glycolysis
Meaning of glycolysis: Every cell in the body runs it, it needs no oxygen, and for a red blood cell it is the only source of energy available.
Definition of glycolysis
Glycolysis is the sequence of chemical steps by which a cell splits glucose, a six carbon sugar, into two smaller molecules of pyruvate, capturing a little usable energy along the way. It takes place in the fluid part of the cell rather than inside any compartment, requires no oxygen, and runs in essentially every cell in the body.
How glycolysis is built
- gluc/o, glyc/o Combining form · Greek sugar, glucose
- -lysis Suffix · Greek breakdown, destruction, separation
A medical term is read from its ending backwards: the suffix first, then the prefix, then the root. See all 223 word parts.
What happens to pyruvate next?
| Conditions | What pyruvate becomes | Energy released |
|---|---|---|
| Oxygen available | Enters the mitochondria and is broken down completely | Many times more than glycolysis alone yields |
| Oxygen limited or mitochondria absent | Converted to lactate in the fluid of the cell | Nothing further, but glycolysis can keep running |
Pyruvate is the end product of the pathway rather than a waste byproduct, and which of those two roads it takes decides how much of the sugar's energy is actually recovered. The lactate route looks wasteful, since most of the energy is still locked inside the lactate molecule, but it serves a purpose that has nothing to do with energy. Glycolysis consumes a carrier molecule that has to be handed back in its original state for the next round, and converting pyruvate to lactate is what regenerates it. Without that step the pathway would stall within seconds.
Why keep such an inefficient pathway?
Because it does things the efficient route cannot. It is fast, delivering energy far more quickly than the full oxygen dependent breakdown, which suits a muscle contracting hard for a short burst. It needs no oxygen, so it keeps working in tissue with a poor blood supply. It needs no mitochondria, which matters because the mature red blood cell has none at all and depends on glycolysis entirely. And the pathway is not only about energy: several of the intermediate molecules formed along the way are pulled out and used as raw material for building fats, amino acids and the units of genetic material.
Why do cancer cells lean on it?
Many tumors run glycolysis hard and convert most of the resulting pyruvate to lactate even when oxygen is plentiful, a pattern that puzzled observers for a long time because it appears to waste fuel. The explanation now favored is that a rapidly dividing cell needs building material more urgently than it needs maximum energy, and a fast flow of sugar through this pathway supplies both. The heavy appetite for glucose is not merely a curiosity. Imaging that tracks where a labeled sugar accumulates uses exactly this behavior to locate active cancer in the body.
Used in a sentence
Laboratory studies measured the rate of glycolysis within the tumor cells.
Good to know
Many cancer cells rely heavily on glycolysis and convert pyruvate to lactate even when oxygen is available, an altered pattern of glucose handling that distinguishes them from most normal cells.
Word origin
Where “glycolysis” comes from
Formed from glyco-, Greek for sweet, and lysis, meaning a loosening or breaking down.