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.
What is the function of DNA polymerase?
DNA polymerase builds new DNA strands by adding complementary nucleotides to each original strand.
How many chromosomes do humans have?
Humans have 46 chromosomes (23 pairs), containing approximately 22,000 genes.
What are the two main steps of protein synthesis?
- Transcription: DNA is copied into messenger RNA (mRNA).
- Translation: mRNA is decoded into a protein.
What happens during transcription?
RNA polymerase creates a complementary mRNA strand from DNA by using A, U, C, G (U replaces T in RNA).
What are the three stages of transcription?
- Initiation: RNA polymerase binds to the promoter region and starts transcription.
- Elongation: RNA polymerase builds mRNA by adding nucleotides.
- Termination: A stop signal causes transcription to end, releasing the mRNA.
What happens to pre-mRNA before leaving the nucleus?
Introns (non-coding regions) are removed, exons (coding regions) are spliced together, and a finalized mRNA strand exits the nucleus.
What are the key players in translation?
- Ribosome: Reads mRNA to build proteins.
- mRNA: Carries the genetic instructions.
- tRNA: Delivers amino acids.
- Amino Acids: Building blocks of proteins.
What are the three stages of translation?
- Initiation: Ribosome binds to mRNA and finds the start codon (AUG).
- Elongation: tRNA delivers amino acids, and the ribosome links them into a chain.
- Termination: A stop codon is reached, and the ribosome releases the new protein.
What is a codon?
A codon is a sequence of three mRNA nucleotides that codes for a specific amino acid.
Why is transcription and translation essential for cells?
These processes allow cells to create proteins, which determine cell structure and function, ensuring proper cellular activity.
What are the two major phases of the cell cycle?
- Interphase – The cell grows and prepares for division.
- Mitotic (M) Phase – The cell divides into two identical daughter cells.
What are the stages of interphase and their functions?
- G1 Phase – Cell grows and performs normal functions.
- S Phase – DNA replication occurs.
- G2 Phase – Cell prepares for division.
- G0 Phase – Resting phase for non-dividing cells.
What are the four stages of mitosis and their key events?
‘Prepare, Meet, Apart, Two’:
P - Prophase, M - Metaphase, A - Anaphase, T - Telophase.
- Prophase – Chromosomes condense, nuclear envelope breaks down.
- Metaphase – Chromosomes align at the metaphase plate.
- Anaphase – Sister chromatids separate.
- Telophase – Two new nuclei form.
What is cytokinesis and how does it occur?
Cytokinesis is the division of the cytoplasm, forming two identical daughter cells. It occurs when a cleavage furrow forms and pinches the cell into two.
What happens when cell cycle regulation fails?
Cells divide uncontrollably, leading to cancer. This can result in benign (non-spreading) or malignant (spreading) tumors.
What is cellular differentiation?
Cellular differentiation is the process by which cells become specialized in structure and function during development.
What are the two key abilities of stem cells?
- Self-renewal – Ability to divide indefinitely.
- Differentiation – Ability to become specialized under the right conditions.
What are the five categories of stem cells based on differentiation potential?
‘Totally Powerful Mothers Only Unite’:
Totipotent, Pluripotent, Multipotent, Oligopotent, Unipotent.
- Totipotent – Can become any cell type, including a whole organism.
- Pluripotent – Can become any human tissue, but not a whole organism.
- Multipotent – Can become a limited range of cells within a specific lineage.
- Oligopotent – Can become a few closely related cell types.
- Unipotent – Can only produce more of its own type.
What are the three main types of stem cells in the body?
- Embryonic stem cells – Found in early development, highly versatile.
- Fetal stem cells – Found in a developing fetus, slightly more specialized.
- Adult stem cells – Found in tissues like bone marrow and skin, responsible for repair and regeneration.
What are examples of adult stem cells and what they differentiate into?
- Hematopoietic stem cells – Differentiate into red and white blood cells.
- Endothelial stem cells – Give rise to blood and lymph vessel linings.
- Mesenchymal stem cells – Develop into muscle, bone, and cartilage cells.
How do cells with the same DNA become different?
Through gene expression: Different transcription factors activate or repress specific genes, determining a cell’s function.
