BIO 111 Lab Practical 2 Study Guide

Effect of Temperature on Enzyme Catalase

Enzyme Function and Experimental Design

Enzymes are biological catalysts that speed up chemical reactions by lowering the activation energy. The catalase enzyme experiment investigates how temperature affects enzyme activity using yeast and hydrogen peroxide.

• Key Terms: Catalyst (substance that increases reaction rate), enzyme (biological catalyst), denatured (loss of enzyme structure and function), substrate (reactant acted on by enzyme), product (result of reaction), active site (region on enzyme where substrate binds), dependent variable (measured outcome), independent variable (manipulated factor).

• Substrate: Hydrogen peroxide (H2O2)

• Enzyme: Catalase (from yeast)

• Products: Water (H2O) and oxygen gas (O2)

• Experimental Steps: Paper disks are dipped in yeast solution and placed in hydrogen peroxide. The production of oxygen gas causes the disks to float to the surface.

• Control Tubes: Tubes without enzyme or with denatured enzyme serve as controls to compare enzyme activity.

• Data Interpretation: Enzyme activity is highest at optimal temperature and decreases at temperatures that denature the enzyme.

• Variables: Independent variable: Temperature; Dependent variable: Rate of disk rising (enzyme activity).

• Graph Type: Line graph is best for showing enzyme activity across temperature ranges.

Example: At high temperatures, catalase may denature, causing fewer disks to float, indicating reduced enzyme activity.

Photosynthesis and Plant Pigments

Photosynthesis Process and Pigment Analysis

Photosynthesis is the process by which plants convert light energy into chemical energy, producing glucose and oxygen. Experiments with leaf disks and chromatography explore photosynthetic activity and pigment properties.

• Chemical Equation for Photosynthesis:

$6CO_2 + 6H_2O \xrightarrow{light} C_6H_{12}O_6 + 6O_2$

• Leaf Disk Experiment: Leaf disks in solutions with varying CO2 concentrations and light conditions are observed for floating (oxygen production).

• Light vs. Dark: In light, photosynthesis produces O2, causing disks to float. In darkness, no O2 is produced, so disks do not float.

• CO2 Concentration: Higher CO2 increases photosynthesis, resulting in more floating disks.

• Variables: Independent variable: Light or CO2 concentration; Dependent variable: Number of floating disks.

• Chromatography: Used to separate plant pigments based on polarity.

• Rf Value: $Rf = \frac{\text{Distance moved by pigment}}{\text{Distance moved by solvent}}$

• Solvents: Water is polar; organic solvents (e.g., acetone) are non-polar.

• Pigment Movement: Influenced by polarity of pigment and solvent; non-polar pigments move further in non-polar solvents.

Example: Chlorophyll b (more polar) moves less than carotene (less polar) in a non-polar solvent.

Mitosis

Cell Cycle and Division

Mitosis is the process by which a eukaryotic cell divides to produce two genetically identical daughter cells. It is part of the cell cycle, which includes interphase and mitotic phases.

• Cell Cycle Stages (in order): Interphase (G1, S, G2), Mitosis (M), Cytokinesis

• Mitosis Stages (in order): Prophase, Metaphase, Anaphase, Telophase

• Interphase: Cell grows, DNA replicates, organelles duplicate.

• Prophase: Chromosomes condense, spindle forms, nuclear envelope breaks down.

• Metaphase: Chromosomes align at cell equator.

• Anaphase: Sister chromatids separate and move to opposite poles.

• Telophase: Nuclear envelopes reform, chromosomes decondense.

• Cytokinesis: Division of cytoplasm, forming two cells.

• Identification: Plant cells in mitosis can be identified by chromosome arrangement and cell structure.

• Comparison with Meiosis:

Feature	Mitosis	Meiosis
Number of divisions	1	2
Number of daughter cells	2	4
Genetic identity	Identical	Unique
Function	Growth, repair	Gamete production

Example: Onion root tip cells are commonly used to observe mitosis stages.

Genetics

Patterns of Inheritance and Punnett Squares

Genetics explores how traits are inherited through genes. Different dominance relationships and inheritance patterns can be analyzed using Punnett squares.

• Key Terms: Genotype (genetic makeup), phenotype (observable traits), recessive (masked allele), homozygous (same alleles), heterozygous (different alleles), complete dominance (one allele masks another), co-dominance (both alleles expressed), incomplete dominance (blended phenotype), sex-linked traits (genes on sex chromosomes).

• Examples:

  • Complete dominance: AA or Aa = dominant phenotype, aa = recessive

  • Co-dominance: AB blood type (both A and B expressed)

  • Incomplete dominance: Red x White flowers = Pink offspring

• Punnett Squares: Used to predict offspring genotypes and phenotypes for autosomal and sex-linked traits.

Example: A cross between a carrier female (XAXa) and a normal male (XAY) for a sex-linked trait.

DNA Extraction and Gel Electrophoresis

Restriction Enzymes and DNA Analysis

DNA extraction and gel electrophoresis are techniques used to analyze genetic material. Restriction enzymes cut DNA at specific sequences, and gel electrophoresis separates DNA fragments by size.

• Restriction Enzymes: Proteins that recognize and cut specific DNA sequences (restriction sites).

• Fragment Number: The number of DNA fragments equals the number of cut sites plus one.

• Restriction Map: Diagram showing locations of restriction sites on DNA; used to predict fragment sizes.

• Gel Electrophoresis: DNA fragments are loaded into a gel and separated by size using an electric field.

• Migration Direction: DNA moves toward the positive electrode (anode) because DNA is negatively charged.

• Fragment Size: Smaller fragments move further; larger fragments remain closer to the wells.

• Lane Analysis: Lanes with more bands have more fragments; the largest fragment is closest to the well, the smallest is furthest.

Example: A plasmid cut at two sites by a restriction enzyme yields three DNA fragments.

Hypothesis Testing and Graphing

Scientific Method and Data Representation

Formulating hypotheses and representing data graphically are essential skills in scientific inquiry. Proper graph construction ensures clear communication of experimental results.

• Hypothesis: A testable statement predicting the outcome of an experiment.

• Prediction: A specific, testable outcome derived from the hypothesis.

• Graph Types: Line graphs for continuous data, bar graphs for categorical data.

• Graph Components:

  • Dependent variable: Plotted on the y-axis

  • Independent variable: Plotted on the x-axis

  • Axis labels: Include units where appropriate

  • Equal intervals: Use consistent spacing for units

  • Title: Clearly describes the experiment

  • Graph size: Large enough for clarity; avoid extraneous units or data beyond the experiment

Example: A graph showing enzyme activity (y-axis) versus temperature (x-axis) with a descriptive title and labeled axes.