Bio principles Chp 6

Digestive System

Accessory Organs to Small Intestine

• Liver

  • Produces bile which aids in absorption of fats.

• Gall Bladder

  • Stores bile and empties it into the small intestine.

• Pancreas

  • Produces digestive enzymes.

  • Produces a buffer that neutralizes the acidity of stomach acid.

Pathway of Food

1. Mouth

   • Teeth reduce the size of food, increasing surface area for digestion by enzymes.

   • Enzymes in saliva start breaking down carbohydrates.

2. Pharynx (Throat)

   • The epiglottis blocks the windpipe during swallowing to ensure food enters the esophagus instead of the lungs.

3. Esophagus

   • Transports food to stomach via rhythmic muscle contractions (peristalsis).

4. Stomach

   • Acidic gastric juices begin digestion.

   • Enzyme pepsin breaks down proteins.

   • Mucous prevents gastric juices from digesting the stomach itself.

   • Pyloric sphincter regulates the movement of food to the small intestine.

5. Small Intestine

   • Site of most digestion for carbohydrates, proteins, fats, and nucleic acids.

   • Nutrient absorption occurs into the bloodstream.

6. Large Intestine (Colon)

   • Reabsorbs water and forms undigested materials (e.g., fiber) into feces.

Absorption of Nutrients

Nutrients in Small Intestine

• Villi

  • Tiny projections that increase surface area for nutrient absorption.

  • Nutrients are absorbed through the intestinal lining into the bloodstream for transport throughout the body.

Transport of Nutrients

Nutrient Absorption

• Nutrients absorbed from the small intestine are transported throughout the body in the bloodstream, along with dissolved oxygen and carbon dioxide.

• Components of All Cells:

  • Plasma membrane, dissolved CO2, cellular wastes, DNA, cytoplasm.

Importance of Eating

• Why do animals eat?

  • To ingest and break down food for absorption by the body.

  • Process includes:

    1. Eating food.

    2. Digesting food.

    3. Transporting food molecules to cells for cellular respiration.

    4. Producing ATP, the energy currency.

Cardiovascular System

Heart Function

• Enables the transport of nutrients, gases, hormones, and wastes to and from all body cells.

Respiratory System

Breathing Purpose

• Enables gas exchange, supplying blood with oxygen and removing carbon dioxide.

Excretory System

Urination Purpose

• Eliminates liquid wastes; regulates water balance.

Summary of Basic Body Functions

1. We eat so cells have nutrients.

2. We breathe so cells have oxygen.

3. We urinate to excrete cellular wastes.

4. Blood carries nutrients and oxygen to cells and removes wastes and carbon dioxide.

Nutrient Digestion and Absorption

Process of Nutrient Absorption

1. After digestion, nutrients are absorbed from the small intestine to the bloodstream.

   • Forms of Nutrients:

     • Fatty acids, glycerol, glucose, pyruvate, and amino acids.

2. Nutrients are transported in the bloodstream to cells.

3. Nutrients enter cells in various forms.

4. Final step of food breakdown occurs during cellular respiration, producing energy stored as ATP.

Learning Objectives for Cells

• Know the different types of cells.

• Understand cell components (name, structure, and function).

• Know how different components of a cell interact to maintain life.

Cells: The Smallest Unit of Life

Cytology

• Robert Hooke (1665) studied cells using lenses and the light microscope.

Types of Microscopes

1. Compound Light Microscopes

   • Magnification of up to 1,000 times.

   • Useful for viewing human cheek cells and other microscopic specimens.

2. Electron Microscopes

   • Higher resolution (up to 100,000 times), useful for detailed cell structures.

Sizes of Cells and Organisms

• Prokaryotic and Eukaryotic Cells

  • Prokaryotic cells: typically 0.2-10 μm.

  • Eukaryotic cells: 10-100 μm.

  • Viruses: 0.05-0.2 μm.

Prokaryotic Cells

Types of Prokaryotes

• Common shapes: Cocci (spherical), Bacilli (rod-shaped), and Spirilla (spiral).

Prokaryotic Structure

• Contains:

  • Pili, nucleoid, ribosomes, plasma membrane, cell wall, flagella, capsule, and plasmid.

Eukaryotic Cells

Eukaryotic Structures

• Animal Cells include:

  • Plasma membrane, cytoplasm, nucleus, rough and smooth endoplasmic reticulum (RER and SER), Golgi apparatus, mitochondria, lysosomes, and cytoskeleton.

• Plant Cells have additional structures:

  • Cell wall, chloroplasts, and central vacuole.

The Plasma Membrane

• A fluid phospholipid bilayer that functions as a selective barrier for passage of oxygen, nutrients, and wastes.

The Nucleus

• Components:

  • Nuclear envelope (double membrane), nucleolus (site of ribosomal RNA synthesis), chromatin (DNA).

Endoplasmic Reticulum (ER)

• Smooth ER: Lacks ribosomes; site for lipid synthesis and detoxification.

• Rough ER: Contains bound ribosomes; site of protein synthesis.

Ribosomes

• Composed of rRNA and proteins; can be bound to RER or free in the cytosol.

Golgi Complex

• Processes, transforms proteins and synthesizes polysaccharides. Vesicles move between ER and Golgi complex.

Lysosomes

• Membrane-bound sacs containing hydrolytic enzymes that digest macromolecules and organelles.

Mitochondrion

• Site of cellular respiration and ATP production; contains inner and outer membranes, cristae, and matrix.

Peroxisomes

• Involved in the degradation of hydrogen peroxide and detoxification of harmful compounds.

The Cytoskeleton

• An internal cell skeleton made of proteins, including microfilaments and microtubules.

• Facilitates movement and structural integrity of the cell.

Types of Cytoskeletal Elements

1. Microtubules: Hollow tubes that maintain cell shape and assist in cell motility.

2. Microfilaments (Actin Filaments): Thinner strands that assist in muscle contraction and motility.

3. Intermediate Filaments: Provide structural support and anchor organelles.

Intercellular Junctions in Animal Cells

1. Tight Junctions: Prevent leakage between adjacent cells.

2. Desmosomes: Fasten cells into sheets.

3. Gap Junctions: Allow communication between adjacent cells.

Unique Structures in Plant Cells

• Chloroplasts: Site of photosynthesis; double membrane structure containing thylakoids.

• Central Vacuole: Storage, breakdown of molecules, and cell expansion.

• Cell Wall: Composed of cellulose in plants; provides structure and support.