Cells

Every living thing on our planet is made of either one, single cell, such as the euglena in the image below, or consists of many cells, like you and all other animals. In this unit, we will explore both unicellular and multicellular organisms, with an emphasis on the function of a cell, and ways parts of plant and animal cells contribute to life's function

Using a Microscope

After learning the parts of a compound microscope and the proper use of one, students will spend time observing examples of unicellular organisms. Taking their exploration further, students will distinguish between prokaryotic and eukaryotic cells, and then begin to discover the functions of major cell parts and organelles. Later in the year, students will explore how our body is composed of trillions of cells, working together to form tissues and organs, ultimately performing the daily processes our body needs to function.

Focusing on plant, animal, and bacterial cells, students will begin by distinguishing some differences between prokaryotic and eukaryotic cells, with the most obvious difference being the lack of a true nucleus in prokaryotic cells, such as bacteria.

To begin exploring prokaryotic and eukaryotic cells, click on the image to the right, and you're be linked to some great resources.

What cell parts or structures do both plant and animal cells have in common?

  • How do these cell structures, like a cell membrane and mitochondria, operate to contribute to keeping the cell functioning?
  • Which structures are found in plant cells, but not animal cells, and how do they contribute to cell processes?

The Major Cell Organelles and Their Functions

  1. Cell Wall: outer layer of plant cell - not found in animal cells. Provides structure, protection, shape. Also found in bacterial cells.
  2. Cell Membrane: second layer of plant cells, but outer layer of animal cells. Is selectively permeable, which means that it allows some substances to pass into and out of the cell, but not all substances.
  3. Cytoplasm: gel-like fluid inside all cells that surrounds organelles.
  4. Nucleus: the "control center" of the cell - contains genetic material. Is surrounded by a nuclear membrane (also known as "nuclear envelope") for protection. Found in eukaryotic cells (plant, animal, fungi, protist), but NOT found in prokaryotic cells (bacteria).
  5. Nucleolus: small structure inside the nucleus that produces ribosomes.
  6. Ribosomes: small grain-like particles that make proteins for the cell and cell parts.
  7. Endoplasmic Reticulum (aka "ER"): maze-like structures closer to the nucleus that pass ribosomes along. When they have ribosomes traveling on them, they are called "rough ER", and when there are no ribosomes, they are called "smooth ER".
  8. Golgi Bodies: flattened tube-like structures that collect proteins from the ribosomes, package them, and transport them to the cell's parts.
  9. Vacuole: larger in plant cells than in animal cells - storage sacs for water, food particles, gases, and waste. Called the "central vacuole" in plant cells.
  10. Lysosome: structures that contain chemicals that break down food and waste particles in cell.
  11. Mitochondria: rod-shaped structures that take food energy and change it into energy that can be used by the cell.
  12. Flagella and Cilia: hair-like structures that help the cell to move and obtain food particles (longer = flagella, shorter = cilia). Found on bacteria, protists, and some animal cells)
  13. Chloroplasts: green structures found in plant cells and other cells of autotrophs - not found in animal cells. They collect/store energy from the sun for photosynthesis.
  14. Capsule: extra outer protective layer on some bacteria

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Below are links to some of the best sites to learn about cell biology, along with reviewing for assessments:

Cell Structure and Function

Diffusion, Osmosis, and Active Transport Through the Cell Membrane

All cells are surrounded by a cell membrane that separates the cell from the outside environment. The cell membrane is SELECTIVELY PERMEABLE, which means that some substances can pass through the membrane, while others cannot. Common household items like strainers, coffee filters, and tea bags are examples of selectively permeable objects. The cell membrane allows certain substances to pass into the cell, such as water, oxygen, and glucose, but also will allow other substances to exit out of the cell (wastes, water, carbon dioxide).

There are 3 main types of transport across cell membranes:

1. passive transport: (includes: diffusion, osmosis, and facilitated diffusion)

        • doesn't require energy (ATP), but in facilitated diffusion, transport proteins are used
        • substances move from higher to lower concentration

2. active transport:

        • requires energy (ATP) and transport proteins
        • substances move against the concentration gradient (lower to higher)

3. exocytosis & endocytosis:

        • uses energy and vesicles to bring larger substances into and out of the cell

Click on the image to the left to link to an incredible website that will teach you more about the cells that make up your body.