Transcript Smooth ER - Home - KSU Faculty Member websites

Cell Structure & Function
There are two types of cells:
1. Prokaryotic- cells that DO NOT have a
membrane around their heredity material
2. Eukaryotic- cells with a NUCLEUS , which is
heredity material surrounded by a membrane
• Which is more complicated?
• EUKARYOTIC!
• Examples of Eukaryotes:
• plants, animals, fungi.
• Examples of Prokaryotes:
• Bacteria
Organelles
• There are many small structures located
inside the cell.
• These structures are called organelles (little
organs).
• These organelles perform functions that
keep the cell alive.
• Some organelles are found only in plant
cells, and some only in animal cells.
Name some organelles inside an
animal cell
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Nucleus
Lysosome
Golgi bodies
Mitochondrion
Ribosome
Vacuole
Cytoplasm
Endoplasmic reticulum (ER)
Types of Cells
Cell Types
Eukaryotic Cells
Plant Cells
Prokaryotic Cells
Animal Cells
Animal Cells
Cellular Anatomy
Biochemistry and Evolution
• Prokaryotes - do not have a membranebounded nucleus
• Eukaryotes - possess nucleus and other
complex internal structures
• Prokaryotes and eukaryotes appear to have
evolved from a common ancestor over three
billion years ago
The Cell is the Basic Unit of Life
• Plasma membrane - surrounds aqueous
environment of the cell
• Cytoplasm - all materials enclosed by the
plasma membrane (except the nucleus)
• Cytosol - aqueous portion of the
cytoplasm minus subcellular structures
• Bacteriophage or phage - viruses that
infect prokaryotic cells
Prokaryotic Cells: Structural Features
• Prokaryotes, or bacteria are usually singlecelled organisms
• Prokaryotes lack a nucleus (their DNA is
packed in a nucleoid region of the cytoplasm)
• Escherichia coli (E. coli) - one of the best
studied of all living organisms
• E. coli cells are ~0.5mm diameter, 1.5mm long
Eukaryotic Cells: Structural Features
• Eukaryotes: plants, animals, fungi, protists
• Have a membrane-enclosed nucleus containing
the chromosomes
• Are commonly 1000-fold greater in volume than
prokaryotic cells
• Have an intracellular membrane network that
subdivides the interior of the cell
Eukaryotic cell (animal)
Eukaryotic cell (plant)
NUCLEUS:
• Most functions of the cell are controlled
by the nucleus.
• Functions: “Brain” of the cell.
• It houses and protects the cell’s genetic
information.
The Cell Nucleus
• Why have nuclear
pores at all?
• What materials can
pass through the
nuclear envelope?
What materials are
retained?
• What is in the
nucleolus?
• What molecules are
in chromatin?
Nucleus
• Large round structure located inside
the cytoplasm.
• Contains genetic material (DNA).
• Has a nuclear membrane (semipermeable).
• Contains a Nucleolus (makes
Ribosomes).
• Controls the activity of the cell.
Name 3 parts of the nucleus
• Nuclear membrane
• Chromatin
• nucleolus
nucleolus
Nuclear
membrane
chromatin
Chromatin
questions
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Where is chromatin located?
In the nucleus.
Where is DNA located?
In the chromatin.
What does DNA do?
In controls the activities in the cell.
Note!
• The shape of chromatin changes when a cell
begins to divide.
• When a cell begins to divide the chromatin
coils and takes the form of chromosomes.
Chromosomes
• Long thread-like structures found
in the nucleus of the cell.
• Contain hereditary information.
• Genes are hereditary units made
up of DNA.
Chromosomes
• Nucleolus: dense part of the nucleus.
• Site where DNA is concentrated.
Nuclear Envelope: double layer that covers
the nucleus. Also made of 2 phospholipid
bilayers.
• Nuclear Pores: holes in the nuclear
envelope that allow passageways for
RNA and other things entering and
leaving the nucleus.
DNA structure and replication
Purine (1) is a heterocyclic aromatic organic compound, consisting of a
pyrimidine ring fused to an imidazole ring
(pyrimidine + imidazole)
+
A
G
Aside from DNA and RNA, purines are biochemically significant components in a
number of other important biomolecules, such as ATP, GTP, cyclic AMP, NADH,
and coenzyme A.
They may also function directly as neurotransmitters, acting upon
purinergic receptors. Adenosine, activates adenosine receptors.
Purines are found in high concentration in meat and meat products, especially
internal organs such as liver and kidney. Plant based diet is generally low in purines
Examples of high purine sources include: sweetbreads, anchovies, liver, beef
kidneys, scallops
A moderate amount of purine is also contained in beef, pork, fish and seafood,
asparagus, spinach, mushrooms, green peas, beans, oatmeal, wheat bran and
wheat germ.[4]
Pyrimidine is a heterocyclic aromatic organic compound similar to
benzene containing two nitrogen atoms at positions 1 and 3 of the
six-member ring
benzene
Pyrimidine
cytosine
thymine
uracil
C
T
U
Chromosome structure
Chromosome Oragnisation
What chromosome is made of?
- chromosome is made of chromatin (nucleic acid and
protein( histone).
- when in mitotic and meiotic stages of cell cycle, chromatin
(euchromatin & heterochromatin) stains readily.
Euchromatin is a lightly packed form of chromatin that is rich in gene
concentration
Heterochromatin is a tightly packed form of DNA. Its major characteristic is that
transcription is limited. As such, it is a means to control gene expression, through
regulation of the transcription initiation.
Chromosome Packaging
Chromatin is organised on three basic levels:
- primary (nucloesome)
- secondary (solenoid)
- tertiary/quaternary (final folding into chromosome
shape)
A typical eukaryotic chromosome contians 1 to 20 cm of
DNA. During metaphase of meiosis/mitosis, this DNA is
package into a chromosome with a length of only 1 to 10
mm (a condensation of almost 104-fold in length from the
naked DNA molecule).
Chromosome Packaging
beaded string – nucleosome structure of chromatin
Chromosome Packaging
- nucleosome contains histones (2 of each H2A, H2B, H3
and H4, and one H1)
- the diameter of nucleosome (bead) is 11nm.
- 200 bp of DNA associated with one bead, 23 bp protected by H1
and 8 to 114bp (depends on species and type of cells) form a linker
between beads.
Chromosome Packaging
Second level of chromatin organization:
solenoid
- the nucleosome is supercoiled and
organised into a solenoid structure, with 67 nucleosomes per turn.
- H1 stabilize the structure of solenoid.
- the supercoiling produces a fibre of
approximately 30nm in diameter.
Chromosome Packaging
Higher order folding of
chromatin into
chromosome
Transcription and Translation
Nucleic Acids
• Polynucleotides - nucleic acid biopolymers
are composed of nucleotide monomers
• Nucleotide monomers are composed of:
(1) A five-carbon sugar
(2) A heterocyclic nitrogenous base
(3) Phosphate group(s)
Deoxyribose
• Deoxyribose lacks a hydroxyl group at C-2.
It is the sugar found in DNA.
Nitrogenous bases
• Major Purines:
Adenine (A)
Guanine (G)
• Major Pyrimidines
Cytosine (C)
Thymine (T)
Uracil (U)
Adenosine Triphosphate (ATP)
• Nitrogenous base (adenine), sugar (ribose)
Structure of a dinucleotide
• Residues are
joined by a
phosphodiester
linkage
Short segment of a DNA
molecule
• Two polynucleotides
associate to form a
double helix
• Genetic information is
carried by the sequence
of base pairs
Deoxyribonucleic Acid (DNA)
• The ‘blueprint of life”
• Unique and unrepeatable
• Located in genes
 Genes make up chromosomes
 Chromosomes in the nucleus of the cell
• DNA composed of units called
nucleotides
 Each nucleotide is made up of a sugar,
phosphate, and hydrogen base.
• Double Helix model of Watson and Crick
• X ray photos by Rosalind Franklin
• Sides of ladder (S-P) with covalent
bonds
• Sugar: deoxyribose
• Steps of ladder (bases)
• Complementary Base Pairs
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Purines (Adenine/Guanine)
Pyrimidines (Cytosine/Thymine)
A-T (2 hydrogen bonds)
C-G (3 hydrogen bonds)
The Race for the DNA Model
King’s College
London
Cavendish Lab
London
Rosalind Franklin
James Watson
Francis Crick
(X ray Diffraction Studies)
Photo
#51
Maurice Wilkins
Nobel Prize
1962
(Double Helix Model)
• Mutation: a mistake in nitrogen base pairs
• Pattern of bases codes for a specific amino acid
• Codon: 3 letter (bases) code for 1 amino acid
• Replication of DNA (Making an identical
copy)
 DNA unzips and hydrogen bases separate (action of DNA
polymerase)
 Free-floating nucleotides match up on each side
 Hydrogen bonds reform
 Result: 2 identical DNA molecules (Each contain 1 of the
original DNA strands)
 Semi-Conservative Model of Replication
• Each DNA molecule with a
new strand and an old
strand
• DNA never leaves the
nucleus
Ribonucleic Acid (RNA)
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Made up of nucleotides
Sugar called ribose
Nitrogen Bases: A, C,G,U
Single-stranded
Located in the nucleus and in the ribosomes
3 Types:
 Messenger RNA (mRNA); carries message of DNA to ribosomes (3 letter
code – codon); single strand of letters
 Transfer RNA (tRNA): reads the mRNA code at the ribosomes (3 letter
code – anticodon); carries an amino acid; shamrock shape
 Ribosomal RNA (rRNA): joins mRNA to tRNA
Transcription
• Making of mRNA from one
side of DNA in nucleus
 DNA polymerase unzips DNA
 Hydrogen bonds break and energy is
released
 One side of DNA acts as a
“template” (model) for making
mRNA
 Free-floating nucleotides line up and
form mRNA
 DNA reforms
 mRNA carries the message of DNA
to ribosomes
Translation
• Occurs at the ribosomes
• Anticodon of tRNA joins with
codon of mRNA (rRNA helps)
• Amino acid pops off end of
tRNA
• Amino acids string together to
form a protein (Protein
Synthesis)
Endoplasmic reticulum (ER)
• cytoplasmic channels from the cell membrane
to the nuclear membrane
• associated with the storage, synthesis, and
transport of materials within the cell
• “HIGHWAY” for cell transport
Endoplasmic Reticulum
• What are the two
types of ER?
• How does the role
of each type
differ?
• What kind of cells
would have a lot
of rough ER?
Smooth ER?
Endoplasmic Reticulum
• A system of channels within the
cytoplasm, that transports
materials.
• Smooth E.R. has no ribosomes on
it.
• Rough E.R. has ribosomes.
– 2 Types:
1.Rough ER:
– Rough appearance because it has
ribosomes
– Function: helps make proteins, that’s why
it has ribosomes
2.Smooth ER:
– NO ribosomes
– Function: makes fats or lipids
The endomembrane system regulates protein traffic and performs
metabolic functions in the cell
Endoplasmic reticulum
Smooth v. Rough
Smooth ER
Nuclear
envelope
Rough ER
Smooth ER
•lacks ribosomes
•Involved in synthesis of
lipids, metabolism of
carbohydrates, and
detoxification of poisons
ER lumen
200 nm
Rough ER
Smooth ER
Rough ER
•Has attached ribosomes
•Makes proteins and
phospholipids
The endomembrane system regulates protein traffic and
performs metabolic functions in the cell
Endoplasmic reticulum
Smooth v. Rough
Smooth ER
Nuclear
envelope
Rough ER
Smooth ER
•lacks
ribosomes
Transport
vesicles-transport materials from the ER to the Golgi
•Involved in synthesis of lipids,
ER lumen
metabolism of carbohydrates,
and detoxification of poisons
200 nm
Rough ER
•Has attached ribosomes
•Makes proteins and
phospholipids
Rough ER
Smooth ER
Endoplasmic Reticulum (ER)
• A system of membranes
that is found in a cell’s
cytoplasm
• Assists in the production,
processing, and transport
of proteins
• Assists in the production
of lipids
The ER
• Rough ER
• Part of the ER with
ribosomes attached
• Where proteins are
made and released by
a vesicle
The ER
• Smooth ER
• Part of the ER that
lacks ribosomes
Endoplasmic Reticulum (ER)
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Network of fluid filled tubules (cisternae)
Roughly ½ of eukaryotic membrane tissue
Continuous with the nuclear envelope
Smooth ER = lacks ribsosomes
Rough ER = ribosomes bound to
cytoplasmic side of ER membrane
Structure of the ER
The Smooth ER
• Synthesis of lipids, steroids (ie: sex hormones)
• Carb metabolism (ie: liver cells hydrolysis
glycogen into glucose utilizes enzymes in
smooth ER)
• Detoxification of drugs/poisons (ie: smooth ER
enzymes make drugs more soluble add –
OH). Tolerance = more Smooth ER
• Involved in Ca ion movement during muscle
contraction.
Functions of Rough ER
• Attached ribosomes = protein synthesis
• Abundant in cells that make proteins
• Manufactured proteins are “threaded”
through pore into the cisternal space of ER.
• Glycoproteins – covalently bonded to carb.
• Secretory proteins are packaged into
transport vescicles and sent to various
locations in the cell.
Rough ER
• Also manufactures phospholipids from
precursors in cytoplasm.
• Assembles phospholipids and proteins
into new membrane sections.
• ER membrane can expand or transfer
new membrane via vescicles to other
parts of endomembrane system.
MITOCHONDRION:
 tiny, double-membrane organelles that
transfer ENERGY from organic molecules to
ATP.
 ATP powers most of the cell’s chemical
reactions.
 Found in large amounts in muscle cells and
cells requiring ENERGY.
 Function: Powerhouse of the cell.
Mitochondria
• The “powerhouse” of the cell.
• Food molecules are broken down and
energy is released.
• Functions in Cellular Respiration.
The Citric Acid
(Krebs) Cycle
consists of eight
steps
TCA Cycle Control
• Citrate Synthase (Synthetase)
– Condensing Enzyme
– Inhibited By:
• ATP
• NADH
• Succinyl CoA
TCA Cycle Control-Cont:
• Isocitrate Dehydrogenase
– Activated By:
• ADP
– Inhibited By:
• ATP
• NADH
TCA Cycle Control-Cont:
• α-Ketoglutarate Dehydrogenase
– Inhibited by:
• Succinyl CoA
• NADH
• ATP
– Contains tightly bound Tpp, lipoamide, FAD
– Similar to PDH complex
• E3 subunit the same
TCA Cycle Control-Cont:
• Succinyl CoA Synthetase
– Coupled reaction with GTP
– Enzyme that catalyses coupled reaction is called
Nucleotidediphosphate Kinase
TCA Cycle Control-Cont:
• Succinate Dehydrogenase
– Has Iron-Sulfur Centers
– Covalently Bound with FAD
• Name 2 parts of mitochondria:
• Outer membrane and folded inner membrane
• What types of cells you expect to have more
mitochondria? why
• More active cells like muscle cells because
they need more energy.
Mitochondrion
• How many
membranes? Why?
• What cells would
have high numbers
of mitochondria?
• What do mito. have
to do with cloning?
• What is the current
theory on mito.
origin?
What are mitochondria?
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An intracellular organelle.
There are 100 to 1000s of mitochondria/cell.
All mitochondria come from the mother.
Mitochondria have their own DNA.
Found in all cell types, except the RBC.
Major functions of mitochondria:
– Makes energy in the form of ATP.
– Programmed cell death (apoptosis).
Chemical Energy
Cars
Cells
Gasoline
ATP
Fate of Ingested Food
Intermediary Energy Metabolism
Fats
Proteins
Glucose
Glycolysis
TCA Cycle
ETC
b-oxidation
TCA Cycle
ETC
ATP Pool
Deamination
TCA Cycle
ETC
Why is energy so important?
• Role of ATP (energy)
– Mechanical Work
• Muscle contraction
– Chemical Work
• Na+/K+ Ion Pump
– Synthetic Work [Anabolism]
• Macromolecules
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Nucleic Acids
Proteins
Lipids
Complex carbohydrates
Bioenergetics: Energy
• 1 teaspoon of sugar weighs 5 gm and contains 20
calories of energy
• 1 teaspoon of sugar contains 10 X 1021 molecules of
sugar or sucrose
– 10,000,000,000,000,000,000,000 molecules
• 1 teaspoon of sugar forms about 3.6 X 1023
molecules of ATP
– 360,000,000,000,000,000,000,000 molecules
Bioenergetics: Energy
• At rest, the average adult male will need 3.0 x
1018 molecules of ATP per second for normal
organ functioning.
• The body produces and makes approximately
70 Kg of ATP daily (average adult male).
• The brain uses approximately 70% of all ATP
produced.
Bioenergetics
Bioenergetics
Bioenergetics: Summary
• Mitochondria function is to produce ATP for energy.
• The mitochondria use electrons and protons from
metabolism and molecular oxygen to reduce water
and generate proton-motive force to produce ATP
from ADP: oxidative phosphorylation.
• When this process is dysfunctional, then disease can
occur.
• Bottomline: mitochondrial cytopathies are diseases
of energy production.
Bioenergetics: Summary
• What happens when an organ does not get
enough ATP or energy?
– Brain dysfunction: when the brain doesn’t get it’s
70% of energy required:
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Seizure
Mental Retardation
Cognitive dysfunctions
Psychological dysfunctions?
Lysosomes
• How many
membranes?
• Where are lysosomes
formed?
• Contain what?
• Describe the internal
environment of a
lysosome.
• List three major
functions.
• What is the
relationship between
Tay Sachs disease
and lysosomes?
Lysosomes
• Internal sacs bound by single membrane
• Originate by budding from Golgi based on sorting
of mannose-6-phosphate “tags” on proteins
• Responsible for degrading cell components that
have become obsolete for cell or organism—
digestive sys of cells
• Internal pH about 5 (very acidic)
• Compartmentalization ESSENTIAL! Failure can
lead to many known disease states that result
from waste accumulation in the organelle
Lysosomes
• contain a mixture of some 40 types of
digestive enzymes, all with optimum activity
at about pH 5
• this acid pH is maintained in lysosomes, as in
endosomes, by proton pumps in the
membrane
• membrane of the lysosome is resistant to
action of its own digestive enzymes due to the
extensive glycosylation of the proteins on the
lumenal side of the membrane.
• A lysosome is a membranous sac of hydrolytic
enzymes that can digest macromolecules
• Lysosomal enzymes can hydrolyze proteins,
fats, polysaccharides, and nucleic acids
Endocytosis/Exocytosis
• Some types of cell can engulf another cell by
phagocytosis; this forms a food vacuole
– pinocytosis; exocytosis
• A lysosome fuses with the food vacuole and digests
the molecules
• Lysosomes also use enzymes to recycle the cell’s own
organelles and macromolecules, a process called
autophagy
Fig. 6-14a
Nucleus
1 µm
Lysosome
Lysosome
Digestive
enzymes
Plasma
membrane
Digestion
Food vacuole
(a) Phagocytosis
Fig. 6-14b
Vesicle containing
two damaged organelles
1 µm
Mitochondrion
fragment
Peroxisome
fragment
Lysosome
Peroxisome
Vesicle
(b) Autophagy
Mitochondrion
Digestion
Peroxisome
• How do the enzymes
in peroxisomes differ
from the enzymes in
lysosomes?
• What cells have many
peroxisomes? Why?
• Plants have special
peroxisomes called
glyoxysomes. What is
their function?
Major Metabolic Functions of the
Peroxisome in Plants
1.
2.
3.
4.
5.
b-oxidation of fatty acids
Glyoxylate cycle
Photorespiration (Glycolate pathway)
Degradation of purines
Decomposition of hydrogen peroxide
Two Types of Peroxisomes in Plants
• Leaves
– Catalyzes oxidation of side product of CO2 fixation
in photorespiration
• Germinating seeds
– Converts fatty acid in seed lipids into sugars
needed for growth in the young plant
b-oxidation occurs in mitochondria
and peroxisomes in mammals, but
exclusively in the peroxisome in
plants and yeast.
Glyoxysomes and Leaf Peroxisomes are
Interconverted During Development
• Immunogold particles of
2 sizes bound to:
– Enzymes of glyoxylate
cycle
– Peroxisomal enzymes
• The same population of
peroxisomes assumes
different metabolic roles
depending on
developmental stage of
cotelydon
Greening cotelydons
Photorespiration and Glycolate
Oxygenase activity of rubisco
Consumption of O2
Glycolate cycle
Production of CO2
Involves 3 organelles (chloroplasts, peroxisomes, & mitochondria)
The Glycolate Cycle
Glycolic acid
oxidase
H2O2 production
The Glycolate Cycle
Purine Degradation
• Nucleic acid purine moieties (adenine and
guanine) are degraded to uric acid
O2
xanthine
H2O2
O2
H2O2
uric acid
Xanthine oxidase
allantoin
Urate oxidase
Urate Oxidase
• High urate oxidase
concentrations
contribute to formation
of crystalline inclusions
• All purine degradation
leads to uric acid
H2O2
O
purines
N
H N
H C
FAD
O2
C
hypoxanthine
H2 O
xanthine
oxidase
O
FAD
N
H N
N
H
O
FADH2
C H
N
H2O2
O2
N
H
H
xanthine
C
H2O
xanthine
oxidase
O
H
N
H N
C H
N
O
FADH2
C O
N
N
H
H
uric acid
Oxidases
• The oxidases use molecular oxygen to remove
hydrogen atoms from specific organic substrates
• A variety of compounds, including L-amino acids,
D-amino acids, polyamines, methanol, urate,
xanthine, and very-long-chain fatty acids, serve as
substrates for the different oxidases
Peroxide Detoxification
Oxidases use O2 to oxidize organic substances and
produce hydrogen peroxide (H2O2)
-- e.g., H2O2 generated by glycolate oxidase reaction,
b-oxidation of fatty acids
Peroxisomes also contain catalase, the enzyme that
degrades H2O2.
Importance of H2O2 degradation
• 2H2O2 catalase
2H2O + O2
• Peroxisomes contain a high concentration of
catalase, a heme protein
H - - O - - O - -H
HO-
-OH (?)
• Other reactive oxygen species (ROS) are
formed in peroxisomes
Reactive Oxygen Species
1e-
1eO2
O-2
1eH2 O2
1eOH- + ·OH
H2 O
.. .
.. . .• .. ..
..
.. - ..
 O : H H : O :H
:
:
:
:
:
:
:
•
:O
:
:
:
+
O
O
O
H
O
O
H
H
O
•..
. ..
..
. ..
..• ..
..
Superoxide anion
(radical)
Hydrogen
peroxide
Hydroxyl radical
• Cause damage to lipids, proteins, DNA
• Amount ROS is reduced by catalase, and superoxide
dismutase (SOD) 2O2O2 + H2O2
Radical Chemistry
Initiation:
RH + O2 -->R· + ·OH
Propagation:
Termination:
R· + O2 --> · + ROO·
R· + R· --> RR
ROO· + RH --> R· + ROOH
R· + ROO·--> ROOR
ROOH--> RO· + HO·
ROO· + ROO· -->
ROOR + O2
Other Peroxisomal Enzymes
Conclusions
• Compartmentalize! To protect the cell from these
destructive byproducts, such reactions are
segregated.
Ribosomes
• Non-membrane bound!
• Composed of ______ and
________.
• Sites to synthesize
__________.
• How are prokaryotic
ribosomes different from
eukaryotic ribosomes?
• Antibiotics, including
tetracycline and
streptomycin, paralyze
prokaryotic ribosomes.
Why don’t these drugs
harm eukaryotic
ribosomes?