Biology Midterm Review

Safety and Nature of Science

1. Julie cuts her finger with a scalpel in the lab. She should first

clean the wound and apply pressure to stop the bleeding. Then, seek medical attention if necessary.

2. When working with chemicals, students should first read an MSDS. What information is included on MSDS sheets?

MSDS (Material Safety Data Sheets) provide important safety information such as chemical properties, hazards, handling instructions, first aid measures, and emergency contact numbers.

3. Explain three things you should do to be safe when heating a liquid in a test tube:

• Wear goggles and gloves for protection.

• Use a test tube holder to avoid direct contact with the hot test tube.

• Heat the test tube gently and point it away from yourself and others to avoid splashing.

Experimental Design

4. Variables that are the same for all groups in an experiment are called

constants.

5. In an experiment, a group that receives no treatment is called a(n)

control group.

6. In an experiment, the factor that is changed or manipulated is called the

independent variable.

7. In an experiment, the factor that is measured is called the

dependent variable.

Analyzing Experimental Design

Experiment with Daphnia:

• Dependent variable: Heart rate of Daphnia (measured as beats per minute).

• Independent variable: The substance tested (e.g., coffee, ethanol).

• Experimental groups: Daphnia in coffee, Daphnia in ethanol.

• Control group: Daphnia in water (no test substance added).

• Improvement in design: To improve, ensure a consistent environment (temperature, amount of water) across all trials and increase the number of Daphnia used for more reliable data.

Biochemistry - Molecules of Life

1. What element must all organic compounds contain?

Carbon.

2. Fill in the chart for organic compounds:

Organic Compound Examples Monomer/Subunit Important Facts & Functions Testing

Carbohydrates glucose, starch monosaccharides Provide energy; store energy Benedict’s (simple sugars), iodine (starch)

Lipids oils, butter, steroids glycerol + fatty acids Long-term energy storage, insulation Brown bag test (translucent spot)

Proteins fish, chicken, nuts amino acids Build and repair tissue, enzymes Biuret test (violet)

Nucleic acids DNA, RNA nucleotides Store and transmit genetic information Not typically tested

3. What are the 3 components of a DNA nucleotide?

• Phosphate group, deoxyribose sugar, nitrogen base.

RNA nucleotide has ribose sugar instead of deoxyribose.

4. Shape determines a molecule’s

function, or how it interacts with other molecules.

Cell Types and Structures

• 2 Structures found in animal cells but not plant cells:

• Lysosomes and centrioles.

• 3 C’s in plant cells not found in animal cells:

• Cell wall, chloroplasts, and central vacuole.

Cellular Transport

1. Label the diagrams as isotonic, hypertonic, or hypotonic:

• Hypotonic: Water moves into the cell.

• Hypertonic: Water moves out of the cell.

• Isotonic: Water moves in and out equally.

2. Mass Change and Water Movement:

• Hypotonic: Cell gains mass (water enters).

• Hypertonic: Cell loses mass (water exits).

• Isotonic: No mass change, water moves in and out equally.

3. Comparing Processes:

• Osmosis vs. Diffusion: Both involve movement of molecules from high to low concentration, but osmosis specifically involves water molecules across a semi-permeable membrane.

• Active vs. Passive Transport: Active requires ATP, moves against concentration gradient; passive does not, moves down

Biology Overview: Safety, Experimentation, Biochemistry, Cell Biology, and Genetics

Biology is a complex and multifaceted field of science that explores the living world at different levels of organization, from the molecular to the ecosystem level. The study of biology encompasses diverse topics such as cellular structures, biochemistry, genetics, and scientific methodology. Understanding these areas requires both theoretical knowledge and practical application, which is why scientific experimentation and safety protocols are crucial. In this essay, we will explore important biological concepts related to safety in the lab, experimental design, molecules of life, cell structures and processes, and genetics.

Safety and the Nature of Science

Safety is paramount in scientific investigations, especially when conducting experiments in a laboratory setting. Whether working with hazardous chemicals or biological specimens, students and researchers must follow specific safety protocols. For example, if a student cuts their finger with a scalpel, the first step should be to clean the wound and apply pressure to stop the bleeding. In a chemical experiment, reading the Material Safety Data Sheet (MSDS) is essential before handling any substance, as it contains vital information about the chemical’s properties, potential hazards, and emergency procedures. In addition to personal safety, students must also adhere to specific guidelines when performing tasks such as heating liquids in test tubes. Simple practices such as wearing safety goggles and gloves, using a test tube holder, and heating the test tube gently and away from others ensure that the experiment proceeds safely.

Experimental Design

The nature of scientific inquiry requires well-structured experiments to answer research questions. In any experiment, certain elements must be controlled to ensure that the results are valid. For instance, when testing the effect of various substances on the heart rate of Daphnia (a small aquatic organism), variables such as the amount of water, type of container, and species of Daphnia must remain constant across experimental groups. The independent variable—such as the substance being tested—can be manipulated, while the dependent variable—heart rate in this case—must be measured accurately. The importance of a control group cannot be overstated; a group with no treatment (such as Daphnia in water only) provides a baseline to compare the effects of the experimental substances. Moreover, improving experimental design by increasing sample size and standardizing environmental factors like temperature and pH ensures more reliable results.

Molecules of Life: Biochemistry

At the molecular level, life is sustained by various classes of organic compounds, each playing a specific role in cellular function. Organic compounds are primarily made up of carbon, and the four major types—carbohydrates, lipids, proteins, and nucleic acids—each have unique structures and functions. Carbohydrates, such as glucose and starch, are vital for energy production and storage, with glucose being a primary source of energy in cellular respiration. Proteins, composed of amino acids, are essential for building and repairing tissues, as well as acting as enzymes that catalyze biochemical reactions. Nucleic acids, such as DNA and RNA, store and transmit genetic information, while lipids like fats provide long-term energy storage and contribute to cell membrane structure. The shape and structure of these molecules are critical to their functions, and any alteration can disrupt normal cellular processes.

Enzymes, which are proteins that facilitate chemical reactions, are also highly dependent on their specific shape. If the shape of an enzyme is altered—due to changes in temperature, pH, or chemical environment—its activity can be impaired, a process known as enzyme denaturation. This concept is critical in understanding metabolic pathways, where the proper functioning of enzymes ensures the smooth operation of cellular processes like digestion and energy production.

Cell Structure and Transport

The cell is the fundamental unit of life, and its structure is intricately designed to support its various functions. Eukaryotic cells, which make up organisms such as animals and plants, have a defined nucleus where genetic material is housed. Plant cells also contain chloroplasts, where photosynthesis occurs, and a large central vacuole, which maintains turgor pressure and stores nutrients. In contrast, prokaryotic cells, such as bacteria, lack a nucleus and other membrane-bound organelles, yet they perform all the essential functions of life.

Cellular processes such as transport are crucial for maintaining homeostasis. Cells must regulate the movement of substances into and out of the cell, a function achieved through the cell membrane. There are two main types of transport: passive and active. Passive transport, including diffusion and osmosis, moves substances from areas of high concentration to low concentration without requiring energy. Active transport, on the other hand, moves substances against their concentration gradient and requires ATP. Both processes are vital for nutrient intake, waste removal, and maintaining ion balance within the cell.

Moreover, processes such as exocytosis and endocytosis allow cells to move larger molecules or particles across their membranes. Exocytosis involves the vesicle-mediated secretion of substances from the cell, while endocytosis allows the cell to engulf and internalize substances, both essential for maintaining cellular function.

Genetics and Protein Synthesis

Genetics is another central field in biology, explaining how traits are inherited through genes. DNA, or deoxyribonucleic acid, is the molecule that carries genetic information, and its sequence determines an organism’s characteristics. Genes, located on chromosomes, are segments of DNA that code for proteins. These proteins ultimately determine the physical and functional traits of an organism. RNA (ribonucleic acid) is crucial in the process of protein synthesis. Through transcription, DNA is used as a template to make messenger RNA (mRNA), which then undergoes translation to form proteins at the ribosomes.

Mutations, or changes in the DNA sequence, can alter the production of proteins and lead to genetic disorders. For instance, a mutation in the hemoglobin gene causes sickle cell anemia, leading to a change in the structure of red blood cells. Genetic disorders can be inherited in different patterns, including autosomal recessive, autosomal dominant, or sex-linked patterns, as seen in conditions like colorblindness.

Conclusion

In conclusion, biology offers a comprehensive understanding of life, from the molecular machinery within cells to the inheritance of traits across generations. The study of cell structure, molecular biology, genetics, and the principles of scientific experimentation all contribute to our knowledge of how living organisms function, grow, and evolve. By adhering to safety protocols, conducting rigorous experiments, and understanding the biochemical and genetic foundations of life, scientists are able to explore the complexities of life and develop solutions to problems ranging from health to environmental sustainability. Whether through lab work, field studies, or theoretical models, biology continues to deepen our understanding of the natural world.