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Unformatted text preview: Cell Theory Cell
Metabolism • The cell is the basic
unit of life
• All living organisms
are made of cells
• All cells arise from
cells The basics of life What does a cell need?
• Selective isolation from environment
• Energy (ATP)
• Instructions (DNA)
• Machinery to carry out instructions and
regulate processes (proteins)
• Compartmentalization of incompatible or
specialized activities (organelles) Smaller cells have more total surface area
• Increased surface area makes it easier for nutrients to
enter a cell Types of Cells a) Prokaryotic — Bacteria
• No organelles
b) Eukaryotic — Plant
• Organelles present, including chloroplasts
• Cell wall outside of plasma membrane
c) Eukaryotic — Animal
• Organelles present, but no chloroplasts nor
d) Eukaryotic — Protists & Fungi
• Organelles present
• Cell types variations of plant/animal models Cells & Metabolism Phospholipid Bilayer
& Plasma Membranes Isolated activity compartments • Cell’s plasma membrane is its boundary. • Phospho-lipid bilayer forms the essential
backbone of cellular membranes. • Cell membrane
• Organelle membranes Cell & organelle membranes Plasma Membrane
Proteins Cell & organelle membranes • Lipid bilayer has proteins embedded in it. Passive & Active Transport Plasma Membrane
& Homeostasis Hormonal System
Controls Cell Activity Immune
System Cells & Metabolism Bulk Transport:
Endo- and Exocytosis Active Transport
• Transport against conc. gradient.
• Proteins are pumps & use ATP Active Transport (Requires energy) Food V acuole (endocytosis ) Cells Eat and Spit Out:
Endo- and Exocytosis
Paramecium ( endocytosis ) Cytoplasm
• Fills cell; contains
– fluids and more
– membrane-bound organelles
• working as do our organs
• carry out cell function. – cytoskeleton
• maintain and alter cell shape
• hold and move organelles, etc. White blood cell Nucleus
• Contains DNA of
• Controls cell
– function • Blueprints for new cells Mitochondria
• Powerhouse of cell
• Converts chemical energy
from catabolism into ATP:
• Have own DNA to maintain
activity when nucleus is
unavailable Cells & Metabolism Disassembly of Proteins &
Assembly of Amino Acids Organisms & Energy •Dietary polymers are not directly assimilated!
•Polymers hydrolyzed into monomers — monomers
absorbed — monomers condensed into new polymers. Molecular motors:
cilia & flagella Using Mitochondrial Energy:
Flagella and Cilia
• Cilia are numerous & short
• Flagella are few & long
• Few cells in our body are flagellated:
ciliated cells are more common. Fig. 4.19 Cell Metabolism Organisms & Energy
• Big animals use more energy than smaller do
- but their metabolic rate is lower. – catabolism: energy producing breaking down
of foods, and
– anabolism: energy-requiring synthesis of
compounds. • Heart rate is inversely related to body size.
Metabolic Rate Elephant = 30
Human = 70
Cat = 125
Mouse = 400
Shrew = 800
Body Mass • Metabolism: sum of cell's chemical
reactions, composed of Cells & Metabolism Enzymes
• They’re proteins.
• Catalyze (speed up) rates
– Some maybe 1,000,000x
faster! • Vital to metabolism.
– Regulate pathways. • Activity depends on
• May need vitamins
minerals (cofactors) to
function. Metabolic Pathways Sequence of enzymatic reactions that begins with
initial substrate, progresses through intermediates
and ends with a final product. Naming of Enzymes
• Enzyme name ends with suffix “-ase.”
• Name = substrate – action – “-ase”
– E.g., glucose phosphory lase is an enzyme that adds a
phosphate to glucose.
– If the “action ” is left out of the name, assume the action is
hydrolysis. E.g., a protease catalyzes the hydrolysis of
proteins into oligopeptides or amino acids. Different organs may make different enzymes
(isoenzymes) that have the same activity.
– Differences in structure do not affect the active sites. Branched Pathways • End-Product Inhibition.
• One of the final products in a divergent pathway inhibits
the activity of the branch-point enzyme.
– Prevents final product accumulation.
– Results in shift to product in alternate pathway. Inborn Errors of Metabolism • Inherited defect in a gene for enzyme synthesis.
• Quantity of intermediates formed prior to the defect
• Final product formed after the defect decreases, producing
a deficiency. Inborn Errors of Metabolism
Example: phenylalanine metabolism • Defective enzyme1 È phenylyketonuria [PKU]
• Defective enzyme5 È alcaptonuria
• Defective enzyme6 È albino Coupled Reactions: Bioenergetics
• Energy transfer from one molecule to another
couples chemical reactions
• Exergonic reaction: reaction releases energy
• Endergonic reaction: reaction requires energy
• Coupled bioenergetic reactions: the energy released
by the exergonic reaction is used to power the
endergonic reaction. Cellular Respiration: ATP is the
cell’s rechargable battery
• Breaking down complex glucose molecule
• That energy is used to convert ADP into
ATP. ADP + P + energy —› ATP
• Energy is released as ATP breaks down into
ADP and AMP.
ATP —› energy + ADP + P Why Make ATP? Cellular Metabolism
• Cellular Respiration provides ATP
• Cellular “Work” requires ATP • Universal energy source for the cell.
• Many different fuels can be used by power plants to make one kind of
electricity to power all the appliances in your home.
• Many different fuel types may be used by the cell to make one
rechargeable energy molecule (ATP) to power all the endergonic
reactions of the cell. ATP drives cellular processes
Coupled Reactions: ATP • The three types of cellular work a re powered by the hydrolysis of ATP
P i P Motor protein
(a) Protein moved Mechanical work : ATP phosphorylates motor proteins Membrane
protein ADP + ATP P P Solute
(b ) i Solute transported Transport work : ATP phosphorylates transport proteins
P Glu + NH 3 Reactants: Glutamic acid
(c) P NH 2 Glu + P i Product (glutamine)
made Chemical work : ATP phosphorylates key reactants i Coupled Pathways: Bioenergetics
• Energy transfer from one metabolic pathway
to another by means of ATP.
• Catabolic pathway (catabolism): breaking down of
macromolecules. Releases energy which may be used
to produce ATP.
• Anabolic pathway (anabolism): building up of
macromolecules. Requires energy from ATP.
• Metabolism: the balance of catabolism and
anabolism in the body. Energy Organelles
• chloroplasts for
• mitochondria for
Fig. 4.14a — Plant cell Animal cells rely upon chemical energy
produced by plants Photosynthesis In the chloroplast… Fig. 6.18 Cellular Respiration (making ATP) • “OXIDIZED COENZYME ” = B-vitamin molecule capable of
picking up high-energy electrons from fuel molecules ( “empty ”)
• “REDUCED COENZYME ” = the B-vitamin molecule with
the high-energy electrons ( “full ”)
* if all the coenzymes get “full”, no more electrons can be
picked up ﬁ the whole process grinds to a stop! Anaerobic Respiration Anaerobic Respiration = “fermentation” Aerobic Respiration
COENZYMES Yeasts and some bacteria Aerobic Respiration REDUCED
COENZYMES Aerobic Respiration Aerobic Respiration
• Anaerobic Respiration
“without air ” • Aerobic Respiration
“with air ” • = glycolysis
+ pyruvate reduction • • Produce ATP in absence of O 2
(or absence of mitochondria) = glycolysis
+ pyruvate oxidation *
+ Krebs cycle *
+ electron transport system * • Produces much more ATP per
sugar molecule • Non-toxic waste product (CO 2) • Allows use of fats and protein
for fuel • * requires mitochondria Cells & Metabolism Uses of Different Energy Sources Cellular Respiration = glycolysis
+ pyruvate reduction • Produce ATP in absence of
O2 Aerobic Respiration
“with air” • = glycolysis
+ pyruvate oxidation
+ Krebs cycle
+ electron transport system • Produces much more ATP per
Non-toxic waste product (CO 2 ) • • • • • Anaerobic Respiration
“without air ” Allows use of fats and protein for
fuel Gluconeogenesis & the Cori Cycle Glycogenesis and Glycogenolysis
4) • Glucose-6-phosphate
cannot leak out of the cell.
• Skeletal muscles generate
own glycolytic needs.
• Only Liver contains the
enzyme glucose-6phosphatase that can
remove the phosphate
group and produce free
glucose. Muscle Fuel Consumption During Exercise
1. 2. 3. 4. 5. At rest: mostly from
aerobic resp . of plama
Start exercise: anaerobic
resp . of plasma glucose;
È blood flow & O 2
delivery ‡ aerobic resp .
of muscle triglycerides.
È plasma glucose for
Lipolysis in adipose tissue
È plama fatty acids for
continued aerobic resp . 5)
6) • Lactic acid produced by
anaerobic respiration in
muscle is released into the
bloodstream and delivered
to the liver.
LDH converts lactic acid
to pyruvic acid.
(“creating new glucose”)
Pyruvic acid converted
G-6-P can be used either
for A. liver glycogenesis
or B. can be converted to free
glucose and released into the
bloodstream. 7A 7B 6 & 7B 6 only occur in liver! Oxygen Debt
Following anaerobic respiration, increased O 2 consumption continues
to support aerobic oxidation of lactate back to pyruvate .
(Reverse of pyruvate reduction. — Uses same LDH enzyme.)
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