Download Enzymes: “Helper” Protein molecules

Enzymes:
“Helper” Protein molecules
Regents Biology
2009-2010
Flow of energy through life
 Life is built on chemical reactions
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Chemical reactions of life
 Processes of life

building molecules
 synthesis

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breaking down molecules
 digestion
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Nothing works without enzymes!
 How important are enzymes?

all chemical reactions in living
organisms require enzymes to work
 building molecules
 synthesis enzymes
enzyme
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 breaking down molecules
 digestive enzymes
We can’t live
without enzymes!

enzymes speed up reactions
 “catalysts”
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enzyme
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Examples
 synthesis
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enzyme
 digestion
enzyme
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Enzymes are proteins
 Each enzyme is the specific helper to
a specific reaction
each enzyme needs to be the right shape
for the job
 enzymes are named for the reaction
they help

Oh, I get it!
They end
in -ase
 sucrase breaks down sucrose
 proteases breakdown proteins
 lipases breakdown lipids
 DNA polymerase builds DNA
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Enzymes aren’t used up
 Enzymes are not changed by the reaction
used only temporarily
 re-used again for the same reaction with
other molecules
 very little enzyme needed to help in many
reactions

substrate
active site
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product
enzyme
It’s shape that matters!
 Lock & Key model

shape of protein
allows enzyme &
substrate to fit

specific enzyme
for each specific
reaction
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Enzyme vocabulary
 Enzyme

helper protein molecule
 Substrate

molecule that enzymes work on
 Products

what the enzyme helps produce from
the reaction
 Active site

part of enzyme
that substrate
molecule fits into
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What affects enzyme action
 Correct protein structure
correct order of amino acids
 why? enzyme has to be right shape

 Temperature

why? enzyme has to be right shape
 pH (acids & bases)

why? enzyme has to be right shape
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Temperature
 Effect on rates of enzyme activity

Optimum temperature
 greatest number of collisions between
enzyme & substrate
 human enzymes
 35°- 40°C (body temp = 37°C)
Raise temperature (boiling)
 denature protein = unfold = lose shape
 Lower temperature T°
 molecules move slower
 fewer collisions between enzyme &
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
Temperature
reaction rate
human
enzymes
37°
temperature
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What’s
happening
here?!
How do cold-blooded creatures do it?
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pH
 Effect on rates of enzyme activity

changes in pH changes protein shape

most human enzymes = pH 6-8
 depends on where in body
 pepsin (stomach) = pH 3
 trypsin (small intestines) = pH 8
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pH
intestines
trypsin
What’s
happening
here?!
reaction rate
stomach
pepsin
0
1
2
3
4
5
6
pH
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For enzymes…
What matters?
SHAPE!
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2009-2010
Phospholipids
 Structure

Glycerol + 2 fatty acids +
phosphate group
 Functions
Component of cell membranes
 Lipid transport as part of
lipoproteins
 Emulsifiers
 Phosphatidylcholine

 Food sources

Egg yolks, liver, soybeans,
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Cell membranes are phospholipid bilayers
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The basic structural unit of biological
membranes is a lipid bilayer
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Energy.
The Cell:
Mitochondria & Chloroplasts
Regents Biology
2005-2006
Overview
 Mitochondria & chloroplasts are the
organelles that convert energy to forms
that cells can use for work
mitochondria:
from glucose to ATP
ATP
 chloroplasts:
from sunlight to ATP & carbohydrates

 ATP = active energy
 carbohydrates = stored energy
ATP
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2005-2006
Mitochondria & Chloroplasts
 Important to see the similarities

transform energy
 generate ATP
double membranes = 2 membranes
 semi-autonomous organelles

 move, change shape, divide

internal ribosomes, DNA & enzymes
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2005-2006
Mitochondria
 Function
cellular respiration
 generate ATP

 from breakdown of sugars, fats
& other fuels
 in the presence of oxygen
 break down larger molecules into smaller to
generate energy = catabolism
 generate energy in presence of O2 = aerobic
respiration
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2005-2006
Mitochondria
 Structure

2 membranes
 smooth outer membrane
 highly folded inner membrane
 the cristae


fluid-filled space between 2
membranes
internal fluid-filled space
 mitochondrial matrix
 DNA, ribosomes & enzymes
Why 2 membranes?
increase surface area for membranebound enzymes that synthesize ATP
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2005-2006
Mitochondria
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2005-2006
Membrane-bound Enzymes
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2005-2006
Dividing Mitochondria
Who else divides
like that?
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What does this tell us about
the evolution of 2005-2006
eukaryotes?
Mitochondria
 Almost all eukaryotic cells have mitochondria


there may be 1 very large mitochondrion or
100s to 1000s of individual mitochondria
number of mitochondria is correlated with
aerobic metabolic activity
 more activity = more energy
needed = more mitochondria
What cells would
have a lot of
mitochondria?
active cells:
• muscle cells
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• nerve cells
2005-2006
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2005-2006
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2005-2006
Chloroplasts
 Chloroplasts are plant organelles

class of plant structures = plastids
 amyloplasts
 store starch in roots & tubers
 chromoplasts
 store pigments for fruits & flowers
 chloroplasts
 store chlorophyll & function
in photosynthesis
 in leaves, other green
structures of plants &
in eukaryotic algae
Regents Biology
2005-2006
Chloroplasts
 Structure

2 membranes
 outer membrane
 inner membrane

internal fluid-filled space =
stroma
 DNA, ribosomes & enzymes
 thylakoids = membranous sacs where ATP is made
 grana = stacks of thylakoids
Why internal sac membranes?
increase surface area for
membrane-bound enzymes
synthesize ATP
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Biology
2005-2006
Membrane-bound Enzymes
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2005-2006
Chloroplasts
 Function
photosynthesis
 generate ATP & synthesize sugars

 transform solar energy into chemical energy
 produce sugars from CO2 & H2O
 Semi-autonomous
 moving, changing shape & dividing
 can reproduce by pinching in two
Who else divides
like that?
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bacteria!
2005-2006
Chloroplasts
Why are chloroplasts green?
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2005-2006
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2005-2006
Mitochondria & chloroplasts are different
 Organelles not part of endomembrane system
 Grow & reproduce

semi-autonomous organelles
 Proteins primarily from free ribosomes in
cytosol & a few from their own ribosomes
 Own circular chromosome

directs synthesis of proteins produced by own
internal ribosomes
Who else has a circular chromosome no
bound within a nucleus?
bacteria
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2005-2006
1981 | ??
Endosymbiosis theory
 Mitochondria & chloroplasts were once
free living bacteria

engulfed by ancestral eukaryote
 Endosymbiont

cell that lives within another cell (host)
 as a partnership
 evolutionary advantage
for both
 one supplies energy
 the other supplies raw materials
& protection
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2005-2006
Endosymbiosis theory
Evolution of eukaryotes
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2005-2006
Any Questions??
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2005-2006