Transcript Slide 1
Figure 5.1
CYTOPLASM Fibers of extracellular matrix (ECM) Enzymatic activity Phospholipid Cholesterol Cell-cell recognition Receptor Signaling molecule Attachment to the cytoskeleton and extracellular matrix (ECM) Signal transduction Transport ATP Intercellular junctions Microfilaments of cytoskeleton Glycoprotein CYTOPLASM
Passive transport
Passive transport
= diffusion across cell membrane – No energy required!!
Moves with concentration gradient Examples: – Urea, CO2, O2, Water, small hydrophobic
Animation: Diffusion Animation: Membrane Selectivity
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Figure 5.3A
Molecules of dye Membrane Pores Net diffusion Net diffusion Equilibrium
Figure 5.3B
Net diffusion Net diffusion Net diffusion Net diffusion Equilibrium Equilibrium
Osmosis
= diffusion of water across a membrane
Lower concentration of solute Higher concentration of solute Solute molecule H 2 O Selectively permeable membrane Equal concentrations of solute Water molecule Solute molecule with cluster of water molecules Osmosis
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Figure 5.5
Hypotonic solution H 2 O Animal cell H 2 O Lysed Plant cell Turgid (normal) H Isotonic solution 2 O H 2 O H 2 O Normal Flaccid Hypertonic solution H Shriveled 2 O Shriveled Plasma membrane H 2 O (plasmolyzed)
Osmoregulation = Water Balance
Osmoreguatation
= all organisms must regulate internal water concentrations to remove excess water or prevent water loss – Remove excess water: – Contractile vacuoles - protists – Freshwater organisms – kidneys, gills – Prevent water loss: – Guard cells in plants
Video: Chlamydomonas
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Video: Paramecium Vacuole Video: Plasmolysis Video: Turgid Elodea
Facilitated Diffusion
= Passive diffusion of solute using a transport protein
Solute molecule Transport protein Only moves solutes with concentration gradient!
Examples: ion channels, aquaporin
5.7 SCIENTIFIC DISCOVERY: Research on another membrane protein led to the discovery of aquaporins
Dr. Peter Agre received the 2003 Nobel Prize in chemistry for his discovery of aquaporins.
His research on the Rh protein used in blood typing led to this discovery.
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Figure 5.7
Active Transport
In active transport, a cell –
must expend energy
to – move a solute against its concentration gradient.
The following figures show the four main stages of active transport.
Examples: Na-K-ATP Pump, H+ Pump, Na Glucose Cotransporter
Animation: Active Transport
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Figure 5.8_s4
Transport protein Solute 1 Solute binding 2 ATP P ADP Phosphate attaching Protein P changes shape.
3 Transport Phosphate detaches.
P 4 Protein reversion
5.9 Exocytosis and endocytosis transport large molecules across membranes
There are three kinds of endocytosis.
1.
Phagocytosis
is the engulfment of a particle by wrapping cell membrane around it, forming a vacuole.
2.
Pinocytosis
is the same thing except that fluids are taken into small vesicles.
3.
Receptor-mediated endocytosis
uses receptors in a receptor-coated pit to interact with a specific protein, initiating the formation of a vesicle.
Animation: Exocytosis and Endocytosis Introduction Animation: Exocytosis Animation: Pinocytosis Animation: Phagocytosis
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Animation: Receptor-Mediated Endocytosis
Figure 5.9
Phagocytosis EXTRACELLULAR FLUID Pseudopodium CYTOPLASM Food being ingested Pinocytosis “Food” or other particle Food vacuole Plasma membrane Vesicle Receptor-mediated endocytosis Coat protein Receptor Coated vesicle Plasma membrane Coated pit Specific molecule Coated pit Material bound to receptor proteins
ENERGY AND THE CELL
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5.10 Cells transform energy as they perform work
Energy
= capacity to cause change or to perform work.
Two kinds of energy:
1.
Kinetic energy
is the energy of motion.
2.
Potential energy
is energy that matter possesses as a result of its location or structure.
Heat
= thermal energy
Chemical energy
=
potential energy
available in bonds within molecules and released in a chemical reaction. – Most relevant energy to living organisms
Animation: Energy Concepts
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Figure 5.10
Fuel Gasoline
Oxygen Glucose
Oxygen Heat energy Energy conversion Waste products Combustion Kinetic energy of movement Energy conversion in a car Heat energy Cellular respiration ATP ATP Energy for cellular work Energy conversion in a cell Carbon dioxide
Water Carbon dioxide
Water
Thermodynamics = study of energy transformations
First law of thermodynamics
constant = energy in the universe is – Biological organisms cannot produce energy - only convert forms of energy
Second law of thermodynamics
= energy conversions increase the disorder (
entropy
) of the universe.
–
No energy transformations are 100 % efficient
– Usuable energy lost as heat – Energy transformations are one-way street –
Biological organisms require constant supply of energy to maintain order!!
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Metabolism = total of an organism’s chemical reactions
Chemical reactions are either –
Exergonic reactions
release energy.
– These reactions release the energy in covalent bonds of the reactants.
– Cellular respiration An
endergonic reaction
– requires an input of energy; products contain more chemical/potential energy – Photosynthesis
Energy coupling
= energy released from exergonic reactions drive endergonic reactions!!
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Figure 5.11A
Reactants Energy Products Amount of energy released
Figure 5.11B
Reactants Energy Products Amount of energy required
Cells need energy to perform work!!
There are three main types of cellular work: 1.
chemical 2.
mechanical 3.
transport ATP drives all three of these types of work.
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ATP = Adenosine triphosphate
ATP: Adenosine Triphosphate Phosphate group P P P Adenine Ribose
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Figure 5.12A_s2
ATP: Adenosine Triphosphate Phosphate group P P P Adenine Ribose Hydrolysis H 2 O P P ADP: Adenosine Diphosphate P Energy
ATP drives cellular work
Hydrolysis of ATP
releases
energy by transferring phosphate from ATP to some other molecule –
phosphorylation
.
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Figure 5.12B
Chemical work ATP P Reactants Mechanical work ATP Transport work ATP Solute Motor protein P P Membrane protein P Product Molecule formed P P Protein filament moved Solute transported ADP P ADP P ADP P
How Does Cell Regenerate ATP?
ATP = renewable source of energy for the cell.
ATP cycle = energy released in an exergonic reaction is used in an endergonic reaction to generate ATP.
ATP Energy from exergonic reactions
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ADP P Energy for endergonic reactions
HOW ENZYMES FUNCTION
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Enzymes = Organic catalysts
Increase RATE of chemical reaction by
decreasing
activation energy
(E A ).
– E A = energy barrier must be overcome before chemical reaction can begin.
any
Activation energy barrier Enzyme Reactant Reactant Activation energy barrier reduced by enzyme Products
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Without enzyme Animation: How Enzymes Work Products With enzyme
a b Reactants c Progress of the reaction Products
Enzymes Only Increase
RATE
of reaction,
NOT
Level of reactants or products!!!
the energy
A specific enzyme catalyzes each cellular reaction
An enzyme – Is specific in substrate(s) it binds – And reaction it catalyzes Substrate = reactant A substrate binds at enzyme
active site
.
Enzymes are specific because their active site fits only specific substrate molecules – Active site is result of 3D folding of protein © 2012 Pearson Education, Inc.
1 Enzyme available with empty active site Active site Glucose Fructose 4 Products are released Enzyme (sucrase) Catalytic cycle of an enzyme Substrate (sucrose) 2 Substrate binds to enzyme with induced fit H 2 O 3 Substrate is converted to products
Factors that Effect Enzyme-Catalyzed Reactions
For every enzyme, there are optimal conditions under which it is most effective.
– Temperature – pH – Substrate Concentration – Enzyme Concentration – Cofactors/coenzymes – Inhibitors © 2012 Pearson Education, Inc.
Factors that Affect Enzyme-Catalyzed Reactions
Many enzymes require nonprotein helpers called
cofactors
, which – bind to the active site and function in catalysis.
– Inorganic molecules
Coenzymes
– Organic molecule that acts as cofactor © 2012 Pearson Education, Inc.
Enzyme Concentration
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
Substrate Concentration
Temperature - affects molecular motion
pH
Enzyme inhibitors can regulate enzyme activity
Inhibitor
= chemical that interferes with an enzyme’s activity.
Competitive inhibitors
– – block substrates from entering the active site and reduce an enzyme’s productivity.
Substrate Enzyme Allosteric site Active site
Noncompetitive inhibitors Normal binding of substrate
– bind to the enzyme somewhere other than the active site,
Competitive inhibitor Noncompetitive inhibitor
– change the shape of the active site, and – prevent the substrate from binding.
Enzyme inhibition
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Enzyme inhibitors are important in regulating cell metabolism.
–
Feedback inhibition
= product of metabolic pathway acts as an inhibitor of one of the enzymes in the pathway
Feedback inhibition Enzyme 1 A Starting molecule Reaction 1 B Enzyme 2 Reaction 2 C Enzyme 3 D Reaction 3 Product
You should now be able to
1.
Describe the fluid mosaic structure of cell membranes.
2.
Describe the diverse functions of membrane proteins.
3.
Relate the structure of phospholipid molecules to the structure and properties of cell membranes.
4.
Define diffusion and describe the process of passive transport.
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You should now be able to
5.
Explain how osmosis can be defined as the diffusion of water across a membrane.
6.
Distinguish between hypertonic, hypotonic, and isotonic solutions.
7.
Explain how transport proteins facilitate diffusion.
8.
Distinguish between exocytosis, endocytosis, phagocytosis, pinocytosis, and receptor-mediated endocytosis.
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You should now be able to
9.
Define and compare kinetic energy, potential energy, chemical energy, and heat.
10.
Define the two laws of thermodynamics and explain how they relate to biological systems. 11.
Define and compare endergonic and exergonic reactions.
12.
Explain how cells use cellular respiration and energy coupling to survive.
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You should now be able to
13.
Explain how ATP functions as an energy shuttle.
14.
Explain how enzymes speed up chemical reactions.
15.
Explain how competitive and noncompetitive inhibitors alter an enzyme’s activity.
16.
Explain how certain drugs, pesticides, and poisons can affect enzymes.
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Table 5.UN05
Figure 5.UN06
0 1 2 3 4 pH 5 6 7 8 9 10