Ch. 3 Text Flashcards
What is the primary function of the cell membrane?
The cell membrane acts as a barrier, separating the cell’s internal components from the extracellular environment while regulating material exchange.
What is the structure of the cell membrane?
The cell membrane is composed of a phospholipid bilayer with hydrophilic heads facing outward and hydrophobic tails facing inward, making it selectively permeable.
What are the roles of cholesterol and fatty acids in membrane fluidity?
Cholesterol maintains membrane flexibility, while saturated and unsaturated fatty acids influence fluidity.
What are the types of membrane proteins and their functions?
- Integral proteins - Embedded within the membrane, including channels for molecule transport.
- Peripheral proteins - Sit on the membrane surface, aiding structure or enzyme function.
- Receptor proteins - Bind specific molecules to trigger cellular responses.
- Glycoproteins & Glycocalyx - Serve as cellular ID markers for immune recognition.
What does selectively permeable mean?
The cell membrane only allows certain substances to pass through, controlling material exchange.
What are the types of passive transport?
- Simple Diffusion - Movement of small, nonpolar molecules (O2, CO2) through the membrane.
- Facilitated Diffusion - Uses carrier or channel proteins to transport large or charged molecules (glucose, sodium ions).
- Osmosis - Movement of water to balance solute concentrations.
- Filtration - Uses pressure to push substances through a membrane (e.g., kidney filtration).
What are the three types of osmotic conditions and their effects on a cell?
- Isotonic - Equal solute concentration; no net water movement.
- Hypertonic - Higher solute outside; water leaves the cell, causing shrinkage.
- Hypotonic - Higher solute inside; water enters the cell, potentially causing lysis (bursting).
What is active transport, and how does it differ from passive transport?
Active transport requires energy (ATP) to move substances against their concentration gradient (low to high), unlike passive transport, which requires no energy.
What are the two types of active transport?
- Primary Active Transport - Uses ATP directly (e.g., Sodium-Potassium Pump moves Na+ out and K+ in).
- Secondary Active Transport - Uses the energy of one molecule’s gradient to transport another (e.g., Sodium-Glucose Symporter pulls glucose into the cell).
What are the types of bulk transport across the cell membrane?
- Endocytosis - The cell engulfs material in a membrane vesicle.
- Phagocytosis (‘cell eating’) - Engulfs large particles like bacteria.
- Pinocytosis (‘cell drinking’) - Engulfs fluids.
- Receptor-Mediated Endocytosis - Selectively captures molecules using receptors.
- Exocytosis - Expels materials using vesicles (e.g., hormone secretion).
What are the main components of the cytoplasm?
The cytoplasm consists of cytosol (a jelly-like fluid) and organelles (membrane-bound structures with specific functions).
What is the function of the endomembrane system?
The endomembrane system produces, modifies, packages, and transports proteins and lipids. It includes the ER, Golgi apparatus, and lysosomes.
What are the two types of Endoplasmic Reticulum (ER) and their functions?
- Rough ER: Studded with ribosomes, synthesizes and modifies proteins.
- Smooth ER: Synthesizes lipids, detoxifies substances, and stores calcium.
What is the function of the Golgi apparatus?
The Golgi apparatus sorts, modifies, and ships proteins from the rough ER and packages them into vesicles for transport within or outside the cell.
What are lysosomes and their functions?
Lysosomes contain digestive enzymes that break down cellular waste, aid in immune defense, and can trigger autolysis (cell self-destruction).
What is the primary role of mitochondria?
Mitochondria generate ATP (cellular energy) by converting nutrients into usable energy through oxygen-dependent reactions.
What are peroxisomes and their functions?
Peroxisomes detoxify harmful substances.
What are the three types of cytoskeletal filaments and their functions?
- Microtubules: Maintain shape, transport materials, assist in cell division.
- Microfilaments: Provide structural support, enable movement.
- Intermediate filaments: Provide tensile strength, anchor organelles.
What is the role of microtubules in cell movement?
Microtubules form cilia and flagella for movement and serve as tracks for organelle transport within the cell.
What is the function of the nucleus?
The nucleus is the control center of the cell, housing DNA and directing all cellular functions.
What is the nuclear envelope and its function?
The nuclear envelope is a double-layered lipid bilayer that surrounds the nucleus, with nuclear pores allowing the passage of molecules like RNA and proteins.
How is DNA organized within the nucleus?
DNA is wrapped around histone proteins, forming nucleosomes. Chromatin is loosely coiled during normal cell function but condenses into chromosomes before cell division.
What are the steps of DNA replication?
- Initiation: Helicase unwinds DNA, creating a replication fork.
- Elongation: DNA polymerase adds complementary nucleotides (A-T, C-G).
- Termination: DNA replication stops, and proofreading enzymes correct errors.
What is meant by ‘semi-conservative’ DNA replication?
Each new DNA molecule consists of one original strand and one newly synthesized complementary strand.
