BIO 120 u1 p3

Cell Membranes and Cellular Biology

  • Overview of Cell Membranes

    • All cells possess a membrane acting as a barrier between the cell's interior and its external environment.

    • The lecture covers how cell membranes operate, their composition, and their primary functions.

    • Comparison of two major cell types: prokaryotes and eukaryotes.

  • Diffusion and Lab Work

    • The upcoming lab will focus on diffusion and osmosis.

    • Students will participate in a diffusion lab this week.

  • History of Microscopy

    • Technological advancement in microscopy has allowed for the exploration of microscopic structures.

    • Robert Hooke (1665) created a rudimentary microscope and observed cells in cork, coining the term "cells" after animal stalls.

    • Anton van Leeuwenhoek improved microscopy significantly and was the first to observe the nucleus of cells using a high-powered microscope.

    • Examples of microscopes include:

    • Compound microscopes: for seeing microscopic structures.

    • Electron microscopes: using electron beams for high-resolution images, including detailed views of the nucleus and chromosomes.

    • Grand Valley has an electron microscope located in Padnos, requiring training and rental for usage.

  • Fundamental Concepts of Cells

    • All organisms are made up of cells, recognized as the basic units of life.

    • Each cell originates from a parent cell, either through clonal reproduction or sexual reproduction.

    • Example tissue: Leaf tissue from Alydeia, an aquatic plant being examined in lab.

  • Examples of Cells

    • Cells observed at magnification of 600 times (note: lab maximum is 400 times).

    • Chloroplasts: responsible for photosynthesis in cells (noted as a green structure).

  • Diversity of Cellular Forms

    • There are numerous diverse habitats and environments supporting a variety of organisms.

    • Single-Celled Organisms:

    • Paramecium: freshwater organisms found in lakes and rivers.

    • Euglena: single-celled photosynthetic organisms.

    • Amoeba: commonly found everywhere, capable of engulfing food.

    • Multi-cellular Organisms: more complex organisms made of billions of cells with specialized structures and functions.

    • Example Cells:

    • Red Blood Cells: concave structure facilitating gas exchange and transport.

    • Muscle Cells: striated for movement and contraction.

    • Nerve Cells (Neurons): long structures essential for signal transmission.

    • Intestinal Cells: equipped with villi to increase nutrient absorption efficiency.

  • Types of Cells

    • Two classifications of cells: Prokaryotic and Eukaryotic.

    • Similarities in Cells:

    • All cells possess:

      • Plasma membrane

      • Cytosol (fluid within cells)

      • Cytoplasm (region containing cytosol)

      • Chromosomes (genetic material storage)

      • Ribosomes (protein synthesis factories).

  • Differences between Prokaryotic and Eukaryotic Cells:

    • Prokaryotic Cells:

    • Lack a nucleus, have a nucleoid region where DNA floats.

    • No membrane-bound organelles; internal organization is absent.

    • Smaller size (1-2 micrometers).

    • Examples include bacteria (e.g., E. Coli, Bacillus).

    • Eukaryotic Cells:

    • Contain a nucleus and membrane-bound organelles.

    • Larger size (approximately 10 times larger).

    • Examples include plants, animals, fungi, and protists (e.g., Paramecium).

  • Cellular Processes

    • Transcription: the process of converting DNA to RNA within the nucleus.

    • Translation: conversion of RNA into proteins at ribosomes in the cytoplasm.

    • In prokaryotes, both transcription and translation occur in the cytoplasm.

  • Cell Membranes

    • Composed primarily of phospholipids, essential for cellular function.

    • Phospholipids: contains a polar head (hydrophilic) and two fatty acid tails (hydrophobic), making them amphipathic.

    • Amphipathic: can interact with water (due to the polar head) and act as a barrier (due to hydrophobic tails).

    • Formation in Water:

    • Phospholipids can self-organize into different structures when added to water:

      • Micelles: spherical structures with tails inward and heads outward.

      • Bilayers: two layers of phospholipids (similar to cell membranes) with tails inward.

      • Liposomes: closed structures with an internal space, acting like early cells.

    • Self-Healing Capacity: bilayers can reorganize to seal any breaches, are fluid and flexible.

    • Components of Membranes:

    • Phospholipids, cholesterol, carbohydrates, and proteins contribute to the membrane's functionality and diversity.

    • Characterized as a Fluid Mosaic Model:

      • Fluidity refers to the mobility of phospholipids; the mosaic aspect denotes the diverse components scattered throughout the membrane structure.

  • Conclusion

    • Future discussions will elaborate on factors impacting membrane fluidity and the roles of specific biomolecules in membranes.