BIO 201 Chapter 4 Notes Dr Sonja Pyott General Features of Cells Concept 1 Cells are the smallest unit of life I Terms to know Microscopes light and electron Magnification Resolution Contrast Cell theory Ribosomes Cytosol Plasma membrane II Microscopes are necessary to view cells The first true microscopes were invented sometime in the 1600s The first observations of cells using light microscopes occurred in the 1660s Three key principles of microscopy include magnification resolution and contrast The two major types of microscopy are light microscopy and electron microscopy Observations of cells using microscopy led to the development of the cell theory III The cell theory established in 1839 includes three fundamental principles 1 Cells are the smallest living things 2 All organisms are composed of one or more cells 3 Cells arise only by division from a previously living cell IV Cell size is inherently limited Smaller sizes increase the surface area to volume ratio and maximize the surface area for diffusion of materials into and out of the cell Larger cells are usually elongated or flattened rather than spherical to increase the surface area to volume ratio Cell size ranges from 1 m some bacteria to 1 cm chicken egg in diameter Most plant and animal eukaryotic cells are between 10 and 100 m in diameter Review the metric scale if necessary V All cells share four structural arrangements or components The genetic material DNA is centrally located Ribosomes synthesize proteins The cytosol fills the interior of the cell The plasma membrane encloses the cell and separates it from its environment VI There are two fundamental classes of cells Page 1 of 8 BIO 201 Chapter 4 Notes Dr Sonja Pyott Prokaryotes lack a true nucleus derived from pro meaning before and karyote meaning kernel to describe the nucleus Eukaryotes have a true nucleus derived from eu meaning true Concept 2 Eukaryotic cells are compartmentalized I Terms to know Nucleus Semiautonomous organelles Cytoskeleton Chromosomes II Functions are compartmentalized within the eukaryotic cell III Important eukaryotic cell structures include the Nucleus and endomembrane system Semiautonomous organelles Cytosol Cytoskeleton Table 1 Comparison of prokaryotic and eukaryotic cell structure Feature Average size of cells Nucleus Prokaryotes 1 10 m Absent have a nucleoid region Absent Nuclear envelope membrane Genetic material DNA Present as one large circular molecule which acts as a chromosome and found in the nucleoid region DNA bound to histones No proteins Cytoskeleton of Absent microtubules and actin filaments Membrane bounded Absent organelles Ribosomes Present Plasma membrane Present Page 2 of 8 Eukaryotes 10 100 m Present as a distinct structure Present surrounds the nucleus Present in linear chromosomes in the nucleus usually many per cell Yes Present Present Present Present BIO 201 Cell wall Chapter 4 Notes Present Dr Sonja Pyott Present in plants and some other organisms Concept 3 The nucleus and endomembrane system organize and express the cell s genetic material I Terms to know Nuclear envelope Phospholipid bilayer Endoplasmic reticulum Nuclear pores Nuclear lamina Nuclear lamins Nucleolus Rough endoplasmic reticulum Smooth endoplasmic reticulum Endoplasmic reticulum lumen or cisterna Golgi apparatus Golgi bodies Cis and trans face of the Golgi apparatus Golgi apparatus lumen or cisterna Glycoproteins Glycolipids Lysosomes Peroxisomes Vacuoles II The nuclear envelope surrounds the nucleus the genetic control center of the cell The nuclear envelope consists of two phospholipid bilayer membranes The outer membrane of the nuclear envelope is continuous with the endoplasmic reticulum more below Nuclear pores comprised of proteins embedded in the in the nuclear envelope form passageways or pores in the nuclear envelop that allow small molecules to pass between the nucleus and cytoplasm The nuclear lamina coats the innermost surface of the nuclear envelop provides the nuclear envelop with structural support and is composed of the intermediate filaments more below known as nuclear lamins The nucleolus is a darkly staining region within the nucleus and is the site of ribosomal RNA synthesis which is important in protein synthesis or translation Module 14 III The endoplasmic reticulum ER constitutes most of the endomembrane system Page 3 of 8 BIO 201 Chapter 4 Notes Dr Sonja Pyott A ER literally means little net within the cytoplasm B Like the plasma membrane the ER is composed of phospholipid bilayer with embedded proteins C The space enclosed in the ER is called the cisternal space or lumen D The ER is divided into two types based on their appearance in electron micrographs rough ER RER and smooth ER SER 1 RER is a site of protein synthesis RER is continuous with the nuclear envelope and gets its rough appearance from ribosomes responsible for protein synthesis that are attached to the cytoplasmic face Proteins destined for transport out of the cell or to lysosomes or vacuoles more below or that will be embedded in the plasma membrane are synthesized on the surface of RER 2 SER has a variety of functions SER is continuous with the RER and is not associated with ribosomes giving it a smooth appearance SER has a number of functions including the synthesis of carbohydrates and lipids including steroid hormones storing of intracellular calcium ions Ca2 and detoxification IV The Golgi apparatus collects processes and directs the traffic of proteins The Golgi apparatus is the collection of multiple Golgi bodies or flattened stacks of membranes The Golgi apparatus functions to collect process and transport molecules synthesized at one location to another location within or outside of the cell Molecules are transported from the ER in transport vesicles that fuse with the Golgi apparatus at its cis face Molecules are emptied into the lumen of the Golgi apparatus and traverse through the lumen of the Golgi apparatus as they are processed Ultimately molecules bud off of the trans face of the Golgi appartus and are transported to their appropriate destinations The most common modifications of molecules that enter the Golgi apparatus are the addition or modification of short chain sugars to form glycoproteins or glycolipids V Lysosomes contain digestive enzymes Lysosomes are membrane bound digestive vesicles that arise from the Golgi apparatus They contain enzymes that degrade proteins lipids nucleic acids and carbohydrates Lysosomes are