The Cell: Basic Unit of Structure and Function

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					Date: Sept. 2, 2009 Source: Details:  Common characterists of cells: o o o o o o o o o o o o o o o o General housekeeping functions Dispose of the wastes they produce Shape and integrity of a cell Capable of undergoing cell division “The Cell: Basic Unit of Structure and Function” – Chapter 2

 The study of cells: Cytology  Using the microscope to study cells: Light microscope Transmission electron microscope Scanning electron microscope

 General functions of human body cells: Covering (protect outer surface of body)         o Ex: epidermal cells in skin

Lining (regulate nutrient movement into body tissues) Ex: epithelial cells in small intestine

Storage (store lipid reserves, and store carbohydrate nutrients as glycogen) Ex: fat cells & liver cells

Movement (pump blood, and move skeleton) Ex: muscle cells of heart & skeletal muscle cells

Connection (form ligaments that attach bone to bone) Ex: collagen (protein) fibers from fibroblasts

Defense (produce antibodies to target antigens or invading cells) Ex: lymphocytes

Communication (send information between regions of the brain) Ex: nerve cells

Reproduction (produce new blood cells, and produce new individual) Ex: bone marrow stem cells & sperm and oocyte cells

 A prototypical cell: 3 basic constituents:   Plasma membrane Cytoplasm


 o           o       o           o o


Major cell components: Plasma (cell) membrane Cytoplasm Cytosol Organelles Inclusions Nucleus Nuclear envelope Nuclear pores Nucleolus (or nucleoli) Chromatin and chromosomes

Membrane-bound organelles: Smooth endoplasmic reticulum (smooth ER) Rough endoplasmic reticulum (rough ER) Golgi apparatus Lysosomes Peroxisomes Mitochondria

Non-membrane-bound organelles: Ribosomes Cytoskeleton Microfilaments Intermediate filaments Microtubules Centrosome Centrioles Cilia Flagellum Microvilli

 Plasma membrane: Plasma membrane Composition and structure of membranes:    Glycocalyx Lipids Phospholipids  Phospholipid bilayer


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Intracellular fluid Extracellular fluid Interstitial fluid

Cholesterol Glycolipids Proteins      Integral proteins Receptors Peripheral proteins Enzymes Glycoproteins


Functions of plasma membrane:     Communication Intercellular connection Physical barrier Selective permeability


Protein-specific functions of the plasma membrane:       Transport  ATP (Adenosine triphosphate)

Intercellular connection Anchorage for the cytoskeleton Enzyme (catalytic) activity Cell-cell recognition Signal transduction


Transport across the plasma membrane:  Factors influence membrane permeability         Transport proteins Plasma membrane structure Concentration gradient Ionic charge o Ion

Lipid solubility Molecular size

Passive transport Simple diffusion  Diffusion


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Equilibrium Net movement

Osmosis Facilitated diffusion Bulk filtration    Solvents Solutes Hydrostatic pressure

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Active transport Ion pumps           Sodium-potassium pump

Bulk transport Exocytosis Vesicles Endocytosis Invagination Phagocytosis Pseudopodia Vacuole Pinocytosis Receptor-mediated endocytosis

 Cytoplasm o o o Cytosol Inclusions  Melanin


 Membrane-bound organelles  Endoplasmic reticulum  Smooth ER  Rough ER  Cisternae  Transport vesicles  Golgi apparatus o o Receiving region Shipping region

 Functions of Endoplasmic Reticulum:


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Synthesis Transport Storage Detoxification

 Steps that move through the Golgi apparatus: RER proteins in transport vesicle Vesicle from RER moves to Golgi apparatus Vesicle fuses with Golgi apparatus receiving region Proteins are modified as they move through Golgi apparatus Modified proteins are packaged in shipping region Vesicles become either (a) lysosomes, (b) secretory vesicles that undergo exocytosis, or (c) plasma membrane  Functions of Golgi apparatus: o o o o o o o o o Modification Packaging Sorting

 Lysosomes Autophagy Autolysis

 Functions of Lysosomes: Digestion Removal Self-destruction

 Function of peroxisomes: Detoxification  Peroxisomes  Mitochondria o o o o Cristae Matrix

 Function of mitochondria: Energy synthesis  Non-membrane-bound organelles: Ribosomes   o  Free ribosomes Fixed ribosomes

Cytoskeleton Microfilaments


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Intermediate filaments Microtubules

Centrosome and centrioles Centrosome Centrioles

Cilia and flagella Cilia Flagella


 Functions of ribosomes: Protein synthesis:   o o o o o o o o Free ribosomes Fixed ribosomes

 Functions of cytoskeleton: Structural Movement

 Functions of centrosomes and centrioles: Microtubule support Cell division

 Nucleus Nuclear envelop Nuclear pores

 Functions of the nucleus: Cellular regulation Production

 Nucleoli  DNA, Chromatin, and Chromosomes o o o o Deoxyribonucleic acid (DNA) Nuclear DNA Genes Nucleotides     o o Adenine Cytosine Guanine Thymine

Chromatin Chromosome


o o o o o o o o o

Histones Nucleosome

 Life cycle of the cell Daughter cells Mitosis Somatic cells Cell cycle Interphase Mitotic (M) phase Interphase    o    G1 phase S phase G2 phase

Mitotic (M) phase Mitosis Cytokinesis Prophase          Sister chromatids Centromere Spindle fibers

Metaphase Mitotic spindle

Anaphase Single-stranded chromosome

Telophase Cleavage furrow

 Study Tips: o Each phase of mitosis:     The p in prophase stands for the puffy ball of chromosomes that forms in the center of the cell. The m in metaphase stands for middle: during this phase, the chromosomes align along the middle of the cell. The a in anaphase stands for apart: during this phase, the sister chromatids are pulled apart. The t in telophase stands for two: during this phase, two new cells begin to form as a cleavage furrow divides the cytoplasm.  Aging and the cell: 7


Cells die by one of two mechanisms:   Necrosis apoptosis

Cues:                        Figure 2.1 – The range of cell sizes Figure 2.2 – Microscopic techniques for cellular studies Table 2.1 – Selected common types of cells and their functions Figure 2.3 – The structure of a cell Table 2.2 – Components of the cell Figure 2.4 – Structure of the plasma membrane Figure 2.5 – Sodium-potassium pump Figure 2.6 – Exocytosis Figure 2.7 – Three forms of endocytosis Table 2.3 - Transport processes across a plasma membrane Figure 2.9 – Golgi apparatus Figure 2.10 – Lysosomes Figure 2.11 – Peroxisomes Figure 2.12 – Mitochondria Figure 2.13 – Ribosomes Figure 2.14 – Cytoskeleton Figure 2.15 – Centrosome and centrioles Figure 2.16 – Cilia and flagella Figure 2.17 – Nucleus Figure 2.18 – DNA and chromatin structure Figure 2.19 – The cell cycle Figure 2.20 – Interphase and mitosis Table 2.4 – Somatic cell cycle events

Summary: 1. Describe an advantage of using TEM rather than LM to study intracellular structure. 2. What are some basic functions of human body cells? 3. Briefly describe the three main constituents of a cell. 4. What is the benefit to the cell of having a plasma membrane that is selectively permeable? What are some disadvantages of having a selectively permeable plasma membrane? 5. What types of lipids are found in the plasma membrane? 6. In general, what materials may cross a selectively permeable membrane?


7. What is diffusion? 8. Describe the process of osmosis. 9. Discuss the similarities between facilitated diffusion and receptor-mediated endocytosis. 10. While examining a cell by microscope, you observe that the cell has few mitochondria. What does this imply about the cell’s energy requirements? 11. Describe the characteristics of the cytosol. 12. Describe the functions of lysosomes, mitochondria, and centrioles. 13. Contrast the fates of proteins synthesized on free ribosomes versus those synthesized on fixed ribosomes. 14. What is the function of cilia? 15. What is the function of the nuclear envelope? 16. What is the difference between chromatin and chromosomes? 17. Observation shows that most cells are suspended in interphase for most of their lives. Identify the parts of interphase, and describe an event that occurs during each part. 18. List the stages of mitosis in order of occurrence. Describe a unique activity associated with each stage. 19. What name is given to programmed cell death? 20. In general, what is the main characteristic of cancer?


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