Cells and Multicellular organisms
The basic unit of life
the movement of particles from high to low concentration
What type of biological molecule are most enzymes?
Proteins.
What are the two main types of circulatory systems?
Open and closed.
Which tissue transports water through plants?
Xylem
The function of the mitochondria
Aerobic Cellular respiration and ATP production
The main requirement of Active Transport
ATP
What is the region where a substrate binds to an enzyme called?
Active Site
What is the name of the oxygen-carrying protein in mammalian red blood cells?
Haemoglobin.
What does the phloem transport?
Sucrose and other organic compounds
The difference between specialised and unspecialised cells.
Specialised cells have structures adapted to specific functions, while unspecialised cells have not yet developed specialised functions.
What is osmosis?
The net movement of water across a selectively permeable membrane from high water concentration to low water concentration.
What is the function of an enzyme?
To act as a biological catalyst, lowering activation energy and increasing reaction rate.
What is the function of the alveoli in mammalian gas exchange?
Increases surface area
What is the loss of water vapour from leaves called?
Transpiration
Why do multicellular organisms require specialised transport systems?
Diffusion alone is too slow to transport substances over large distances to all cells.
How does facilitated diffusion differ from simple diffusion?
Facilitated diffusion uses transport proteins, while simple diffusion occurs directly through the phospholipid bilayer. Neither requires ATP.
Why does an enzyme stop functioning effectively at extreme temperatures?
Its structure can denature, changing the shape of its active site so the substrate can no longer bind effectively.
Why do mammals have a four-chambered heart?
It completely separates oxygenated and deoxygenated blood, allowing efficient oxygen delivery to the body.
What causes water to move upwards through the xylem?
Transpiration creates tension that pulls water upwards. Cohesion maintains a continuous water column, while adhesion helps water interact with xylem walls.
Why do larger organisms have a lower surface area-to-volume ratio?
Volume increases faster than surface area as an organism grows, reducing the surface area available for exchange relative to its volume.
How can root hair cells absorb mineral ions when their concentration is lower in the soil than inside the cells?
Active transport uses carrier proteins and energy from ATP to move mineral ions against their concentration gradient.
Why does enzyme activity eventually stop increasing when substrate concentration continues to rise?
All enzyme active sites become occupied, so the enzymes are working at maximum rate (saturation).
Why can insects not grow as large as many mammals?
Their tracheal system relies on diffusion to deliver oxygen directly to cells, while their open circulatory system does not transport significant oxygen. This limits oxygen delivery over greater distances.
Why does closing stomata during drought reduce photosynthesis?
Closing stomata reduces water loss but also limits carbon dioxide entry, reducing the rate of photosynthesis.