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Cell parts and functions

Review your understanding of cell parts and functions in this free article aligned to NGSS standards.

Key points:

  • All cells have a cell membrane that separates the inside and the outside of the cell, and controls what goes in and comes out. The cell membrane surrounds a cell’s cytoplasm, which is a jelly-like substance containing the cell’s parts.
  • Cells contain parts called organelles. Each organelle carries out a specific function in the cell. A cell’s organelles work alone and together to keep the whole cell functioning.
  • Mitochondria are organelles that break down sugars. This process releases energy that the cell can use.
  • The nucleus is an organelle that contains a cell’s genes.
  • Chloroplasts are organelles that carry out photosynthesis, which makes the food plant cells need to live. This food is in the form of sugars.
  • Plant cells have chloroplasts and a cell wall, but animal cells do not. The plant cell wall is outside the cell membrane, and it provides structure for the cell.
On the left is a circle representing an animal cell. The cell contains many cell parts with different shapes. A small bean-shaped cell part is labeled mitochondrion. A medium-sized circular cell part that has squiggly lines inside is labeled nucleus. The outermost part of the cell, which is shown as an outline of the cell, is labeled cell membrane. On the right is a four-sided figure with rounded corners that represents a plant cell. The cell contains many cell parts with different shapes. A small green oval with stacks of darker green ovals inside is labeled chloroplast. A medium-sized circle that has squiggly lines inside is labeled nucleus. The outermost part of the cell, which is shown as a thick outline of the figure, is labeled cell wall. A thinner layer just inside the cell wall is labeled cell membrane. A small bean-shaped cell part is labeled mitochondrion.
Cell diagrams showing a typical animal cell and plant cell. Image created with Biorender.com.

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