Name ______Date ______Period _____
METABOLISM AND ENZYMES
Raven Ch.8
Big Idea 2: BIOLOGICAL SYSTEMS UTILIZE FREE ENERGY AND MOLECULAR BUILDING BLOCKS TO GROW, TO REPRODUCE AND TO MAINTAIN HOMEOSTASIS.
Essential Knowledge:
Cell membranes are selectively permeable due to their structure.
Growth and dynamic homeostasis are maintained by the constant movement of molecules across membranes.
Eukaryotic cells maintain internal membranes that partition the cell into specialized regions.
- All biological systems from cells and organisms to populations, communities and ecosystems are affected by complex biotic and abiotic interactions involving exchange of matter and free energy.
- Homeostatic mechanisms reflect both common ancestry and divergence due to adaptation in different environments.
Flow of energy through life
- Life is built on chemical reactions
- transforming energy from one form to another
Metabolism
- Chemical reactions of life
- ______between molecules
- dehydration synthesis
- synthesis
- ______reactions
- ______between molecules
- hydrolysis
- digestion
- ______reactions
Chemical reactions & energy
- Some chemical reactions ______
- ______
- digesting polymers
- hydrolysis = catabolism
- Some chemical reactions require ______
- ______
- building polymers
- dehydration synthesis = anabolism
Exergonicvs.Endergonic
______
______
G = ______
- Organisms require energy to live
- Where does that energy come from?
- couplingexergonic reactions (______energy) with endergonic reactions (______energy)
______
______
What drives reactions?
- If reactions are “downhill”, why don’t they just happen spontaneously?
- ______
Activation energy
- Breaking down large molecules requires an initial input of energy
- ______
- large biomolecules are stable
- must absorb energy to break bonds
Too much activation energy for life
- Activation energy
- amount of energy needed to destabilize the bonds of a molecule
- moves the reaction over an “energy hill”
Reducing Activation energy
- ______
- reducing the amount of energy to start a reaction
- So what’s a cell got to do to reduce activation energy?
- get help! … chemical help…______
Enzymes
- ______
- proteins (& RNA)
- facilitate chemical reactions
- ______rate of reaction without being consumed
- ______activation energy
- don’t change ______released or required
- required for most biological reactions
Enzymes vocabulary:•highly ______
- thousands of different enzymes in cells
______•______reactionsof life
- reactant which binds to enzyme
- enzyme-substrate complex: temporary association
______
- end result of reaction
______
- enzyme’s catalytic site; substrate fits into active site
Properties of enzymes
- ______
- each enzyme works with a specific substrate
- chemical fit between active site & substrate
H bonds & ionic bonds
- ______
- single enzyme molecule can catalyze thousands or more reactions per second
- enzymes unaffected by the reaction
- Affected by ______
- any condition that affects protein structure
- temperature, pH, salinity
Naming conventions
- Enzymes named for reaction they catalyze
- ______breaks down sucrose
- ______break down proteins
- ______break down lipids
- DNA ______builds DNA
- adds nucleotides to DNA strand
- ______breaks down
proteins (polypeptides)
Lock and Key model
- ______model of enzyme action
- substrate fits into 3-D structure of enzyme’ active site
- H bonds between substrate & enzyme
- like “key fits into lock”
Induced fit model
- ______model of enzyme action
- 3-D structure of enzyme fits substrate
- substrate binding cause enzyme to change shape leading to a tighter fit
- “______”
- bring chemical groups in position to catalyze reaction
How does it work?
- Variety of mechanisms to lower activation energy & speed up reaction
- ______
- active site orients substrates in correct position for reaction
enzyme brings substrate closer together
- ______
- active site binds substrate & puts stress on bonds that must be broken, making it easier to separate molecules
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