1. CELLULAR RESPIRATION
Both photosynthesis and cellular respiration provide energy for metabolism = life’s processes
Photosynthesis traps sunlight energy and converts it to energy in chemical bonds of sugar
Cellular respiration makes ATP for the organism by breaking apart the chemical bonds of sugar
The “big picture” ---

2. Photosynthesis uses solar energy
In an Ecosystem:
CO2
H2O
Glucose O2
ATP
ECOSYSTEM
Sunlight energy
Photosynthesis in chloroplasts
Cellular respiration in mitochondria
(for cellular work)
Heat energy +
Photosynthesis uses solar energy
To produce glucose and O2 from CO2 and H2O
Cellular respiration uses glucose to make ATP
Produces CO2 and H2O from glucose and O2

3. Cells trap energy in ATP – ADP + Pi  ATP
by two (2) different processes:
1. By directly coupling ATP synthesis to a specific exergonic reaction
“Substrate-level phosphorylation”
By indirectly coupling ATP synthesis to exergonic reactions
“Oxidative Phosphorylation”
“Chemiosmosis”
“Electron-transport Pathway”
- Trap energy from breaking bonds in glucose
- High-energy electrons carried by NADH & FADH2
- Energy transferred to ATP synthesis enzyme on a membrane

4. Organic molecule (substrate)
1. ATP made by substrate-level phosphorylation
A phosphate group is directly transferred from an organic molecule to ADP
Directly couple an exergonic reaction to the endergonic reaction than makes ATP, all on an enzyme
Enzyme
Adenosine
Organic molecule (substrate)
ADP
ATP P

5. 2. ATP made by
Oxidative Phosphorylation / Chemiosmosis
Uses diffusion of a H+ across a membrane to provide energy for the synthesis of ATP
So –
Let’s take a look at how membranes transport substances to see how this works:

6. MEMBRANE STRUCTURE AND FUNCTION
Membranes organize and compartmentalize the chemical reactions in cells
Membranes
Provide structural order for metabolism
Provide an efficient way for making ATP using energy from electrons in the chemical bonds of your food
Use enzyme-like proteins and other organic chemicals for transporting substances across the membrane

7. Membrane Structure and Function
© 2015 Pearson Education, Inc. 7

8. The plasma membrane of the cell is selectively permeable
Controlling the flow of substances into or out of the cell
Cytoplasm
Outside of cell
TEM 200,000 

9. VISUALIZING THE CONCEPT: Membranes are fluid mosaics of lipids and proteins with many functions
Biologists use the fluid mosaic model to describe a membrane’s structure, a patchwork of diverse protein molecules embedded in a phospholipid bilayer.
The plasma membrane exhibits selective permeability.
The proteins embedded in a membrane’s phospholipid bilayer perform various functions.
Teaching Tips
You might wish to share a very simple analogy that seems to work well for some students. A cell membrane is a little like a peanut butter and jelly sandwich with jelly beans poked into it. The bread represents the hydrophilic portions of the bilayer (and bread does indeed quickly absorb water). The peanut butter and jelly represent the hydrophobic regions (and peanut butter, containing plenty of oil, is generally hydrophobic). The jelly beans stuck into the sandwich represent proteins variously embedded partially into or completely through the membrane. Transport proteins would be like the jelly beans that poke completely through the sandwich. Analogies are rarely perfect. Challenge your students to critique this analogy by finding exceptions. (For example, this analogy does not include a model of the carbohydrates on the cell surface.)
© 2015 Pearson Education, Inc. 9

10. The membrane is a fluid mosaic of phospholipids and proteins
proteins and other molecules embedded in a phospholipid bilayer
Fibers of the extracellular matrix
Carbohydrate (of glycoprotein)
Glycoprotein
Microfilaments of cytoskeleton
Phospholipid
Cholesterol
Proteins
Plasma membrane
Glycolipid
Cytoplasm

11. Membrane phospholipids form a bilayer
Have a hydrophilic head and two hydrophobic tails
Are the main structural components of membranes
CH2
CH3 CH N + O O– P C
Phosphate group
Symbol
Hydrophilic head
Hydrophobic tails

12. Phospholipids in water form a two-layer sheet
Called a phospholipid bilayer, with the heads facing outward and the tails facing inward
Water
Hydrophilic heads
Hydrophobic tails

13. Small nonpolar molecules such as O2 and CO2
and even ethanol and some organic solvents –
Diffuse easily across the phospholipid bilayer of a membrane
Water can’t “grab onto” small molecules that don’t have a charge, so they can move into the fatty acid chains in the middle of the membrane
These molecules always cross cell membranes

14. Passive transport is diffusion across a membrane
In passive transport, substances diffuse through membranes without work by the cell
Spreading from areas of high concentration to areas of low concentration
Equilibrium
Membrane
Molecules of dye

15. Transport proteins may facilitate diffusion across membranes
Many kinds of molecules do not diffuse freely across membranes
For these molecules, transport proteins provide passage across membranes through a process called facilitated diffusion
Solute molecule
Transport protein

16. Osmosis is the diffusion of water across a membrane
In osmosis, water travels from a solution of lower solute concentration to one of higher solute concentration
Lower concentration of solute
Higher concentration of solute
Equal concentration of solute
H2O
Solute molecule
Selectively permeable membrane
Water molecule
Solute molecule with
cluster of water molecules
Net flow of water

17. The control of water balance in organisms
Is called osmoregulation
Some definitions:
solute = chemical dissolved in a solvent
solvent = chemical that dissolves a solute
solution = a solute dissolved in a solvent
hypotonic = less concentrated solution
hypertonic = more concentrated solution
isotonic = two solutions of equal concentrations

18. Water balance between cells and their surroundings is crucial to organisms
Osmosis causes cells to shrink in hypertonic solutions and swell in hypotonic solutions
In isotonic solutions, animal cells are normal, but plant cells are limp
Plant cell
H2O
Plasma membrane
(1) Normal
(2) Lysed
(3) Shriveled
(4) Flaccid
(5) Turgid
(6) Shriveled (plasmolyzed)
Isotonic solution
Hypotonic solution
Hypertonic solution
Animal cell

19. The membrane is a “fluid mosaic” of phospholipids and proteins
proteins and other molecules embedded in a liquid phospholipid bilayer
Fibers of the extracellular matrix
Carbohydrate (of glycoprotein)
Glycoprotein
Microfilaments of cytoskeleton
Phospholipid
Cholesterol
Proteins
Plasma membrane
Glycolipid
Cytoplasm

20. Proteins give the membrane a great variety of functions
Many membrane proteins function as enzymes

21. Other membrane proteins
Function as receptors for chemical messages from other cells
Messenger molecule
Receptor
Activated molecule

22. Membrane proteins also function in transport
Moving substances across the membrane
ATP
Active
Transport
Requires
energy
Concentrates a chemical
Runs diffusion in reverse
Passive Transport
Requires no energy input
Relies on diffusion
“Facilitated”
Uses proteins

23. Cells expend energy for active transport
Transport proteins can move solutes against a concentration gradient that needs ATP
“Pumps” = pump a chemical across a membrane P
Protein changes shape
Phosphate detaches
ATP
ADP
Solute
Transport protein
Solute binding 1
Phosphorylation 2
Transport 3
Protein reversion 4

24. Active Transport - “Bulk” transport
Exocytosis and endocytosis transport large molecules and/or large amounts of molecules
To move large molecules or particles through a membrane, a vesicle may fuse with the membrane and expel its contents (exocytosis)
Fluid outside cell
Cytoplasm
Protein
Vesicle

25. Membranes may fold inward, enclosing material from the outside (endocytosis)
Vesicle forming

26. Endocytosis can occur in three ways
Phagocytosis
Pinocytosis
Receptor-mediated endocytosis
Pseudopodium of amoeba
Food being ingested
Phagocytosis
Pinocytosis
Receptor-mediated endocytosis
Material bound to receptor proteins
PIT
Cytoplasm
Plasma membrane
TEM 54,000
TEM 96,500 
LM 230

27. CONNECTION Faulty membranes can overload the blood with cholesterol
Harmful levels of cholesterol can accumulate in the blood if membranes lack cholesterol receptors
LDL particle
Protein
Phospholipid outer layer
Cytoplasm
Receptor protein
Plasma membrane
Vesicle
Cholesterol

28. Review: Proteins make the membrane a mosaic of function
Many membrane proteins function as enzymes
Membrane proteins also function in transporting substances across the membrane
ATP

29. Membranes are Selectively Permeable
The membranes that form the
plasma (cell) membrane
And
organelles like ER, nucleus, Golgi body, lysosome
Are BARRIERS to certain chemicals and molecules
They won’t let solutions on opposite sides of
the membrane mix together –
So -

30. So, why you need to know about membranes:
The most efficient mechanism to make ATP is
Chemiosmosis, or the
Electron transport pathway, or
Oxidative phosphorylation
----- Terms for the same process -----
Takes place on the inner mitochondrial membrane & depends on the
diffusion of H+ across that membrane

31. Electron transport chain
Electron Transport Pathway
H2O
NAD+
NADH
ATP H+
Controlled release of energy for synthesis of ATP
Electron transport chain 2 O2
2e + 1

32. In oxidative phosphorylation, the mitochondrion –
transfers energy in electrons removed from the chemical bonds in your food, and
uses that energy to concentrate H+ on one side of a membrane.
Then the H+ diffuses across the membrane through a protein channel next to
an enzyme that makes high energy bonds of ATP.

33. Then, diffusion & phosphorylation of ADP
Intermembrane space
Inner mitochondrial membrane
Mitochondrial matrix
Protein complex
Electron flow
Electron carrier
NADH
NAD+
FADH2
FAD
H2O
ATP
ADP
ATP synthase H+ + P O2
Electron Transport Chain
Chemiosmosis .
OXIDATIVE PHOSPHORYLATION
+ 2 1 2