Inside the jelly

The idea

Most cells have a plasma membrane, a semi-fluid jelly-like cytoplasm and a nucleus; the cytoplasm also contains sub-cellular components called organelles, most of them visible only with an electron microscope.

Three basic parts

Most cells have a boundary, a jelly-like filling and a control centre.

What fills the space between the boundary and the control centre?

• A semi-fluid, jelly-like cytoplasm
• Empty space
• Solid rock

Zoom in with two microscopes

Look with each microscope. What new things appear?

Membrane, cytoplasm, nucleus, and organelles

Most cells have a plasma membrane, a semi-fluid, jelly-like cytoplasm and a nucleus. The cytoplasm also contains sub-cellular parts called organelles, most of which are visible only with an electron microscope.

Next we meet the organelles one by one.

• Part | What it is
• Plasma membrane | selectively permeable boundary
• Cytoplasm | semi-fluid, jelly-like filling
• Nucleus | prominent control centre
• Organelles | sub-cellular parts in the cytoplasm

Notes

Most cells have a plasma membrane, a jelly-like cytoplasm and a nucleus; the cytoplasm also holds organelles, mostly seen only with an electron microscope.

Check yourself

Cytoplasm is…

Organelles are…

Most organelles can be seen only with…

Which is not one of the three basic parts of most cells?

• a semi-fluid, jelly-like substance — correct. Yes.
• a hard shell. The shell-like layer would be the wall.
• an empty space. It is filled with jelly and organelles.
• sub-cellular components in the cytoplasm — correct. Yes.
• whole organs of the body. Organs are made of many cells.
• the cell membrane. The membrane is the boundary.
• an electron microscope — correct. Yes.
• the naked eye. They are far too small.
• a school magnifying glass. They are far too small for that.
• A cell wall — correct. It is found only in some cells.
• Plasma membrane. It is one of the three.
• Cytoplasm. It is one of the three.
• Nucleus. It is one of the three.