Cells and Systems Learning Pack Notes

Characteristics of Living Things

  • Living organisms have several key characteristics and needs:
    • Functions: They perform various functions to sustain life.
    • Energy: They require energy to power their activities.
    • Environment: They respond and adapt to their environment.
    • Reproduction: They reproduce to create offspring.
    • Growth: They grow and develop over time.
    • Wastes: They produce wastes that need to be eliminated.
    • Structures: Their bodies are organized into specific structures.

Levels of Organization in Organisms

  • Organisms are organized into different levels:
    • Systems: Perform functions to keep the organism alive.
    • Organs: Made up of tissues.
    • Tissues: Composed of cells.
    • Cells: The basic unit of life.
  • Examples:
    • Human Circulatory System (Figure 2.1A)
    • Plant's Shoot System (Figure 2.1C)

Cells Work Together

  • Cells collaborate to perform necessary functions for survival.
    • Specialized cells carry out tasks that enable the organism to survive.
  • Examples:
    • Pikas rely on bacteria in their stomachs to digest plants.
    • Seabirds have cells that concentrate and eliminate excess salt.
    • Moose obtain nutrients from salt licks.

Microscopes and Cells

  • Magnification: Making an object appear larger than its actual size.
  • Early Microscopes:
    • Anton van Leeuwenhoek discovered micro-organisms by grinding lenses; he studied blood samples, pond water and plaque using his simple microscope, calling the single cells he found 'animalcules'.
    • Robert Hooke examined cork and described the small holes as 'little rooms or boxes,' naming them cellulae (Latin for 'cell').

Cells in All Living Things

  • Cell Theory:
    • Matthias Schleiden and Theodore Schwann hypothesized that all living things are made up of cells.
    • Cells are the basic units of life, carrying out all functions performed by living things.
    • Rudolf Virchow contributed his observations, leading to the formulation of the Cell Theory:
      • All living things are composed of one or more cells.
      • Cells are the basic units of structure and function in all organisms.

Microscopes Today

  • Technology has improved microscopes:
    • Compound light microscopes (2000X magnification).
    • Electron microscopes (2,000,000X magnification).
  • Types of electron microscopes:
    • TEM (transmission electron microscope).
    • SEM (scanning electron microscope).
  • Microscopes are valuable tools for investigating the microscopic world.

The Cell and Its Structures

  • Cell Structures:
    • All cells (plant and animal) have structures that perform specific functions.
    • These structures, called organelles, become visible with a compound light microscope.
  • Cell Structures and Functions:
    • Cell Membrane: Surrounds and protects the cell's contents.
    • Cell Wall: Provides support for plant or fungal cells (thicker and more rigid than membranes).
    • Cytoplasm: Distributes materials to different parts of the cell.
    • Nucleus: Controls the cell's activities.
    • Vacuoles: Store surplus food, wastes, and other substances.
    • Chloroplasts: Structures in green plants where photosynthesis takes place.

Cell Size and Function

  • Cells need a constant supply of materials (oxygen, water, food particles) and must eliminate waste products.
  • Materials pass through the cell membrane.
  • Most cells range in size from 10 - 50 micrometers (\\mum).

The Cell Membrane

  • The cell membrane is selectively permeable, allowing some substances to pass while blocking others.
    • Permeable membrane: Allows all materials through.
    • Impermeable membrane: Does not allow anything through.

Diffusion

  • The structure of the cell membrane controls what moves in and out.
  • Particles move in all directions, eventually spreading out evenly (diffusion).
  • Concentration determines the direction of movement:
    • Particles move from higher to lower concentration areas until there is a balance.

Osmosis

  • Osmosis is the diffusion of water through a selectively permeable membrane.
  • Water dissolves substances involved in cell processes.
    • Water loss leads to a high concentration of dissolved substances.
    • Water returning dilutes the substances for use by the cell.

Fluid Movement in Plants

  • Plants need water for photosynthesis.
  • Tissues are groups of cells performing similar functions.
  • Vascular tissues connect roots to leaves.
    • Phloem tissue transports sugars from leaves to the rest of the plant.
    • Xylem tissue conducts water and minerals from roots to cells.
    • Xylem and Phloem tissue usually occur together, along the length of plant stems and roots.

From Root to Leaf

  • The root system has fine root hairs.
    • Root hairs are extensions of epidermal cells that protect the outside of the plant.
  • Water moves into root hairs by osmosis when the concentration is greater outside.
  • Water moves from cell to cell until it reaches the xylem tissue.
  • Tube-shaped xylem cells move water by pressure from root hairs (high to low pressure).
  • Leaves are the food-producing organs where photosynthesis occurs.
    • Palisade cells contain chloroplasts and are thin, allowing light and gases to diffuse.
  • Stomata are tiny openings that allow air to enter the leaf, with guard cells controlling their opening and closing.

Transpiration

  • Transpiration is the loss of water through evaporation.
  • Water movement happens due to pressure differences (high pressure in root hairs to lower pressure in leaves).

Pushing and Pulling

  • Water particles are attracted to each other throughout the plant.
  • Water is drawn in by osmosis, pushed up by pressure, and pulled up by transpiration.

Specialized Cells

  • Different cells have different structures and functions:
    • Muscle cells: Elongated and tapered, used to move parts of the body.
    • Skin cells: Flat and thin, forming a protective layer.
    • Nerve cells: Long, branched fibers that carry nerve signals.
    • Blood cells: Thin, disc-like cells that carry oxygen.
    • Bone cells: Thick mineral matrix for support.

Tissues

  • Epithelial:
    • Cilia
    • Squamous
    • Columnar
    • Cuboidal
  • Muscle:
    • Skeletal
    • Cardiac
    • Smooth
  • Connective:
    • Cartilage
    • Bone
      • Extracellular matrix
    • Tendon
    • Ligament
    • Adipose Tissue
  • Nervous
  • Blood:
    • White Blood Cells
    • Red Blood Cells
    • Platelets

The Advantages of Being Multi-cellular

  • Multi-cellular organisms can:
    • Live in a wide variety of environments.
    • Grow very large.
    • Obtain energy from a wide variety of foods.
    • Have complex bodies.

Versatility

  • Cells can specialize functions and work in harmony with other cells.
  • Cells with the same structure and function form tissue
  • Tissues form organs
  • Organs work together in organ systems
  • Systems work together to form an organism

Tissues

  • Tissues are groups of similar cells that work together, having similar structure and function.

Organs

  • Each organ is made up of several tissues all working together. They are distinct structures in the body that perform particular functions. (Plants have organs as well - roots, stem and leaves)

Systems

  • Organs work together to perform activities that help the organism function as a whole.
  • Plants typically have two systems (root system and shoot -stems and leaves - system).
  • A reproductive system (flowers, fruits and seeds) is often produced at certain times as well.

Body Systems in Humans

  • The Digestive System: Breaks down food into usable particles (Figure 2.26).
  • The Respiratory System: Exchanges gases (inhalation and expiration) (Figure 2.27).
  • The Circulatory System: Transports food and gases (Figures 2.28 and 2.29).

How the Respiratory and Circulatory Systems Connect

  • The respiratory system exchanges oxygen and carbon dioxide, while the circulatory system transports those gases throughout the body.
  • Interaction happens in the tissues of the lungs.
  • Diffusion occurs between the alveoli and the capillaries.
  • Oxygen goes from the alveoli to the capillaries and carbon dioxide goes from the capillaries to the alveoli.

How the Digestive and Circulatory Systems Connect

  • The transfer of food particles, from the digestive system to the circulatory system, takes place at the inner lining of the small intestine, through millions of tiny, finger-like projections, called villi, which contain a network of capillaries.
  • The transfer of food particles is possible because of absorption (the villi absorb the food particles from the capillaries and then transport the nutrients to the cells, to be used as fuel).

The Excretory System

  • Filters waste materials from the blood.

The Sensory Awareness System

  • Allows systems to respond to changing conditions and maintain a stable internal environment.
    • Quivering muscles generate heat.
      • 90% of heat loss is through the skin (most of the rest is through the lungs).
    • Hairs on the skin stand on end when the tiny muscle cells near the surface
      contract, creating gooseflesh ‘ (goosebumps).
    • Fluffing body hair (in animals with thick fur) reduces heat loss by improving
      insulation.
    • Feeling flushed (red and hot) happens because tiny blood vessels in the skin
      expand, which increases blood flow.
    • Sweating helps cool down your body as moisture evaporates from the skin
      surface
  • The nervous system monitors conditions and regulates body temperature through the hypothalamus.
  • Response to stimuli is co-ordinated by the nervous system (brain, spinal cord and nerves) and the endocrine system (glands that produce hormones).
  • Diet, exercise, drugs, injury and disease can affect body systems and how they perform their functions.

Blood - The Body's Transportation System

  • About 8% of an adult's body weight is blood.
  • Components of blood:
    • Plasma: 55% of blood volume, carries nutrients, waste, hormones, and blood cells.
    • Red blood cells: 44% of blood volume, carries oxygen via hemoglobin.
    • White blood cells: Less than 1%, defends against infection.
    • Platelets: Less than 1%, causes blood to clot.

A Healthy Circulatory System

  • The heart circulates blood throughout the body.
  • Disorders: high blood pressure (hypertension), heart attacks (damage to heart muscle) and strokes (brain damage).

Blood Pressure

  • Measured using a sphygmomanometer.
  • Indicates:
    • Blood volume
    • Heart rate
    • Artery size
    • Artery elasticity
    • Blood viscosity

Disorders of the Circulatory System

  • Risk factors:
    • Smoking (nicotine constricts blood vessels, carbon monoxide reduces oxygen).
    • Poor diet (high cholesterol).
    • Little exercise (increases fatty deposits).

A Healthy Digestive System

  • Food provides carbohydrates, fats, proteins, vitamins, minerals, and water.

Nutrients in Food

  • Starch and sugars are carbohydrates: provide energy.
  • Fats: provide energy and cushion organs.
  • Proteins: essential for growth and repair.
  • Minerals and vitamins: are also needed for good health.

Disorders of the Digestive System

  • Low-fibre can irritate the colon wall and lead to colon cancer).
  • Long-term stress, smoking, excessive use of alcohol or aspirin can lead to a peptic ulcer.

A Healthy Respiratory System

  • Smoking, air pollution and industrial by-products (coal dust) can lead to disorders of the respiratory system.

Disorders of the Respiratory System

  • Cilia removes airborne particles.
  • Poisons irritate the lining of the lungs, causing certain cells to produce more mucus.
  • Inflammation can lead to bronchitis, which can lead to emphysema.
  • Lung cancer is caused by tar and smoke, which cause the lung cells to grow out of control and overcome healthy cells.