Cell transport

What is diffusion?

spreading out of particles from lower to higher concentration.

Kinetic theory

molecules in constant random motion bc of their kinetic energy

kinetic theory in solids

particles held together, so they can only vibrate

kinetic theory in liquids

forces of attraction between particles weaker, particles can move freely

kinetic theory in gases

forces of attraction very weak, can freely move.

Diffusion is fastest in gases

how temperature affects movement of particles

higher temperature, more energy particles have, faster movement

Effect of temperature on rate of diffusion

particles gain more kinetic energy when temp is high. quicker movement. collides more often. speeds up diffusion

Effect of greater SA on rate of diffusion

faster bc more SA to pass through in diffusion

What is osmosis?

movement of water molecules across a selectively permeable membrane from high to low water concentration.

Hypotonic solution

more concentrated than the surrounding solution. Water moves into cell. Cell swells and becomes turgid.

Isotonic solution

solution is same concentration. water will move in and out of the cell equally.

Hypertonic solution

Solution more concentrated than cells content. Water moves out of the cell. Cell membrane pulls away from the cell wall; plasmolysis

Turgid

swollen cell

Plasmolysis

water leaves plant cell. Plant cell & cytoplasm shrinks and cell membrane pulls away from cell wall.

Flaccid

cell lacking water

Why is osmosis important?

controls the balance of water in cells, maintaining cell shape and function, prevents them from shrinking or bursting.

homeostasis

maintains a constant internal environment and prevents these changes having a serious impact on our cells.

Equation for % change:

new-old/old x 100

What is needed if particles want to go against the concentration gradient?

energy from respiration to push other particles. Transport proteins transports low conc molecules to high concentrated molecules.

Active transport

movement of substances from low to high concentration against a concentration gradient. Require energy released by respiration.

Process of active transport

- Random movement means useful molecules enters special site on transport protein.

- Rotates and drops useful molecule inside the cell.

- Once protein energised again, process repeats.

Word equation for aerobic respiration

glucose + oxygen --> carbon dioxide + water + energy

Effect of rate of respiration on rate of active transport

Increased respiration increases rate of active transport. More energy provided allows transport protein to do its job.

Root hair cells

Mineral ions in the soil like nitrate ions. Using active transport, plants can absorb them against a concentration gradient. Mineral ions required for healthy growth.

In the guts

Sugar/glucose, is always actively absorbed out of the gut and kidney tubules into blood. Done against a concentration gradient. Glucose needed for cellular respiration.

Alveoli adaptions

- ventilation of air in & out maintains a steep conc gradient.

- very thin alveolus walls, short distance between air & blood makes diffusion faster.

- spherical shape for larger SA

- good blood supply, maintains conc gradient for diffusion by removing oxygen and bringing lots of co2

Small intestine adaptions

Lining of small intestine is folded into thousand villi, further covered with microvilli which increases SA for exchange. Thin and have good blood supply