SA:VOL ratio Flashcards
What is the relationship between metabolic rate and cell volume?
The metabolic rate of a cell (the rate of all its chemical reactions) is proportional to the volume of the cell.
Why is surface area important for a cell?
The surface area is important because it determines the rate at which substances can be absorbed into the cell and waste products can be removed.
What is the surface area-to-volume ratio?
Surfacearea-to-volumeratio=
sa/vol
What happens if the surface area-to-volume ratio is too small?
If the surface area-to-volume ratio is too small, substances will not be absorbed quickly enough, and waste products will accumulate because they are produced faster than they can be excreted.
How does the surface area-to-volume ratio affect heat production and loss in cells?
A small surface area-to-volume ratio may cause the cell to overheat because the metabolism produces heat faster than it can be lost across the cell’s surface.
What happens when the surface area is too large compared to the volume?
When the surface area is much larger than the volume, the cell can exchange substances (like nutrients and waste) more efficiently, but it may be less efficient at maintaining internal conditions due to the limits of its metabolic capacity.
Why do larger cells face challenges related to surface area and volume?
Larger cells have a smaller surface area-to-volume ratio, meaning they struggle to absorb enough substances quickly enough and remove waste efficiently, which can limit their metabolic efficiency.
How does the shape and size of red blood cells help increase their surface area-to-volume ratio?
Red blood cells are small (~8μm in diameter) and have a biconcave disc shape, which gives them a large surface area-to-volume ratio. This helps with the rapid loading and unloading of oxygen molecules.
Why is a biconcave disc shape beneficial for red blood cells?
The biconcave disc shape of red blood cells reduces their volume compared to a sphere of the same diameter and decreases the distance between the cytoplasm and the surface membrane, making gas exchange more efficient.
What is the role of proximal convoluted tubule (PCT) cells in the kidneys?
Proximal convoluted tubule (PCT) cells in the kidneys reabsorb most of the glomerular filtrate, including useful molecules like glucose, through selective reabsorption.
How do PCT cells adapt to facilitate selective reabsorption?
- Their walls are one cell thick, making it easy for molecules to pass through.
- The apical membrane (inner surface) has many microvilli, increasing surface area for absorption.
- The basal membrane (outer surface) has invaginations, further increasing surface area for transport proteins.
Why is microvilli important in PCT cells?
Microvilli on the apical membrane of PCT cells increase the surface area, allowing for more channel and pump proteins to facilitate the absorption of ions and molecules.
How do the membranes of PCT cells aid in selective reabsorption?
The inner apical membrane is in contact with the filtrate, while the outer basal membrane is close to capillaries. This allows molecules to pass through both membranes and be selectively absorbed. The membranes are rich in channel and pump proteins, ensuring that only required substances are reabsorbed.
