Describe in detail the process that is illustrated above. Include details from each step, using correct science terms.

Homeostasis and Cellular Transport

To stay alive, a cell must exchange materials such as food and waste with its environment. These materials must cross the cell membrane.

Passive Transport Does not require the cell to use energy Diffusion Osmosis Facilitated diffusion

SimpleDiffusion is the movement of molecules from an area of higher concentration to an area of lower concentration. (down its concentration gradient) concentration gradient - the difference in the concentration of molecules across a space Driven by kinetic energy energy of motion

Diffusion

Diffusion causes the concentration of molecules to be the same throughout space When molecules are dispersed evenly, there is no longer any diffusion because there is no longer a concentration gradient. a state of equilibrium exists (balance)

Rate of Diffusion molecules diffuse faster at higher temperatures than at lower temperatures smaller molecules diffuse faster than larger molecules Type of molecule

Water and Diffusion The diffusion of water across a semipermeable membrane is called osmosis. Osmosis occurs in response to the concentration of solutes dissolved in water.

Diffusion of Water

The net direction of osmosis depends on the

Hypertonic Solution In a hypertonic solution, the concentration of solute molecules outside the cell is higher than inside the cell. What direction will the water diffuse?

Water diffuses out of the cell until equilibrium is reached.

What do you think will happen if the cell loses too much water? The cell will shrink and shrivel. plasmolysis

Hypotonic Solution In a hypotonic solution, the concentration of solutes outside the cell is lower than the concentration of solutes inside the cell. What direction will the water diffuse?

Water diffuses into the cell until equilibrium is reached.

How does this affect the cell? The cell will swell and possibly burst. Cytolysis

Isotonic Solution In an isotonic solution, the concentration of solutes outside and inside the cell are equal. How will the water diffuse across the cellular membrane?

Water will diffuse in and out of the cell at equal rates.

Red Blood Cell in different Solutions

Facilitated Diffusion To facilitate means to help. Channel proteins and carrier proteins

Carrier proteins change shape when molecules attach. The change in shape of the carrier protein allows the molecule to cross the membrane.

Active Transport Movement of molecules across the membrane from an area of low concentration to areas of high concentration. This requires the cell to expend energy(ATP).

Cell Membrane Pumps SODIUM-POTASSIUM PUMPS IN ANIMAL CELLS PUMP SODIUM IONS OUT, AND POTASSIUM IN, UP THEIR CONCENTRATION GRADIENT.

IMPORTANT FOR MUSCLE CONTRACTIONS, and THE TRANSMISSION OF NERVE IMPULSES

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Endocytosis and Exocytosis Molecules that are too large to cross the cell membrane are packaged in membrane-bound sacs (vesicles) and moved across the membrane

Endocytosis

TWO TYPES ON ENDOCYTOSIS PINOCYTOSIS – uptake of liquids “cell drinking” PHAGOCYTOSIS - uptake of solids “cell eating”

Exocytosis

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Think: Apply what you have learned! In plants, cells that transport water against the concentration gradient are found to contain many more mitochondria than do some other plant cells. Give a possible explanation for this?