Cell Membrane and Transport Methods

Cell Membrane

• The cell membrane acts as a protective covering and allows materials to enter and exit the cell.
• It is selectively permeable, allowing some materials to pass through while blocking others.
• It is composed of lipids and proteins, primarily a phospholipid bilayer, which prevents polar molecules from passing through, but allows hydrophobic molecules to pass easily.
• Proteins in the membrane function as identification markers and channels for substances to enter the cell.

Transport Methods

• Passive transport requires no energy and moves substances down their concentration gradient:
  • Diffusion: substances move from areas of high concentration to areas of low concentration.
  • Osmosis: water moves across a semipermeable membrane from areas of low solute concentration to areas of high solute concentration.
  • Filtration: pressure forces water and dissolved materials across a membrane.
  • Facilitated diffusion: a substance moves across a membrane with the help of a transport protein.
• Active transport requires energy and moves substances up their concentration gradient.

Microscopy

• Light microscopes have a resolution of about 0.1µm and can be used to examine tissues and cells.
• Electron microscopes have a resolution of about 0.1nm and are used to view internal structures.
  • Scanning electron microscopy (SEM) provides three-dimensional surface images.
  • Transmission electron microscopy (TEM) reveals internal structures.
• Atomic force microscopy (AFM) has very high resolution and can reveal surface topography.

Osmosis

• Osmosis is a type of passive transport involving water movement across a selectively permeable membrane from a low solute concentration to a high solute concentration.
• Osmotic pressure is a substance's ability to pull water towards areas of higher concentration.
  • Hypertonic solutions have a higher impermeable solute concentration outside the cell than inside.
  • Hypotonic solutions have a lower impermeable solute concentration outside the cell than inside.
  • Isotonic solutions have equal amounts of impermeable solutes inside and outside the cell.

Cellular Respiration

• Cellular respiration is a critical process that allows cells to generate energy from food.
• In simple terms, the body digests food, releasing energy.
• Glucose, a simple sugar, is the primary source of energy for cells.
• During cellular respiration, glucose combines with oxygen in the mitochondria to produce ATP (adenosine triphosphate).
• The equation for cellular respiration is: Glucose + Oxygen → Carbon Dioxide + Water + ATP.

Gene Expression

• Genes are units of heredity that determine the structure of RNA molecules, which can function independently or produce proteins.
• Gene expression is the process of producing RNA and/or proteins from the information stored in DNA.

Asexual Reproduction in Eukaryotic Cells

• Asexual reproduction allows cells to create identical copies of themselves, contributing to growth and repair.
• Mitosis and cytokinesis are essential processes in eukaryotic asexual reproduction.
• Mitosis, the division of genetic material, occurs in four phases: prophase, metaphase, anaphase, and telophase.
• Cytokinesis, the division of cytoplasm and organelles, follows mitosis.

Microorganisms: A Summary

• Bacteria are simple one-celled organisms that lack a nucleus and organelles.
• Viruses are not cells; they require another cell to replicate.
• Fungi can be single-celled or multicellular and can cause infections.
• Protozoa are single-celled organisms that can cause disease.
• Prions are misfolded proteins that cause disease.

Explore the structure and function of the cell membrane, including its role in selective permeability and transport methods. This quiz covers key concepts such as diffusion, osmosis, and facilitated diffusion, explaining how substances move in and out of the cell. Test your understanding of these fundamental biological processes!