T1 - transport in cells Flashcards
(42 cards)
Define the term diffusion.
Diffusion is the spreading out of particles in a solution or a gas, resulting in net movement of particles from a region of higher concentration to a region of lower concentration.
What is a concentration gradient?
A concentration gradient is a difference in concentration between two regions.
True or False? Diffusion is an active process.
False. Diffusion is a passive process that occurs when molecules spread out due to their random movement.
What is a partially permeable cell membrane?
A partially permeable cell membrane allows some substances to pass through while preventing others from entering or leaving a cell.
Name an example of diffusion that takes place in the human lungs.
Examples of diffusion in the lungs include: oxygen diffuses from the inhaled air into the blood through the alveolar lining, carbon dioxide diffuses from the blood into the exhaled air through the alveolar lining.
True or False? The waste product urea diffuses from body cells into the blood.
True. Urea is a metabolic waste product produced in the cells. It diffuses into the blood before being excreted by the kidneys.
What is the relationship between surface area and rate of diffusion into a cell?
As surface area to volume ratio increases, so does the rate of diffusion (and vice versa). This is because a larger surface area provides more space across which diffusion can occur.
What is the effect of increasing temperature on the movement of particles?
At higher temperatures particles move around faster; this is because they have more kinetic energy.
True or False? Increasing temperature decreases the rate of diffusion.
False. As temperature increases, the rate of diffusion also increases. Molecules move around faster at higher temperatures, resulting in faster diffusion.
True or False? Increasing the concentration gradient will increase the rate of diffusion.
True. As concentration gradient increases the rate of diffusion also increases.
Define the phrase surface area to volume ratio.
Surface area to volume ratio is the surface area of an object in relation to its volume.
What happens to the surface area to volume ratio as cell size increases?
As cell size increases the surface area to volume ratio decreases.
Why do multicellular organisms need exchange surfaces and transport systems?
Multicellular organisms need exchange surfaces because their small surface area to volume ratio means that exchange of substances at their body surface is too slow to meet their needs. Multicellular organisms need transport systems because of their large volume; their bodies contain many layers of cells, meaning that internal transport by diffusion alone is too slow.
What are the features of an efficient exchange surface?
Features of an exchange surface include: A large surface area, A thin barrier / short diffusion distance, A steep concentration gradient, maintained by having a good blood supply and a good supply of required substances.
True or False? The alveoli provide an exchange surface in mammals.
True. The alveoli provide an exchange surface for gas exchange between the lungs and the blood.
How do the alveoli aid gas exchange?
Alveoli facilitate gas exchange as follows: They have a large surface area, Their walls are thin, They have a good blood supply, They are well ventilated. These are all features of an efficient exchange surface.
What is the function of stomata in leaves?
Stomata are tiny openings that allow air to move in and out of leaves. This decreases the diffusion distance for gas exchange inside the leaf.
What is the name of the leaf cell type across which gas exchange occurs inside leaves?
Gas exchange occurs between the leaf air spaces and the interior of the spongy mesophyll cells.
How are fish gills adapted for efficient gas exchange?
Fish gills are adapted for gas exchange as follows: Many filaments covered in lamellae increase the surface area, A dense capillary network maintains concentration gradients.
True or False? Villi in the small intestine of mammals have a large surface area but are not well supplied with blood.
False. The villi in the small intestine do have a large surface area, but they also have a good blood supply to maintain a steep concentration gradient between the intestine and the blood.
Define the term osmosis.
Osmosis is the diffusion of water molecules from a region of higher water concentration (dilute solution) to a region of lower water concentration (concentrated solution), through a partially permeable membrane.
True or False? Only water can move by osmosis.
True. Only water can be transported by osmosis.
What type of concentration difference leads to osmosis?
The type of concentration difference that leads to osmosis is a difference in water concentration between two regions. This can also be referred to as water potential.
True or False? Osmosis only occurs across a partially permeable membrane.
True. Osmosis must take place across a partially permeable membrane. If water moves in any other way, e.g. water vapour moving out of a leaf via the stomata, this is diffusion.