Fundamental Characteristics of Life and Cell Biology

Characteristics of Living Organisms

• Respiration and Metabolism

  Cells carry out chemical reactions, such as respiration, to produce energy.

• Reproduction

  The process of creating new organisms, which can be sexual or asexual.

• Nutrition

  Chemical substances used for growth, repair, and other vital functions.

• Growth

  An increase in the size and number of cells.

• Homeostasis

  The ability to regulate the internal environment to maintain it constant or within certain limits.

• Excretion

  The removal of waste products generated by metabolism.

• Movement

  The ability to change position.

• Sensitivity

  The ability to detect changes in the external environment.

Comparing Animal and Plant Cells

Animal Cell Structure

Key components include the nucleus, vacuole, cell membrane, and granular cytoplasm.

• Irregular shape.
• Central nucleus.
• One to many transitory small vacuoles.
• Storage of glycogen.

Plant Cell Structure

Key components include the nucleus, sap vacuole, cell wall, cell membrane, and chloroplasts.

• Possesses a rigid cell wall.
• Contains chloroplasts.
• Nucleus is often pushed to the side.
• Features a big, central, and permanent sap vacuole.
• Storage of starch.

Functions of Cell Organelles

• Cell Wall

  • Gives shape and structural support to the cell.
  • Prevents the cell from bursting when water flows into it by osmosis.

• Cell Membrane

  • Controls what enters and what leaves the cell (selective permeability).

• Cytoplasm

  • Contains enzymes that speed up chemical reactions within the cell.
  • Houses organelles that carry out specific functions.

• Nucleus

  • Controls all the functions of the cell.
  • Contains the genetic information in the form of DNA.

• Chloroplasts

  • Carry out photosynthesis.
  • Contain the green pigment chlorophyll.

• Sap Vacuole

  • Contains a solution of sugars and salts.

Movement In and Out of the Cell (Transport Mechanisms)

Diffusion

The movement of molecules from an area of high concentration to an area of lower concentration, moving down a concentration gradient.

Concentration Gradient

The difference in concentration between two points. Substances naturally move from highly concentrated areas to lower concentrated areas.

Osmosis

Osmosis is the passive movement of water molecules through a semipermeable membrane from a region of low solute concentration to a region of higher solute concentration.

Solution Terminology in Osmosis

Plasmolysis in Plant Cells

When water leaves a plant cell, the cell does not burst because of the cell wall. The process involves:

1. Incipient Plasmolysis
2. Full Plasmolysis