Download Ch 16.4 Enzymes and rest

Warm-up
List any facts you know about the
molecule shown
Chapter 16.6 & 16.7
Enzymes & Enzyme Actions
SWBAT:
Describe how enzymes function as catalysts and give their names
Describe the role of an enzyme in an enzyme-catalyzed reaction
Enzymes are….
biological catalyst which speed up Rx by
lowering the Activation Energy
proteins
not used up in the reaction
What is an enzyme?
Enzymes are
globular proteins
small, compact, strong with a unique 3-D
shape
Have a special pocket called
active site
The Active Site
Is an area where the enzyme binds the
substrate and helps catalyze the reaction
fits only a few types of substrates
Active Site
Substrate
Enzyme Rx
Formation of the enzyme substrate (ES)
complex weakens covalent bonds in the
substrate
E + S
ES
EP
E + P
E = enzyme
S = substrate
P = product
How enzymes work?
A. “Lock and Key” Theory
Active site = lock; substrate = key
1. enzyme binds one specific substrate to
form ES complex
2. Substrate is converted to product
3. Product leaves active site
4. Enzyme binds next substrate
B. “Induced Fit” Model
Enzyme changes shape when binding
substrate
Enzyme serves a range of similar
substrates
Enzyme Naming
Most end with –ase
Reflect substrate or reaction types:
amylase, oxidase
Older enzyme names often end in –in
Ex: pepsin, rennin, trypsin
Enzyme Rx classifications
Anabolic reactions
Synthesis of complex substances from simple
building blocks (growth, repair)
a) Amino Acids  Polypeptides  Proteins
b) Monosaccharides → Disacchar.→Polysacch.
c) FA+ Glycerol → Lipid
Catabolic reactions
Breakdown of complex substance into building
blocks (digestion, removal of old macromol.)
a) Proteins → Polypeptides → Aminoacids
b) Polysaccharides → Disacchar.→Monosacch.
c) Lipid → FA + Glycerol
Classification of Enzyme Reactions
 Oxidoreductoases: oxidation/reduction Rx
 Transferases: transfer functional groups (Kinase:
transfers phosphates)
 Hydrolases: breaking molecules in presence of
H2O (Carbohydrases, Proteases, Lipases)
 Lyases: (Add/Remove groups with double bonds
 Isomerases: rearrange to form isomers (cis/trans)
 Ligases: connect molecules using ATP (DNA
strands in replication)
Reaction Pathways
Most enzymes do not catalyze a stand-alone
Rx
They are part of greater pathway E1, E2, E3
The product of Rx 1 is the substrate for Rx 2
E1
E2
E3
A
B
C
D --Rx1
Rx2
Rx3
Warm-up
Label the energy flow chart of the Rx
shown
Is it an endo or exothermic Rx?
Chapter 16.8
Factors Affecting Enzyme
Activity
SWBAT:
Describe the effect of temperature, pH, concentration of
substrate and inhibitors on enzyme activity
Factors Affecting Enzyme Reaction
Rates
Temperature
pH
Concentrations of substrates
Concentration of enzyme
Presence of inhibitors
Temperature
 Too high: denaturation, loss of 3D (often
reversible if not too high!)
 Too low: slow Rx rates
 Optimum Temperature depends on species:
 Mammals: 37°C
 Thermophile bacteria: 80-90oC (thermal springs)
 Arctic flies: 5oC temperature
pH
Optimum pH depends on natural enzyme
environment
Too high/low denatures enzyme and/or
affects 2o,3o,4o structure/active site (ionic
bds, H-bonds)
Tissue and blood enzymes: pH 7.4
Stomach enzyme (pepsin) : pH 2.0
Pancreatic enzyme (trypsin): pH 8.0
pH (cont.)
Substrate & Enzyme Concentrations
 Generally: increasing substrate concentration
increases Rx rate
Vmax
All enzyme molecules work at max speed,
adding more substrate does not increase
rate
Only increase in enzyme concentration
further increases rates!
Animation
Animation comparing
Enzymes
Substrates
Inhibitors
Temperature
pH
Link to animation
Enzyme Inhibitor
Competitive Inhibition
Non-Competitive Inhibition
Enzyme Cofactors
Complex enzymes: require cofactors:
metal ions
Metal ions: Cu2+, Fe2+/3+, Zn2+, Mg2+,
Mn2+, Ni2+ - (food)
Enzymes of the electron transport chain in
mitochondrial membranes: oxidorecutases
Enzyme without the cofactor: apoenzyme
Enzyme with cofactor bound: holoenzyme
Cofactor function
Vitamins and Coenzymes
Vitamins are organic molecules
Essential Vitamins: B, C, Biotin, folic acid
Coenzymes NADH, FADH, ATP (Kinases)
Coupled Rx:
Special food proteins A. Gluten
 The “glue-protein”
 Protein found in wheat, barley, rye makes dough
elastic!
 Oats, rice, corn, quinoa are gluten free grains
 About 1% of the population is allergic to gluten
or has celiac disease
 Symptoms: include bloating, abdominal pain,
diarrhea, muscle, bone or joint pain
 Correlation between thyroid problems and gluten
allergies….
B. Casein
 Main protein in mammalian milk, highest in
cow’s milk (80%)
 Adults can be allergic to casein (just like with
lactose)
 Animal experiments show a correlation of high
casein intake and cancer development
 Population studies from China (China Study)
and Norway (WWII) correlate significant lower
rates of breast and prostate cancer in dairy free
populations….
Warm-up
Sort the following biological molecule into
the their respective biochemical substance
classes (excluding Nucleic Acids)
Rennin, Albumin, Stearate, Xylose,
Xylase, Lipase, Cholesterol, Gluten,
Insulin, Lactose, Linolate, Lactase,
Glucagon, Glucose, Pepsin, Estrogen
C. Prions – misfolded proteins
Invalidates current pathogen definitions as
being only bacteria or viruses
Misfolded “diseased” peptides induce
wrong folding in normal proteins: seeded
induction
Cannot be cleared out of cells (lack of
enzyme!) but accumulate and form
amyloid aggregates in brain and nervous
tissue (lots of beta pleated sheets)
From Amyloid to Spongiform brain
Amyloid Accumulation to Spongelike holes
Protein Diseases
 Mad Cow Disease: Bovine Spongiform
Encephalitis
 Human Spongiform Encephalitis: (CreutzfeldtJacob D)
 Hereditary or
 transmitted from consumption of infected meat:
cows, sheep, canibalism
 Certain forms of Alzheimer’s D
 Huntington’s D
 Parkinson’s D