Transport Across Membranes

Question 1

What is active transport?

Answer 1

The active movement of substances from a low concentration to a higher concentration (up their concentration gradient) with the use of energy in the form of ATP and specific carrier proteins

Question 2

What is a calibration curve?

Answer 2

A graph used to determine unknown concentrations by plotting known concentrations against a measurable property

Question 3

What is a carrier protein?

Answer 3

A membrane protein, that binds to specific molecules, undergoes a conformational change and transports them across the membrane, either by facilitated diffusion or active transport.

Question 4

What is the cell membrane?

Answer 4

A semipermeable layer that surrounds and protects the cell and controls what exits and enters the cell

Question 5

What is the cell wall?

Answer 5

A rigid structure that surrounds prokaryotic cells, it provides structural support and protection

Question 6

What is cholesterol?

Answer 6

A lipid that is an important component of cell-surface membranes adds stability, and regulates membrane fluidity. Preventing it becoming too rigid or permeable

Question 7

What is a concentration gradient?

Answer 7

Process of particles moving through a are of high to low concentration

Question 8

What is concentration?

Answer 8

The amount of solute in a given volume of solution, determining the strength of the solution.

Question 9

What is co-transport?

Answer 9

A form of active transport where two substances are transported together using the same carrier protein. One substance moves down its concentration gradient, providing energy for the other to move against its gradient

Question 10

What is the cytoplasm?

Answer 10

The jelly like fluid that fills the inside of the cell, made up of water, salts, and organic molecules
Where most chemical reactions occur

Question 11

What is diffusion?

Answer 11

The passive movement of molecules or ions from a region where they are in high concentration to one where their concentration is lower, down the concentration gradient.

Question 12

What does dilute mean?

Answer 12

The more dilute the less concentrated the solute is in a solution since there is more solvent

Question 13

What does dissolve mean?

Answer 13

The process where a solute mixes with a solvent to form a solution, with the solute particles becoming evenly distributed.

Question 14

What is exocytosis?

Answer 14

The outward bulk transport of materials through the cell-surface membrane

Question 15

What is endocytosis?

Answer 15

The inward transport of large molecules through the cell-surface membrane

Question 16

What is facilitated diffusion?

Answer 16

Diffusion involving the presence of protein carrier molecules to allow the passive movement of substances across plasma membranes

Question 17

What does flaccid mean?

Answer 17

A plant cell or tissue that has become soft and limp due to water loss by osmosis - will eventually shrivel

Question 18

What is the fluid mosaic model?

Answer 18

A model that describes membrane structure as a sea of mobile phospholipids embedded with various proteins

Question 19

What are glycolipids?

Answer 19

A substance made up of a carbohydrate molecule and a lipid molecule

Question 20

What are glycoproteins?

Answer 20

A substance made up of a carbohydrate molecule and a protein molecule. Parts of cell surface membrane and certain hormones are glycoproteins.

Question 21

What does hypertonic mean?

Answer 21

A hypertonic solution is when the solute concentration is higher than the concentration inside the cell
In a hypertonic solution, the water moves out of the cell and causes the cell to shrivel

Question 22

What does hypotonic mean?

Answer 22

When the solute concentration is lower than the concentration inside the cell
In a hypotonic solution, the water moves into the cell and can cause the cell to swell; cells that don’t have a cell wall, such as animal cells, could explode in this type of solution

Question 23

What does isotonic mean?

Answer 23

A solution that has the same water potential as the inside of a cell, resulting in no net movement of water in or out of the cell.

Question 24

What does net movement mean?

Answer 24

The overall movement of molecules in one direction due to a concentration gradient, even though individual molecules move randomly.

Question 25

What is permeability?

Answer 25

The ability of a membrane to allow substances to pass through

Question 26

What does partially permeable mean?

Answer 26

A membrane that allows certain small molecules like water to pass through but not larger ions or molecules

Question 27

What are phospolipids?

Answer 27

The type of lipid which forms the cell surface membrane bilayer. It is formed by the condensation of one molecule of glycerol, two molecules of fatty acid and a phosphate group. The two fatty acid chains are the non-polar hydrophobic tails whilst the phosphate group is the polar hydrophilic head.

Question 28

What is the phospholipid bilayer?

Answer 28

A polar membrane made of two layers of phospholipid molecules. The hydrophilic heads facing outwards and the hydrophobic tails facing inwards forming a selectively permeable barrier to the passage of ions and molecules into and out of cells

Question 29

What is the plasma membrane?

Answer 29

A thin semipermeable barrier that surrounds and protects a cell, controls what materials can pass in and out of the cell

Question 30

What does plasmolysed mean?

Answer 30

A state in plant cells where excessive water loss causes the cell membrane to pull away from the cell wall due to osmosis in a highly concentrated solution.

Question 31

What is the protein channel?

Answer 31

A transmembrane protein that forms a pore or tunnel across the cell membrane, allowing specific molecules, like ions, to pass through by facilitated diffusion, a passive transport process

Question 32

What does serial dilution mean?

Answer 32

A series of dilutions that are preformed in a stepwise manner to reduce the concentration of a substance in a solution by a fixed factor

Question 33

What does solvent mean?

Answer 33

A substance usually a liquid that dissolves a solute to form a solution

Question 34

What does solution mean?

Answer 34

A homogeneous mixture of two or more substances where one substance dissolves into the other

Question 35

What does solute mean?

Answer 35

A substance that dissolves in a solvent to form a solution

Question 36

What does turgid mean?

Answer 36

A plant cell that contains the maximum volume of water it can becoming firm. Additional entry of water is prevented by the cell wall stopping further expansion of the cell.

Question 37

What is osmosis?

Answer 37

The movement of water particles from a region of high water potential to a region of lower water potential through a semi permeable membrane Passive and down gradient

Question 38

What is the vacuole?

Answer 38

A membrane-bound organelle in plant cells that stores water, nutrients, and waste. It helps maintain turgor pressure and supports the cell structure.

Question 39

What does volume mean?

Answer 39

The total amount of space occupied by an organism or part of one or substance

Question 40

What is water potential?

Answer 40

A measure of the tendency of water molecules to move from one area to another measured in kilopascals (kPa) influenced by solute concentration and pressure and given the symbol ψ