B1 cells and organisation Flashcards Preview

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Flashcards in B1 cells and organisation Deck (23):

what is a light microscope

a microscope that uses a beam of light to form an image of an object


what is an electron microscope

a microscope that uses a beam of electrons to form an image and can magnify up to 2,000,000 times which lets you see the subcellular structures inside cells


what is the equation for calculating image size

magnification x size of real object


what happens in diffusion when SA:V ratio gets smaller

gases and food molecules can no longer reach every cell by simple diffusion
metabolic waste cannot be removed fast enough to avoid poisoning the cells


name adaptations for exchanging materials

1) large surface area
2) thin membrane (short diffusion path)
3) efficient blood supply- maintains steep concentration gradient


what is diffusion

process that allows dissolved substances to pass through the cell membrane (enter or exit cell)


what process is it that moves from high concentration to low concentration

diffusion and osmosis


what factors speed up the rate of diffusion

bigger the difference in concentration gradient

increase in temperature

increase in surface area


what is osmosis

when water molecules move across a partially permeable cell membrane


what is isotonic

when the concentration of solutes in the solution outside the cell is the same as the internal concentration


what is hypertonic

when the concentration of solutes in the solution outside the cell is higher than the internal concentration


what is hypotonic

if the concentration of solutes in the solution outside the cell is lower than the internal concentration


what is turgor

pressure that makes cells hard and rigid


what is plasmolysis

when water is lost by osmosis and the vacuole and cytoplasm shrink and the cell membrane pulls away from the cell wall. these cells die quickly unless osmotic balance restored


what is active transport

when the substances needed by a cell have to be moved against a concentration gradient across a partially permeable membrane


which process moves from low concentration to high

active transport


how can the rate of active transport increase?

if a cell respires and releases a lot of energy


how does active transport take place in plants

allows root hair cells to absorb mineral ions from very dilute soil solutions


how does active transport take place in humans

allows sugar molecules used for respiration to be absorbed from lower concentrations in gut to higher concentrations in blood


what is a eukaryotic cell

a cell that has a cell membrane, cytoplasm and genetic material in a nucleus e.g. animal, plant, fungi and protista


what is a prokaryotic cell

single called living organism that had a single dna loop found free in the cytoplasm e.g. bacteria


what is a plasmid and what is its function

small rings of dna code for specific features e.g. antibiotic resistance. used in genetic engineering to carry new genes into the genetic material of other organisms


what is glycogen

a chemical used in cellular respiration by the mitochondria to transfer energy needed for fibres to contract