The Cell Biology 105 Lecture 4 Reading: Chapter 3 (pages 47 62)
Outline I. Prokaryotic vs. Eukaryotic II. Eukaryotic A. Plasma membrane transport across B. Main features of animal cells and their functions
Cells Cells are the basic units of life. Cells are highly structured. They are enclosed in a membrane the plasma membrane. Cells vary in size, but there is a limit to how big a cell can be and survive. There are different types of cells specialized cells.
Some organisms are just one cell (example: yeast)
Multi-celled organisms have specialized cells Blood Cells Nerve Cells
Some cells are very small
Prokaryotic vs. Eukaryotic Prokaryotic Pro (before) karyotic (nucleus) Eukaryotic Eu (true) karyotic (nucleus) The presence or absence of a nucleus is the biggest difference between these types of cells.
Prokaryotic vs. Eukaryotic Prokaryotic cells = bacteria and archaea Do not have a nucleus or organelles Do have ribosomes In eukaryotic cells, the DNA is contained within the nucleus. Animal cells, plant cells, fungi, protists
Figure 3.1 Prokaryotic cells, such as bacterium, lack internal membrane-bound organelles. Plasma membrane DNA region (no nucleus) Cytoplasm Ribosome Cell wall 1 10 µm
Table 3.1 Review of Features of Prokaryotic and Eukaryotic Cells
Which are examples of prokaryotic organisms? 1. Animals 2. Plants 3. Bacteria 4. Protists 5. Fungus 20% 20% 20% 20% 20% Animals Plants Bacteria Protists Fungus
Prokaryotic cells have a nucleus. 1. True 2. False 50% 50% True False
Major Features of Eukaryotic Cells Figure 3.2 (2 of 2)
Cell Size Cells vary in size, but they can never exceed the volume that can be nourished by materials passing through the surface membrane.
Cell Size Figure 3.3
Major Features of Animal Cells Plasma membrane controls entry in/out of cell Cytoplasm semi-fluid matrix (liquid is cytosol) Cytoskeleton gives shape, structure, transport Ribosomes assembling polypeptide chains
Major Features of Animal Cells Organelles membrane-bound internal compartments in cells for specialized functions Nucleus contains the DNA Mitochondria energy production Endoplasmic reticulum Rough: modifies new polypeptide chains Smooth: synthesizes lipids Golgi body modifies, sorts, ships new proteins and lipids Vesicles storage, transport, digestion
Plasma Membrane Fluid mosaic model Molecules are free to move around Mixture of phospholipids, steroids (cholesterol), and proteins Bilayer Phospholipids arrange such that the polar heads are on the outside and the nonpolar, lipid portions are on the inside Proteins and sterols (cholesterol) are arranged on surfaces and can form channels Selectively permeable
Table 3.2 Review of Plasma Membrane Functions
Main components of the membrane 1. Phospholipid bilayer Phosphate head (hydrophilic) Fatty acid tail (hydrophobic) Function controls what passes through the membrane 2. Cholesterol: maintains fluidity of membrane
Main components of the membrane 3. Proteins: transport, support, communication, recognition 4. Glycoproteins: proteins with chains of sugars attached to them Functions attachment sites, cell recognition 5. Glycolipids: lipids with chains of sugars attached to them Functions - attachment sites, cell recognition
Plasma Membrane Carbohydrate Plasma membrane Embedded protein Extracellular fluid Cholesterol Glycoprotein Glycolipid Outer surface of plasma membrane Plasma membrane Phospholipid bilayer Inner surface of plasma membrane Cytoplasm Surface protein Filaments of cytoskeleton Figure 3.6
Hydrophilic: Water loving = lipophobic Hydrophobic: Water hating = lipophilic
Simple Diffusion Figure 3.7
Movement through the membrane Concentration gradient Molecules will go from higher concentration to lower concentration. If you add molecules to water, they will disperse (diffuse) until they are equally distributed in the water.
Movement through the membrane The plasma membrane divides the inside of the cell from the outside of the cell. It is semi-permeable: not everything can freely pass through the membrane.
What passes freely through the membrane? 1. Gases oxygen, carbon dioxide 2. Hydrophobic compounds (nonpolar) 3. Very small uncharged molecules 1. Even though water is polar, it is small enough to pass through the membrane.
What cannot pass freely through the membrane? 1. Ions 2. Hydrophillic (polar compounds) larger than water 3. Charged compounds 4. Macromolecule compounds 1. Large proteins, complex carbohydrates, triglycerides
Osmosis The cell membrane is semi-permeable: This means that some things can pass, while others can not pass through. The cell membrane is somewhat permeable to water, but not to charged ions and molecules. Water will travel across the membrane to try to restore the balance of solutes = this process is called osmosis.
How does salt concentration affect a cell? Hypertonic: concentration of solutes is higher outside than inside. Isotonic: inside and outside have the same concentration of solutes. Hypotonic: concentration of solutes is lower outside the cell than inside.
Osmosis Osmosis is the movement of water across a selectively permeable membrane from a region of higher water concentration to a region of lower water concentration. Osmosis restores the solute balance.
Transporting molecules across the membrane Passive transport does not require energy, uses the concentration gradient Simple diffusion Facilitated diffusion Active transport requires energy, goes against the concentration gradient
Simple Diffusion Figure 3.7
Passive Transport Simple Diffusion Simple diffusion: molecules that can freely pass through the membrane are controlled by their concentration gradient. Gases like oxygen and CO 2 Very small molecules that are not charged (H 2 O) Hydrophobic (nonpolar) molecules
Facilitated Diffusion Figure 3.8
Passive Transport Facilitated Diffusion Facilitated diffusion: movement of molecules is aided by a transport protein, still controlled by the concentration gradient of the molecules Hydrophilic molecules like glucose and amino acids
Active Transport Figure 3.10
Active Transport Sometimes our cells want to move a molecule across the membrane, but there is not an energetically favorable concentration gradient. The cell wants more of the solute on one side of the membrane. The cell will use energy to maintain the higher concentration. Used to transport sugars, amino acids and ions
Active Transport Often the movement occurs from a region of lower concentration to a region of higher concentration with the aid of a carrier protein and energy (usually from ATP).
Can calcium (Ca 2+ ) pass freely through the membrane? 1. Yes 2. No 50% 50% Yes No
Can glucose pass freely through the membrane? 1. Yes 2. No 50% 50% Yes No
If a transport protein is used to move glucose and the process is controlled by the concentration gradient of glucose, this is called: 1. Simple diffusion 2. Facilitated diffusion 3. Active transport 33% 33% 33% Simple diffusion Facilitated diffusion Active transport
Transport using a vesicle When the cell needs to transport larger things, it can use vesicles to transport these larger things in and out of the cell. Exocytosis: moving things out of the cell using a vesicle. Endocytosis: moving things into the cell using a vesicle. Used to transport macromolecules, including: whole cells (bacteria), cholesterol, fluids, and proteins
Endocytosis Phagocytosis when a cell transports large particles and cells (bacteria) into the cell using vesicles Pinocytosis when a cell transports fluid into the cell using vesicles
Endocytosis - Phagocytosis Figure 3.11a
Endocytosis - Pinocytosis Figure 3.11b
Exocytosis Figure 3.12
Table 3.3 Review of Mechanisms of Transport Across the Plasma Membrane
Major Features of Eukaryotic Cells Figure 3.2 (2 of 2)
Nucleus Nucleus contains DNA = instructions for building proteins Number of DNA molecules varies between species: Humans have 46 DNA molecules in each cell Frogs have 26 DNA molecules in each cell Nucleus protects DNA Separates DNA from the rest of cell Place where DNA duplicates itself
Chromosomes Human chromosomes They are visible under the light microscope during cell division when they shorten and condense. At other times, the chromosomes are extended in an uncondensed form and are called chromatin.
Nucleus Figure 3.14a
Chromatin Figure 3.14b
Parts of the Nucleus 1. Nuclear Envelope double membrane (two different bilayers) Inside layer contains sites for DNA to attach Outside surface layer has many ribosomes 2. Nucleolus dense area in the nucleus where ribosomes are produced 3. Nucleoplasm area inside the nucleus 4. Chromatin DNA and its associated proteins
Nucleus
Ribosomes Function: site of protein synthesis This is where amino acids are chained together with peptide bonds to make a polypeptide chain. Ribosomes are composed of proteins and ribosomal RNA (rrna).
Endoplasmic Reticulum There are two types of endoplasmic reticulum: Rough endoplasmic reticulum Smooth endoplasmic reticulum
Figure 3.15 The endoplasmic reticulum (ER) Endoplasmic reticulum Nucleus Rough endoplasmic reticulum (RER) has ribosomes attached to its surface and is involved in modifying proteins made by the ribosomes. Smooth endoplasmic reticulum (SER) lacks ribosomes and is involved in detoxifying certain drugs and in producing phospholipids for incorporation into membranes.
Rough Endoplasmic Reticulum Endoplasmic reticulum that has ribosomes associated with it is called rough endoplasmic reticulum. Functions: important in protein modification 1. This is where polypeptide chains (chains of amino acids) are folded into their shape by chaperones. 2. Carbohydrate tags are also added to the proteins here.
Smooth Endoplasmic Reticulum Endoplasmic reticulum that does not have ribosomes associated with it is called smooth endoplasmic reticulum. Functions: 1. Phospholipids and steroids are synthesized here. 2. Contains enzymes that detoxify alcohol and some drugs.
Transport Vesicles Membrane-bound compartments used for transporting molecules within the cell. Also can be used to transport molecules into and out of the cell.
Golgi Complex A series of flattened membranous sacs Vesicles from rough and smooth endoplasmic reticulum bring their products to the golgi to be modified and repackaged. Functions: processes, sorts, and packages proteins and lipids
Figure 3.16a The Golgi complex Golgi complex New vesicle forming (a) Diagram of the Golgi complex. This organelle serves as tsite for protein processing and packaging within the cell.
Figure 3.17 Transport of proteins from RER to Golgi to plasma membrane Proteins Rough endoplasmic reticulum Ribosome Transport vesicle Vesicles carrying proteins from the RER arrive at the receiving side of the Golgi complex and empty their contents to the inside, where the proteins are modified. Golgi complex Lysosome with proteins Secretory vesicle Vesicles containing the modified proteins leave the shipping side of the Golgi complex and travel to their specific destinations. Plasma membrane Protein expelled
Lysosomes Figure 3.18
Lysosomes Lysosomes are digestion vesicles that contain strong acids and enzymes. They can fuse with the plasma membrane to expel waste. Made by the Golgi complex Functions: Engulf molecules and digest them Fuse with other organelles to destroy them Destroy bacteria
Tay-Sachs Disease Tay-Sachs is an autosomal recessive genetic (hereditary) disease. Affected individuals do not have an enzyme normally found in lysosomes that breaks down lipids in nerve cells. Infants develop normally for the first few months, but as nerve cells become clogged with fatty material, mental and physical deterioration occurs. Progression of the disease is irreversible and there is no treatment. Affected children usually die by 4 years of age.
Mitochondria All eukaryotic cells contain mitochondria. Mitochondria are bound by a double membrane: Outer membrane faces the cytoplasm. Inner membrane is folded forms cristae that increase surface area for cellular respiration. Functions: 1. Produces energy for the cell (ATP). This process requires oxygen. 2. Important in apoptosis (programmed cell death).
Mitochondria Figure 3.19
Where are polypeptide chains/proteins produced? 1. Nucleus 2. Ribosomes 3. Golgi complex 4. Rough endoplasmic reticulum 25% 25% 25% 25% 1 2 3 4
Where are polypeptide chains/proteins folded? 1. Nucleus 2. Ribosomes 3. Golgi complex 4. Rough endoplasmic reticulum 25% 25% 25% 25% 1 2 3 4
Which organelle produces energy for the cell? 1. Nucleus 2. Ribosomes 3. Mitochondria 4. Rough endoplasmic reticulum 25% 25% 25% 25% 1 2 3 4
Cytoskeleton Interconnected system of fibers and lattices between the nucleus and the plasma membrane. Functions: Gives cells their organization and shape Ability to move and transport things in cell Aid in cell division
Cytoskeleton Wide variety of cytoskeleton: Microfilaments Microtubules (including cilia and flagella) Intermediate filaments Some are permanent (intermediate). Others self-assemble and are only present when needed (microfilaments and microtubules).
Microtubules - Functions 1. Microtubules serve as tracks along which organelles or vesicles move. 2. Aid in cell division 3. Microtubules are also responsible for the structure and movement of cilia and flagella. Cilia are numerous short extensions from a cell that move back and forth. Flagella are larger than cilia and move in an undulating manner.
Cytoskeleton Microtubules
Cytoskeleton - Microtubules serve as tracks along which organelles or vesicles move.
Cytoskeleton Microtubules of a Centriole Figure 3.21
Microtubules - Cilia Figure 3.22a
Microtubules - Flagella Figure 3.22b
Cytoskeleton - Microfilaments Made of the protein actin Functions: 1. Important for muscle contraction 2. Responsible for the movement of pseudopodia 3. Role in dividing cells during cell division
Intermediate Filaments A diverse group of ropelike fibers Functions: maintain cell shape and anchor organelles
Cilia is made of this type of cytoskeleton: 1. Intermediate filaments 2. Microtubules 3. Microfilaments 33% 33% 33% Intermediate filaments Microtubules Microfilaments
Important Concepts Read chapter 4 Why are most cells small? What are the main differences between prokaryotic cells and eukaryotic cells? Know some examples of prokaryotic cells and eukaryotic cells Major features of cells and their functions, including: Plasma membrane, cytoplasm, nucleus, cytoskeleton, mitochondria, ribosomes, endoplasmic reticulum (smooth and rough), Golgi complex, vesicles, lysosomes
Important Concepts What are lysosomes, and what disorder is associated with a missing enzyme in lysosomes? What are the functions of cytoskeleton, and what are examples of cytoskeleton? What are the functions of microtubules? Which cytoskeleton makes up cilia and flagella? Know the functions of microfilaments, and which protein makes up microfilaments Know the functions of intermediate filaments
Important Concepts Functions of the plasma membrane Know the main components of the plasma membrane and the function of each component. Be able to draw a membrane Be able to identify what can pass freely through a membrane and what cannot pass freely
Important Concepts Know how small molecules are transported into the cell Know the differences between passive diffusion, facilitated diffusion, and active transport Know which molecules each mode can transport Know how things are transported in and out of a cell using a vesicle
Definitions Prokaryotic cells, eukaryotic cells, semipermeable, osmosis, hypertonic, hypotonic, isotonic, hydrophobic compounds, nonpolar, hydrophilic compounds, polar, passive transport, active transport, simple diffusion, facilitated diffusion, exocytosis, endocytosis, phagocytosis, pinocytosis, nucleolus, nuclear envelope, nucleoplasm, chromatin, cristae, apoptosis