BIOLOGY OF HUMANS Concepts, Applications, and Issues Fifth Edition Judith Goodenough Betty McGuire 3 The Cell Lecture Presentation Anne Gasc Hawaii Pacific University and University of Hawaii Honolulu Community College
The Cell OUTLINE: Eukaryotic Cells Compared with Prokaryotic Cells Cell Size and Microscopy Cell Structure and Function Plasma Membrane Organelles Cytoskeleton Cellular Respiration and Fermentation in the Generation of ATP
Eukaryotic Cells Compared with Prokaryotic Cells The Cell Theory is a fundamental organizing principle of biology that states: A cell is the smallest unit of life Cells make up all living things, from unicellular to multicellular organisms New cells can arise only from preexisting cells There are two basic types of cells Prokaryotic Eukaryotic
Eukaryotic Cells Compared with Prokaryotic Cells Prokaryotic cells - Structurally simpler - Typically smaller - Lack membranebound organelles - Include bacteria and archaea Eukaryotic cells - Structurally more complex - Typically larger - Have membrane-bound organelles - Found in plants, animals, fungi, protists
Figure 3.1 A prokaryotic cell.
Figure 3.2 An eukaryotic cell.
TABLE 3.1 Review of Features of Prokaryotic and Eukaryotic Cells
Cell Size and Microscopy Cells vary in size, but they can never exceed the volume that can be nourished by materials passing through the surface membrane The small size of cells is dictated by a physical relationship known as the surface-to-volume ratio As a cell gets larger, its surface area increases much more slowly than its volume
Figure 3.3 Cells size and surface area to volume ratio.
Cell Size and Microscopy Most eukaryotic and prokaryotic cells are typically measured in micrometers ( m) which is 10 6 meters They can be seen through either light or electron microscopes
Figure 3.4 Micrographs are photographs taken through a microscope.
Cell Structure and Function Although we begin life as only one cell, that cell differentiates into many specialized cells These specialized cells have structures that reflect their particular functions
Figure 3.5 A cell s structure reflects its specific function.
Plasma Membrane The outer boundary of the cell Controls the movement of substances in and out of the cell The phospholipid bilayer separates the extracellular fluid from the material inside the cell contained in the cytoplasm Proteins, cholesterol, and carbohydrates are also part of the membrane and give it the qualities of a fluid mosaic
Plasma Membrane Web Activity: Membrane Structure
Figure 3.6 The structure of the plasma membrane of a cell.
Plasma Membrane Structure Functions of the plasma membrane Maintains structural integrity of the cell Regulates movement of substances into and out of the cell Provides recognition between cells (glycoproteins) Provides communication between cells (receptors) Sticks cells together to form tissues and organs (cell adhesion molecules)
Movement Across the Plasma Membrane Two types: Passive transport Movement across the membrane that doesn t require energy Simple diffusion Facilitated diffusion Osmosis Active transport Movement across the membrane that requires energy
Movement Across the Plasma Membrane Web Activity: Passive and Active Transport
Simple Diffusion Movement of a substance following a concentration gradient: from high concentration to low concentration End result is an equal distribution of the substance in the two areas Eliminates concentration gradient
Figure 3.7 Simple diffusion.
Facilitated diffusion Movement of a substance from a region of higher concentration to a region of lower concentration with the aid of a membrane protein Water-soluble substances need to be assisted or facilitated by certain proteins (carrier proteins) to cross a cell membrane
Figure 3.8 Facilitated diffusion.
Osmosis Movement of water across a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration The water molecules move to dilute the solution
Osmosis Web Activity: Diffusion and Osmosis
Figure 3.9 Osmosis is the diffusion of water across a selectively permeable membrane.
Active Transport Movement often from a region of lower to higher concentration with the aid of a carrier protein and energy (usually from ATP)
Figure 3.10 Active transport.
Endocytosis A region of the plasma membrane engulfs the substance to be ingested and then pinches off from the rest of the membrane, enclosing the substances in a vesicle which travels through the cytoplasm Applies to large molecules, single-celled organisms, and droplets of fluid containing dissolved substances Two types: Phagocytosis (cell eating) large particles or bacteria Pinocytosis (cell drinking) droplets of fluid
Figure 3.11 Endocytosis phagocytosis or pinocytosis.
Exocytosis Large molecules are enclosed in membrane-bound vesicles that travel to plasma membranes where they are released to the outside Exo, exit: outside Endo: inside
Exocytosis Web Activity: Endocytosis and Exocytosis
Figure 3.12 Cells package large molecules in membrane-bound vesicles, which then spill their contents by exocytosis.
TABLE 3.2 Review of Mechanisms of Transport across the Plasma Membrane
Organelles Inside eukaryotic cells are membrane-bound organelles that have different functions Nonmembranous organelles also perform specific cellular functions Organelles include: Nucleus Endoplasmic Reticulum Golgi apparatus Lysosomes Mitochondrion
Nucleus Contains almost all of the genetic information of the cell, the DNA Surrounded by a nuclear envelope, which is a double membrane that allows communication through nuclear pores The genetic information is organized into chromosomes Chromosomes are threadlike structures made of DNA and associated proteins called histones Humans have 46 chromosomes (23 pairs) in the loose form (chromatin) or condensed and are then visible in the light microscope during cell division
Figure 3.13 The nucleus contains almost all the genetic information of a cell.
Figure 3.14 Chromosomes are composed of DNA and associated proteins.
Nucleus Nucleoplasm Made of chromatin and the other contents of the nucleus Nucleolus A specialized region within the nucleus Involved in the production of ribosomal RNA
Endoplasmic Reticulum An extensive network of channels connected to the plasma membrane, the nuclear envelope, and certain organelles Two types of endoplasmic reticulum Rough endoplasmic reticulum (RER) Contains ribosomes that guide the production of cell products Smooth endoplasmic reticulum (SER) Lacks ribosomes Is involved in the production of phospholipids and detoxification
Figure 3.15 The endoplasmic reticulum (ER) is continuous with the nuclear membrane and consists of two regions: rough ER and smooth ER.
Golgi Complex and Lysosomes Golgi complex A series of interconnected, flattened membranous sacs Cell products are packaged in vesicles and transferred to the Golgi complex for processing and packaging Lysosomes Contain enzymes that break down macromolecules, old organelles, and invaders
Figure 3.16 The Golgi complex.
Figure 3.17 The route by which protein-filled vesicles from the rough endoplasmic reticulum travel to the Golgi complex for processing and eventual release.
Figure 3.18 Lysosome formation and function in intracellular digestion.
Mitochondria Sites of cellular respiration, provide cell with energy through the breakdown of glucose to produce ATP Double-membrane organelle Contains inner foldings (cristae) that provide increased membrane surface for cellular respiration Singular: mitochondrion
Figure 3.19 Mitochondria are sites of energy conversion in the cell.
Cytoskeleton Provides shape and support for the cell Is composed of microtubules (thickest), intermediate filaments, and microfilaments (thinnest) Centriole: a microtubule-organizing center located near the nucleus Microtubules and microfilaments are seen to disassemble and reassemble Intermediate filaments tend to be more permanent
Centrioles Organized in a pair of centrioles Each composed of nine sets of three microtubules arranged in a ring May function in cell division and in the formation of cilia and flagella.
Figure 3.20 Centrioles may play a role in cell division.
Microtubules Made of the protein tubulin Responsible for the structure and movement of cilia and flagella Cilia are numerous short extensions in a cell that move back and forth (on cells lining the respiratory tract) Flagella are larger than cilia and move in an undulating manner (In humans, found only on sperm cells)
Figure 3.21 Microtubules are responsible for the movement of cilia and flagella.
Microfilaments and Intermediate Filaments Microfilaments: Made of the protein actin Function in muscle contraction Form a band that pinches cell in two during cell division Intermediate filaments Protein composition varies from one type of cell to another Diverse group of ropelike fibers that maintain cell shape and anchor organelles
Summary of Prokaryotic and Eukaryotic Cell Structures Web Activity: Cell Structures
Cellular Respiration and Fermentation in the Generation of ATP Cell metabolism Includes all of the chemical reactions that take place in a cell Organized into metabolic pathways Each contains a series of steps Specific enzymes speed up each step of the pathway
Cellular Respiration and Fermentation in the Generation of ATP Both are catabolic pathways that generate cellular energy Complex molecules are broken down into simpler compounds Energy is released Cellular respiration requires oxygen to break down glucose into final products: Carbon dioxide Water Energy
Cellular Respiration and Fermentation in the Generation of ATP Four phases of cellular respiration Glycolysis Transition reaction Citric acid cycle Electron transport chain Phases occur continuously in the cell
Cellular Respiration Phase 1: Glycolysis Occurs in the cytoplasm Splits glucose into two pyruvate molecules Generates a net gain of 2 ATP and 2 NADH molecules Does not require oxygen
Figure 3.22 Glycolysis.
Cellular Respiration Phase 2: Transition reaction Occurs within the mitochondria CO 2 is removed from each pyruvate Forms 2 acetyl CoA molecules
Figure 3.23 The transition reaction.
Cellular Respiration Phase 3: Citric acid cycle or Krebs cycle Occurs within the mitochondria Acetyl CoA enters the citric acid cycle Releases 2 ATP, 2 FADH 2, and 6 NADH molecules Requires oxygen
Figure 3.24 The citric acid cycle.
Cellular Respiration Phase 4: Electron transport chain Occurs within the mitochondria (inner membrane) Electrons of FADH 2 and NADH are transferred from one protein to another, until they reach oxygen Releases energy that results in 32 ATP Requires oxygen
Figure 3.25 The electron transport chain.
TABLE 3.4 Review of Cellular Respiration
Figure 3.26 Summary of cellular respiration.
Fermentation Breakdown of glucose without oxygen Takes place entirely in the cytoplasm It is very inefficient (compared with cellular respiration) resulting in only 2 ATP Lactic acid fermentation takes place in the human body in muscles during strenuous exercise when the oxygen supply in the muscle cells runs low The muscle pain is caused partly by the accumulation of the waste product lactic acid The soreness disappears as lactic acid is converted back to pyruvate in the liver
Cellular Respiration and Fermentation in the Generation of ATP Web Activity: Breaking Down Glucose for Energy
You Should Now Be Able To: Compare eukaryotic with prokaryotic cells Understand cell size and microscopy Describe cell structure and function Describe the plasma membrane Know and describe all organelles Define the cytoskeleton and its structures Understand and carefully describe cellular respiration and fermentation in the generation of ATP