Cellular Transport and Fluid Balance

Bulk Transfer of Substances for Cells

• Endocytosis is a process used to bring molecules like polar substances and large molecules into the cell.
• Exocytosis is a process used to move packages of substances from inside the cell to the outside.

Body Fluid Compartments

• The body has two main fluid compartments: intracellular and extracellular.
• Intracellular fluid is the fluid found inside the cell.
• Extracellular fluid is the fluid found outside the cell.
• Extracellular fluid includes interstitial fluid, which surrounds cells, and plasma, the fluid component of blood.

Clinical Application (Vomiting and Diarrhea)

• When a patient experiences vomiting and diarrhea, fluid loss can lead to dehydration.
• Dehydration can cause an electrolyte imbalance, leading to low sodium (hyponatremia) and low potassium (hypokalemia).
• The nursing staff must administer intravenous fluids to restore the body's normal balance.

Question 1: Dehydration and Water Transport

• Osmosis is the process that allows water to move into cells if the concentration of solutes inside the cells is higher than the concentration outside.

Question 2: Potassium Transport

• Active transport is the mechanism that allows potassium ions to move against their concentration gradient.

The Cell: The Basic Unit of Life

• The cell is the smallest living unit.
• Cells contain their own complete set of instructions (genetic material - DNA) for carrying out their individual activities.

Inside the Cell: The Cytoplasm

• Cytoplasm consists of the cytosol and the organelles.
• Cytosol is a jelly-like fluid that suspends the organelles within the cell.
• Organelles are structures within the cell that perform specific functions.

Organelles of the Cytoplasm

• Mitochondria are responsible for providing energy for the cell.
• Ribosomes are the site of protein synthesis.
• The Rough Endoplasmic Reticulum (RER) processes proteins produced by ribosomes and sends them to the Golgi apparatus.
• The Smooth Endoplasmic Reticulum (SER) synthesizes lipids, mobilizes glucose from glycogen, and stores calcium in muscle cells.
• The Golgi apparatus receives proteins from the RER and prepares them for distribution.
• Lysosomes are membranous sacs containing digestive enzymes that break down toxic substances and waste products.
• Peroxisomes are membranous sacs containing oxidase enzymes that detoxify harmful substances.
• Microfilaments, intermediate filaments, and microtubules provide structural support and facilitate movement within the cell.
• Centrosomes are composed of two centrioles and microtubules, generating microtubules and mitotic spindles.

The Nucleus

• The nucleus is considered the brain of the cell.
• The nuclear envelope contains the genetic material, DNA.
• The nucleolus is responsible for forming ribosome components.
• Chromatin consists of DNA and histone proteins that organize the DNA.

Cellular Extensions

• Cilia are short, hair-like projections that move substances along the cell surface.
• Flagella are longer projections that propel the cell itself.
• Microvilli are small, finger-like projections that increase the surface area of the cell, facilitating absorption.

The Plasma Membrane

• The plasma membrane is a lipid bilayer that surrounds the cell, separating the extracellular and intracellular environments.
• The plasma membrane is selectively permeable, regulating the passage of substances across it.

Transportation Across the Plasma Membrane

• Passive transport does not require energy and moves substances down their gradients.
  • Simple diffusion allows fat-soluble molecules to move directly through the phospholipid bilayer.
  • Facilitated carrier-mediated diffusion uses protein carriers specific for a particular chemical to move substances.
  • Facilitated channel-mediated diffusion uses protein channels that are selective based on size and charge to move substances.
  • Osmosis refers to the diffusion of water through a specific channel protein (aquaporin) or the lipid bilayer.
• Active transport requires energy and moves substances against their gradients.
  • Primary active transport requires ATP to move solutes.
  • Secondary active transport harnesses the energy released from one particle going down its electrochemical gradient to drive another particle up its gradient.

This quiz covers important processes such as endocytosis and exocytosis for the movement of substances into and out of cells. It also discusses body fluid compartments and the clinical implications of dehydration due to conditions like vomiting and diarrhea. Test your knowledge on osmosis and the management of electrolyte imbalances.