Download Lecture 7: Intro to the cell, cont

A Tour of the Cell, cont…
Last Time: The Nucleus and the
Endomembrane System
Today: Other Organelles and the
Cytoskeleton
Cells need energy to work
Sunlight 

glucose
phot osynthesis
Glucose 

ATP
cell respiration
ATP 

ADP + energy
hydrol ysi s
Figure 6.8 The structure and hydrolysis of ATP
Chloroplasts in plant cells convert
sunlight into chemical energy that will
be used to make ATP
ATP is manufactured through cellular respiration
that takes place in the mitochondria
Peroxisomes
H 2  O 2  H2 O2
H 2O 2  H 2  2H 2O
The cytoskeleton
3 types of cytoskeletal structures
Microfilaments
Protein
subunits
Structure
Actin
Keratin, others
Two intertwined
strands
7 nm
Actin subunit
Functions
Intermediate
filaments
Fibers wound into
thick cables
10 nm
Keratin subunits
a-tubulin and btubulin dimers
Hollow tube
25 nm
Tubulin dimer
• maintain cell shape by
resisting compression
• motility via
flagella/cilia
• anchor nucleus
• move organelles
and some other
organelles
• move chromosomes
during cell division
• maintain cell shape by
resisting tension
• motility via pseudopodia
• muscle contraction
• cell division
in animals
Microtubules
Motor molecules like kinesin, myosin, and
dynein work with the cytoskeleton to produce
movement
Structure of kinesin
Tail
Stalk
Head
Kinesin "walks" along a microtubule track
Transport
vesicle
ATP
Kinesin
Microtubule
ADP+Pi
ATP
ADP+Pi
Microfilaments and Intermediate Filaments
Networks of filaments
near the plasma
membrane help to
maintain a cell’s shape
Microfilaments aid in motility
Centrosome containing a pair of centrioles
Microtubules often
grow out from the
region called the
centrosome
Cilia and Flagella move the entire cell
Cilia
Flagella
Cilia and Flagella have a “9 +2”
arrangement of microtubule doublets
TEM of flagella
Cell
membrane
Central
pair
Outer
doublet
Dynein
Microtu
bule
doublet
Spoke
The motor protein Dynein “walks” along the
microtubules within the flagella on one side,
causing bending
Figure 7.23 A comparison of the beating of flagella and cilia
Plant cells are surrounded by cell walls
made of cellulose
Plasmodesmata connect adjacent plant cells
Animal cells are connected through
Intercellular junctions
Review of an animal cell
(centrioles)
Review of a plant cell