Central Idea: All living things are composed of cells these cells have different structures and organelles that support life processes. Cell theory describes the current understanding of cells. Theories and laws in science are used by scientists to describe natural phenomena. Theories and laws are equal in terms of scientific validity.

Theories and Laws

Theories and laws are two different types of knowledge used by scientists to describe natural phenomena. They are equal in terms of scientific validity.

• Theories are generally used to explain complex natural processes not easily quantifiable (e.g., cells, evolution).
• Laws often use mathematical formulas to show relationships and make predictions about the natural world (e.g., heredity).
• The cell theory is a shared understanding that encapsulates our current understanding of the cell. 
•  The development of this theory illustrates the nature of science

Models

• Scientists and engineers use two-dimensional (2-D), three-dimensional (3-D), mathematical, and virtual models to represent, predict, and elaborate upon objects and systems and their interactions.
• Scientists use models when the object of investigation is too large, too small, or too complex to be studied directly.

• Explain the difference between scientific hypothesis, theory, and law.
•  know the three components of the original cell theory.
• explain how advances in microscope technology have improved our understanding of cells and their parts.

the Nature of Science

• the natural world is understandable
• science is based on evidence—both observational and experimental
• science is a blend of logic and innovation
• scientific ideas are durable yet subject to change as new data are collected
• science is a complex social endeavor
• scientists try to remain objective and engage in peer review to help avoid bias.

Science and Technology are tightly linked

• Science seeks to understand the natural world through observation and experimentation.
• Technologies are developed to aid in gathering data.
  • New data bring fresh insights, raise new questions, and prompt further investigation.
• In this way, scientific knowledge evolves slowly over time.
• A good example of the link between science and technology is how advances in microscopes have helped us investigate cells—the smallest part of living things—and how they work to sustain life processes.

Cell Structure & Organelles support Life Processes

Sustaining life requires substantial energy and matter inputs.

• Living cells are full of highly organized organelles that function as a system to carry out life processes within the cell.
  • Life processes include growth and repair, reproduction, gas exchange, metabolism, and response.
  • Metabolism refers to all interactions among molecules within the well-ordered environment of the cell.
  • Photosynthesis and cellular respiration are two important metabolic activities within living cells.
• The structure of an object or living thing determines many of its properties and functions.

Plant Cells vs. Animal Cells

• Animal and plant cells may differ in shape, size, and the organelles they contain. 
•  Most often these differences are in structure.
• Similarities and differences between plants and animals are evident at the cellular level.
• Plant cells differ from animal cells in that plant cells contain cell walls, chloroplasts, and large, central vacuoles to aid in photosynthesis that help them convert matter and energy to usable forms

• identify these organelles and know what they do - (cell membrane, cytoplasm, nucleus, cell wall, vacuole, mitochondrion, endoplasmic reticulum and chloroplasts
• compare plant and animal cells (both structure and function)

Cell Division for growth and reproduction

• Reproduction is a life process by which living things transfer genetic information to their offspring.
• All living things grow and reproduce.

Mitosis for Growth and Repair

• As an organism grows and repairs itself, the number of its cells increase.
• For this to happen, existing cells divide through the process of mitosis so that new cells can be made.
• The cells which divide go through the cell cycle.
  • The cell cycle has two main components—interphase and mitosis.
• During mitosis, a body cell first duplicates its chromosomes and then divides into two identical daughter cells, each one with a complete set of chromosomes identical to the original parent cell.
• The purpose of mitosis is to produce new cells for growth and repair that are identical to the parent cell.

Meiosis for Reproduction

• The purpose of meiosis is to produce reproductive (sex) cells that carry half the genetic material of the parent.

• sequence the steps, recognize images, and explain the role of each stage in the cell cycle, including mitosis .
• explain why cell division is essential to the growth and reproduction of all living things
• differentiate between the purpose of mitosis and meiosis

Cellular Transport - Osmosis and Diffusion

• Living things must move materials into, out of, and within the cell.
• Two passive processes that allow for this exchange of materials are diffusion and osmosis. 
• These processes require no energy on the part of the cell.
• Substances merely move toward equilibrium (from an area of high concentration to an area of low concentration) .

Osmosis

• Osmosis is the movement of water molecules across a cell membrane.

Diffusion

• Diffusion is the movement of substances other than water across a cell membrane. 
• Cell membranes are selectively permeable to various substances

• model how materials move into and out of cells in the processes of osmosis, diffusion, and selective permeability