Brooker Biology Chapter 4: General Features Of Cells

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Cell theory/Cell doctrine

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1. All living things are composed of one or more cells
2. Cells are the smallest units of living organisms
3. New cells come only from pre-existing cells by cell division
Credited to Schleiden and Schwann

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Cell biology

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The study of individual cells and their interactions with each other.

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Microscope

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A magnification tool that enables researchers to study the structure and function of cells.

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Who invented the first compound microscope, and what is a compound microscope?

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A compound microscope is a microscope with more than one lens, and the first one was invented in 1595 by Zacharias Jansen.

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What did Robert Hooke do?

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Studied cork under a microscope and coined the word cell for the small structures he saw.

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What did Anton van Leeuwenhoek do?

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Refined lens techniques and saw single-celled microorganisms such as bacteria.

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What are the three important parameters in microscopy?

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Magnification, resolution, and contrast

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What is magnification?

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The ratio between the size of an image produced by the microscope and its actual size; if the image size is 100 times larger than its actual size, then the magnification is designated 100x.

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What is resolution?

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A measure of the clarity of an image, the ability to observe two adjacent objects as distinct from one another.

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What is contrast?

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How different a particular cell structure looks from an adjacent structure; affects the ability to visualize the structure. Contrast can be improved by methods such as staining.

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Light microscope

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Utilizes light for illumination; can resolve structures that are 0.2 micrometers apart or greater.

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Electron microscope

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Uses an electron beam for illumination; resolution is much better than a light microscope because the wavelength of an electron beam is much shorter than visible light. Limit is typically around 2 nanometers, 100 times better than the light microscope.

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Resolution is improved when the illumination source has a ____ wavelength.

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Shorter.

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Transmission electron microscopy

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A biological sample has its molecules fixed in place, and then embedded in a resin block which is then sliced into very thin sections. The sample is stained with heavy metal to provide contrast, and the metal binds to certain cellular structures such as membranes. The stained sample sections are placed in a transmission electron microscope. The microscope sends a beam of electrons that strikes the sample, and some of them hit the heavy metal and scatter, while those that pass through without being scattered are focused to form an image on a photographic plate or screen.
TEM has the best resolution of any microscope, but are expensive.

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Scanning electron microscopy (SEM)

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Uses an electron beam to produce an image of the 3-D surface of a biological sample by coating it with a thin layer of heavy metal and then exposing it to an electron beam that scans the surface of the spectrum.

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Prokaryotes

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Prokaryotic cells lack a membrane-bound nucleus. Are divided into two categories: bacteria and archaea.

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Bacteria

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Prokaryotic microorganisms, found throughout the world, most not harmful to humans but some are pathogenic (cause disease). Have a plasma membrane, cell wall, cytoplasm, nucleoid, and ribosomes.

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Archaea

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Less common than bacteria and often occupy extreme environments such as hot springs and deep-sea vents.

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Cytoplasm

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Region of the cell that is contained within the plasma membrane

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Plasma membrane

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A double layer of phospholipids and embedded proteins, forms an important barrier between the cell and its external environment.

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Prokaryotes

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Prokaryotic cells lack a membrane-bound nucleus. Are divided into two categories: bacteria and archaea.

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Bacteria

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Prokaryotic microorganisms, found throughout the world, most not harmful to humans but some are pathogenic (cause disease). Have a plasma membrane, cell wall, cytoplasm, nucleoid, and ribosomes.

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Archaea

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Less common than bacteria and often occupy extreme environments such as hot springs and deep-sea vents.

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Cytoplasm

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Region of the cell that is contained within the plasma membrane

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Plasma membrane

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A double layer of phospholipids and embedded proteins, forms an important barrier between the cell and its external environment.

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Prokaryotes

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Prokaryotic cells lack a membrane-bound nucleus. Are divided into two categories: bacteria and archaea.

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Bacteria

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Prokaryotic microorganisms, found throughout the world, most not harmful to humans but some are pathogenic (cause disease). Have a plasma membrane, cell wall, cytoplasm, nucleoid, and ribosomes.

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Archaea

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Less common than bacteria and often occupy extreme environments such as hot springs and deep-sea vents.

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Cytoplasm

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Region of the cell that is contained within the plasma membrane

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Plasma membrane

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A double layer of phospholipids and embedded proteins, forms an important barrier between the cell and its external environment.

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Nucleiod

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Structure in bacteria cells where its genetic material in the form of DNA is located.

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Ribosomes

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Polypeptide synthesis, located in the cytoplasm.

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Cell wall (bacterial)

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Relatively rigid structure that supports and protects the plasma membrane and cytoplasm. Is porous.

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Glycocalyx

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A viscous covering that surrounds the bacterium that traps water and helps protect bacteria from drying out.

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Capsule

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A very thick gelatinous glycocalyx secreted by certain strands of bacteria that invade animals bodies. May help the bacteria to not be destroyed by the animal's immune system.

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Pili

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Appendages that allow prokaryotes to attach to surfaces and to each other.

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Flagella

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Provide a way for prokaryotes to swim

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What is the function of protein FtsZ in bacteria?

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Cell division, found at the site where a cell divides into two cells.

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What is the function of the protein MreB in bacteria?

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Cell polarity, forms a spiral structure in the cell necessary for the polarity of the cell.

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What is the function of the protein CreS in bacteria?

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Cell shape.

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What eukaryotic protein is evolutionarily related to the prokaryotic protein FtsZ?

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Tubulin

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What eukaryotic protein is evolutionarily related to the prokaryotic protein MreB?

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Actin

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What eukaryotic protein is evolutionarily related to the prokaryotic protein CreS?

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Intermediate filament proteins

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Eukaryotes

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Means true nucleus, everything besides prokaryotes; includes protists, fungi, plants, and animals. DNA is housed in a nucleus, and eukaryotic cells exhibit compartmentalization.

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Nucleus

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Distinct compartment in eukaryotic cells that houses the DNA.

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Compartmentalization

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There are many organelles that separate the cell into different regions, allowing a cell to carry out specialized chemical reactions in different places.

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Proteome

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All of the types and relative amounts of proteins that are made in a particular cell at a particular time and under specific conditions.

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What determines the structure and function of a cell?

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The proteome of that cell

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Proteome

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All of the types and relative amounts of proteins that are made in a particular cell at a particular time and under specific conditions.

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What determines the structure and function of a cell?

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The proteome of that cell

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True or false: The proteomes of cancer cells are different from those of healthy cells.

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True.

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Cytosol (eukaryotic)

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The region of the eukarytotic cell that is outside the cell organelles but inside the plasma membrane.

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The cytosol typically occupies about ____ % of the total cell volume in eukaryotic cells.

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50%

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Where does the synthesis of cellular proteins occur?

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In the cytosol.

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Metabolism

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The sum of the chemical reactions by which cells produce the materials and energy that are necessary to sustain life. Mostly occurs in the cytosol.

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Metabolic pathway

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Series of steps of metabolism, sped up by enzymes.

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Catabolism

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The metabolic pathways involving breakdown of a molecule into smaller components, needed to capture energy for use by the cell, and also to generate molecules that provide the building blocks to construct cellular macromolecules.

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Anabolism

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The synthesis of cellular molecules and macromolecules.

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Polypeptide

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Composed of a linear sequence of amino acids, describes a unit of structure, vs protein, which describes a unit of function. One or more polypeptides assemble into a protein.

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Protein

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A 3D molecule composed of one or more polypeptides, performs a particular function.

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Translation

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The synthesis of polypeptides. Called translation because the information within a gene is ultimately translated into the sequence of amino acids in a polypeptide.

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On which organelle does polypeptide synthesis occur?

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Ribosome

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Describe the process of translation

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-Messenger RNA is produced from a gene and provides the information to make a polypeptide.
-Transfer RNA molecules, which carry amino acids, bind to the mRNA so that a polypeptide can be made, one amino acid at a time.
-The ribosole facilitates the binding between the mRNA and tRNA molecules, and catalyzes the formation of covalent bonds between adjacent amino acids.
-Once the polypeptide is made, it is released from the ribosome.

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Cytoskeleton

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A network of three different types of protein filaments; provides cell organization, shape, and movement.

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Which three filaments make up a cytoskeleton?

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Microtubules, intermediate filaments, and actin filaments.

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Microtubules

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Long, hollow, cylindrical structures about 25 nm in diameter, composed of protein tubulin. A microtubule has a positive end and a negative end. Growth of microtubules occurs at the plus end, while shortening can occur at either the plus or minus end.

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Dynamic instability

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The ability of a single microtubule to oscillate between growing and shortening phases. Is important in many cellular activities including the sorting of chromosomes during cell division.

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Centrosome

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Also called the microtubule-organizing center. Contains centrioles. Found in animal cells that are preparing to divide.

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Centrioles

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Conspicuous pair of structures arranged perpendicular to each other.

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Where does microtubule growth start in animal cells?

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At the centrosome, such that the minus end is anchored there.

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What is the function of microtubules?

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Cell shape and organization, sorting of chromosomes during mitosis, and organization of cells during cell division. Cell motility (cilia and flagella)

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Intermediate filaments

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-Cytosolic filament found in the cells of many but not all animal species. -In size, between actin filaments and myosin filaments.
-Tend to be more stable than microtubules and actin filaments.
-Bind to each other in a staggered array to form a twisted, ropelike structure with a diameter of about 10 nm.
-Several types of related proteins can assemble into intermediate filaments (keratins, desmins, lamins)
-Can be found inside the cell nucleus, nuclear lamins form a network of intermediate filaments that line the inner nuclear membrane and provide anchorage points for the nuclear pores.

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Actin filaments

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-Aka microfilaments, they are the thinnest cytoskeletal filaments
-Long thin fibers about 7 nm in diameter.
-Each strand composed of two strands of actin monomers that spiral around each other.
-Actin filaments have plus and minus ends, very dynamic

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Where do actin filaments tend to be highly concentrated?

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Near the plasma membrane, but are also dispersed throughout the cytosol. Support the plasma membrane and provide strength and shape to the cell.

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Which end of the actin filament does the filament grow at?

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Positive end.

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Which end of the actin filament is usually attached to the plasma membrane?

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Negative end

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Motor proteins

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A category of cellular proteins that use ATP as a source of energy to promote movement.

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What are the three domains of a motor protein?

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The head, the hinge, and the tail.

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Motor protein movement

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-Head is initially attached to a cytosolic filament, while the tail region is attached to other proteins or cellular molecules.
-ATP binds to head and is hydrolyzed to ADP and inorganic phosphate
-ATP binding and hydrolysis cases a bend in the hinge, which results in movement.
-Head is released from cytoskeletal filament
-Head cocks forward and binds to filament
-Head cocks backward (moves the tail up along the filament, "walking")

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What are the three different kinds of movements facilitated by the actions of motor proteins used by cells?

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1. Motor proteins walk along a filament carrying a cargo
2. Motor proteins are fixed in place and cause a filament to move.
3. The motor proteins and filaments are not free to move so the actions of the motor proteins cause a bend.