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Hypertonic - there is more solution inside the cell.
Hypotonic - there is more solution outside the cell.
Isotonic - there is equal water molecules in & out of the cell.

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Animal cells have no cell walls, so pressure potential isn't considered. ψ=ψ(s). If red blood cells are in distilled water, water enters by osmosis & cells will burst. This is haemolysis. If they are put in concentrated salt solutions, water leaves & they shrink, becoming 'crenated'.

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ψ(s) - solute potential, always negative value, conc. of dissolved solutes
ψ(p) - pressure potential, usually positive value, pressure exerted by the cell walll

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Water entering the cell by osmosis expands the vacuole & pushes the cytoplasm against the cell wall. Wall can only expand a little, so pressure outward builds up, resisting entry of more water, making the cell turgid. This pressure, is the pressure potential.

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A cell can transport material inbuilt, in my endocytosis.
Endocytosis occurs when material is engulfed by extensions of the plasma membrane & cytoplasm surrounding it, making a vesicle. There are 2 types:
Phagocytosis is the uptake of solid materials that are too large to be taken in by diffusion or active transport. When granulocytes engulf bacteria, a lysosome fuses with the vesicle formed & enzymes digest the cells. The products are absorbed into the cytoplasm.
Pinocytosis is the uptake of liquid by the same mechanism, although the vesicle produced are smaller.

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It measures how easily water molecules move out of a solution. The more solute present, the tighter the water molecules are held, less tendency for water to move out

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Pure water has a water potential(ψ) of 0.
Water potential is measured in kilo pascals(kPa). When solutes are added(NaCl, glucose)this causes the ψ to decrease - solute conc. increase, ψ becomes negative. Always moves from a high ψ to a lower ψ.

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The diffusion of water across a differentially permeable membrane from an area of high water potential to an area of low water potential, until both sides are in equilibrium.

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A cell can transport material in bulk, out by exocytosis.
Exocytosis is the process in which substances leave the cell, having been transported through the cytoplasm in a vesicle, which fuses with the cell membrane. Digestive enzymes are often secreted this way. E.g gland cells(pituatery cells).
When bulk transport occurs the cell membrane has to change shape which requires energy, therefore the ATP produced during respiration is used. The cell membrane flows with endocytosis decreasing the area of the cell membrane & exocytosis increasing it. The property of fluidity is vital for the process.

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A type of facilitated diffusion that brings ions/molecules down a concentration gradient of another molecule. Sodium-Glucose co-transport is significant in absorbing glucose & sodium ions across a cell membrane & into the blood in the ileum

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Ions & molecules are moved from an area of low concentration to high, against the gradient. The process requires ATP. The process occurs through intrinsic carrier proteins spanning the membrane, rate is limited by availability of membranes.
In muscle cells, mitochondria produces ATP but because glucose is being used up, more glucose from outside the cell needs to be transported into the cell from a low to high concentration gradient.

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The rate is affected by..

the conc. gradient, larger the difference the more molecules diffuse in a given time

distance over which the diffusion takes place. A thinner membrane means the shorter the distance, the more molecules diffuse in a given time

the temperature can affect it, at higher temp. particle moves faster, diffusion happens faster

the surface area of a membrane, the larger the area, the more room the molecules have room to diffuse in a given time

Fick's law- rate is proportional to:
surface area x difference in conc. ÷ length of diffusion path(membrane thickness)

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Diffusion is the passive movement of gases & liquids from an area of high concentration to an area of low concentration until they reach equilibrium.
Oxygen & carbon dioxide would be able to pass through a membrane by simple diffusion because they're both small, non-polar molecules.

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The passive movement of large molecules & ions from an area of high concentration to low concentration.
Carrier proteins - Allow diffusion of larger polar molecules(sugars, amino acids) across the membrane. Molecules attach to its binding site on the carrier protein. The protein then changes shape & releases the molecule on the other aide of the membrane.
Channel proteins - Molecules with pores lined with polar groups. As the channels are hydrophobic, ions being water-soluble, can pass through. The channels open & close according to the needs of the cell.

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lipid-soluble substances e.g vitamin A, small molecules(oxgen & carbon dioxide can diffuse across a membrane). The phospholipid layer is hydrophobic so lipid-soluble molecules move through the cell membrane more easily than water-soluble molecules.

water-soluble substances e.g glucose, polar molecules & ions cannot readily diffuse through the phospholipids & must pass through intrinsic protein molecules, which form water-filled channels across the membrane. As a result, the cell surface membrane is selectively permeable to water & some solutes.

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Communication between cells(partially permeable)

controls movement in/out of cells

contains biological material

flexible, allowing growth

protects the cell - changes in environment

specific in what it transports(partially permeable)

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'Fluid-Mosaic' because...

Each phospholipid molecule can move within a layer(fluid)

proteins embedded in the bilayer vary in shape, size & pattern(mosaic)