cells on a basis Flashcards
Size
Smaller molecules can move across the cell membrane easily compared to larger molecules.
Example sentence: Small molecules like oxygen (O2) can pass through the membrane more easily than larger molecules.
Electrical charge
Charged molecules are not soluble in lipids and have low permeability across the membrane (e.g., Na+). Neutral molecules have high permeability and can cross the membrane easily.
Example sentence: Sodium ions (Na+) have low permeability due to their charge.
Lipid solubility
Water-soluble molecules have difficulty moving across the membrane due to the hydrophobic tails. Lipid-soluble molecules can easily pass through the phospholipid bilayer.
what are the cell membrane pores called
aquaporins that allow water to move through by osmosis.
Additional information: Aquaporins are specific channels in the membrane that facilitate the movement of water molecules.
diffusion
diffusion is the movement of molecules from a region of high concentration to a region of low concentration along a concentration gradient until equilibrium (equal concentration) is reached.
it does not require energy, passive
The higher the temperature, the faster the rate of diffusion
Molecules gain kinetic energy from heat energy
The rate of diffusion also depends on the concentration gradient the higher the gradient the faster the rate of diffusion
facilitated diffusion
Relatively large molecule such as glucose and charged particles such as sodium does not pass through the phospholipid bilayer
they require certain proteins such as co-proteins and channel proteins to assist the using them into the cell. This process is called facilitated diffusion.
osmosis
Osmosis is the diffusion of water molecules only from a region of high water concentration to region of low water concentration across a semi permeable membrane
Does not require energy, passive
Water moves through protein channels called Aquaporins
Water concentration outside of the cell is higher than the inside cell water will move into the cell causing the cell to expand and burst, lysis.
If the water concentration inside the cell is higher than the outside water will move out of the cell causing the cell to shrink
hypotonic environment
The total concentration of dissolved solute is less in the environment than in the cell. Therefore water concentration is higher outside the cell therefore water moves into the cell causing osmosis and animal cells burst and plant cells turgid
Hypotonic environment
The total concentration of dissolved solute is high in the environment. Therefore inside the cell is dilute. Water moves out of the cell causing it to shrink.
isotonic environment
Concentrate of solute and solvent inside and outside is equal. The movement of water is balanced. no net movement.
Active transport
Active transport is the movement of molecules from region of low concentration to region of high concentration and requires energy
This movement goes against the concentration gradient
Involves movement across the cell membrane that has receptors for the molecule
Requires a carrier protein that spans the membrane to actively move chemicals across
Utilises cellular energy such as ATP, Adenosine triphosphate
ATP respiration formula
Oxygen + glucose —— carbon dioxide + water + energy
example of active transport
Movement of sodium and potassium across nerve cells
Reabsorption of glucose from the kidney
during chemical reactions the third phosphate group of ATP can be hydrolysed to release energy for use in cell. ATP breaks down into what molecule.
ADP, adenosine diphosphate
Endocytosis
The process still takes in macro molecule by forming vesicle from the plasma membrane. It requires energy and is therefore a form of active transport.
There are two types pinocytosis and phagocytosis
pinocytosis, cell drinking, a process with a cell engulfs extracellular fluid
phagocytosis, cell eating, a process whereby the cell engulfs a solid particle
exocytosis
The process by which vesicles inside the self use with the cell membrane and the contents of the vessel are secreted from the cell
It is used for
Secretion of substances synthesise by the cell
Elimination of indigestible remains of food vacuole
factors affecting the exchange of materials across membranes
Chemical
Physical
Concentration gradient
Surface area to volume ratio
Chemical
The chemical properties of the substances affect its transport across cell membranes. Many uncharged molecules can easily pass through as they dissolve in the phospholipid bilayer.
hydrophyllic charged ions cannot pass through the hydrophobic centre of the membrane and requires carry proteins.
Water is not lipid soluble which means it requires aquaporins.
Physical
physical properties such as size and shape of molecules affect the movement of substances across the membrane
Small molecules diffuse easily larger molecules use carrier proteins through
very large molecules need to be transported by endocytosis and exocytosis
concentration gradient
The concentration of the substance on either side of the membrane affects the rate of diffusion
If the concentration gradient is high diffusion rate will be high
As the concentration gradient decreases, the rate of diffusion also decreases
surface area volume ratio
Surface area is the surface area divided by the volume
This ratio affects the movement of substances in and out of cells
A smaller cell has a larger surface area to volume ratio which means the rate of diffusion is faster or higher between the centre of the cell and the surface
A larger cell has a smaller surface area volume ratio so the rate of diffusion is slower
Size increases surface area to volume decreases, which means it decreases efficiency of cells to transport substances in an out of the cell
This places a limit on cell size
what do cells do to increase surface area to volume ratio and therefore efficiency of diffusion?
Cells will divide
Cells can flatten themselves
Equation for photosynthesis
carbon dioxide + water —— glucose + oxygen
The light dependent stage - photolysis
Occurs in the grana or granum of chloroplast
absorption of light occurs the thyroid membranes of the chloroplast
The energy is used to split water molecules into hydrogen ions and oxygen
The oxygen is released into the atmosphere and the hydrogen ions are carried into the next phase
ATP is formed at this state
