Electron Microscopy Basics Quiz
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Questions and Answers

The maximum useful magnification of an electron microscope is about ______.

1,500,000

The basic types of electron microscopes are Transmission Electron Microscope (TEM) and ______.

Scanning Electron Microscope (SEM)

TEMs use ______ to focus a beam of electrons.

electromagnets

Scanning electron microscopes create images by scanning a beam of electrons over the ______.

<p>specimen</p> Signup and view all the answers

The densest parts of the specimen in TEMs appear ______ because they absorb more electrons.

<p>darker</p> Signup and view all the answers

SEM images often give a ______ resolution image compared to TEMs.

<p>lower</p> Signup and view all the answers

For light microscopy, specimens are typically prepared by ______ and/or staining.

<p>fixation</p> Signup and view all the answers

To prepare a temporary mount of a specimen on a slide, one should add a drop of ______ first.

<p>water</p> Signup and view all the answers

Optical microscopes use ______ to form the image.

<p>light</p> Signup and view all the answers

Electron microscopes have a higher ______ than optical microscopes.

<p>resolution</p> Signup and view all the answers

The maximum resolution of optical microscopes is about ______ micrometres (μm).

<p>0.2</p> Signup and view all the answers

You can see the ______ in optical microscopy but details of smaller organelles may not be clear.

<p>nucleus</p> Signup and view all the answers

Electron microscopes can achieve a maximum resolution of about ______ micrometres (μm).

<p>0.0002</p> Signup and view all the answers

Ribosomes and the endoplasmic reticulum cannot be viewed using optical microscopes because they are smaller than ______ micrometres (μm).

<p>0.2</p> Signup and view all the answers

The ______ is crucial for maintaining cell shape and facilitating movement within the cell.

<p>cytoskeleton</p> Signup and view all the answers

When preparing slides for use in light microscopy, the use of ______ can enhance the visibility of certain structures.

<p>staining</p> Signup and view all the answers

The three main monosaccharides are glucose, fructose, and ______.

<p>galactose</p> Signup and view all the answers

Disaccharides are formed by joining two monosaccharides with a ______ bond.

<p>glycosidic</p> Signup and view all the answers

Maltose is formed from two molecules of ______.

<p>glucose</p> Signup and view all the answers

The bond between carbon 1 of one glucose molecule and carbon 4 of another is called a ______ glycosidic bond.

<p>1-4</p> Signup and view all the answers

Cellulose is a polymer made up of long chains of ______ glucose.

<p>beta</p> Signup and view all the answers

The chains of cellulose are linked by ______ bonds to provide structural support.

<p>hydrogen</p> Signup and view all the answers

Plants store excess glucose as ______.

<p>starch</p> Signup and view all the answers

Cellulose provides tensile strength and prevents plant cells from ______ under high pressure.

<p>bursting</p> Signup and view all the answers

Starch is a mixture of two polysaccharides of alpha-glucose - amylose and ______.

<p>amylopectin</p> Signup and view all the answers

Amylose is a long, unbranched chain of ______.

<p>α-glucose</p> Signup and view all the answers

The angle of the glycosidic bonds gives amylose a coiled, ______-like structure.

<p>cylinder</p> Signup and view all the answers

Glycogen is the main energy storage material in ______.

<p>animals</p> Signup and view all the answers

This polymer consists of repeating ______ sub-units.

<p>glucose</p> Signup and view all the answers

Glycogen has a similar structure to amylopectin but has a lot more ______.

<p>side branches</p> Signup and view all the answers

Lipids are a mixed group of hydrophobic compounds composed of ______, hydrogen and oxygen.

<p>carbon</p> Signup and view all the answers

The stored glucose in animals is typically found in the ______ and some muscles.

<p>liver</p> Signup and view all the answers

If the test is positive, it will form a coloured ______ (solid particles suspended in the solution).

<p>precipitate</p> Signup and view all the answers

The higher the concentration of reducing sugar, the further the change of ______ goes.

<p>colour</p> Signup and view all the answers

To test for a non-reducing sugar, you first need to break them down into ______.

<p>monosaccharides</p> Signup and view all the answers

You can neutralise it with sodium ______.

<p>hydrogencarbonate</p> Signup and view all the answers

If the test is negative, the solution stays ______ and it means the solution does not contain any sugar.

<p>blue</p> Signup and view all the answers

Whenever you want to experiment on the digestion of ______ and need to know if there is any left, you need the iodine test.

<p>starch</p> Signup and view all the answers

If there is starch present, the sample changes from ______ to a dark blue-black colour.

<p>brown-orange</p> Signup and view all the answers

Iodine is dissolved in potassium ______ solution to create the iodine test.

<p>iodide</p> Signup and view all the answers

Non-competitive inhibitors can bind to a region away from the ______ site.

<p>active</p> Signup and view all the answers

High temperatures can cause ______ due to breaking of bonds holding the tertiary structure together.

<p>denaturation</p> Signup and view all the answers

As enzyme concentration increases, the rate of reaction also ______.

<p>increases</p> Signup and view all the answers

Deviations from the optimum ______ cause a decrease in enzyme activity.

<p>pH</p> Signup and view all the answers

Enzyme activity can be prevented by enzyme ______.

<p>inhibitors</p> Signup and view all the answers

At higher substrate concentrations, enzyme molecules become ______ with substrate.

<p>saturated</p> Signup and view all the answers

The breaking of hydrogen and ionic bonds can lead to enzyme ______.

<p>denaturation</p> Signup and view all the answers

Competitive inhibitors bind to the ______ site or other similar molecules.

<p>active</p> Signup and view all the answers

Flashcards

Microscopy (light)

A technique using visible light and lenses to view small objects, including cells and cell parts.

Microscopy (electron)

A technique that uses beams of electrons to view very small structures with more detail than a light microscope.

Resolution

The ability of a microscope to distinguish two closely spaced points as separate.

Magnification

The increase in the apparent size of an object.

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Eukaryotic cell

A type of cell that contains a nucleus and other membrane-bound organelles.

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Prokaryotic cell

A type of cell that lacks a nucleus and membrane-bound organelles. Bacteria are prokaryotic.

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Cellular organelles

Specialized structures within a cell that perform specific functions.

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Magnification formula

A mathematical formula used to calculate the total magnification of a specimen using a microscope.

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Monosaccharide

A simple sugar, the basic building block of carbohydrates.

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Disaccharide

Two monosaccharides joined together by a glycosidic bond.

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Glycosidic bond

A chemical bond that joins two monosaccharides together.

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Polysaccharide

A long chain of monosaccharides linked by glycosidic bonds.

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Cellulose

A polysaccharide made of beta-glucose molecules, forming strong fibers for plant cell walls.

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Starch

A polysaccharide used by plants to store glucose energy.

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1-4 glycosidic bond

A glycosidic bond formed between carbon 1 of one monosaccharide and carbon 4 of another.

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Glucose

A common monosaccharide.

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Amylose structure

A long, unbranched chain of alpha-glucose molecules, forming a coiled, cylinder-like structure.

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Amylopectin structure

A long, branched chain of alpha-glucose molecules, with side branches that allow for easy access to glycosidic bonds.

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Glycogen function

The primary energy storage material in animals, stored mainly in the liver and muscles.

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Glycogen structure

Similar to amylopectin, but with even more side branches, enabling rapid glucose release.

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Starch's insolubility

Starch is insoluble in water, preventing water from entering cells by osmosis, ideal for storage.

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Starch function

A primary energy storage material in plants.

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Lipids

A class of hydrophobic compounds made of carbon, hydrogen, and oxygen.

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Maximum useful magnification of optical microscope

About 1500 times.

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Maximum useful magnification of electron microscope

About 1,500,000 times.

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Transmission Electron Microscope (TEM)

A type of electron microscope that transmits electrons through a specimen to create an image.

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Scanning Electron Microscope (SEM)

A type of electron microscope that scans a beam of electrons over a specimen's surface to create an image.

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TEM image resolution

High resolution, allowing for detailed internal structure observation.

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SEM image resolution

Lower resolution than TEMs.

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Specimen preparation for light microscopy

Specimens are often fixed and/or stained for brightfield microscopy.

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Preparing a temporary mount

A method for viewing a specimen under a microscope. First, a drop of water is placed on a slide, and then the specimen is added. A stain is then added and covered by a cover slip.

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Benedict's Test for Reducing Sugars

A chemical test used to detect reducing sugars in a solution. The test produces a colored precipitate whose intensity corresponds to the concentration of reducing sugars.

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Reducing Sugar

A type of sugar that can donate electrons to other substances (an oxidant), leading to a color change detected by Benedict's test.

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Benedict's test positive result

A positive Benedict's test result shows a precipitate forms. The color of precipitate indicates concentration.

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Non-reducing sugar

A type of sugar that cannot donate electrons in the way reducing sugars do.

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Testing for Non-reducing sugars

First hydrolyze the non-reducing sugar converting them into reducing sugars, then run the Benedict's test to detect the reducing sugars.

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Iodine Test for Starch

A simple chemical test used to detect the presence of starch.

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Iodine Test Positive Result

When starch is present, the solution turns dark blue-black from brown-orange when iodine solution is added.

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Hydrolysis

A chemical process that breaks down a non-reducing sugar molecule into simpler reducing sugars.

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Non-competitive inhibitor

A molecule that binds to an enzyme at a site other than the active site, changing the enzyme's shape and reducing its activity.

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Competitive inhibitor

A molecule that binds to the active site of an enzyme, preventing substrate binding.

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Enzyme activity

The rate at which an enzyme catalyzes a reaction.

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Enzyme inhibitor

A molecule that reduces or stops an enzyme's activity.

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Enzyme concentration

The amount of enzyme present in a reaction.

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Substrate concentration

The amount of substrate present in a reaction..

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Enzyme denaturation

The loss of an enzyme's 3D structure, which reduces or stops its function.

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Active site

The specific region of an enzyme that binds to the substrate.

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Study Notes

Biological Molecules

  • Key biological molecules are carbohydrates, proteins, and lipids.
  • These molecules are composed of monomers that are joined together.
  • Condensation reactions join the monomers and produce water.
  • Hydrolysis reactions break down the polymers by using water.

Water as a Solvent

  • Water is a polar molecule due to its uneven charge distribution.
  • The polarity of water allows it to dissolve many substances.
  • Water molecules form hydrogen bonds with each other, resulting in high surface tension, viscosity, heat capacity, and density.
  • These properties of water are crucial to life.

Monosaccharides

  • Monosaccharides are simple sugars, such as glucose, fructose, and galactose.
  • Glucose is the most common monosaccharide and is a major energy source.
  • All monosaccharides have an identical molecular formula (CH₂O)ₙ
  • The arrangements of atoms within a monosaccharide affects its structure and function.

Disaccharides

  • Disaccharides are formed when two monosaccharides combine through a glycosidic bond.
  • Common disaccharides include sucrose, lactose, and maltose.

Polysaccharides

  • Polysaccharides are polymers made of many monosaccharides.
  • Examples include starch, glycogen, and cellulose.
  • The structure and properties of polysaccharides affect their function within living organisms.
  • Starch is a storage polysaccharide in plants, formed of amylose and amylopectin.
  • Glycogen is a storage polysaccharide in animals.
  • Cellulose is a structural polysaccharide in plants, forming plant cell walls.

Lipids

  • Lipids are a diverse group of hydrophobic molecules.
  • They include triglycerides, phospholipids, and steroids.
  • Triglycerides are composed of glycerol and three fatty acids.
  • They are important for energy storage, insulation, and protection.
  • Phospholipids have a hydrophilic head and two hydrophobic tails, and are essential components of cell membranes.
  • Steroids, such as cholesterol, have a complex ring structure and are involved in various functions, like structural support, and hormone production.

Proteins

  • Proteins are polymers made of amino acids.
  • Twenty different amino acids are commonly found in proteins.
  • The sequence of amino acids determines the protein's primary structure.
  • Interactions between amino acids cause folding, creating secondary, tertiary, and quaternary protein structures.
  • Protein structure affects their function including enzymatic activity, structural support and transportation.

Enzymes

  • Enzymes are biological catalysts that speed up biochemical reactions.
  • Enzymes have specific active sites for binding substrates.
  • Factors, including temperature, pH and substrate concentration, influence enzyme activity.
  • Enzyme activity can be inhibited by various molecules, affecting reaction rates.

Nucleotides and Nucleic Acids

  • Nucleotides are the monomers of nucleic acids (DNA and RNA).
  • Nucleotides have a pentose sugar, a nitrogenous base, and a phosphate group.
  • DNA is a double helix structure composed of two polynucleotide chains held together by hydrogen bonds between the bases.
  • DNA carries genetic information and is responsible for the synthesis of proteins.
  • RNA is typically a single-stranded structure that assists in protein synthesis.

Cell Membranes

  • Cell membranes separate the interior from the exterior of the cell.
  • The fluid mosaic model describes the cell membrane's structure composed of a phospholipid bilayer, proteins, and cholesterol.
  • Cell membranes are selectively permeable, allowing specific substances to pass through.
  • Various mechanisms including simple diffusion, osmosis, facilitated diffusion, and active transport, regulate the movement of substances across the membrane.
  • Cotransport simultaneously moves two substances across the membrane.

Cell Cycle

  • The cell cycle is a series of events that lead to cell growth and duplication.
  • Regulation of the cell cycle involves internal and external checkpoints to ensure proper division.
  • Mitosis is a process that divides a single cell into two genetically identical daughter cells, essential for growth, repair, and asexual reproduction.
  • Meiosis involves two divisions that produce four genetically different haploid cells, critical for sexual reproduction.

Specialised Cells

  • Cells in multicellular organisms can differentiate into various specialized types, each with specific functions.
  • Examples include epithelial cells, muscle cells, and nerve cells.
  • Specialised cells work together to form tissues, organs, and organ systems, maintaining and carrying out complex bodily activities.
  • Understanding specialized cell function is crucial to understanding human and other complex biological systems.
  • Plant cells display specialization too; the root hair cells absorb water and minerals whilst the guard cells control stomata opening and closing. .

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Test your knowledge on the principles of electron microscopy including the types, uses, and preparation techniques of specimens. This quiz covers key concepts related to Transmission Electron Microscopes (TEM) and Scanning Electron Microscopes (SEM). See how well you understand the differences between optical and electron microscopes.

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