Download The energy currency of the cell The ATP Cycle

ATP: The energy currency of the
cell
Changing the rate of catabolic
and anabolic reactions- How do
you control these chemical
reactions?
The ATP Cycle:
Enzymes and Activation Energy
Enzymes as biological catalysts
– Activation Energy - the probability of a
reaction
• Enzymes effect the rate of reactions by changing the
amount of activation energy needed for the reaction
Enzymes and Activation Energy
A cartoon view of sucrase activity:
breaking down sucrose
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Other factors that influence
enzyme activity:
Temperature and pH Optima
• Cofactors: metal ions
and coenzymes
– Vitamins like niacin and
riboflavin
• Temperature, pH
• Metabolic Pathways
– Regulation and
Organization
– Negative feedback
Enzyme regulation
Metabolism
• The sum total of all the chemical reactions
happening in a cell (or living thing)
• Two main types of chemical reactions
– Anabolic: unfavorable; uses energy to do work,
transport, synthesize, move…
– Catabolic: favorable; breakdown of molecules
release energy used to fuel other reactions
Anabolic and Catabolic Reactions
Intro to Cell Structure
• Cell Theory:
– All organisms are made of one or more cells
– Cells are the smallest living thing
– Cells come from other cells (today)
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Two Main Classes of Cells
3 Domains of Life
• Prokaryotic (Bacteria and Archaea)
– Pro = “Before”; Karyon = “Kernel”
– No nucleus, DNA coiled up inside cell
• Eukaryotic (Everything else)
– Eu = “True”
– DNA inside membrane bound organelle inside
cell, the nucleus
Size Differences
Eukaryotic Cell (non bacterial)
Prokaryotic Cell (bacteria)
Prokaryotic Cell
Animal Cell
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Plant Cell
Why are cells so
small?
i.e. What are the
determinants of
cell size?
1- Surface area to
volume ratio
2- Diffusion rates
Surface Area to Volume Ratios
Mechanisms of Cellular Transport
• Molecular Mechanisms- Solutes and Solvents
Diffusion of oxygen in
solution
1 µm in .5 msec
10 µm in 50 msec
100µ
100µm in 5 sec
1000 µm (1mm) in 8.3 min
10000 µm (1cm) in 14 h!
Hypotonic
Passive Diffusion and Osmosis
Active Transport
Osmoregulation
Hypo-, Iso-, and Hypertonic
• Below, Equal, and Above
• Bulk transport: Endo- and Exocytosis
Diffusion goes in all directions
…along the Concentration Gradient
Diffusion
Hypertonic
–
–
–
–
Isotonic
Passive Transport- important to all cells… O2 and CO2
What about molecules that can’t get through the Plasma Membrane?
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Transport ProteinsFacilitated Diffusion
Osmosis- passive transport of
water across a membrane
Why?
Osmosis and living cells
Still
doesn’t
use any
energy!
Just High
conc. to
low
Examples:
Sugar,
A.a., ions,
even
water!?
Transport
Freshwater
Fish
• Passive- (downhill) Free or gated (chemical or ion)
• Facilitated- (downhill with a “push”)
• Active-ATP mediated (uphill)
Saltwater
Fish
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Active Transport
Sodium-Potassium Pumps
Active Transport
1. Solute attaches to binding site of transport protein
2. ATP causes the protein to change shape 3. so that solute is
taken outside membrane
– Na-K pumps…up to 40% of all our energy is
used for this pumping
4. Phosphate groups leaves and causes the reverse change.
Active Transport of Large
Molecules, etc.
- Exocytosis
Active Transport of Large
Molecules, etc.
- Endocytosis
moving things outside cell.
moving things inside cell- 3 ways
Crying
Insulin
others
Endocytosis
Review: passive and active transport compared
Phagocytosis- “cell eating”
Pinocytosis- “cell drinking”
Receptor-mediated- highly
specific
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The Plasma Membrane
What Controls all this Transport
in Living Cells???
General functions of the Plasma
Membrane
•
•
•
•
•
•
•
Selective permeability to maintain separation
Control exchange of wastes and metabolites
Framework for organization of enzymes
Anchorage between cells
Binding site for hormones
Receptors for selective uptake
Intercellular identification
Membrane Structure: The Fluid
Mosaic Membrane Model
•
•
•
•
Lipid bilayer (double layer)
Nonpolar tails point inward, polar outside
Layers are “fluid”
Many things embedded within membrane
– Phospohlipids and cholesterol
– Carbohydrates
– Proteins
• Much of the structure and functions of the PM
depend on these embedded proteins
The Singer Nicholson Fluid Mosaic Model of
The fluidity of membranes
Membrane Structure: General Properties
• Free movements of:
• Phospholipid bilayer: 50%
– Backbone of most membranes
– Lateral movement only
– Oily core forms hydrophobic
barrier
• Proteins: 50%
– Integral and peripheral
– cytosolic and exoplasmic faces
– lipids
– proteins
• Healing properties
• The variable nature
of the fluidity of
membranes:
– Sat. vs Unsat. FA’s
– Cholesterol
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Some functions of membrane proteins
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