Transcript Enzymes - Warren`s Science Page

Carbohydrates, Proteins, Lipids,
Nucleic Acids
Section 3
Energy and Chemical Reactions
Grade 10 Biology
Fall 2010
Bell Ringer
1. What energy forms do each of these
represent?
1.
2.
3.
4.
Tuning fork?
Flashlight?
Vinegar and baking soda?
Explosion?
Objectives
• Evaluate the importance of energy to living
things
• Relate energy and chemical reactions
• Describe the role of enzymes in chemical
reactions
• Identify the effect of enzymes on food
molecules
Energy for Life Processes
• Energy: is the ability to move or change
matter
• Energy exists in many forms
– Light, heat, chemical energy, mechanical energy,
and electrical energy
• It can be converted from one form to another
• If you kick a ball, the energy of your kick
makes the ball move
Energy for Life Processes
• Energy can be stored or released by chemical
reactions
• A chemical reaction is a process during which
chemical bonds between atoms are broken
and new ones are formed, producing one or
more different substances
Energy for Life Processes
• Reactants: starting materials for chemical
reactants
• Products: newly formed substances
• Chemical equations: summarize chemical
reactions
Reactants  Products
• The arrow reads changes to or forms
Energy in Chemical Reactions
• In chemical rxn.’s, energy is absorbed or
released when chemical bonds are broken and
new ones are formed
Energy in Chemical Reactions
• This graph represents an energy releasing reaction
• When water freezes, the process that leads to the
formation of ice crystals causes heat energy to be released
• When you fill an ice cube tray with water and place it in the
freezer to make ice, heat is released from the water as the
water freezes
Products
Reactants
Energy in Chemical Reactions
• This graph represents an energy absorbing graph
• When you remove ice cubes from the freezer, the ice cubes
begin to melt
• When ice melts, it absorbs heat from the environment
Energy absorbed
Activation Energy
• Activation energy: the
energy needed to start
a chemical reaction
– Ea
• Even in a chemical
reaction that releases
energy, activation
energy must be
supplied before the
reaction can occur
Enzymes
• Chemical reactions in cells occur at relatively
low temperatures because of the action of
many enzymes
• Enzymes: substances that increase the speed
of chemical reactions
• Most enzymes are proteins
• Enzymes are catalysts, which are substances
that reduce the activation energy of a
chemical reaction
Enzymes
• An enzyme increases the speed of a chemical
reaction by reducing the activation energy of
the reaction
Enzymes
• Help organisms maintain homeostasis
• Without enzymes chemical reactions wouldn’t
occur quick enough to sustain life
• Ex. Pg 40, blood and carbon dioxide
Enzyme Specificity
• Substrate: a substance on which an enzyme
acts during a chemical reaction
• Enzymes act only on specific substrates
• Ex. Enzyme amylase assists in the breakdown
of starch to glucose in the following chemical
rxn.
starch  (amylase)  glucose
• Starch is amylase’s substrate
Enzyme Specificity
• An enzyme’s shape determines its activity
• Typically, an enzyme is a large protein with
one or more folds on its surface
• Active site: site on an enzyme that attaches to
a substrate
• Enzyme acts only on one substrate because
only that substrate fits into its active site (lock
and key model modified to induced fit model)
Enzyme Specificity
• Step 1: when an enzyme first attaches to a substrate
during a chemical reaction, the enzyme’s shape
changes slightly so that the substrate fits more tightly
in the enzyme’s active site (page 41, figure 15)
Enzyme Specificity
• Step 2: at an active site, an enzyme and a
substrate interact in a way that reduces the
activation energy of the reaction, making the
substrate more likely to react
Enzyme Specificity
• Step 3: the reaction is complete when
products have formed. The enzyme is now
free to catalyze further reactions.
Factors in Enzyme Activity
• Any factor that changes the shape of an
enzyme can affect the enzyme’s activity
• Enzymes operate best within a specific temp.
range, changing the temp. outside of this
range will affect enzyme activity
• Enzymes operate best within a specific pH
range, enzymes operating outside this range
will loose effectiveness
Review
1. _______________ energy is the energy required to start a
chemical reaction.
2. _______________ increase the speed of chemical
reactions by reducing the activation energy.
3. List 3 ways that organisms use energy.
4. Carboxypeptidase is an enzyme that catalyzes reactions in
the small intestines. The products of these reactions are
amino acids. What are the substrates of
carboxypeptidase?
1.
2.
3.
4.
Proteins
Carbohydrates
Lipids
Nucleic acids
Answers
1. Activation
2. Enzymes
3. Organisms store energy, use energy to power
the chemical reactions of metabolism, and use
energy to build cell structures.
4. Answers
1. Correct. Amino acids are the building blocks of
proteins
2. Incorrect. Carbohydrates are made up of sugars
3. Incorrect. Lipids are not made up of amino acids
4. Incorrect. Nucleic acids are made up of nucleotides