Module 1: Cell Structure

1670

• By the 1670s Anton van Leeuwenhoek started making drawings of bacteria and spermatozoa which he called "animalicules". He also made detailed descriptions of the red blood cell. • He used a microscope that he made himself at home (his actual profession was draper) that could magnify up to 200X compared to only 50X of the previously built microscopes. His trick was to use one very good quality lens that didn't give a blurred image.

1930

• In the 1930s the electron microscope was developed. Instead of using light, it applied a beam of electrons to view the specimens at around 100,000x magnification. • There are two kinds of electron microscopes in use today, the Scanning Electron Microscope (SEM) which gives an image of the surface of a specimen, and the Transmission Electron Microscope (TEM) which sends electrons through the specimen.

1732 and 1831

• In the USA, the first compound microscope appeared at Harvard College in 1732 - although simple microscopes would have been used before this. • By 1831 there were about a dozen microscopes in the US. Instructors were using them by 1850 and some students by 1875. • They were in general use in 1890. IDENTIFY BONANNUS 1691

The first microscope

• Most microscopes consist of either a single lens (simple microscope) or multiple lenses (compound microscope) that allows us to magnify something to a size greater than we could see with the naked eye. • Not all microscopes have lenses, the electron microscope uses a beam of electrons to create a detailed image of a specimen. • It is difficult to trace the origins of the first lenses, but rock crystals found in northern Iraq in the 8th century B.C. may have been used as lenses. • The word 'microscope' was first coined by members of the first "Academia dei Lincei" - which was a scientific society that included Galileo. • The seventeenth century was a period of great interest in the microscope. But back then the microscope was not only engaged as a scientific tool, but also as a recreational toy used by upper-class citizens to look at things close up, such as the legs and wings of insects. Many of these citizens thought this was very interesting, but most could not imagine that a tool like this could make too many new scientific discoveries. • The first microscope was reported in use in 1590. It was invented by two Dutchmen named Hans and Janssen and had two ground lenses - this made it a compound microscope. • In 1660 Marcello Malpighi used the microscope to see capillaries. • The drawing below shows an early microscope used by Robert Hooke. The eye views from point A. The 3 lens system remains the standard configuration in microscopes today, except that each lens may be made out of a combination of close lenses.

Activity 3 Calculating specimen size using magnification of an image

1. Measure the length of the specimen in mm 2. convert the length of the specimen to um 3. divide the length of the specimen by the magnificaiton (will be um)

Activity 2 Calculating the size of a specimen using it's scale bar

1. measure thhe length of the specimen 2. measure length of scale bar in mm 3. calculate how many scale bar lengths make the specimen (divide length of specimen by length of scale bar 4. calculate the size. multiply the scale bar label by the last answer

Activity 1 Calculating magnification of an image using it's scale bar

1. use a ruler to measure the length of the scale bar in mm 1. convert into the same units as the scale bar (um) 3. divide image scale bar length by the actual object scale bar length

Mobility of Prokaryotes

A-Monotrichous; B- Polar; C-Lophotrichous; D-Peritichous Many types of bacteria have the ability to move. Movement in microorganisms allows them to locate food and to remove themselves from toxic micro-environments and less than desirable temperature conditions. Bacteria expend a large amount of energy during this process. Bacteria use appendages called flagella to move. Flagella are composed of protein subunits called flagellin. Flagella can be located at one or both ends of a bacteria (polar flagellation) or spaced over the entire surface of the cell (peritrichous flagellation). The appendages are not straight, but helical shaped (like a wave). The flagella for each species of bacteria have a constant wavelength (the distance between each wave in the flagella). Unlike the human hair, a flagellum grows from the tip, not the base. Flagellin protein is made in the cell and transported through a hollow centre to the tip of the flagellum. Therefore, if a tip is broke off, a new one is regenerated. The flagella are stiff structures and move only at the base, like a propeller. The average speed of a bacteria is 50 micrometers per second. If the bacteria were the size of a cheetah, it would move at about 30 miles an hour.

Explain why it is useful for the pancreas cells that secrete digestive

Explain why it is useful for the pancreas cells that secrete digestive enzymes to have lots of rough endoplasmic reticulum and Golgi apparatus. It is useful because that way the cell is able to secrete the protein and therefore be able to break it down.

Channel Protein Carrier Protein Receptor Protein Cell regulation proteins Enzymatic protein The 5 components of the cell

Channel Protein Allows charged and polar particles through the membrane Carrier Protein Forces charged and polar particles through the membrane (uses ATP) Receptor Protein Signalling molecules (hormones) bind to it, and trigger a cell response (cell-cell communication) Cell regulation proteins Acts as an ID tag so other cells can recognize it (glycoprotein) Enzymatic protein Act as a catalyst in chemical reactions but are fixed in place in the membrane The 5 components of the cell Cholesterol, glycoprotein, glycolipid, protein and phospholipids

Electron Microscopes

Electron Microscopes allowed Scientists to identify new and different structures within cells. This enabled them to classify cells into three basic types. All Cells = Prokaryotes (no nucleus) and Eukaryotes (nucleus) • As with the bacteria, the electron microscope can pick up much greater detail. • Here we can even see some of the organelles inside the cell. • Let's have a closer look... • Much greater detail is evident on the surface of this bacteria.

Magnification, Resolution, Advantages, Disadvantages, How image is produced Light microscope Fluorescent microscope Transmission electron microscope (TEM) Scanning Electron Microscope (SEM) Confocal laser scanning microscopy

Light microscope - 2000× 200 nm - Living samples can be used; no treatment of samples necessary; natural colour can be seen; easy to use in many different locations including a school room - Fine structures within the cell will not be visible - Beam of light passing through lenses Fluorescent microscope - 2000× 250 nm - Capable of imaging with very high contrast and visibility; highly sensitive and selective -Sensitivity is compromised by other materials; fluorescence fades with time - Same as light microscope but using higher intensity light causing the fluorescent substance to emit light Transmission electron microscope (TEM) - 1 500 000× 2 nm - Sees what is inside or beyond the surface of the sample; very high magnification; samples in use do not require metallic stain coating to produce images - Sample must be thin; only provides two dimensional images; may require interpretation of image; TEMs are large and very expensive; operation and analysis requires special training - Beam of electrons are transmitted (pass through) the specimen; interactions between the electrons and the object are recorded on a photographic plate Scanning Electron Microscope (SEM) - 1 500 000× 10 nm - Focuses on the sample's surface and its composition; provides threedimensional images; accurate representation of sample; very high magnification; analysis is quick - Samples are viewed in a vacuum; samples in use are required to have their surface stained with metals; only shows sample bit by bit; SEMs are expensive, large and must be housed in an area free of any possible electric, magnetic or vibration interference; special training is required to operate as well as prepare samples - Bombards solid specimens with a beam of electrons, which causes secondary electrons to be emitted from the surface layers of the specimen. Confocal laser scanning microscopy - 0.5-1.5 µm slices - 200 nm - Slices from different depths can be used; elimination of background interference - Limited number of excitation wavelengths available with common lasers; harmful nature of highintensity laser irradiation to living cells and tissues; high cost of purchasing and operating - An image of the sample is taken at many different levels using laser beams; a computer program is then used to reconstruct a 3D image

Microfilaments and microtubules are ....

Microfilaments and microtubules are key components of the cytoskeleton in eukaryotic cells. A cytoskeleton provides structure to the cell and connects to every part of the cell membrane and every organelle. Microtubules and microfilaments together allow the cell to hold its shape, and move itself and its organelles. Microtubules are composed of globular proteins called tubulin. Tubulin molecules are bead like structures. They form heterodimers of alpha and beta tubulin. A protofilament is a linear row of tubulin dimers. 12-17 protofilaments associate laterally to form a regular helical lattice. Individual subunits of microfilaments are known as globular actin (G-actin). G-actin subunits assemble into long filamentous polymers called F-actin. Two parallel F-actin strands must rotate 166 degrees to layer correctly on top of each other to form the double helix structure of microfilaments. Microfilaments measure approximately 7 nm in diameter with a loop of the helix repeating every 37 nm. The electron transport chain and chemiosmosis takes place on this membrane as part of cellular respiration to create ATP and can be seen in the diagram: The cristae increase the surface area of the inner membrane, allowing for faster production of ATP because there are more places to perform the process. Your fat cells have many mitochondria because they store a lot of energy. Muscle cells have many mitochondria, which allows them to respond quickly to the need for doing work. Mitochondria occupy 15 to 20 percent of mammalian liver cells according to Karp.

No scale bar =

No scale bar = measured length/magnification

Summary of transport

Passive Transport Selective permeability: integral membrane proteins allow the cell to be selective about what passes through the membrane. Channel proteins have a polar interior allowing polar molecules to pass through. Carrier proteins bind to a specific molecule to facilitate its passage. Channel proteins include: -ion channels allow the passage of ions (charged atoms or molecules) which are associated with water -gated channels are opened or closed in response to a stimulus -the stimulus may be chemical or electrical Carrier proteins bind to the molecule that they transport across the membrane. Facilitated diffusion is movement of a molecule from high to low concentration with the help of a carrier protein. -is specific -is passive -saturates when all carriers are occupied In an aqueous solution -water is the solvent -dissolved substances are the solutes Osmosis is the movement of water from an area of high to low concentration of water -movement of water toward an area of high solute concentration When 2 solutions have different osmotic concentrations -the hypertonic solution has a higher solute concentration -the hypotonic solution has a lower solute concentration Osmosis moves water through aquaporins toward the hypertonic solution. Organisms can maintain osmotic balance in different ways. 1. Some cells use extrusion in which water is ejected through contractile vacuoles. 2. Isosmotic regulation involves keeping cells isotonic with their environment. 3. Plant cells use turgor pressure to push the cell membrane against the cell wall and keep the cell rigid. Active transport -requires energy - ATP is used directly or indirectly to fuel active transport -moves substances from low to high concentration -requires the use of carrier proteins Carrier proteins used in active transport include: -uniporters - move one molecule at a time -symporters - move two molecules in the same direction -antiporters - move two molecules in opposite directions Sodium-potassium (Na+-K+) pump -an active transport mechanism -uses an antiporter to move 3 Na+ out of the cell and 2 K+ into the cell -ATP energy is used to change the conformation of the carrier protein -the affinity of the carrier protein for either Na+ or K+ changes so the ions can be carried across the membrane Coupled transport -uses the energy released when a molecule moves by diffusion to supply energy to active transport of a different molecule -a symporter is used -glucose-Na+ symporter captures the energy from Na+ diffusion to move glucose against a concentration gradient Bulk transport of substances is accomplished by 1. endocytosis - movement of substances into the cell 2. exocytosis - movement of materials out of the cell Endocytosis occurs when the plasma membrane envelops food particles and liquids. 1. phagocytosis - the cell takes in particulate matter 2. pinocytosis - the cell takes in only fluid 3. receptor-mediated endocytosis - specific molecules are taken in after they bind to a receptor Exocytosis occurs when material is discharged from the cell. -vesicles in the cytoplasm fuse with the cell membrane and release their contents to the exterior of the cell -used in plants to export cell wall material -used in animals to secrete hormones, neurotransmitters, digestive enzymes

plant vs animal cells

Plant cells: - Rigid cell wall - Large vacuole - Chloroplasts - Flagella only in gametes - Plasids (site of manufacture and storage of important chemical compounds) Animal: - No cell wall (irregular cell-like shape) - Small or no vacuole - No chloplast - Flagella Smiliar: - Mitochondria - Nucleus - Cytoplasm - Ribosomes - Eukaryotic - Cell membrane - Cytoskeleton (structure that helps cells maintain shape and internal organtisation

Prokaryotes and Eukaryotes

Prokaryotes Eukaryotes Size of cell = Small cell size (0.2 - 2 µm.) / Larger cell size(10 -200 µm.) Nucleus = No nuclear membrane or nucleoli / True nucleus consisting of nuclear membrane and nucleoli Membrane enclosed organelles = Absent / Present Cell wall = Usually present, chemically complex. Rigid cell walls / When present, chemically simple. Flexible cell walls Chromosomes(DNA)= Single circular chromosome / Multiple linear chromosomes, enclosed in nucleus Cell division = Binary fission (cell splitting) / Mitosis

Robert Hooke

Robert Hooke was an English microscopist who made this microscope in 1665. The magnifying power was from about 10x to 40x. Can you pick the light source, condenser and eyepiece? • In 1665 Hooke published his book of drawings - 'Micrographia' - where he showed micrographs of cork with small pockets of air. • This reminded him of cells in a monastery and so the name "cell" was first used. Hooke didn't understand though that these hollow spaces of air were once living.

Lens

The lens of this simple microscope sat between two metal plates • Magnification: the number of times larger an image is than the actual specimen. By adding stronger lenses a microscope can magnify an image many thousands of time, but resolution may be limited. • Resolution: the degree of detail which can be achieved. An electron microscope has greater resolution than a light microscope.

Role of the Thylakoid in Photosynthesis. There are several chloroplasts in the plant cell because Plastids are Organelles, called plastids, are the Ribosomes are found Secretory vesicles are

There are several chloroplasts in the plant cell because plants require a lot of energy. Just one chloroplast would not be able to handle this demand on its own. A chloroplast is an organelle not found in animals cells that can carry out the process of photosynthesis. Role of the Thylakoid in Photosynthesis. Reactions performed in the thylakoid include water photolysis, the electron transport chain, and ATP synthesis. Photosynthetic pigments (e.g., chlorophyll) are embedded into the thylakoid membrane, making it the site of the light-dependent reactions in photosynthesis. Thylakoid membranes contain integral membrane proteins which play an important role in light harvesting and the light-dependent reactions of photosynthesis. There are four major protein complexes in the thylakoid membrane: Photosystems I and II. Cytochrome b6f complex. A thylakoid is a membrane-bound compartment inside chloroplasts and cyanobacteria. They are the site of the light-dependent reactions of photosynthesis. ... Grana are connected by intergranal or stroma thylakoids, which join granum stacks together as a single functional compartment. Plastids are major organelles found in the cells of plants and algae. Plastids are the site of manufacture and storage of important chemical compounds used by the cell. Plastids often contain pigments used in photosynthesis, and the types of pigments present can change or determine the cell's colour. Organelles, called plastids, are the main sites of photosynthesis in eukaryotic cells. Chloroplasts, as well as any other pigment containing cytoplasmic organelles that enables the harvesting and conversion of light and carbon dioxide into food and energy, are plastids. Ribosomes are found in many places around a eukaryotic cell. You might find them floating in the cytosol. Those floating ribosomes make proteins that will be used inside of the cell. Other ribosomes are found on the endoplasmic reticulum. Secretory vesicles are tiny little packages in which certain cell secretions can be transported. The vesicles are membrane bound and produced by the golgi apparatus or endoplasmic reticulum. ... The release of the substances inside of the secretory vesicle can be stimulated by a neural or hormonal signal.

- examining a variety of prokaryotic and eukaryotic cells (ACSBL032, ACSBL048)

We can group all living things into two main groups based on the presence or absence of membrane bound organelles. Prokaryotes -> No membrane bound organelles (e.g. DNA is found throughout the cell instead of being held within a nucleus) Eukaryotes-> Have membrane bound organelles REFER TO TABLES Prokaryotic cells = exist as single cells and have no membrane-bound nucleus or organelles Eukaryotic cells = have a membrane-bound nucleus and mebrane-bound organelles Organelles = Plasmids (DNA) = genetic material that forms a large loop Pili (pilus a structure used y bacteria to exchange genetic material) = hair-like structures on the surface of a cell Flagella (flagellum) = a whip-like tail that provides a cell with locomotion Capsule = the outer layer of a bacterial cell, composed of complex carbohydrates Archaea = one of the two domains of prokaryotes, often living in extreme environments (similar to bacteria) Eukaryotic: - Complex and large cells - Membrane bound e.g. mitochondira - Multiple linear (Extending) chromosomes - Multicellular and unicellular - Cell division by mitosis or meiosis - Everything that is not bacteria - Cytoskeleton Prokaryotic: - Relatively simple, small - Obsent of membrane-bound organelles no membrane bound nucleus - Unicellular single circular chromosome found in cytoplasma region nucleoid - Cell divisioni by bdding or fission (no mitosis) - All bacteria - Live in a wide variety of envionments (abundant) Similarities: - Have ribosomes - Dna - Have cytoplasm - Have some flagella - Cell membrane

What is nucleoli made of ... Nuclear pore complexes allow ... Cytosol is the ... The cytoskeleton of a cell is made up of ...

What is nucleoli made of = The nucleolus is a distinct structure in the nucleus of the cell composed of filamentous and granular material. It is the site of synthesis and processing of ribosomal RNA and the assembly of this RNA with ribosomal proteins into ribosomal subunits. Nuclear pore complexes allow the transport of molecules across the nuclear envelope. This transport includes RNA and ribosomal proteins moving from nucleus to the cytoplasm and proteins (such as DNA polymerase and lamins), carbohydrates, signaling molecules and lipids moving into the nucleus Cytosol is the liquid found inside of cells. It is the water-based solution in which organelles, proteins, and other cell structures float. These processes include protein synthesis known as translation, the first stage of cellular respiration known as glycolysis and cell division known as mitosis and meiosis. The cytosol allows intracellular transport of molecules across the cell and between cellular organelles. The cytoskeleton of a cell is made up of microtubules, actin filaments, and intermediate filaments. These structures give the cell its shape and help organize the cell's parts. In addition, they provide a basis for movement and cell division.

Cell Theory

While the Cell Theory has been altered and revised, most biologists today list three or four general characteristics shared by all cells: 1. The cell is the basic unit of life. Anything smaller than a cell is not alive by definition. 2. All organisms are composed of one or more cells. 3. Cells arise from pre-existing cells. 4. All cells, at some point in their life cycle, contain the genetic material for the entire organism.

Slide preparation

Why methylene blue was used wgeb oreparing the wet mount of the onion cell = in order to make the DNA and other microscopic properities more visible and distinguishable under the microscope Bacterial cells = not organised, no clear nucleus or organelles Limitations of a light microscope = low resolution image is blurred, preparation of slides may distort the living organisms Differences in prokaryotic and eukaryotic = complex and size, multicellular and unicellular Describe how the prepared slides used compared to the pre-prepared = provided more active cell with details Summary of what was found with differences to the cells = when examined under light microscopes it shows certain structural properities that are similar. However, the size of prokaryotic cells are smaller and prove to have a more simplistic framework.

The Phase contrast microscope

• The Phase contrast microscope looks like a light microscope but works on the principle of creating a type of shadow of the specimen. • This sort of microscope has limited use for looking at specimens in great detail, but can be used in tissue culture where the general growth of cells is monitored. • The beauty is that slides do not need to be prepared and specimens can be viewed actually in the dished they are growing in.

The most common microscope in use today

• The most common microscope in use today is the light microscope. • This is similar to the one we use in our laboratory at school. • With the advent of the light microscope, scientists were able to study cells with the kind of detail never known before. • Before we discuss cells in any detail, first we must consider a cell and the cell theory • The cell theory states that: • All living things are made up of one or more cells or of products of cells • The cell is the simplest unit of life • All cells are produced from existing cell • Here are 3 light micrographs of onion skin (epidermis) at different magnifications • You can just about make out the nucleus in the middle of the cell • There is a rigid cell wall, which helps to identify it as a plant • You could also label the cytoplasm