Biology Chapter: Proteins and Lipids Quiz

Protein Molecules

• Proteins are organic molecules composed of carbon, hydrogen, nitrogen, oxygen, and sulfur.
• Proteins are formed from amino acids linked into polypeptide chains during translation.
• Primary structure refers to the specific sequence of amino acids.
• Secondary structure involves hydrogen bonding, creating beta sheets or alpha helices.
• Tertiary structure represents the overall three-dimensional shape of the protein.
• Quaternary structure arises from the assembly of multiple polypeptide chains.
• Extreme pH or high temperature can cause proteins to denature, losing their functional conformation.

Lipids

• Lipids are biological molecules that are insoluble in water, primarily composed of fatty acids.
• Types of lipids include triglycerides (fats), waxes, steroids, and phospholipids.
• Triglycerides consist of three fatty acids linked to glycerol, well-known for energy storage.
• Fat-soluble vitamins, essential for the body, include A, D, E, and K.
• Steroids are formed from four fused hydrocarbon rings and are crucial for hormone production.
• Waxes protect plant leaves and provide structural functions for organisms, such as bees.
• Phospholipids make up cell membranes, enabling passive transport of necessary substances.

Nucleic Acids

• Nucleic acids, long-chain polymers of nucleotides, are key components of living organisms.
• Major types include DNA and RNA, with DNA consisting of purines (adenine, guanine) and pyrimidines (cytosine, thymine).
• DNA forms a double helix structure, resembling a twisted ladder.
• Nucleotides form base pairs via hydrogen bonds: Guanine-Cytosine (three bonds) and Adenine-Thymine (two bonds).
• Primary functions include storage of genetic information and guiding cell reproduction.

Abiotic Synthesis

• Abiotic synthesis creates organic molecules from non-living components.
• The Oparin-Haldane hypothesis suggests life originated from gases in the early Earth's atmosphere.
• The Miller-Urey experiment demonstrated potential pathways for organic molecule formation without cellular life.

Characteristics of Organisms

• An organism can respond to stimuli, reproduce, grow, adapt, and maintain homeostasis.
• Homeostasis involves internal balancing processes crucial for organism function.
• Three domains of life are Bacteria, Archaea (prokaryotes), and Eukarya (eukaryotes).
• Cellular organization ranges from unicellular prokaryotes to multicellular eukaryotes, with cells as the smallest unit of life.

Animal Cells

• Animal cells, eukaryotic in nature, possess a nucleus, mitochondria, and various organelles.
• The structure includes a cell membrane, cytoplasm, and organelles like ribosomes and Golgi bodies.
• Mitochondria act as powerhouses by converting food into energy through cellular respiration.
• Ribosomes synthesize proteins, found freely in the cytoplasm or attached to the endoplasmic reticulum.

Cell Membrane

• The cell membrane is a flexible barrier, primarily composed of phospholipids arranged in a bilayer.
• The membrane contains cholesterol for fluidity and proteins for transport, signaling, and adhesion.
• Carbohydrates form the glycocalyx, enhancing cell adhesion and recognition.
• The fluid mosaic model describes the membrane's dynamic structure.

Homeostasis

• Homeostasis maintains optimal internal conditions in organisms through negative feedback mechanisms.
• Mechanisms include temperature regulation, water and salt balance, and glucose levels.
• The cell membrane plays a vital role in regulating substance movement and ion concentration.

Organelles and Their Functions

• The nucleus controls cellular activities, contains genetic material, and regulates gene expression.
• The endoplasmic reticulum (ER) transports materials inside the cell; rough ER has ribosomes and synthesizes proteins.
• Mitochondria conduct cellular respiration, producing ATP for energy.
• Lysosomes digest food and waste, while Golgi bodies package proteins for transport.

Mitochondria

• Mitochondria are double-membrane organelles involved in cellular respiration and ATP production.
• The inner membrane is folded into cristae, enhancing the surface area for energy production.
• Prokaryotic cells rely solely on their environment for energy as they lack mitochondria.

Cytoskeleton

• The cytoskeleton provides structural support and facilitates intracellular transport and chromosome separation during cell division.
• Composed of protein fibers (microfilaments, intermediate filaments, microtubules) that vary in size and function.

Prokaryotes vs. Eukaryotes

• Prokaryotic cells lack a nucleus and membrane-bound organelles, are typically unicellular, and have circular DNA.
• Eukaryotic cells contain a nucleus and organelles, can be unicellular or multicellular, and possess linear DNA.

Plant Cells

• Plant cells have central vacuoles for water storage, waste elimination, and maintaining turgor pressure.
• Cell walls, made of cellulose, provide structural rigidity and flexibility.
• Turgor pressure is crucial for plant cell stability and occurs in hypotonic environments.

Chloroplasts

• Chloroplasts are organelles in plant and algae cells involved in photosynthesis.
• They contain two membranes and structures like thylakoids where light energy is converted into chemical energy.

Viral Replication Cycles

• Bacteriophages undergo lytic and lysogenic cycles for replication.
• Lytic cycle results in host cell lysis and rapid virus reproduction; lysogenic cycle integrates virus DNA into the host genome without immediate cell damage.### Phage and Lysogeny
• Phage genome that integrates into the host genome is termed a prophage.
• Bacteria harboring a prophage are known as lysogens.
• Phage genome replication occurs in tandem with host DNA replication, but it does not completely dominate host cellular machinery.

Lysogenic Cycle

• The productivity of phage genome is low during the lysogenic cycle.
• This cycle is characterized by a lack of progeny virus particles, making it a time-consuming process.
• Environmental factors like UV light, nutrient deprivation, or specific chemicals can trigger the transition from the lysogenic cycle to the lytic cycle.

Lytic Cycle Steps

• Adsorption: Phage attaches to the bacterial surface.
• Penetration: Bacterial cell entry occurs, allowing the phage to inject its genome.
• Replication and Biosynthesis: Phage genome replicates, and components for new virions are synthesized.
• Maturation: Newly formed virions assemble into complete virus particles.
• Lysis and Release: The host cell lyses, releasing new virus particles into the environment.

Additional Concepts

• An empty phage particle remaining outside the host is referred to as a ghost.
• The lysogenic cycle consists of adsorption, penetration, integration of phage genome into the bacterial chromosome as a prophage, followed by phage genome replication along with the host genome.
• Prophage presence can induce changes in the host’s phenotypes, a phenomenon known as lysogenic conversion.

Test your knowledge of biological macromolecules in this quiz focused on proteins, fats, and nucleic acids. Answer questions about the structure and functions of these essential biomolecules and understand their roles in the body. Perfect for biology students looking to reinforce their understanding of this crucial topic.