Biology Unit 3: The Cell


  • Explain how the same 5 types of molecules control the functions and processes in all living things?
  • Explain how nutrients needed by cells get inside.
  • Explain how substances produced by cells get out.
  • Explain that the role of selective permeability and types of active and passive transport in the movement of materials into and out of cells is to maintain homeostasis in a living organism.

Course Essential Questions

  • How do the same 5 types of molecules control the functions and processes in all living things?
  • How do substances get in and out of cells?
  • Why is this important?

Unit Essential Understandings

  • The cell is a system that conducts a variety of functions associated with life - Details of cellular processes such as photosynthesis, chemosynthesis, cellular respiration, cell division and differentiation are studied at this grade level. Additionally, cellular organelles studied are cytoskeleton, Golgi complex and endoplasmic reticulum.
  • From about 4 billion years ago to about 2 billion years ago, only simple, single-celled microorganisms are found in the fossil record. Once cells with nuclei developed about a billion years ago, increasingly complex multicellular organisms evolved.
  • Every cell is covered by a membrane that controls what can enter and leave the cell. In all but quite primitive cells, a complex network of proteins provides organization and shape.
  • Within the cell are specialized parts for the transport of materials, energy transformation, protein building, waste disposal, information feedback and movement. In addition to these basic cellular functions, most cells in multicellular organisms perform some specific functions that others do not.
  • Cell functions are regulated. Complex interactions among the different kinds of molecules in the cell cause distinct cycles of activities, such as growth and division.
  • Most cells function within a narrow range of temperature and pH. At very low temperatures, reaction rates are slow. High temperatures and/or extremes of pH can irreversibly change the structure of most protein molecules. Even small changes in pH can alter how molecules interact.
  • The sequence of DNA bases on a chromosome determines the sequence of amino acids in a protein. Proteins catalyze most chemical reactions in cells.
  • Protein molecules are long, usually folded chains made from combinations of the 20 typical aminoacid sub-units found in the cell.
  • The function of each protein molecule depends on its specific sequence of amino acids and the shape the chain takes as a result of that sequence.

Chapter 3.3 Cell Membrane

  • Define homeostasis. Give examples of how living organisms maintain homeostasis.
  • Describe the biological molecules that make up the cell membrane.
  • Describe the structure of the cell membrane as a fluid mosaic.
  • Describe the structures in a cell membrane used for signaling and how they work.
Chapter 3.4 Diffusion and Osmosis
  • Describe passive transport.
  • Explain that a concentration gradient is responsible for the movement of a substance through a membrane by passive transport.
  • Distinguish between osmosis, diffusion, ion channels, and facilitated transport.
  • Describe how water and solutes move through solutions or across membranes in hypotonic, hypertonic, and isotonic solutions.
  • Tell which process is used by gases, water, and small particles to enter or exit cells, and why.
Chapter 3.5 Active Transport, Endocytosis and Exocytosis
  • Describe active transport and explain how it is different from passive transport.
  • Explain how a protein pump works, using a sodium-potassium pump as an example.
  • Distinguish among endocytosis, exocytosis, and phagocytosis.

Links and Resources

Next Generation Science Standards:

SEP 1 Asking questions (for science) and defining problems (for engineering)

SEP 3 Planning and carrying out investigations

SEP 4 Analyzing and interpreting data

SEP 5 Using mathematics and computational thinking

SEP 6 Constructing explanations (science) and designing solutions (engineering)

SEP 7 Engaging in argument from evidence

SEP 8 Obtaining, evaluating, and communicating evidence

Common Core State Standards:

RI.9-10.4 Determine the meaning of words and phrases as they are used in a text, including figurative, connotative, and technical meanings; analyze the cumulative impact of specific word choices on meaning and tone (e.g., how the language of a court opinion differs from that of a newspaper).

RI.9-10.6 Determine an author's point of view or purpose in a text and analyze how an author uses rhetoric to advance that point of view or purpose.