1. CHAPTER 5 The Working Cell
Modules 5.10 – 5.21

2. The Structure of the Plasma Membrane
Glycoprotein
Carbohydrate (of glycoprotein)
Fibers of the extracellular matrix
Glycolipid
Phospholipid
Cholesterol
Microfilaments of the cytoskeleton
Proteins
CYTOPLASM
Figure 5.12

3. Membrane phospholipids form a bilayer
Phospholipids are the main structural components of membranes
They each have a hydrophilic head and two hydrophobic tails
Head
Symbol
Tails
Figure 5.11A

4. In water, phospholipids form a stable bilayer
The heads face outward and the tails face inward
Water
Hydrophilic heads
Hydrophobic tails
Water
Figure 5.11B

5. The cell membrane is about 10 nm thick discernable only faintly with a transmission electron microscope.
The membrane is specialized in that it contains specific proteins and lipid components that enable it to perform its unique roles for the cell.

6. The membrane is a fluid mosaic made of phospholipids and proteins
Phospholipid molecules form a flexible bilayer
Phospholipid molecules in the cell membrane are "fluid," in the sense that they are free to diffuse and exhibit rapid lateral diffusion. Lipid rafts and caveolae are examples of cholesterol-enriched microdomains in the cell membrane
The plasma membrane lipids consist of 1/3 cholesterol and 2/3 phospholipids (65-80%) and sphingolipids (20-35%). The outer leaflet contains 5% glycolipids.
Cholesterol is embedded in the plasma membrane
Phospholipids flow at a rate of 2 micrometers/second

7. Membrane proteins can span the lipid bilayer while others are peripheral.

8. MEMBRANE FUNCTION
Membranes organize the chemical reactions making up metabolism  
Cytoplasm
Figure 5.10

9. The membrane :
Sorts what goes in and out of the cell. Membranes are selectively permeable.
Anchors of the cytoskeleton to provide shape to the cell
Attaches to the extracellular matrix to help group cells together in the formation of tissues
Transports particles by way of ion pumps, ion channels, and carrier proteins
Contains receptors that allow chemical messages to pass between cells and systems
Participates in enzyme activity important in such things as metabolism and immunity

10. Membranes are selectively permeable
They control the flow of substances into and out of a cell

11. Some membrane proteins form cell junctions
The Membrane Proteins: allow chemical messages to pass between cells and systems
Some membrane proteins form cell junctions
Others transport substances across the membrane
Figure 5.13
Transport

12. Many membrane proteins are enzymes
Some proteins function as receptors for chemical messages from other cells
The binding of a messenger to a receptor may trigger signal transduction
Messenger molecule
Receptor
Activated molecule
Figure 5.13
Enzyme activity
Signal transduction

13. Passive and Active Transport Across the Membrane
Passive Transport does not require energy
1. Simple diffusion
2. Osmosis
3. Diffusion by transport proteins (carrier proteins,
channel proteins).
B. Active Transport requires energy

14. Passive transport is diffusion across a membrane without expending energy
In simple diffusion, substances diffuse through membranes without work by the cell
They spread from areas of high concentration to areas of lower concentration
Solutes move with the concentration gradient
Solute specific
Molecule of dye
Membrane
EQUILIBRIUM
EQUILIBRIUM
Figure 5.14A & B

15. Osmosis is the passive transport of water
Hypotonic solution
Hypertonic solution
In osmosis, water travels from an area of lower solute concentration to an area of higher solute concentration
Not solute specific
Selectively permeable membrane
Solute molecule
HYPOTONIC SOLUTION
HYPERTONIC SOLUTION
Water molecule
Selectively permeable membrane
Solute molecule with cluster of water molecules
NET FLOW OF WATER
Figure 5.15

16. Water balance between cells and their surroundings is crucial to organisms
Osmosis causes cells to shrink in a hypertonic solution and swell in a hypotonic solution
The control of water balance (osmoregulation) is essential for organisms
ISOTONIC SOLUTION
HYPOTONIC SOLUTION
HYPERTONIC SOLUTION
ANIMAL CELL
(1) Normal
(2) Lysing
(3) Shriveled
Plasma membrane
PLANT CELL
Figure 5.16
(4) Flaccid
(5) Turgid
(6) Shriveled

17. Transport proteins facilitate diffusion across membranes as passive transport.
Small nonpolar molecules diffuse freely through the phospholipid bilayer but:
Many other kinds of molecules pass through selective protein pores (carrier proteins) by facilitated diffusion
Solute molecule
Transport protein
Figure 5.17

18. Facilitated Diffusion

19. Channel Proteins move ions passively through the membrane.

21. Cells expend energy for active transport
Transport proteins can move solutes across a membrane against a concentration gradient
This is called active transport
Active transport requires ATP

22. Active transport in two solutes across a membrane
FLUID OUTSIDE CELL
Phosphorylated transport protein
Active transport in two solutes across a membrane
Transport protein
First solute 1
First solute, inside cell, binds to protein 2
ATP transfers phosphate to protein 3
Protein releases solute outside cell
Second solute 4
Second solute binds to protein 5
Phosphate detaches from protein 6
Protein releases second solute into cell
Figure 5.18

24. Direction of transport
Uniports
Co-transports-symports and antiports

25. To move large molecules or particles through a membrane
5.19 Exocytosis and endocytosis transport large molecules---active transport
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
Figure 5.19A

26. or the membrane may fold inward, trapping material from the outside (endocytosis)
Figure 5.19B

27. Material bound to receptor proteins
Three kinds of endocytosis
Pseudopod of amoeba
Food being ingested
Plasma membrane
Material bound to receptor proteins
PIT
Cytoplasm
Figure 5.19C

28. 5.20 Connection: Faulty membranes can overload the blood with cholesterol
Harmful levels of cholesterol can accumulate in the blood if membranes lack cholesterol receptors
Phospholipid outer layer
LDL PARTICLE
Receptor protein
Protein
Cholesterol
Plasma membrane
Vesicle
CYTOPLASM
Figure 5.20

29. 5.21 Chloroplasts and mitochondria make energy available for cellular work
Enzymes and membranes are central to the processes that make energy available to the cell
Chloroplasts carry out photosynthesis, using solar energy to produce glucose and oxygen from carbon dioxide and water
Mitochondria consume oxygen in cellular respiration, using the energy stored in glucose to make ATP

30. Chemicals recycle among living organisms and their environment
Sunlight energy
Nearly all the chemical energy that organisms use comes ultimately from sunlight
Chloroplasts, site of photosynthesis
CO2 + H2O
Glucose + O2
Mitochondria sites of cellular respiration
Chemicals recycle among living organisms and their environment
(for cellular work)
Heat energy
Figure 5.21