A busy town

About this video

Is a cell just a tiny bag of liquid? No: it is full of parts, and each part has a job, a little like a town with walls and gates, a library of plans, power stations and factories.

Every cell is wrapped in a thin, soft skin called the cell membrane. It keeps the inside in and the outside out, but it is not a solid wall: it lets water, oxygen and food in, lets waste out, and controls what else may pass. Inside it is the cytoplasm, a jelly-like liquid, mostly water, with all the cell's parts floating in it; many of the cell's chemical jobs happen here.

Most cells of plants and animals have a nucleus, a round part with its own skin around it. The nucleus holds the cell's DNA: the instructions for building and running the cell, and for making new cells. The mitochondria are small bean-shaped parts that release the energy stored in food so the rest of the cell can use it; cells that work hard, like muscle cells, have many of them. Ribosomes are tiny grains that build proteins, the molecules that do most of the work in a cell and build much of it, following the instructions from the nucleus.

A cell has more parts than these five, but these are enough to understand how a cell stays alive. This video goes with the lesson Inside a Cell in Biology Level 1 on Knaph.

Transcript

1. 0:00Is a cell just a tiny bag of liquid? No. It is full of parts, and each part has a job.
2. 0:09Around the edge is the cell membrane, a thin skin. It lets water, oxygen and food in, lets waste out, and controls what else may pass. Like a town wall with gates.
3. 0:22Inside is the cytoplasm, a jelly that is mostly water. The parts float in it, and many of the cell's jobs happen here.
4. 0:32Most plant and animal cells have a nucleus. It holds the DNA, the instructions for building and running the cell, and for making new cells. Like a library of plans.
5. 0:46Mitochondria release the energy stored in food, so the rest of the cell can use it. They are the cell's power stations. Hard-working muscle cells have many.
6. 1:00Ribosomes are tiny grains that build proteins, following the instructions from the nucleus. Proteins do most of the work in a cell, and build much of it.
7. 1:14A cell is not a bag of liquid. It is a tiny, busy town.