Download cytoplasm

Bell Ringer
• Obtain a pencil and a blank sheet of loose-leaf
paper.
• Clear off your desk
Exam
•
•
•
•
100 Points
60 minutes
50 MC
3 short answer
Objective
• Identify the internal and external structures of a
prokaryotic cell and define the function of each.
Chapter 3
Cell Structure
and Function
© 2012 Pearson Education Inc.
Lecture prepared by Mindy Miller-Kittrell
North Carolina State University
Bacterial Cytoplasmic Membranes
• Structure
– Phospholipid bilayer
– Composed of lipids and associated proteins
– Integral and peripheral proteins
– Head is hydrophilic, tail is hydrophobic
– Fluid mosaic model
– Proteins and lipids flow laterally within membrane
© 2012 Pearson Education Inc.
Figure 3.16 The structure of a prokaryotic cytoplasmic membrane: a phospholipid bilayer
Head, which
contains phosphate
(hydrophilic)
Phospholipid
Tail
(hydrophobic)
Integral
proteins
Cytoplasm
Integral
protein
Phospholipid
bilayer
Peripheral protein
Integral protein
Bacterial Cytoplasmic Membranes
• Function
–
–
–
–
–
Energy storage
Selectively permeable
Naturally impermeable to most substances
Proteins allow substances to cross membrane
Maintain concentration and electrical gradient
© 2012 Pearson Education Inc.
Figure 3.17 Electrical potential of a cytoplasmic membrane
Cell exterior (extracellular fluid)
Cytoplasmic membrane
Integral
protein
Protein
DNA
Protein
Cell interior (cytoplasm)
Bacterial Cytoplasmic Membranes
• Function
– Passive processes- No energy expanded!
– Due to electrochemical gradient
– 1) Diffusion – movement of chemical down
concentration gradient
– 2) Facilitated diffusion – protein channels that
allow certain molecules through membrane
– 3) Osmosis – movement of water through a
selectively permeable membrane from low to high
concentration
© 2012 Pearson Education Inc.
Figure 3.18 Passive processes of movement across a cytoplasmic membrane-overview
Extracellular fluid
Cytoplasm
Diffusion
through the
phospholipid
bilayer
Facilitated
diffusion
through a
nonspecific
channel
protein
Facilitated diffusion
Osmosis,
through a permease
specific for one chemical;
binding of substrate
causes shape change in
the channel protein
the diffusion of
water through a
specific channel
protein or through
the phospholipid
bilayer
Figure 3.19 Osmosis, the diffusion of water across a selectively permeable membrane-overview
Solutes
Semipermeable
membrane allows
movement of H2O,
but not of solutes
Figure 3.20 Effects of isotonic, hypertonic, and hypotonic solutions on cells-overview
Cells without a wall
(e.g., mycoplasmas,
animal cells)
H2O
H2O
H2O
Cell wall
Cells with a wall
(e.g., plants, fungal
and bacterial cells)
Cell wall
H2O
H2O
Cell membrane
Isotonic solution
H2O
Cell membrane
Hypertonic solution
Hypotonic solution
A bacterial cell, which has a cytoplasmic
solute concentration equal to 0.85% NaCl, is
placed into a tube containing a solution that
has a NaCl concentration of 0.2%. Into what
type of solution has the cell been placed?
a. hypotonic
b. isotonic
c. pyrotonic
d. hypertonic
Bell Ringer
• What is the purpose of heat-fixing when making a
smear?
Finish Simple Staining Lab
• Turn in extra credit
• I will collect worksheets in 15 minutes
Objective
• Identify the internal and external structures of
prokaryotic and eukaryotic cells and define the
function of each.
– By doing this, students understand how antibiotics
take advantage of difference between human cells
and bacteria cells.
• Quiz
– 15 points
– 16 Questions
Figure 3.17 Electrical potential of a cytoplasmic membrane
Cell exterior (extracellular fluid)
Cytoplasmic membrane
Integral
protein
Protein
DNA
Protein
Cell interior (cytoplasm)
Bacterial Cytoplasmic Membranes
• Function
– A) Active Transport– Require energy!
– Move against electrochemical gradient
– 1) Uniport – One substance transported
– 2) Antiport – Two molecules transported in
opposite directions
– 3) Symports – Two molecules transported in same
direction
– 4) Coupled transport – one chemicals
electrochemical gradient provides the energy to
transport a second chemical
© 2012 Pearson Education Inc.
Figure 3.21 Mechanisms of active transport-overview
Extracellular fluid
Uniport
Cytoplasmic
membrane
Symport
Cytoplasm
Uniport
Antiport
Coupled transport:
uniport and symport
Transport Review
• https://www.youtube.com/watch?v=svAAiKsJa-Y
Bacterial Cytoplasmic Membranes
• Function
– B) Group translocation – Require energy!
– Substance chemically modified during transport
– Membrane is then impermeable to altered molecule
© 2012 Pearson Education Inc.
Figure 3.22 Group translocation
Glucose
Extracellular
fluid
Cytoplasm
Glucose 6-PO4
A cell may allow a large or charged chemical
to move across the cytoplasmic membrane,
down the chemical’s electrical and chemical
gradients, in a process called
a. active transport.
b. facilitated diffusion.
c. endocytosis.
d. pinocytosis.
Cytoplasm of Bacteria
• Cytosol – Liquid portion of cytoplasm
– Contain ions, organic molecules, and nucleoid in
prokaryotes
• Inclusions – May include reserve deposits of
chemicals
• Endospores –defensive strategy against
unfavorable conditions
– Bacillus and Clostridium species
– Survive boiling water, alcohols, bleach, UV
radiation
© 2012 Pearson Education Inc.
Figure 3.24 The formation of an endospore-overview
Cell wall
Cytoplasmic
membrane
DNA is replicated.
DNA
A cortex of calcium and
dipicolinic acid is
deposited between
the membranes.
Cortex
Vegetative cell
Spore coat forms
around endospore.
DNA aligns along
the cell’s long axis.
Cytoplasmic membrane
invaginates to form
forespore.
Forespore
Endospore matures:
completion of spore coat
and increase in resistance
to heat and chemicals by
unknown process.
Endospore is released from
original cell.
Cytoplasmic membrane
grows and engulfs
forespore within a
second membrane.
Vegetative cell’s DNA
disintegrates.
First
membrane
Second
membrane
Spore coat
Outer
spore coat
Endospore
Outer
spore coat
Cytoplasm of Bacteria
• Nonmembranous Organelles
– Ribosomes
– Sites of protein synthesis
– 70S compared to 80S in eukaryotic cells
– Cytoskeleton
– Plays a role in forming the cell’s basic shape
© 2012 Pearson Education Inc.
Practice
• Worksheet
Antibiotics
• Most antibacterial drugs disrupt or destroy
prokaryotic cellular processes that are different
from eukaryotic ones.
– In what ways are bacterial cells different from
human cells?
– 1) Cell wall: peptidoglycan & LPS
– 2) Ribosomes: Bacteria have a 70s structure,
eukaryotic cells have a 80s structure
– 3) Cellular appendages: Fimbriae and pili only
found in bacteria
Antibiotics
• Inhibit cell wall synthesis
– Stop NAG and NAM subunits from binding
• Inhibit protein synthesis
– Prevent protein synthesis at either 30s or 50s
subunit
• Inhibit Nucleic Acid Synthesis
– Prevent transcription
• Antimetabolite
– Stop folic acid synthesis