2 - Foundations in Biology

What is a light microscope used for?

Observing living and dead specimens.

What are the pros of a light microscope?

Cheap, portable, easy to use, can study living specimens.

What are the cons of a light microscope?

Limited magnification, poor resolution.

What is a laser scanning confocal microscope used for?

Creating a high resolution, high contrast image, at different depths of the specimen.

What is a transmission electron microscope used for?

Observing the internal ultrastructure of cells under high magnification and resolution.

What is a scanning electron microscope used for?

Viewing the surface of objects under high magnification and resolution.

What are the pros of an electron microscope?

Very high magnification and excellent resolution.

What are the cons of an electron microscope?

Specimen has to be dead, very expensive, very large, needs great skill and training to use.

What is the difference between a transmission and a scanning electron microscope?

TEM sends a beam of electrons through the specimen; SEM bounces electrons off the surface.

What is the difference between light and electron microscopes?

Light uses lenses to focus a beam of light; electron uses a beam of electrons focused by magnets.

What is an eye piece graticule?

A small ruler fitted to a light microscope's eyepiece, must be calibrated using a stage micrometer.

What is a stage micrometer?

A millimeter long ruler etched onto a slide used to calibrate the eyepiece graticule.

Why do we stain specimens?

To provide more contrast and make it easier to distinguish certain parts.

What is differential staining?

Using a stain to distinguish between 2 different organisms or organelles due to preferential absorption.

What is the formula to calculate magnification?

Magnification = Image size / Actual size.

What is the formula to calculate actual object size?

Actual size = Image size / Magnification.

How do we work out image size?

Use a ruler to measure the image.

What is magnification?

A measure of how much larger the image of a specimen looks under the microscope.

What is resolution?

The ability to distinguish between two adjacent individual points as separate.

What are the maximum resolutions of the different microscopes?

Light: 200nm; SEM: 10nm; TEM: 0.2nm.

What is the maximum magnification of the different microscopes?

Light: 1,500X; SEM: 100,000X; TEM: 500,000X.

What are the main structures of all eukaryotic cells?

Nucleus, nucleolus, cytoplasm, cytoskeleton, plasma membrane, mitochondria, Golgi apparatus, smooth and rough endoplasmic reticulum, ribosomes.

What is the structure and function of the nucleus?

Surrounded by a double membrane, stores DNA and controls the cell by providing instructions for protein synthesis.

What is the structure and function of the nucleolus?

Made of RNA, produces ribosomes.

What is the structure and function of the nuclear envelope?

A double membrane with pores that separates the nucleus from the rest of the cell and allows transport.

What is the structure and function of the rough endoplasmic reticulum (RER)?

Studded with ribosomes, involved in protein synthesis and transport of proteins to the Golgi apparatus.

What is the structure and function of the smooth endoplasmic reticulum (SER)?

A system of membranes without ribosomes, involved in lipid synthesis and processing.

What is the structure and function of the Golgi apparatus?

A series of flattened membranous sacs that modify, package, and distribute proteins and lipids.

What is the structure and function of ribosomes?

Composed of two subunits, synthesize proteins.

What is the structure and function of mitochondria?

Double membrane-bound, site of aerobic respiration and energy production.

What is the structure and function of lysosomes?

Membrane-bound sacs containing digestive enzymes for breaking down waste.

What is the structure and function of chloroplasts?

Site of photosynthesis, containing thylakoids and pigments.

What is the structure and function of the plasma membrane?

Phospholipid bilayer that controls entry and exit of substances, maintains homeostasis.

What is the structure and function of centrioles?

Bundles of microtubules that help in cell division by organizing spindle fibers.

What is the structure and function of the cell wall?

Provides structural support and protection, made of cellulose in plants.

What is the structure and function of flagella?

Long, whip-like structures that aid in locomotion of cells.

What is the structure and function of cilia?

Short, hair-like structures that aid in movement and fluid transport over cell surfaces.

Which structures are involved in the production of proteins?

Nucleus, RER, transport vesicles, Golgi apparatus.

What is the structure and function of the cytoskeleton?

Network of fibers that provide structure, facilitate movement, and organize cellular components.

What do prokaryotic and eukaryotic cells have in common?

Plasma membrane, cytoplasm, ribosomes, DNA, and RNA.

What is different between prokaryotic and eukaryotic cells?

Prokaryotes lack a nucleus and membrane-bound organelles; they have a peptidoglycan cell wall.

How do prokaryotes divide?

Binary fission.

List the elements that make up proteins.

C, H, O, N, S.

Explain the polar nature of water.

Oxygen is more electronegative than hydrogen, leading to partial positive and negative regions.

What allows water molecules to have cohesive and adhesive properties?

Hydrogen bonds.

Describe the structure of amylose, including the bonds involved and the shape.

Straight chain of glucose units linked by 1,4-glycosidic bonds, forming a helical structure.

Describe the structure of amylopectin, including the bonds involved and the shape.

Branching structure with both 1,4 and 1,6 glycosidic bonds.

State the two structures that make up starch.

Amylose and Amylopectin.

State the reaction that breaks down maltose.

Hydrolysis.

What is the reaction to join monosaccharides together?

Condensation.

What are the 3 types of polysaccharides that α-glucose can form?

Amylose, Amylopectin, Glycogen.

What are the two monosaccharides that join up to make sucrose?

Glucose and Fructose.

1,6 glycosidic bonds are found on ........

Amylopectin or Glycogen.

β-glucose can only be found in ........

Cellulose.

How are the monosaccharides in cellulose arranged?

Alternative β-glucose molecules are turned upside down.

Based on the arrangement of cellulose molecules, explain why cell walls provide strength and support to plant cells.

Cellulose forms hydrogen bonds to create microfibrils, which provide structural integrity.

What does the Benedict's test test for?

Reducing sugars.

Explain how a positive result is formed in the Benedict's test.

Reducing sugar reacts with blue Cu2+ to produce brick-red Cu+.

How can we test for starch?

Using iodine solution.

How can we use a colorimeter to do a quantitative Benedict's test?

Measures light absorbance by the colored solution to determine sugar concentration.

What are the two parts that make up a carboxylic acid?

Carboxyl group and hydrocarbon chain.

How many water molecules are needed when breaking down a triglyceride?

Three.

What is another term for the condensation reaction that makes lipids?

Esterification.

What is the difference in structure between saturated and unsaturated lipids?

Saturated: all single C-C bonds; Unsaturated: one or more double C=C bonds.

Why do oils contain unsaturated triglycerides rather than saturated?

Unsaturated fatty acids cause a kink, preventing tight packing.

What is the difference in structure between triglyceride and phospholipid?

Triglyceride: 3 fatty acids; Phospholipid: 2 fatty acids and 1 phosphate group.

Describe the phospholipid bilayer arrangement.

Hydrophilic heads outward, hydrophobic tails inward.

Describe 2 similarities and 1 difference between phospholipids and sterols.

Similarities: both have hydrophilic/hydrophobic characteristics and are membrane components; Difference: sterols are complex alcohols, phospholipids are fats.

Describe the steps in identifying lipids and state the positive result.

Mix with ethanol, add water; a white emulsion confirms the presence of lipids.

State the monomer of a protein.

Amino acids.

What are the components that make up an amino acid?

Central carbon, H atom, amine group, carboxyl group.

Name the bond formed between two amino acids.

Peptide bond.

What is the primary structure of a protein?

Amino acid sequence.

What is the secondary structure of a protein?

Alpha-helix and beta-pleated sheets.

What is the tertiary structure of a protein?

The overall 3D shape of the protein.

What is the quaternary structure of a protein?

The arrangement of multiple polypeptide chains.

State the bond involved in the primary structure of a protein.

Peptide bond.

State the bond involved in the secondary structure of a protein.

Hydrogen bond.

State the bond involved in the tertiary structure of a protein.

Ionic, covalent, hydrogen, hydrophobic interactions, disulfide bridges.

State the bond involved in the quaternary structure of a protein.

Ionic, covalent, hydrogen, hydrophobic interactions, disulfide bridges.

Name the reaction that breaks down proteins.

Hydrolysis.

What is the solution used to test for the presence of proteins?

Biuret solution.

Describe a positive result for proteins.

Biuret solution changes from blue to purple.

What is thin layer chromatography?

A technique to separate components of a mixture, like amino acids.

Based on what principles are the amino acids separated in TLC?

Interactions with silica and solubility in the mobile phase.

Why should the chromatography plate be only handled by the edges?

To prevent contamination with proteins from hands.

What are the three types of proteins?

Globular, conjugated, fibrous.

Explain why insulin is soluble in blood.

Hydrophilic amino acids are on the protein surface.

What are prosthetic groups?

Non-protein components in a conjugated protein.

Give an example of a conjugated protein.

Hemoglobin or catalase.

Compare the haem groups in hemoglobin and catalase.

Hb binds reversibly with O2; Catalase interacts with H2O2 to speed up breakdown.

How many haem groups does a hemoglobin contain?

Four.

Explain why keratin is relatively strong, inflexible and insoluble.

Contains numerous strong disulfide bridges.

Briefly describe the structure of collagen.

Three polypeptides in a long, strong rope-like structure.

What bonds do DNA/RNA polymerase catalyse?

Phosphodiester bonds.

Name the monomer of a nucleic acid.

Nucleotide.

State the five possible bases of a nucleotide.

Adenine, guanine, thymine, cytosine, uracil.

State the three components to a DNA nucleotide.

Deoxyribose, nitrogenous base, phosphate group.

The two strands of the double helix are ............. to each other.

Antiparallel.

Thymine, cytosine and uracil belong to a group of bases. Name the group.

Pyrimidines.