Download A Tour of the Cell

A Tour of the Cell
Chapter 6

Objectives
 Distinguish
between a prokaryotic and eukaryotic
cell
 Describe the unique structures of a prokaryotic cell
 Describe the structural differences between plant
and animal cells
 Describe the complex structural and functional
interconnections among the organelles of the
endomembrane system
 Describe the structure of the eukaryotic nucleus,
mitochondrion and chloroplast
 Describe
the surface structures of the cell that
provide support, protection, and movement in, and
communication with, the extracellular environment
Introduction

Cell is smallest functional unit of life
 cell
theory:
• all organisms composed of cells
• all existing cells arise from pre-existing cells

Common characteristics of all cells:
 cell
contents surrounded by plasma membrane
 cytoplasm consists of semifluid matrix
 organelles are embedded in cytoplasm
 contain genes in the form of DNA
Fundamental Features of Life

Features of cells are characteristic of life
 cells
are highly structured
 cell structure and function are related
 cell membranes separate the cell from the
external environment
 each cell has DNA as the genetic material
 each cell carries out metabolism
Cell Organization
Two types of cells-prokaryotic and
eukaryotic
 Prokaryotic:

 small
 lacks
nucleus; DNA in nucleoid region
 cytoplasm surrounded by plasma membrane
and outer cell wall
 flagella and pili may be present
Cell Organization

Eukaryotic
 Larger
than prokaryotic cells
 complex internal structure with membranous and nonmembranous organelles
Membranous
components: nucleus, endoplasmic
reticulum, Golgi apparatus,mitochondria,
lysosomes and peroxisomes
Non-membranous
components: ribosomes,
microtubules, centrioles, flagella and cytoskeleton
Plant vs. Animal Cells
 Animal
 Plant
cells surrounded by plasma membrane only
cells surrounded by plasma membrane and rigid
cell wall; also have central vacuole and chloroplasts
Eukaryotic Cell Organization

Eukaryotic organelles form four functional groups:
 manufacture
 breakdown
 energy
processing
 support, movement and communication
Manufacturing

Nucleus is cell’s genetic control center
 surrounded
by double membrane
 contains
pores to allow passage of material between nucleus
and cytoplasm
 DNA
normally present as strands of chromatin
 During
cell division, chromatin coils up to form
chromosomes
 Nucleolus-organelle
within nucleus-responsible for
ribosomal RNA synthesis
Endomembrane system

Collection of membranes either inside or
surrounding the eukaryotic cell, related through
direct physical contact or by transfer of vesicles
Endomembrane system

Endomembrane system: RER and SER
 Rough
endoplasmic reticulum contains ribosomes;
protein synthesis ( RER)
 Smooth
endoplasmic reticulum synthesizes lipids,
processes materials, acts as storage and detoxifies
substances (SER)
Golgi

Golgi apparatus recieves products from ER

Chemically modifies the products sent to it

Puts “Zip Codes” on products so they know where
to go in the cell

Puts these modified products in vesicles and sends
them out
Golgi

The Golgi Apparatus is the “UPS” of the cell

Its recieves, warehouses, sorts, modifies, packs and
reships substances
Lysosomes

Lysosomes contain enzymes to digest substances
and wastes; defective lysosomes cause fatal diseases

Lysosomes help your cells recycle materials: Each
Liver cell recycles half of its synthesized
macromolecules per week

Whey else do they do?
Vacuoles

Vacuoles function in general cell maintenance

In plants they can hold organic substances

In protists vacuoles can hold food or water, or
act as pumps
Energy Processing

Mitochondria:
 found
in all eukaryotic cells, except anaerobic
protozoans
 surrounded by double membrane
 site of cellular respiration
 Prokaryotes don’t have them… What do they do??
 Inner and outer membrane
 Matrix and Cristae
Chloroplasts

Chloroplasts:
 found
in plants and algae
 convert solar energy to chemical energy
 Surrounded by double membrane
 site of photosynthesis
 More
on these organelles in Ch 10
Peroxisomes
 What
is the function of Peroxisomes?
 Read
all about them in your book
 What
is the difference between the terms
detoxification and degredation???
Support, Movement, and Communication

Internal cell skeleton-cytoskeleton
 composed
of 3D meshwork of proteins
 rods of globular proteins-microfilaments
 ropelike
strands of fibrous proteins-intermediate filaments
 hollow tubes of globular proteins-microtubules
 microtubules
provide anchors for organelles, act as
conveyor belts and form cilia and flagella

Cilia and flagella
 function
to move whole cell
 structure consists of 9 microtubule doublets
arranged around central pair (9+2)

Movement of cilia and flagella occurs when
arms consisting of the protein dynein move
the microtubule doublets past each other
Microfilaments cause contraction of muscle
cells
 They also function in ameboid movement,
cytoplasmic streaming and support for
cellular projections

Centrioles

Centrioles, located adjacent to the nucleus,
anchor and organize the microtubules that
form the spindle during cell division
Eukaryotic Cell Organization

Cell surfaces
 protect,
support and join cells
 in plants, neighboring cells joined to form
interconnected and coordinated group
 cell
walls multi-layered, composed of mixtures of
polysaccharides and proteins
 plasmodesmata-channels through cell walls connecting
cytoplasm of adjacent cells- plants
Extracellular Matrix
 in
multi-cellular animals cells often surrounded by
sticky mixture of polysaccharides and proteins
 Extends
 Lots
outward from the cell membrane
of collagen is found there……
Eukaryotic Cell Organization

Several type of junctions between cells:
 tight
junctions: leak proof; block movement of
substances
 anchoring
junctions- join cells and provide structural
support; like the rivets in your blue jeans
 communicating
junctions ( gap junctions)-provide
channels between cells; allow rapid transport of
materials