1. Cell Structure and Function
Chapter 4 and 5

2. Cell Theory 1. All Living things are made of cells
1838 – Matthias Schleiden – plants are made of cells.
1839 – Theodor Schwann – animals are made of cells.
1. All Living things are made of cells
2. Cells are the basic unit of life
1855 – Virchow – studied cell division and…
3. All cells come from preexisting cells.

3. plasma membrane
Fig. 5-23a, p.88

5. Cell Membrane Structure
Phospholipid Bilayer
Phosphate head towards the water (hydrophilic)
Lipid tails towards each other (hydrophobic)

6. Fluid Mosaic Model of the Cell Membrane
Fluid (dynamic)
Phopholipids are not rigid
Proteins also move around within the membrane
Mosiac
A network of many proteins/molecules/cholesterol
Some proteins go through the membrane (integral)
Others stay on one side of the membrane (peripheral)

7. Function of the Cell Membrane
Protects the cells from surroundings
and
Selectively allows substances to pass through the membrane (what kind of substances?)
Enzyme activity, cell recognition, cell signaling, cell transport

8. glucose and other large, polar, water-soluble molecules; ions (e.g.,
oxygen, carbon
dioxide, and other
small, nonpolar
molecules; some
water molecules
glucose and other large,
polar, water-soluble
molecules; ions (e.g.,
H+, Na+, K+, Ca++,
Cl–); water molecules
Fig. 5-15, p.82

9. Passive Transport
Flow of solutes down their concentration gradients: High to low conc.
Can move both ways
Does not require any energy input
Ex. Diffusion, Osmosis and facilitated diffusion

10. Passive Transport
Diffusion
Small molecules move from a region of high concentration to a region of low concentration till they are equally dispersed (equilibrium is reached)
Ex. Oxygen, carbon-dioxide
Fig. 5-16, p.82

11. Passive transport Osmosis
Diffusion of water molecules across a selectively permeable membrane
Direction of net flow is determined by water concentration gradient
Side with the most solute molecules has the lowest water concentration

12. Tonicity and Osmosis Passive Transport Osmosis2%
sucrose
Tonicity and Osmosis
water
10% sucrose
2% sucrose
Hypotonic: lower conc. solutes outside the membrane High conc. of water outside – more water flows in
Hypertonic: higher conc. solutes outside the membrane
So lower conc. of water outside – more water flows out
Isotonic: equal conc. solutes across the water flows across
in equal amounts

13. Passive transport- Facilitated Diffusion
glucose transporter
solute (glucose)
high
low
Passive transport- Facilitated Diffusion
Stepped Art
Fig. 5-18b, p.84

14. Active transport

15. Against the concentration gradient Needs energy (ATP)
Active transport
Against the concentration gradient
Needs energy (ATP)
Uses membrane proteins
Example: Sodium and potassium pumps in nerve cells

16. Bulk Transport Endocytosis (vesicles in) Exocytosis (vesicles out)
Fig. 5-17b, p.83

17. Cells need energy to live and work
What is cell work?
Transport of substances across and within the cell
Breakdown and build up of compounds
Chromosomes in nucleus duplicates
In most ecosystems the ultimate form of energy is from ____
Used to form the bonds of energy in _____
Breaking bonds releases energy to form ATP
ATP does the actual work in cell

18. Energy Cycle in Cells

19. Energy Flow First Law of Thermodynamics Second Law of Thermodynamics
Energy cannot be created or destroyed
Can be converted from one form to another
Ex. Energy is released when burning wood
Second Law of Thermodynamics
During energy conversions, some forms of energy cannot be used for work
Entropy or disorder

20. Energy Flow in Ecosystems
Photosynthesis transfers the energy from light to…
Energy in the chemical bonds of sugars
Cell respiration breaks the bonds of the sugars to make ATP
Metabolism = sum total of all the reactions in a cell.
Catabolism (break down)
Anabolism (build up)

21. Nature of Metabolism Most reactions occur controlled stepwise fashion
Reactants > Intermediates > products
These reactions can also happen in reverse
Example: Glucose + Glucose > Maltose + Maltose > Starch etc.
Reverse Starch > Glucose + Glucose + Glucose ……

22. Metabolic reaction rate
Must happen very quickly
Need catalysts to speed up reactions which would otherwise happen slowly
Ex glucose will degrade into CO2 and H2O but would take a long time
Biological catalysts –ENZYMES speed up this reaction so cells can use the energy

23. How do enzymes work?
For a reaction to occur, an energy barrier must be surmounted
Enzymes make the energy barrier smaller

24. Enzyme - Catalase

25. How do enzymes work?

26. Enzymes Biological catalysts – Proteins
Lowers activation energy needed to begin a reaction
Have an active site where the reactants attach
Remain unchanged at the end of the reaction
Can be reused
Specific to the reaction it catalyzes
Each reaction has its own specific protein

27. Factors effecting enzyme activitypH
Temp changes
Salt concentrations
Cofactors
Inhibitors – competitive and noncompetitive

28. Cell transport review Go to: