1. Cell Transport, Photosynthesis, & Cellular Respiration
Unit 6 Notes
Cell Transport, Photosynthesis, & Cellular Respiration

2. 4/3 Monday’s Notes: Cell Membrane and Passive Transport

3. Chapter 7: Cell Structure & Function
Section 2: Cell Structure

4. Membrane
Cells need to maintain homeostasis and to do so the cells must control what crosses the cell membrane; the lipid bilayer does this
The Lipid Bilayer (Cell Membrane) is made of phospholipids;
Phosophorus - hydrophilic head – polar
2 Lipids/Fatty Acids - hydrophobic tails - nonpolar
The bilayer only allows few ions & nonpolar; most ions and polar substances are repelled

5. Membrane Proteins
Various proteins are in the membrane; some face in, some face out, some face both inside & outside
Proteins are amino acids, which are sometimes polar; they are therefore held in the membrane because they repel against the polar water on either side of the membrane & they are attracted to the nonpolar center of the cell membrane

6. Cell-Surface Marker: Receptor Proteins: Enzymes: Transport Proteins:
A long chain of sugars that identifies each type of cell
The sugars on the chain are attracted to the cell surface proteins; glycoproteins(which help cells work together)
Receptor Proteins:
Enable a cell to sense its surroundings by binding to certain substances outside the cell; this causes changes inside the cell
Enzymes:
Proteins in the cell membrane that help with important biochemical reactions inside the cell
Transport Proteins:
Aid in the movement of substances that cannot pass through the lipid bilayer across the cell membrane into & out of the cell

8. Chapter 7: Cell Structure & Function
Section 3: Cell Transport

9. Cells move substances of varying size, electrical charge & composition in & out of themselves
Sometimes cells require energy to move substances across its membrane, and sometimes they don’t
Passive Transport is when cells do not require energy to move substances
Active Transport is when cells require energy to move substances

10. Cell Transport
Passive transport:
The movement of substances across a cell membrane WITHOUT the use of cell energy
Substances move from an area of high concentration to an area of low concentration

11. Types of passive transport
Simple diffusion
Facilitated diffusion
osmosis

12. Concentration Gradient:
In a solution the randomly moving molecules want to fill spaces evenly; when the spaces are filled evenly it is called equilibrium
Concentration:
The amount of a particular substance in a given volume
The number of particles (solute) dissolved in a given amount of solution
Concentration Gradient:
When one area has a higher concentration than another area does

13. The direction of movement across the cell membrane depends on the concentration gradient
Some substances diffuse through the lipid bilayer
Other substances diffuse through transport proteins

14. Types of Passive Transport
Diffusion:
The gradual mixing of two or more substances by random motion
Movement down the concentration gradient
The movement to make the two areas equal in concentration; movement from high concentration to low concentration
After diffusion the concentration will become equal on both sides of the cell membrane
Examples:
sugar dissolves (spreads out evenly) in water to make Kool-Aid
Sugar cube dispersing in a beaker of water
Ink dispersing in a beaker of water
Eventually all of the molecules spread out evenly and reach equilibrium; equilibrium=when molecules are evenly spaced within a substance
High Concentration Low Concentration

15. When small, nonpolar molecules pass directly through the lipid bilayer
Simple Diffusion:
When small, nonpolar molecules pass directly through the lipid bilayer
Facilitated Diffusion:
Occurs when many types of ions & polar molecules do not diffuse easily through the nonpolar lipid bilayer
Transport proteins help these ions & polar molecules diffuse through the cell membrane
Two types of transport proteins that assist are Channel Proteins & Carrier Proteins

16. Channel Proteins: Carrier Proteins:
Ions, sugars, & amino acids diffuse through the aid of channel proteins
Often called Pores
Serve as tunnels through the lipid bilayer
Each channel aids specific substances of a specific size and/or charge
Carrier Proteins:
Substances that fit with their binding sites are transported by carrier proteins
Once the substance & protein bind the protein’s shape changes & transports the substance across the membrane where it is released

17. Simple Diffusion

18. Facilitated Diffusion

19. The size of the molecule The type of molecule
What determines whether a molecule can diffuse across the cell membrane?
The size of the molecule
The type of molecule

20. The diffusion of water across a membrane
Osmosis:
The diffusion of water across a membrane
Allows cells to maintain water balance as their environment changes
If there is a concentration gradient for solutes, there must also be a concentration gradient for free water molecules; osmosis occurs as water molecules work for EQUILLIBRIUM and move from high concentration to low concentration

21. Osmosis is a form of facilitated diffusion
Water is a polar molecule & therefore does not diffuse directly across the bilayer
Water must use channel proteins that only water molecules can move through

22. Isotonic environment/solution:
When the concentration of solute molecules inside the cell is equal to the concentration outside the cell
Water goes in and out of the cell at the same rate
There is no net change in water movement
The cell remains the same size

23. Water moves out of the cell The cell loses water & therefore shrinks
Hypertonic environment/solution:
When the concentration of solute molecules outside the cell is greater than the concentration inside the cell
Water moves out of the cell
The cell loses water & therefore shrinks

24. Water moves into the cell The cell gains water & therefore expands
Hypotonic environment/solution:
When the concentration of solute molecules inside the cell is greater than the concentration outside the cell
Water moves into the cell
The cell gains water & therefore expands

25. The swelling caused by a hypotonic solution can cause a cell to burst
The rigid cell walls of plants & fungi prevent cells from expanding too much
Many unicellular organisms have contractile vacuoles that collect excess water inside the cell & force it out of the cell to prevent swelling
Animal cells have the ability to avoid swelling by removing the dissolved solutes from the cell, which will leave the water & remove the particles causing the water concentration inside the cell to increase

26. Turgor Pressure:
The pressure that water molecules exert against the cell membrane
causes cells to swell up
Plasmolysis
When water leaves the cell and turgor pressure is lost
The reason plants wilt (shrivel up) when they don’t get enough water
When a cell takes in too much water it will eventually burst open
This process is called cytolysis or lysis

27. Organism Images

28. Facilitated Diffusion:
When substances move across the membrane with the help of protein carriers
Even if there is a concentration gradient and molecules want to move across the cell membrane, some still can’t cross it
They may be too large
They may not dissolve in lipids (which make up the cell membrane)

29. Carrier Proteins carry molecules across the cell membrane during facilitated diffusion
This requires no energy, so it’s a passive form of transport
Carrier proteins are specific for the type of molecule
A glucose carrier protein will only work for glucose

30. sodium (Na+) calcium (Ca2+) potassium (K+) chloride (Cl-)
Diffusion through Ion Channels:
When ions pass through the cell membrane through ion channels
Ions can’t pass through the cell membrane on their own so they move through ion channels
Examples of Ions that must pass through Ion Channels:
sodium (Na+)
calcium (Ca2+)
potassium (K+)
chloride (Cl-)