Biology Lab Exam II (labs 10-15)

Photosynthesis

plants absorb sunlight and use it to generate glucose, starch, and eventually all other organic molecules

equation:

• 6H₂O + 6CO₂ —> 6O₂ + C₆H₁₂O₆ + H₂O

involves three stages:

1. capturing energy from sunlight

2. using captured energy to produce ATP and NADPH

3. using the ATP and NADPH to make carbohydrates from CO₂ in the atmosphere

Pigments

molecules that absorb light energy

main ones in plants are chlorophyll a and b

chlorophyll absorbs light at the ends of the visible spectrum, mainly blue and red light, but reflects green light

in photosynthesis, they are bound to proteins in the thylakoid membranes of chloroplasts

Accessory pigments

absorb light levels that chlorophyll doesn’t

give color to flowers, fruits, vegetables

carotenoids (yellow, orange): present with chlorophyll in chloroplasts (and contribute to photosynthesis)

two groups:

• carotene (yellow, orange, and red)

• xanthophylls (yellow and brown)

anthocyanins (dark red and violet): found in cell vacuole

also includes chlorophyll b

Paper chromatography

technique used to separate different components in a mixture

there is a stationary phase (paper, polar) and a mobile phase (solvent, less polar)

a mixture is applied to the paper and placed in the solvent

solvent moves up the paper carrying different components of the mixture

polarity:

• polar molecules bind to paper (stationary phase), less polar molecules dissolve in solvent (mobile phase)

• more polar components: move slower and stay closer to application site

• non-polar components: get carried with solvent up the paper, moves faster and further

• estimate polarity by counting oxygen groups in chemical structure of a compound

Electromagnetic spectrum

light is comprised of packets of energy called photons

sunlight has photons of varying energy levels—these varying levels are represented by this

human eyes only perceive photons of intermediate energy levels

• this range of the spectrum is visible light

Coleus leaves

leaves that contain multiple pigments that are visible:

• areas that are green contain chlorophyll

• areas that are pink contain anthocyanins

• areas that are dark purple contain both chlorophyll and anthocyanin pigments

• areas that are white and light yellow contain no pigments

Absorption spectrum of leaf pigments

the absorption pattern of a particular pigment across different wavelengths of light

1. cut each pigment band from chromatography paper

2. place pigment bands into 20mL beaker w/ 10mL ethanol and swirl

3. label cuvettes for each of the pigments as well as a blank

4. pour 8mL of each pigment beaker liquid into each cuvette and 8mL of ethanol to blank cuvette

5. turn on spectrophotometer, set wavelength to 400nm

6. blank the spectrophotometer

7. record the absorbance of each cuvette from 400nm to 720nm, blanking in between each wavelength, at 20nm intervals

Mitosis

part of the cell cycle

generates two genetically identical cells

carried out when an organism grows in size or when worn out cells need to be replaced

Meiosis

found in the life cycle of sexually reproducing organisms

reduces diploid chromosome numbers by half (makes them haploid)

Genome

the complete collection of all the genetic information of a cell

Chromatin

DNA can exist as this:

• made up of DNA and histone protein complex

forms that chromosomes within the nucleus of eukaryotic cells

Chromosomes

DNA can exist in the form of this:

• highly condensed chromatin, coiled to fit into small spaces

structures found in the nucleus of most cells that contain genes

determine physical traits and are made of DNA wrapped around proteins

can occur in pairs (homologs) in somatic cells, making them diploid cells (2n)

Gametes

reproductive cells (sperm and ova) with half as many chromosomes as somatic cells, making them haploid (n)

Homologous chromosomes

chromosomes that are similar in:

• size

• shape

• centromere location

• hereditary information (for the same traits and situated in the same relative chromosomal location)

they carry information on the same traits, but the information may varry

• one is inherited from the mother, one from the father