Biology: Module 2

What microscope produced this image and why?

TEM

High magnification, high resolution, 2D image

What are the advantages of light microscopes?

Living organisms, cheap, easy to use

What are the disadvantages of light microscopes?

Low magnification, low resolution, requires thin specimens

Explain which microscope produced this image?

High magnification, high resolution, 3D image

Which microscope produced this image?

Laser scanning microscope

Are laser scanning microscope images B&W or coloured?

Coloured

What are advantages of laser scanning microscopes?

Depth selectivity, high resolution, high contrast

What are the disadvantages of electron microscopes?

Large, expensive, only dead specimens, training required to use

What is the approximate size of a bacterium?

1μm

What is the approximate size of a mitochondria/chloroplast?

1μm

What is the approximate size of a virus?

100 nanometres

What is the approximate size of a ribosome?

10 nanometres

What is the approximate size of a protein?

10 nanometres

What is the approximate size of a human cell?

25μm

Outline how to measure a cell with a light microscope?

• Eyepiece graticule

• Calibrate eyepiece graticule with stage micrometer

• Measure the (something) in epu

• Take repeat measurements and calculate mean

• Use calibrated epu to calculate actual distance in micrometers

What does differential staining distinguish?

Cell types, cellular components, organisms

What is the purpose of staining a slide?

•  Image clearer

• Higher contrast

• More named (e.g. mitochondria) organelles visible as they bind to the stain

• See internal structures

State key rules/improvements for scientific drawings?

• Add scale/magnification

• Do not shade

• Sharp pencil

• Add a (descriptive) title

• Correct proportions of components

State the magnification formula?

I=AM

What is the resolution (of a microscope) defined as?

Smallest distance between two points still distinguishable as two points

What is magnification?

How much bigger the image is than the original orbject

What does acetic orcein stain, and what colour?

Chromosomes dark red

What does iodine stain, and what colour?

Carbohydrates blue/black

What is the approximate magnification of a SEM vs TEM?

• SEM is lower - roughly 100,000x

• TEM is higher - roughly 50,000,000x

What is the max. magnification of a light microscope?

1500x

Is the nuclear membrane single or double?

Double

What is the function of the nucleus?

Store DNA, control the cell, provide instruction for protein synthesis

What is the function of the nucleolus?

Synthesise ribosomes

What is the function of the RER?

Fold proteins, intracellular transport, large surface area for ribosomes

What is the function of the SER?

Synthesis of cholesterol, lipids, steroid hormones and absorption of lipids from the gut

What is the function of the golgi apparatus?

Modify proteins, package proteins into secretory vesicles

What is the function of mitochondria?

Produce ATP through aerobic respiration

What is the function of chloroplasts?

Site of photosynthesis

What is the function of lysosomes?

Compartmentalising hydrolytic enzymes, engulf old organelles/foreign matter

What is the function of cilia?

Move mucus

What is the function of flagella?

Aid movement of cell

What is the function of the cell wall?

Mechanical strength for the cell

What is the function of centrioles?

Organise spindle fibres to separate chromosomes

State the organelles from top to bottom of this plant cell?

Cell wall, cell membrane, nucleus, cytoplasm, nucleolus, vacuoles, mitochondria

What is the structure near the edge of the cytoplasm with a stringy look?

Chloroplasts

How is a protein synthesised and secreted?

• Gene is transcribed to produce mRNA

• mRNA is translated by ribosomes

• Polypeptide is folded in the RER

• Protein travels in vesicles to golgi apparatus

• Golgi modifies protein and packages into secretory vesicles

• Protein released via exocytosis

What is the function of the cytoskeleton?

• Provides mechanical strength to cells

• Enabling cell movement

• Movement of organelles

• Movement of chromosomes/chromatids

What are similarities between prokaryotic and eukaryotic cells?

Both have:

• plasma membrane

• cytoplasm

• ribosomes

• DNA and RNA

What are differences of prokaryotic compared to eukaryotic cells?

• Circular DNA, not chromosomal

• Smaller size

• No nucleus

• No membrane bound organelles

• Smaller 70s ribosomes

What evidence supports the endosymbiosis theory?

Mitochondria…

• Are similar shape/length to bacterium

• Contains 70s ribosomes

• Has circular DNA

• May have plasmids

• Has double membrane

How doba

What are the roles of water?

Solvent, transport medium, coolant, habitat

What are properties of water related to its function?

Polar, hydrogen bonding, high surface tension, adhesion and cohesion, high specific heat capacity, high latent heat of vaporisation

What two groups react in a condensation reaction?

OH

What chemical elements are present in carbohydrates?

C, H and O

What chemical elements are present in lipids?

C, H and O

What chemical elements are present in proteins?

C, H, O, N and S

What chemical elements are present in nucleic acids?

C, H, O, N and P

State the difference between alpha and beta glucose?

Hydroxyl on carbon 1 in alpha glucose is below and beta glucose is above

What are the properties of glucose?

Soluble in water, reducing sugar

What is the structure of ribose?

What is the structure of alpha glucose?

What is the structure of beta glucose?

What type of monosaccharide is ribose?

Pentose

What type of monosaccharide is glucose?

Hexose

What is sucrose made from?

Alpha glucose and fructose

What is lactose made from?

Alpha glucose and galactose

What is maltose made from?

2 alpha glucose

State the bond in sucrose, maltose and lactose?

1-4 glycosidic

Describe the structure of starch?

• Monomers of alpha glucose

• 10-30% amylose - coiled

• 70-90% amylopectin - branched

  • 1-4 and 1-6 glycosidic bonds

Describe the properties and related function of starch?

• Insoluble - doesn’t affect WP of cell

• Coiled/branched - takes up less space in cell

• Longer to hydrolyse - plants don’t require energy immediately

• Many terminal glucose in amylopectin - hydrolysis/addition

Describe the structure of glycogen?

• Monomers of alpha glucose

• 1-4 and 1-6 glycosidic bonds

• 1-6 produces branching

Describe the properties and related function of glycogen?

• Alpha glucose - respired to release energy

• Glycosidic bonds - easily hydrolysed to release glucose

• Branches - rapid release of glucose monomers

• Insoluble - doesn’t affect WP of cell

Describe the structure of cellulose?

• Monomers of beta glucose

• Alternate monomers flipped 180°

• Forms hydrogen bonds between long chains

Describe the properties and related function of cellulose?

• Hydrogen bonds - increase mechanical strength to support plant

• High tensile strength - withstand turgor pressure

• Freely permeable - molecules enter/exit cell

• Beta glucose - few organisms have cellulase to hydrolyse cellulose

Draw the structure of a triglyceride?

What is a triglyceride made from?

Glycerol and 3 fatty acids

Draw the structure of a phosphlipid?

What is a phospholipid made from?

Phosphate, glycerol, 2 fatty acids

What is the structure of unsaturated phosphlipids?

C=C bond, cis acid causes bending of chain - increases membrane fluidity

State the bond in a triglyceride?

Ester

Explain how the properties of a triglyceride is related to its function?

• Insulation - myelin sheath/adipose tissue

• Oxidising C-H - releases metabolic water for desert animals

• Energy - lots of C-H bonds so contain lots of energy

• Buoyancy - low density

• Protection - cushion organs from damage

Explain how the properties of a phospholipid is related to its function?

• Higher proportion of unsaturated fatty acids - more fluid of membrane

• Polar and non-polar region - form phospholipid bilayer

• Lipid core of bilayer - only lipid soluble molecules can diffuse through

Explain how the properties of cholesterol is related to its function?

• Hydrophilic and phobic regions - exist in bilayer

• Disrupts packing of phospholipids - increase rigidity of membrane

• Acts as barrier - prevents water soluble substances passing through bilayer

Draw an amino acid?

What type of reaction is forming a di/polypeptide?

Condensation

What bonds are formed in primary protein structure?

Peptide bonds

What bonds are formed in secondary protein structure?

Hydrogen

What structures can be formed in secondary protein structure?

B-plated sheet or A-helix

What bonds are formed in tertiary protein structure?

Disulfide bridges, ionic bonds, hydrophilic/phobic interactions

What is only present in quaternary protein structure?

Multiple subunits (polypeptides), prosthetic groups

Describe the structure of haemoglobin?

• 2 alpha and 2 beta subunits

• 4 prosthetic haem groups - bind to oxygen

• Hydrophobic R groups inward and hydrophilic outwards

• Globular protein

• Variable amino acid sequence

Describe the structure of insulin?

• 2 polypeptide chains

  • A has 21 amino acid

  • B has 30 amino acids 

• 3 disulfide bridges

• Hydrophilic R groups face outwards - soluble

Circle the peptide bond?

Describe the properties and functions of collagen?

• Mechanical strength

  • prevent arterial wall bursting under high pressure

  • harden bones reinforced with collagen

• Tensile strength - tendons connect muscles to bone so muscles can pull

Describe the properties and functions of keratin?

• Mechanical protection - nails, hair, claws, hooves, scalels

• Impermeable to pathogen - prevents infection

• Waterproof - prevents entry of waterborne pathogen

Describe the properties and functions of elastin?

Elastic:

• Skin stretches around bones and muscles

• Lungs to inflate and deflate

• Bladder expands and contain urine

  • Arteries can stretch and recoil

What is the structure and function of pepsin?

• Globular protein - complementary active site to substrate

• Mostly acidic R groups - stable in acidic environment of stomach

• Hydrogen bonds and disulfide bridges - maintain 3D shape

Describe the test for protein?

• Add biuret reagent slowly and shake

• Positive - violet colour

Describe the test for reducing sugar?

• Add benedict’s reagent and heat

• ++ brick red, + yellow, - green

Describe the test for non-reducing sugar?

• Add dilute HCl and boil

• Cool and neutralise

• Add benedict’s reagent

• ++ brick red, + yellow, - green

Describe the test for starch?

• Add iodine

• + turns blue/black

Describe the test for lipids?

• Add water and ethanol and shake

• + cloudy emulsion forms

What are key points for colorimetry?

• Measures % absorbance

• Provides quantitative data, not subjective

• Calibrate colorimeter

• Use a calibration curve to estimate concentration

Outline chromatography for a protein?

• Hydrolyse protein with protease enzyme

• Place sample on pencil line on chromatography paper

• Dry and repeat

• Place in solvent

• Ensure solvent lower than pencil line

• Leave for a few hours

• Stain with ninhydrin to visualise amino acids

• Calculate R_f and compare with known R_f values