Biology Revision (Unit 1: Bodily Transport Processes)

Question 1

What is diffusion?

Answer 1

• Passive transport process (does not require energy)
• Moves molecules from area of high concentration to low concentration
• Speed influenced by the concentration gradient (difference in concentration between two regions)
• Important in maintaining cellular homeostasis and for respiration
  0 Regulates ions and gases

Question 2

What is osmosis?

Answer 2

• Passive transport process
• Net movement of water across a selectively permeable membrane from region of low solute concentration to high solute concentration
• Moves from high water potential (dilute solution) to low water potential (concentrated solution)
• Used to get nutrients out of food and get waste out of the blood
• Used in maintaining water content in a plant cell and its firmness

Question 3

What is hypertonic, isotonic, and hypotonic?

Answer 3

Hypertonic: solution has higher solute concentration

Hypotonic: solution has lower solute concentration

Isotonic: both solutions have equal solute concentration

Question 4

What is active transport?

Answer 4

• The movement of particles against the concentration gradient (from low to high concentration)
• Protein membrane uses ATP energy to move nutrients into cell through cell membrane
• Once nutrients are in cell, ATP has been broken down into ADP and phosphate
• ADP and phosphate are brough to mitochondria to be converted back into ATp to be used again
• Energy-dependent and is selective and regulated
• Commonly used in cellular processes such as ion balance and nutrient uptake

Question 5

What is the effect of hypertonic and hypotonic solutions on plant and animal cells?

Answer 5

Animal Cells:
- If animal cell is in a hypotonic solution, water moves into the cell causing it to swell and burst
- If animal cell is in a hypertonic solution, the water diffuses out of the cells, causing the cytoplasm to shrink and shrivel up

Plant Cells:
- If plant cell is in a hypotonic solution, water diffuses into the cell
- This causes the cytoplasm and vacuole to swell
- However, due to the strong cell wall, it keeps the cytoplasm from expanding until it bursts
- Causes the plant cell to be in a blown-up state, referred to as turgid

• If plant cell is in a hypertonic solution, it loses water through osmosis
• This causes the cytoplasm to shrink and stop pushing against the cell wall
• This means that the cell becomes floppy, known as flaccid, making the cell will
• If the solution is very concentrated, the cytoplasm shrinks further to the center while the cell wall remains stiff
• This causes the cytoplasm to tear away from the cell wall
• This means that the cell is plasmolysed and typically kills the cell

Question 6

What is endocytosis

Answer 6

• The various types of active transport that moves particles through the cell membreane
• Include phagocytosis, pinocytosis, and exocytosis
• Basic process is envlosing particles in a vesicle made of plasma membrane by the cell membrane folding inward on the target particles then pinching it off with specialized proteins
• This contains particles in a vacuole/vesicle

Question 7

What is pinocytosis?

Answer 7

• Extracellular fluids are brought into the cell in small amounts
• Useful in nutrient absorption for fluids with various solutes (e.g., villi lining on small intestine absorbing nutrients)

Question 8

What is phagocytosis?

Answer 8

• Large particles like cells or cell debris are transported into the cell using active transport
• Used in immune responses when cells engulf and digest pathogens
• Also used in single-celled eukaryotes to hunt prey

Question 9

What is exocytosis?

Answer 9

• Materials are transported from inside a cell to the outside using membrane-bound vesicles
• Uses include cellular waste excretion, hormone secretion, and neurotransmitter release