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Facilitated diffusion is the process of spontaneous passive transport of molecules or ions across a cell's membrane via specific transmembrane integral proteins.

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Phospholipid arrangement in a plasma membrane:
Two layers of phospholipids with hydrophilic phosphate heads facing outwards, and hydrophilic lipid tails facing inwards, towards the middle.

Phospholipid tails:
The more unsaturated - The more fluid the membrane will be. This is because of the unsaturated fatty acid tails that are bent (due to the double bonds) and therefore fit together more loosely.

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Nuclear pores:
mall channels or gaps on the surface of the nuclear envelope, which lets substances in and out of the nucleus. The nucleus pore complex are a lining of proteins that control which molecules go in and out.

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Active Transport:
The movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy. Active transport does not require a concentration gradient.

Example of Active Transport:
- Metal ions in the human body, such as K+  and Ca²⁺ require energy in order to cross cell membranes in the human body

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Endocytosis
- the taking in of matter by a living cell by invagination of its membrane to form a vacuole. It engulfs and fuses them with its plasma membrane.

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Bulk Transport
-Pinocytosis
Also known as 'cell drinking '. This is a bulk uptake of liquid . The vacuoles (vesicles) formed are extremely small, in which case the process is called micropinocytosis

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The movement of molecules from regions of low concentration to a region of low concentration down a concentration gradient
(no energy impute required = slow process)

Simple Diffusion
-Molecules move directly through the membrane without assistance of energy
Eg. O2 into blood & CO2 out
Carrier-mediated facilitated diffusion
-Carrier proteins allow large lipid-insoluble molecules to be transported through the membrane
Eg. Glucose into RBC's
Channel-mediated facilitated diffusion
-Channels (hydrophilic pores) in membrane allow inorganic ions to pass membrane
Eg. K+ ions leaving nerve cell to restore resting potential

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adores beagle puppies/the fluidity of the phospholipid layer depends on the

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Functions of the Cell surface membrane:
- It controls what enters and leaves the cell
- It regulates exchange of materials with it's surroundings
- It prevents the cell from bursting
- It is linked together by plasmodesmata

Cell membrane's structure consists of...
- Phospholipids:
- these allow the membrane to reseal itself when disrupted
- they contain non polar tail, making it difficult for polar ions to pass through (act as a barrier to most water substances)

Cholesterol:
- they regulate the fluidity of the membrane
- stop cells bursting open

Glycolipids:
- Act as receptor molecules binding with particular substances like hormones and neurotransmitters so are involved in cell signaling.

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Always there sometimes there
Functions/structures
Structures/processes

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phospholipid, carrier protein, partially permeable, phosphate group, channel protein, cholesterol, fluid mosaic, glycoprotein, glycolipids, protein , endocytosis, plasma membrane, exocytosis, plasmodesmata, cho, lipid bilayer, hydrophilic, hydrophobic , facilitated diffusion, nuclear envelope, tonoplast, trilaminar , intrinsic cell wall, cristae, extrinsic protein, microvilli, active transport, cell surface membrane osmosis, diffusion, protein receptors, fully permeable, peripheral, concentration gradient, capsid, nuclear pore,  Surface Area vs volume (ratio)