Cell Functions
What your cells do on a daily basis to keep themselves – and you – alive!
This happens mainly in the
Mitochondrion!
Cellular Respiration:All cells need energy to survive. Your cells perform cellular respiration, a series of chemical reactions that extracts energy gradually from glucose. The process is complex, but can be summarized as:
C6H12O6 + 6O2 6CO2 + 6H2O + ATP*Glucose + Oxygen Carbon dioxide + Water + Energy
Cell Transport: Phospholipid Bilayer:
Moving things in & out of the cell is the main job of the cell membrane.It is a double layer of fatty molecules called phospholipids. Gaps between the phospholipids let some things in, and keep other things out.The membrane is semipermeable.
Passive Transport:Some materials move through on
their own; the cell doesn’t use any of its energy to help the transport.
This is called passive transport.It can happen through membrane
pores, or special protein channels (facilitated diffusion).
Facilitated Diffusion:
Passive Transport:In order for passive transport to
happen, there has to be a concentration gradient:
High concentration outside of cellLow concentration inside the cellMolecules will tend to move from
high to low concentration. This is called Diffusion.
Diffusion:
As the sugar dissolves, the particles diffuse
through the water until they’re evenly
‘mixed’ or distributed.
Active Transport:Sometimes, the cell needs to
obtain a material that is:- A charged particle (an ion)- Rare, or Low in concentration- Too big to diffuse through the
membraneThis is when Active Transport is
used…
Active Transport:Active transport requires the cell
to use some of its energy in order to obtain & move materials in/out of the cell.
This may involve the proteins in the membrane, acting as pumps. They are able to change shape in order to move materials in/out of the cell.
Active Transport:… Goes against the concentration
gradient; it will move particles from Low Concentration areas to Higher Concentration areas.
A good example is the Sodium-Potassium Pump: It changes shape to release 3Na+ & bring in 2K+. The energy comes from ATP, a molecule cells derive from glucose metabolism.
Both Na+ & K+ are needed for several cell functions, but too much has a dehydrating effect…
… Keeping these two ions in balance is a constant job for all of your body’s cells… one of many, many jobs!
Active Transport:Sometimes, the cell needs to obtain
a material that is so large that it has to bend its entire membrane around it. This is called Endocytosis, & it takes energy.
(endo = into, cyto = cell, osis = process)
Taking in liquids = PinocytosisTaking in solids = Phagocytosis
(pino = to drink, phago = to eat)
Single-celled organisms, like Amoeba, rely on endocytosis a lot. Some of your white blood cells are phagocytes.
Active Transport:Sometimes, the cell needs to expel or
secrete a large quantity of a material. They do this by first producing the material (a hormone, a signalling chemical, or just a waste…), packaging it into a vacuole or vesicle, then fusing the vesicle to the cell membrane. The vesicle bursts, releasing the material. around it. This is called Exocytosis, & it usually involves the Golgi & RER.
(exo = out of, cyto = cell, osis = process)
In your body, a process like this would happen when white blood cells engulf, destroy & expel remnants of bacteria.
Remember: it’s all about energy use & concentration…
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