Cells 3 Flashcards
(26 cards)
Why do substances move into and out of cells?
To supply the organelles with necessary materials (e.g. glucose, oxygen) and remove waste products (e.g. carbon dioxide, urea) or secreted materials (e.g. enzymes, hormones).
What is secretion?
The release of substances from a cell that are needed by other cells, like enzymes and hormones.
How can substances move into and out of a cell?
Via vesicles (endocytosis and exocytosis), diffusion, or osmosis.
What is diffusion?
The movement of molecules from an area of high concentration to an area of lower concentration, down a concentration gradient.
What is a concentration gradient?
The difference in concentration between two regions; diffusion occurs down the concentration gradient
Where can diffusion take place?
In gases and liquids, and across permeable membranes.
Give three examples of diffusion in the human body.
Oxygen diffuses from the lungs into the blood capillaries .
Carbon dioxide diffuses from the blood into the lungs.
In the small intestine, food molecules diffuses from the intestine to the bloodstream.
How does oxygen enter cells from the blood?
It diffuses from the blood (high concentration) into cells (low concentration).
What happens to carbon dioxide produced in cells?
It diffuses out of the cells into the blood, where its concentration is lower.
What factors increase the rate of diffusion in organisms?
Large concentration gradient
Thin surfaces
Large surface area to volume ratio
What is osmosis?
A:
The movement of water molecules across a selectively permeable membrane from a region of high water concentration to low water concentration.
What is a selectively permeable membrane?
A membrane that allows some substances (like water) to pass through while blocking others.
What happens when a plant cell is placed in an isotonic solution?
Water moves in and out at equal rates, so there is no net flow of water. The cell remains the same.
What is a hypotonic solution?
A solution that has a lower concentration of solutes and a higher concentration of water than the cell contents.
What happens to a plant cell in a hypotonic solution?
Water enters the cell, making it turgid (swollen but supported by the cell wall).
What is a hypertonic solution?
A solution that has a higher concentration of solutes and a lower concentration of water than the cell contents.
What happens to a plant cell in a hypertonic solution?
Water leaves the cell, making it flaccid (soft), and the cell membrane pulls away from the cell wall.
Why doesn’t a plant cell burst in a hypotonic solution?
The strong cell wall prevents over-expansion of the cell.
What happens to an animal cell in a hypotonic solution?
Water enters the cell, which may cause it to swell and burst (lysis) since it lacks a cell wall.
What happens to an animal cell in a hypertonic solution?
Water leaves the cell, causing it to shrink (crenation).
How does Amoeba take in food particles?
By engulfing them using extensions of the cell membrane (endocytosis), forming a food vacuole.
What happens when you add a drop of dye to water?
The dye molecules move from where they are plentiful to where they are less concentrated, eventually spreading evenly—this is diffusion.
Can diffusion happen across membranes?
Yes, if the membrane is permeable and there’s a difference in concentration on both sides.
What does ‘turgid’ mean?
It means the plant cell is swollen with water
