1What is diffusion?
The spreading out of particles resulting in a net movement from higher to lower concentration
2Is diffusion a passive or active process?
Passive
3What molecule types can cross cell membranes via diffusion?
Small molecules like oxygen, glucose, amino acids, and water
4Why can single-celled organisms rely solely on diffusion?
They have a relatively large surface area to volume ratio and low metabolic demands
5Why can multicellular organisms not rely on diffusion alone?
They have a small surface area to volume ratio
6What are the four main factors that affect the rate of diffusion?
Concentration gradient, temperature, surface area of the membrane, and diffusion distance/membrane thickness
7What is osmosis?
The movement of water from a less concentrated solution to a more concentrated one through a partially permeable membrane
8What type of water potential does a dilute sugar solution have?
High water potential
9What type of water potential does a concentrated sugar solution have?
Low water potential
10What term describes an external solution with the same concentration as the cell interior?
Isotonic
11What term describes a more concentrated external solution causing water to leave a cell?
Hypertonic
12What term describes a more dilute external solution causing water to enter a cell?
Hypotonic
13What happens to animal cells in a very dilute external solution?
They swell and burst
14What happens to animal cells in a concentrated external solution?
They become shrivelled
15What is turgor pressure in plant cells?
Pressure caused by water entering the vacuole, keeping leaves and stems rigid
16What is plasmolysis in plant cells?
When water moves out, causing the cell membrane to pull away from the cell wall, leading to death
17What is active transport?
The movement of particles against the concentration gradient from lower to higher concentration
18Does active transport require energy?
Yes, from respiration
19Why do root hair cells require active transport?
To absorb mineral ions from the soil against their concentration gradient
20Why is active transport required in the gut?
To move sugar molecules into the blood when gut concentration is lower than blood concentration
21What is mitosis?
A type of cell division where one cell forms two identical daughter cells
22What happens during Stage 1 (Interphase) of the cell cycle?
The cell grows, organelles increase, proteins are synthesized, and 46 chromosomes are replicated
23What happens during Stage 2 (Mitosis) of the cell cycle?
Chromosomes line up at the equator and spindle fibres pull them to opposite sides
24What happens during Stage 3 (Cytokinesis)?
The cytoplasm and cell membranes divide to form two identical daughter cells
25Why is mitosis important in multicellular organisms?
For growth, development, replacing damaged cells, and asexual reproduction
26What is cellular differentiation?
The process where a cell gains new sub-cellular structures to suit a specialized role
27What are stem cells?
Undifferentiated cells that can undergo division to produce more cells and differentiate into specialized types
28What are the three main structural adaptations of a sperm cell?
Streamlined head and long tail, many mitochondria, and an acrosome with digestive enzymes
29What are the key structural features of a nerve cell?
A long axon for long-distance impulses, dendrites for connections, and mitochondria at endings for neurotransmitters
30Which special proteins slide over each other to cause muscle cell contraction?
Myosin and actin
31What chemical do muscle cells store to use in respiration?
Glycogen
32What are the structural adaptations of root hair cells?
Large surface area from root hairs, large permanent vacuole, and mitochondria for active transport
33How are xylem cells adapted for water transport?
Lignin causes cells to die making them hollow, joined end-to-end to form continuous tubes with spirals for pressure resistance
34What are sieve plates in phloem cells?
Cell walls with broken-down structures allowing substances to move between cells
35What cells supply the energy needed by phloem cells to stay alive?
Companion cells
36Where do embryonic stem cells form and what can they become?
They form from a zygote and can differentiate into any type of cell in the body
37What can adult stem cells found in bone marrow form?
Many cell types, including blood cells
38Where are plant meristems found and what is their role?
Found in root and shoot tips, they can differentiate into any plant type throughout the plant's life
39How is the surface area to volume ratio calculated?
By finding volume (length x width x height) and surface area (length x width) and reducing the ratio
40What is the approximate total surface area of human alveoli?
75m^2
41What tiny projections increase the surface area of the small intestine?
Villi
42What structures increase the surface area of fish gills?
Lamellae
43Why do mammals require a double circulatory system?
Because they have a high metabolic rate requiring a faster system
44Which chamber of the heart pumps deoxygenated blood to the lungs?
Right ventricle
45Which heart chamber has a thicker muscular wall and why?
Left ventricle, because it must pump blood all around the body
46What is the function of heart valves?
To prevent blood from flowing backwards
47What blood vessels supply the heart muscle with its own oxygenated blood?
Coronary arteries
48Through which major vessels do blood enter the right and left atria respectively?
Vena cava and pulmonary vein
49What are the structural adaptations of arteries?
Thick muscle layers and elastic fibres to withstand high pressure
50What structural features do veins have to help return blood to the heart?
A wide lumen and valves to ensure correct direction of flow
51How are capillaries adapted for exchange?
Walls are one cell thick to create a short diffusion pathway and are permeable
52What is haemoglobin?
A red protein in red blood cells that combines with oxygen
53Why do red blood cells lack a nucleus?
To create more space for haemoglobin
54What is plasma?
The liquid component of blood that carries cells, platelets, dissolved nutrients, and waste products
55What is transpiration?
The loss of water vapour from leaves and stems as a consequence of gaseous exchange
56What force maintains a continuous column of water up the plant xylem?
Hydrogen bonding causing water molecules to be attracted to each other
57What are bordered pits in xylem cell walls?
Holes that allow specific areas for water and minerals to enter the plant
58What role do guard cells play in the leaf?
They open and close stomata and are kidney-shaped with thin outer and thick inner walls
59Where are more stomata typically found on a leaf and why?
On the bottom surface, to minimize water loss by evaporation in the shade
60What effect does increased light intensity have on transpiration?
It increases photosynthesis, causing more stomata to open and transpiration to rise
61How does increased air movement (wind) affect transpiration?
It blows away water vapour, maintaining a steeper concentration gradient and increasing diffusion
62How does an increase in humidity affect transpiration rate?
It decreases the rate of transpiration by reducing the concentration gradient between inside and outside the leaf
63What apparatus is used to investigate factors affecting plant water uptake?
A potometer
64What is translocation?
The movement of food substances made in leaves up or down the phloem
65What are embryonic stem cells used for in potential medical research?
Replacing insulin-producing cells in diabetes, neural cells for Alzheimer's, or nerve cells for spinal cord injuries
66What are the main adaptations of gas exchange surfaces?
Large surface area, thin membrane, and efficient blood supply or ventilation
67Which blood vessel carries blood from the right ventricle?
Pulmonary artery
68Which blood vessel carries blood from the left ventricle?
Aorta
69What shape are red blood cells to maximize surface area?
Biconcave