Cell Transport

TEKS

• (4) Science concepts. The student knows that cells are the basic structures of all living things with specialized parts that perform specific functions and that viruses are different from cells. The student is expected to:

• (B) investigate and explain cellular processes, including homeostasis, energy conversions, transport of molecules, and synthesis of new molecules

Important Vocabulary

1. PhosphoLipid bi-layer

2. Membrane

3. Integral proteins

4. Selectively permeable

5. Diffusion

6. Facilitated diffusion

7. Osmosis

8. Active transport

9. Aquaporins10. Solute, solvent,

solution11. Concentration

gradient12. Slope 13. Hypertonic14. Hypotonic15. Isotonic16. Equilibrium17. Net-movement

18. Osmotic potential

19. Osmotic pressure

20. Turgor

21. Plasmolysis

22. Cytolysis

Plasma (Cell) Membrane (Phospholipid Bilayer)

• Outer boundary of cytoplasm

• Semipermiable (only certain molecules enter

& leave)

Outside

of cell

Inside

of cell

(cytoplasm)

Cell

membrane

Proteins

Protein

channelLipid bilayer

Carbohydrate

chains

Phospholipid bilayer

• A double layer that is an effective barrier for most molecules

• Hydrophobic = “water fearing” tails in the center, prevent most things from entering

• Hydrophilic = “water loving” heads attract water to edges of membrane

Outside

of cell

Inside

of cell

(cytoplasm)

Cell

membrane

Proteins

Protein

channelLipid bilayer

Carbohydrate

chains

Fluid Mosaic Model

• Cell membranes are mosaics that contain many different molecules like proteins, cholesterol, glycoproteins, etc.

Proteins embedded in membranes can be:

• Channels “gates” to interior for transporting into & out of cytoplasm

• Receptors “windows” for gathering information about cell surroundings

• Markers “name tags” that identify type of cell to others

Membranes are Selectively permeable

• The plasma membrane enables only certain molecules to enter or exit the cell.

• Why is this important?

Surface to volume ratio

• Why are larger organisms are multicellular? Why aren’t they just one big ol’ cell?

• Because materials must be transported across cell membranes, maximizing the amount of membrane surface area increases transport efficiency.

Comparing surface area to volume(Complete the calculations with your table partner and be ready to share)

• Surface area: 6 mm x 6 mm x 6 sides = ___ mm2

• Volume: ___ mm3

• S / V = ___

• Surface area: 3 mm x 3 mm x 6 sides x 8 cubes = ___ mm2

• Volume = ___ mm3

• S / V = ___

Types of passive transport

• Diffusion

• random spread of molecules from higher to lower concentration

• Examples?

Types of transport across membranes

1. Diffusion (Simple Diffusion) movement from an area of high concentration to an area of low concentration.

2. Facilitated diffusionlarge molecules (ie. Glucose or water) move through protein channels in the cell membrane.

3. Active transportmovement of molecules against the concentration gradient – requires cellular energy

current

(Concentration gradient)

Passive or Active transport?

Passive vs Active transport:which requires energy output?

Diffusion across a membrane

In which pictures do we see the greatest gradient?

In which pictures do we see equilibrium?

Osmosis across a membrane

Osmosis

• Diffusion of water across a selectively permeable membrane from higher water purity to lower water purity

• When solutions of varying water concentrations are found across a membrane, the solutions are given names.

• Hypertonic

• Hypotonic

• Isotonic

Types of osmotic solutionsHypotonic

• High water purity & less solutes = water moves in & cell expands and may burst (Cytolysis)

Isotonic

• Equal solutes & water, so equal movement of water into and out of the cell

Hypertonic

• Low water purity because of more solutes = water moves out & cell shrinks (Plasmolysis)

Cells in hypotonic solution Cells in hypertonic solution

Cells in isotonic solution

Cells in various solutionsCopy this chart in your IAN

LYSE

TURGID

NORMAL

FLACCID

PLASMOLYSIS

Plant,

fungus,

algae,

bacteria

animal

Hypotonic Isotonic Hypertonic

Achieving equilibrium

Active transport video

Types of Active Transport

Endocytosis

• cell brings moleculesin.

Pinocytosis

• Liquids are brought in.

Phagocytosis• Phage means to “eat”

• large particles (food or bacteria) are surrounded & engulfed by cell.

• Examples = an ameba feeding &

a white blood cell destroying an invader.

Why are white blood cells called MacroPhages?

“Cell eating”

Exocytosis

cell deposits particles outside of

cytoplasm

• Secretion = cell products given off

• Excretion = wastes products given off

The Big Idea: Cell structure is related to it’s function

• All cells are different.

• Cell specialization → different cells have different jobs.

• Each cell serves different needs.

• Diversity on a individual scale helps stabilize the organism

• Diversity on a large scale helps stabilize the ecosystem