Biology Paper 1 - Transport In Cells

Question 1

Cell Cycle (Mitosis)

Answer 1

(1) Replication of DNA to produce 2 copies of each chromosome and synthesis of new sub-cellular structures (number of sub-cellular structures increase).
(2) One set of each chromosome is pulled to each side of the cell (The nucleus divides)
(3) Cytokinesis occurs and this is where the cytoplasm and the cell membrane begin to deform in the middle of the cell and the cell divides into 2 identical cells

Question 2

Diffusion

Answer 2

The passive net movement of particles from a high concentration to a low concentration.

Question 3

Factors Affecting Rate Of Diffusion

Answer 3

• Greater concentration gradient = greater rate of diffusion
• Increase in temperature = increase KE in particles so increase in rate of diffusion
• Increase surface area of membrane = Increase rate of diffusion

Question 4

How Organisms Are Adapted For Exchanging Materials

Answer 4

Mammals: Lungs - Human SA:V ratio is low, so simple diffusion is not likely to get a person a sufficient amount of food. Air moved in and out of lungs when you breathe, ventilating millions of air sacs known as Alveoli. Alveoli have a large SA and a rich blood supply, for effective gaseous exchange.
Mammals: Small intestines - The Villi has a large SA, short diffusion paths and a rich blood supply for more effective gaseous exchange.
Fish: Gills - made of stacks of thin filaments, each with a rich blood supply. Fish need a constant flow of water over their gills to maintain a conc. gradient needed for effective gas exchange. They get this by pumping water over their gills using a flap called the Operculum.
Plant: Roots - Large SA, made bigger by root hair cells - uptake of water and mineral ions more efficient. Water constantly moving away from roots in transpiration stream, maintaining a steep conc. gradient.
Plant: Leaves - Flat, thin leaves, the presence of air spaces in the leaf tissue and Stomata provide a large SA, maintaining a steep conc. gradient for diffusion of water, mineral ions and CO2.

Question 5

Active Transport

Answer 5

The movement of particles from a more dilute solution to a more concentrated solution, which requires ENERGY from respiration.

Question 6

Active Transport in Root Hair Cells

Answer 6

Active transport allows mineral ions to be absorbed into plant root hairs
from very dilute solutions in the soil. Plants require ions for healthy
growth.