1. Enzymes

2. Q: What cellular organelle makes proteins?
What are enzymes?
Enzymes
are
proteins.
Tertiary an d
quaternary
structure.
Q: What cellular organelle makes proteins?

3. What do enzymes do? Q: What does a catalyst do?
Enzymes act as catalysts in cellular reactions.
Q: What does a catalyst do?
catalysts

4. How do enzymes work?
Enzymes catalyze reactions by weakening chemical bonds, which lowers activation energy.
Video:
Activation Energy

5. Video: How Enzymes Work
How do enzymes work?
Each enzyme has a unique 3-D shape, including a surface groove called
an active site.
The enzyme works by binding a specific chemical reactant (substrate) to its active site, causing the substrate to become unstable and react.
The resulting product(s) is then released from the active site.
Video: How Enzymes Work

6. Enzymes… are specific for what they will catalyze.
fit with substrate like a key and lock

7. When an enzyme is interacting with it’s substrate, during the chemical
reaction, together they are referred
to as the …

8. Video: Enzyme Hydrolysis of Sucrose
Enzymes…
…are reusable.
They are not consumed (used up) in the reactions they catalyze. May perform thousands of reactions per second.
Video: Enzyme Hydrolysis of Sucrose

9. Enzymes… Have names that usually end in -ase. - Sucrase - Lactase
- Maltase
- ase

10. Formats for writing an enzymatic reaction.
( ________ )
_______ + ________ > _________
__________ > ________ ________
Reactant, reactant, (enzyme) > product
Reactant, (enzyme) > product, product
One or more of the reactants in an enzymatic reaction is the substrate, the reactant(s) that specifically interacts with the enzyme.

11. Q: How do you sabotage an enzyme?
• Denature it!
Alteration of a protein shape through some form of external stress
• Example, by applying heat, acidic or
alkaline environment
• Denatured enzyme can’t carry out its
cellular function .
Irreversible egg protein denaturation caused by high temperature (while cooking it).
Video: Denaturation in Food

12. Factors That Influence Enzyme Activity
Temperature pH
Cofactors & Coenzymes
Inhibitors

13. Temperature & pH
Think about what kind of cell or organism an enzyme may work in…
Temperatures far above the normal range denature enzymes. (This is why very high fevers are so dangerous. They can cook the body’s proteins.)
Most enzymes work best near neutral pH (6 to 8).

14. Factors That Influence Enzyme Activity
Temperature pH
Cofactors & Coenzymes
Inhibitors

15. Cofactors / Coenzymes
Non-protein portion of the enzyme (ex. zinc, iron, copper, vitamins) that is needed for proper enzymatic activity.

16. Coenzyme: Vitamin B12
Most vitamins are coenzymes essential in helping move atoms between molecules in the formation of carbohydrates, fats, and proteins.
Exclusively synthesized by bacteria.
Dietary sources include meat, eggs, dairy products and supplements.

17. Factors That Influence Enzyme Activity
Temperature pH
Cofactors & Coenzymes
Inhibitors

18. Two Types of Enzyme Inhibitors
1. Competitive
inhibitor
Chemicals that resemble an enzyme’s normal substrate and compete with it for the active site.
Reversible depending on concentration of inhibitor and substrate.
EXAMPLE: The drug Antabuse is used to help alcoholics quit drinking. Antabuse inhibits aldehyde oxidase, resulting in the accumulation of acetaldehyde during the metabolism of alcohol. Elevated acetaldehyde levels cause symptoms of nausea and vomiting.

19. Two Types of Enzyme Inhibitors
2. Non-competitive inhibitor
Do not enter active site, but bind to another part of the enzyme, causing the enzyme & active site to change shape.
Usually reversible, depending on concentration of inhibitor & substrate.
EXAMPLE: You may know that compounds containing heavy metals such as lead, mercury, copper or silver are poisonous. This is because ions of these metals are non-competitive inhibitors for several enzymes.

20. Enzyme Inhibitors
Blocking an enzyme's activity can kill a pathogen or correct a metabolic imbalance.
EXAMPLE:
Another example of competitive inhibition is protease inhibitors.
They are a class of anti-retroviral drugs used to treat HIV.
The structure of the drug ritonavir (say ri-TAHN-a-veer) resembles the substrate of HIV protease, an enzyme required for HIV to be made.
Many medications are
enzyme inhibitors.
Enzyme inhibitors are also used as herbicides and pesticides.

21. Q: What type of inhibition is this?
REVIEW!
Enzyme Inhibition:
1. Enzyme Inhibition I
2. Enzyme Inhibition II
3. Feedback Inhibition
of a Metabolic Pathway
Q: What type of inhibition is this?

22. Metabolic Pathways Series of chemical reactions that regulate the concentration of substances within the organism.
Has order, like an assembly line.
Molecules are altered in a series of steps.
Use many smaller
steps rather than
one big step.
Enzymes are workers that control each station along the pathway.
May be turned on and off as needed.

23. Molecular Genetics DNA Replication

24. Everyday Biology How do bacteria become resistant to antibiotics?
Genes for antibiotic resistance arise through DNA mutations (mistakes when copying DNA).
These resistance genes spread as resistant bacteria multiply and through horizontal gene transfer.
Q: How would overuse and incorrect use of antibiotics contribute to
antibiotic resistance in bacteria?

25. Prokaryotic Genomes Made of DNA Chromosomes can be circular or linear
Genome floats freely within
cytoplasm
Q: Where is DNA found in
prokaryotes?
______________
Nucleoid
Plasmids

26. Eukaryotic Genomes Genomes of eukaryotic organisms made of DNA.
Eukaryotic genomes frequently include many linear chromosomes within a membrane-bound nucleus
(Q: How many do we have?).
Where is DNA found in eukaryotes?
Nuclear DNA
Extranuclear DNA
(Q: What is extranuclear DNA?)
Eukaryotic

27. Chromosomes & Genes Genome - Complete complement of an organism’s DNA.
Cellular DNA is organized in chromosomes.
Genes have specific places on chromosomes.

28. Nucleotides
and
Nucleic Acids

29. Q: What type of monomer are nucleic acids made of?

30. DNA Structure Double stranded molecule, analogous to a spiral
staircase:
- two deoxyribose-phosphate
chains as the “side rails”
- base pairs, linked by hydrogen bonds, are the “steps”
Purine Bases
(double ring)
Adenine & Guanine
Pyrimidine Bases
(single ring)
Cytosine & Thymine

32. DNA Replication Copying of a double-stranded DNA molecule.
Each DNA strand holds the same genetic information, so each strand can serve as a template for the new, opposite strand.
The parent (a.k.a. __________ )
strand is preserved and the daughter (a.k.a. ___________) strand is assembled from nucleotides.
This is called semi-conservative replication.
Resulting double-stranded DNA molecules are identical.
Q: Why would a cell need to copy its DNA?
template
new
semi-conservative

33. DNA Replication
In a cell, DNA replication must happen before cell division.
Prokaryotes replicate their DNA throughout the interval between cell divisions.
In eukaryotes, timing of replication is highly regulated.

34. DNA Replication

35. EUKARYOTIC DNA Replication: Replication “Bubbles”
Multiple origins of replication > These “bubbles”
are the start points of replication.
Replication fork: ‘Y’-shaped region where new
strands of DNA are elongating.

36. PROKARYOTIC DNA Replication One Origin
Prokaryotic DNA is arranged in a circular shape, and there is only one replication origin.
Despite these differences, the underlying process of replication is the same for both prokaryotic and eukaryotic DNA.

37. How Do Nucleotides Put Themselves Together Into Nucleic Acids?
An anabolic polymerization process.
Q: Anabolic or Anabolism is….? _______________________
Q: Polymerization is …? ____________________________
Polymerization requires monomers (building blocks) and energy.
- Triphosphate deoxyribonucleotides provide both.
- These building blocks of DNA bring their own energy for polymerization.

38. DNA Replication: Anti-parallel Nature of DNA
• Sugar/phosphate backbone runs in opposite directions.
• One strand runs 5’ to 3’, while the other runs 3’ to 5’.
• DNA polymerase: enzyme that
facilitates addition of nucleotides in building the new DNA strand.
• Can only adds nucleotides at the
free 3’ end.
Q: Why is this important?

39. DNA Replication: Leading & Lagging Strand
Leading Strand
Synthesis proceeds smoothly as the replication fork unzips.
Lagging Strand
Synthesis away from the replication fork (Okazaki fragments); joined by DNA ligase.

40. Let’s Practice How Leading & Lagging Daughter Strands Are Built Within the Replication Bubble?’ ?’ 5’ ?’
RNA Primers ?’ ?’ ?’ ?’
Replication Fork
Replication Fork
Now lets look at how replication of the leading and lagging strands occurs at each of the two replication forks within the replication bubble:
1. Label each end of the parent strands as either 5’ or 3’.
2. Start a RNA primer for each daughter strand and label its 5’ and 3’ ends.
3. Show how new strands are built (continuously or discontinuously).

41. Reminder…Why is the DNA copied?
Replication occurs prior to cell division, because the new, daughter cell will also need a complete copy of cellular DNA.

42. If binary fission creates clones…
Genetic Diversity in Prokaryotes
If binary fission creates clones…
…then:
Why isn’t there just one type of bacteria?
How do bacteria change (for example develop resistance to antibiotics)?

43. Replication Mistakes: Mutations of Genes
Change in the nucleotide base sequence of a genome; rare.
Almost always bad news, but...
Rarely leads to a protein having a novel property that improves ability of organism and its descendants to survive and reproduce.

44. Mutation and Bacterial Change
_________ __________= When a microorganism is able to survive exposure to an antibiotic.
Genetic mutation in bacteria can produce resistance to antimicrobial drugs (example: beta-lactamase).
If those genes are on a plasmid, they can be transferred between bacteria by conjugation and other forms of horizontal gene transfer.
If a bacterium carries several resistance genes, it is called multidrug resistant (MDR) or, informally, a superbug or super bacterium.
Any use of antibiotics can increase selective pressure in a population of bacteria to allow the resistant bacteria to thrive and the susceptible bacteria to die off.
Antibiotic resistance