1. The Working Cell Chemical Energy ATP & Cellular Work Enzymes
Membrane Function

2. Chemical Energy Where do our muscles get energy to perform work?
From food we eat
When body breaks down food molecules what happens?
Energy from food molecules is stored
Potential energy

3. When, how is stored energy released?
During the process of cellular respiration
What does cell respiration do?
Converts chemical energy (food)
To another form of energy: ATP
What is the significance of ATP?
Can be converted to kinetic energy
Or, muscle activity
More cellular respiration and ATP in Chapter 6

4. Cell respiration
Food ? ? ? ? ?
Energy for cellular work
Muscle work

5. How much energy do we get to use for cellular work?
The diagram gives us a clue
What percent is given off as heat?
~60%
What is the ~60% heat converted to?
~40%
What percent is captured as ATP?

6. Food Calories What is a calorie? And, how is it measured?
A unit of energy
And, how is it measured?
is the amount of energy
that raises the temperature
of one gram (g) of water
by one degree (1o) Celsius
How much energy is in this handful of peanuts?
Enough to boil a quart of water!

7. The kilocalorie (Kcal or C) is 1,000 calories
(in kilocalories)
(as fuel for energy)
The kilocalorie (Kcal or C) is 1,000 calories
The unit used to measure the energy in food

9. Pizza! You’d have to run about 14 miles!
What would you have to do to burn off the calories from this pizza?
You’d have to run about 14 miles!

10. ATP What is ATP? Why is ATP so important? How?
(adenosine triphosphate)
What is ATP?
It is a nucleotide that performs many essential roles in the cell
Why is ATP so important?
It ‘powers’ all cellular work
How?
It releases ‘free’ energy
When its phosphate bonds are hydrolyzed
(or, broken down)

11. What does the ATP structure look like?
Adenosine
Phosphate ‘tail’
Ribose sugar +
ADP?
ATP is broken down to ADP
(adenosine diphosphate)
Accompanied by release of energy

12. Where’s the power in ATP?
In the phosphate tail
Release of last P makes energy available
Unstable. Why?
(adenosine diphosphate)
Repulsion between negatively charged phosphate groups

13. What about that ‘leftover’ phosphate?
Its used to energize other molecules
What do these other molecules do?
Help cells do 3 main types of work
Mechanical
Transport
Chemical

14. ATP and Mechanical Work?
Phosphate transferred to special motor proteins
(muscles)
What happens then?
Proteins change shape
Muscle cells contract
Perform mechanical work

15. ATP and Transport Work? What happens then?
Phosphate transferred to brain cells
What happens then?
Ions pumped across membranes

16. ATP and Chemical Work? What happens then? Make cell’s giant molecules
Reactants
Products
What happens then?
Amino acids are linked to make a protein
Via a dehydration reaction

17. What is the ATP cycle? Our cells need energy (ATP) all the time!
Its recyclable!
Our cells need energy (ATP) all the time!
Food
Energy out…
Cellular respiration
For cellular work
Energy in…
The 3rd phosphate
To regenerate ATP
Acts as an energy shuttle

18. Learning check
1. What is the source of energy for regenerating ATP from ADP?
2. A kilocalorie is equal to _______?
3. Most cellular work is accomplished by _____ energizing molecules by _____ them.
a. enzymes ... activating
b. diffusion ... activating
c. substrates ... transferring a phosphate group to
d. ATP ... transferring a phosphate group to

19. Enzymes What is the barrier for reactions to occur?
Energy must be added
What is this energy called?
Energy of activation EA
How does the cell overcome the barrier?
Uses a specialized protein, an enzyme

20. What does the enzyme do? Serves as a biological catalyst
Increases the rate of the reaction
‘lowers the energy barrier’
Reduces activation energy

21. What are the details? Enzyme very selective
Binds to specific molecules (substrates)
At the enzymes active site
Puts them under physical or chemical stress
Which makes it easier to break bonds
And start a reaction

22. Induced fit? Identify the steps? Substrate ? Sucrose
What is this site?
sucrase
What are these molecules?
Identify the steps?
1. Enzyme available with empty active site
2. Substrate binds to enzyme
3. Substrate converted to products
4. Products are released

23. What are enzyme inhibitors?
‘Imposters’ that plug up the active site
Or at some remote site
How do they function?
Binding changes the shape of the enzyme
Active site no longer receptive

24. Examples of enzyme inhibitors?
Poisons
e.g., malathion
Inhibits an enzyme required for normal function of the insect nervous system
Antibiotics
e.g., penicillin
Inhibits an enzyme bacteria use to make cell walls

25. Membrane Function
1. Endocytosis moves materials _____ a cell via _____. a.
into ... facilitated diffusion b.
into ... membranous vesicles c.
into ... a transport protein d.
out of ... diffusion e.
out of ... membranous vesicles

26. 3. Active transport ______.
2. What name is given to the process by which water crosses a selectively permeable membrane? a.
diffusion b.
passive transport c.
phagocytosis d.
pinocytosis e.
osmosis
3. Active transport ______.
Can move solutes against their concentration gradient
Can involve the transport of ions
Requires the cell to expend energy
Uses ATP as an energy source
All of the above

27. 2. A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mothers milk. These molecules probably enter the cells lining the baby’s digestive tract via ____________? a.
osmosis b.
passive transport c.
exocytosis d.
active transport e.
endocytosis

28. Hydrolysis Decomposition of a substance by the insertion of water molecules between certain of its bonds. Food is digested by hydrolysis.
protein A three-dimensional biological polymer constructed from a set of 20 different monomers called amino acids.
enzyme A protein serving as a catalyst, a chemical agent that changes the rate of a reaction without being consumed by the reaction.
substrate The reactant on which an enzyme works.
active site The specific portion of an enzyme that attaches to the substrate by means of weak chemical bonds.