA molecule located in
nucleoid region
plasma membrane, cytoplasm &
ribosomes
most have a cell wall (peptidoglycan)
may have a polysaccharide capsule
Ex. bacteria & cyanobacteria
Examples
A. E. coli- inhabits the intestines of animal
species, including humans.
B. Streptococcus pyogenes
C. Cyanobacteria
Bacteria – classified based on
•Cell wall structure
•Biochemical characteristics (metabolic pathways and
shape)
Bacterial cells may be
Round (cocci)
Rod shaped (bacilli)
Spiral (spirilla)
Comm-shaped (vibrious)
Spindle-shaped (fusiform)
2. Archaean cells
•
•
•
•
1-10 m in diameter
NO membrane-bound organelles
cell walls lack peptidoglycan
have characteristics of both
bacteria & eukaryotic cells
Ex. methanogens,
extreme halophiles &
extreme thermophiles
Archaea
transport ions within their cells like bacteria
Like eukaryotes histone proteins are
associated with their genetic material.
Identified from environments that have
extremes of temperature, pH or salinity.
3. Eukaryotic cells
•
•
•
•
•
10-100 m in diameter
nucleus & other membrane-bound
organelles
2 or more linear DNA molecules
located in nucleus
plasma membrane, cytoplasm &
ribosomes
some have a cell wall (cellulose or chitin)
Ex. plants, animals, fungi, protista
Three basic types of cells
Bacteria do not contain organelles.
Archaea – share features of both bacteria
and eukaryotes and have unique biochemical
featues.
Eukaryotic cells use membranes to increase
surface area to allow bigger cells
Provide compartmentalization for unique
chemical processes.
Generalized
Animal Cell
Generalized
Plant Cell
D. Organelles of Eukaryotic Cells
Organelles:
• compartmentalize a cell’s
activities
• keep reactions isolated from one
another
• increase efficiency in the cell
Organelles synthesize and process proteins
Genes- (instructions for building each protein)
stored in the nucleus.
Connected to nucleus- endomembrane system
(series of compartments formed from highly
folded membranes.
In Rough endoplasmic reticulum (ER)- cell’s
proteins are manufactured.
Other compartments have unique enzymes which
process the synthesized proteins.
Smooth endoplasmic reticulum- lipids are
synthesized and modified, toxins – neutralized.
Golgi apparatus- complete the processing and
sorts proteis for export out of cell or into
lysosomes (digestive enzymes).
Other compartments within the cell provide energy,
contain special enzymes for oxidation reactions, or
store useful molecules.
1. Nucleus (exports RNA
instructions)
•
•
•
surrounded by a double membrane
(nuclear envelope), perforated with
nuclear pores
contains DNA & nucleolus (stores
RNA nucleotides)
functions to separate DNA from
rest of cell
The Endomembrane System
•
a series of compartments made from
folded membrane and connected via
vesicles
endoplasmic reticulum
•
•
•
•
rough
smooth
Golgi apparatus
lysosomes
2. Endoplasmic reticulum (ER)
•
interconnected network of
membranes extending from
nucleus to plasma membrane
Rough ER - studded with ribosomes
• site of protein synthesis (most will be
exported out of the cell)
Free ribosomes in the cytoplasm synthesize
proteins that remain in cell.
Smooth ER - lacks ribosomes
• site of lipid synthesis
• contains enzymes that detoxify
drugs & poisons
3. Golgi apparatus
•
stacks of membrane-enclosed sacs
Functions:
• links simple carbohydrates together
to form starch
• links simple carbohydrates to
proteins (glycoprotein) or lipids
(glycolipid)
•
•
completes folding of proteins
temporarily stores secretions (milk)
Organelle interaction in a mammary
gland cell.
4. Lysosomes (suicide sacs)
•
•
vesicles containing > 40 types of
digestive enzymes
function to recycle damaged organelles, break
down cellular byproducts & destroy invading
microbes
5. Peroxisomes (oxidative
reactions)
vesicles containing several types
of enzymes (produced in cytoplasm)
found in all eukaryotic cells
function to help cell use oxygen &
metabolize potentially toxic
compounds
•
•
•
•
•
hydrogen peroxide is produced as a
by-product of peroxisome activity
the enzyme catalase converts
hydrogen peroxide to water
6. Mitochondria
•
double-membrane
outer is smooth
• inner is highly
folded (cristae)
•
•
•
•
•
#/cell varies
contain DNA
inherited from female parent
site of cellular respiration (production
of ATP)
7. Chloroplasts
•
possess 3 membranes
•
•
•
•
•
•
outer/inner membranes surround stroma
3rd membrane system folded into flattened sacs
(thylakoids)
#/cell varies
contain DNA
found in plants & protists
function in photosynthesis
E. The Endosymbiont Theory
Proposes that chloroplasts and
mitochondria evolved from once
free-living bacteria engulfed by
larger archaea.
Based on fact that mitochondria &
chloroplasts resemble certain
bacteria (size, shape, membrane
structure & method of making proteins).
Summary
Cell theory
Types of cells
Bacteria do not contain organelles
Archaea – unique cells
Eukaryotic cells- compartmentalization for
unique chemical processes.
Organelles- synthesize and process proteins
Nucleus- exports RNA instructions
Nuclear pores- movement of RNA from the
nucleus to the cytoplasm
Ribosomes- manufactured in the nucleolus and
transported to the cytoplasm.
The endomembrane system- site for protein
synthesis and provides mechanisms for protein
processing and packaging.
Rough ER- involved in synthesis
Smooth ER and Golgi apparatus- process proteins
Vesicles- used to package and transport proteins
Lysosomes- packages of digestive enzymesused to recycle cellular components and release
nutrient molecules from ingested products.
Peroxisomes store oxidative enzymes –
breakdown molecules and protect cell.
Mitochondria and chloroplasts- unique
membrane structure
Manipulate energy by manufacturing nutrients
or extracting energy from them.
Contain unique DNA
Questions
1.DNA is found in the ---------- of bacterial cells
2.The interior of the cell minus the nucleus is called --3.Name the organelle essential for protein synthesis.
4.The site of synthesis of ribosomes in the nucleus is
called -----5.Water storing organelle in plant cell is called --6.Which organelle contains the digestive enzymes?
7.Name the enzyme present in peroxisomes.