GENBIO Midterms PDF

**SIGNIFICANCE OF MITOSIS AND MEIOSIS** **REGULATING THE CELL CYCLE** - Cell growth and cell division in eukaryotes are controlled  - Not all cells move through the cell cycle at the same rate - Two types of regulation: positive and negative - **POSITIVE REGULATION** - Dr...

**SIGNIFICANCE OF MITOSIS AND MEIOSIS** **REGULATING THE CELL CYCLE** - Cell growth and cell division in eukaryotes are controlled  - Not all cells move through the cell cycle at the same rate - Two types of regulation: positive and negative - **POSITIVE REGULATION** - Drives *[progression]* of cell cycle (*[keeps moving forward]*) - Examples: Cyclins and cyclin-dependent kinases (Cdks) - Cyclin fluctuates, activating Cdks, which phosphorylate proteins to advance the cycle - Phosphorylate -- addition of phosphate to proteins - Cyclins were discovered through sea urchin embryo - A protein was observed to be present in high levels after fertilization but disappeared during cell division. - Reappearance and disappearance of protein = Cyclins - Cdk/cyclin complexes (Cdk + cyclin) must be fully activated for the cell cycle to proceed - Cdks and Cdk/Cyclin complex are the same - **NEGATIVE REGULATION** - *[Pauses]* cell cycle when needed - Examples: Regulatory proteins (Retinoblastoma protein (Rb), p53, p21) - p53 detects DNA damage, halts the cycle, and can trigger apoptosis if needed. - Apoptosis -- programmed cell death - Rb regulates the G1-S transition by controlling transcription factors, blocking cell cycle progression until certain conditions are met. - Transcription is part of the process of synthesizing DNA https://lh7-rt.googleusercontent.com/docsz/AD\_4nXfTBRa6EcSprpvdKV6OyFqFadE3qjLsiTTlv9NWyScS3a\_1xuLhOR-LbVJ\_zLgS\_HbNhUspSEJc8F2upfKUPG2eNfwjTRwgenKY5e-PPeSqCP87Qz1KZ08bN3WVUSMQHuD5IpdHE8FOu\_vIcbJ04CAvWZY?key=eP1gM\_5SxdjNygDKkSKp5Q **BIRTH OF REGULATORY PROTEINS** **REGULATORY PROTEIN** - Molecules that [control the progression of the cell cycle] - DNA-binding protein that controls the activation of genes based on certain conditions - They either promote or prevent gene expression through changing its shape **TWO TYPES OF REGULATORY PROTEINS** - - - - - - ***So, what happens if a cell during a cell cycle has damages?*** - Cells will be [arrested] (paused to give time for development and maturation) - Cells will be [killed] by the [immune] [system] - Cells will undergo *[apoptosis]* (cell death) **SIGNIFICANCE OF THE CELL CYCLE: MITOSIS** - Number of chromosomes is identical - Wound-healing - Maturation of organisms  - Growth - Of *offspring* - Of *cells* **SIGNIFICANCE OF THE CELL CYCLE: MEIOSIS** - Makes only [*one set* of chromosomes] - Allows diversity  - Variation in its processes **DISEASES ASSOCIATED WITH CELL CYCLE MECHANISM**  **MITOTIC DISEASES** - When mitosis is ***unregulated***, the growth or production of identical cells will also be unregulated. Thus, this would lead to the production of tumor which eventually can either be benign or malignant becoming cancer - [Cancer cells come from tumors that grow uncontrollably.] A tumor can be either *benign* (not harmful) or *malignant* (cancerous). If a tumor is tested and found to be malignant, it means it is cancer. - **MITOTIC DISEASES: Cancer** - **Proto-oncogenes** - Normal genes -- Oncogenes → Cancer - Code for positive cell-cycle regulators - Example: Cdk protein - **Tumor suppressor genes** - Normal genes → Cancer - Code for negative cell-cycle regulatory proteins  - Prevent uncontrolled division when activated - Example: mutated p53 gene **MEIOTIC DISEASES** - When *chromatids* fail to separate during anaphase I and II it leads to *imbalances* of chromosomes in each daughter cell. This process is called ***nondisjunction*** which is the cause of some **genetic disorders**. People with genetic disorders can either become incompatible with life or with a spectrum of developmental disorders. 1. **TRISOMY 21** - Common Name: Down syndrome - Cause: An extra copy of chromosome 21 - Symptoms: - Distinct facial features (flattened face, small ears, upward-slanting eyes, small mouth) - Treatment: No cure, but treatment focuses on managing symptoms 2. **CAT-CRY SYNDROME** - Common Name: Cri du Chat (French for \"cry of the cat\") - Cause: Deletion of a portion of the short arm of chromosome 5 (5p deletion) - Symptoms: - High-pitched, cat-like cry in infancy - Microcephaly (small head size) - Treatment: No specific cure 3. **MONOSOMY X** - Common Name: Turner Syndrome - Cause: Missing or incomplete X chromosome in females (monosomy X). - Symptoms: - Short stature - Delayed puberty, infertility, and ovarian failure - Webbed neck, broad chest, low-set ears - Treatment: No cure 4. **TRISOMY 18** - Common Name: Edwards Syndrome - Cause: An extra copy of chromosome 18 (trisomy 18). - Symptoms: - Low birth weight, clenched fists, overlapping fingers - Small jaw and malformed feet (rocker-bottom feet) - Treatment: No cure 5. **TRISOMY 13** - Common Name: Patau Syndrome - Cause: An extra copy of chromosome 13 (trisomy 13). - Symptoms: - Cleft lip or palate, extra fingers or toes (polydactyly) - Treatment: No cure 6. **TRISOMY X** - Common Name: Triple X Syndrome - Cause: Extra X chromosome in females (47,XXX). - Symptoms: - Increased risk of early ovarian failure and infertility - Treatment: No specific treatment required 7. **XXY SYNDROME** - Common Name: Klinefelter Syndrome - Cause: Extra X chromosome in males (47,XXY). - Symptoms: - Low testosterone, reduced facial and body hair - Infertility and small testes - Delayed puberty, breast development (gynecomastia) - Learning disabilities, especially with language and reading - Treatment: No cure 8. **XYY SYNDROME** - Common Name: Jacobs Syndrome - Cause: Extra Y chromosome in males (47,XYY). - Symptoms: - Increased risk of behavioral issues such as ADHD - Treatment: No specific treatment required **CELL MEMBRANE** https://lh7-rt.googleusercontent.com/docsz/AD\_4nXfNn5o0z8pkybERve51jbET-A4pGsresLanVmvkJglB6fcd0GlU2b4VsM4Lj3GzNqrx0gvISvAg76s2q1lLgitHwXWD-TUwEwyn7xnt7cfydPGHwuo\_7aYWlr1fLv6Q1s-0\_uOy1LKoVGHfV\_TUNgjm7w?key=eP1gM\_5SxdjNygDKkSKp5Q **STRUCTURAL COMPOSITION OF THE CELL MEMBRANE** - **PRIMARY FUNCTION:** - Regulates what goes in and out of the cell - Regulates passage of material into and out of the cell - **OTHER FUNCTIONS:** - Separates the cell from the outside world - Defines it as a distinct entity - **STRUCTURES** - **Phospholipids** - Basic fabric of the plasma membrane - Arranged in **bilayer** - **Amphipathic** -- both hydrophilic and hydrophobic - **Hydrophilic regions** - Head of the bilayer - Water-loving region which has charged phosphate group - Faces outward contacting the aqueous fluid both inside and outside the cell - **Hydrophobic regions** - Tail of the bilayer - Water-fearing region composed of long, nonpolar fatty acid tails which interact with other nonpolar molecules - It interacts poorly with water making it a good barrier between the interior and exterior of the cell - **Proteins** - Second major component of plasma membranes - Two types: Main difference between integral and peripheral membrane proteins is their [location] - **Integral** membrane proteins  - **Peripheral** membrane proteins - **Functions of Membrane Proteins ** - Intercellular joining  - Form junction between adjacent cells and serve as [anchoring points] for networks of cytoskeletal elementshttps://lh7-rt.googleusercontent.com/docsz/AD\_4nXeRwNX11vhL1fxE0raaAne\_lDcQBEbShSCnykhrP24ezkDyH-KK9ypKpNkNeMizoLx0MRQGP0IB1tt9k3wPu-PwgdVXC6YSoLByxz6dTZXvDXDbuuVAohv6xTJS0Ch2EQvBUkUd1GFJYyUBvGUBwI\_M8OA?key=eP1gM\_5SxdjNygDKkSKp5Q - Active or Passive transport - Pumps that use ATP or other energy sources to transport solutes across the membrane - Active -- *lower* concentration to *higher* - Passive -- higher concentration to lower - Anchoringhttps://lh7-rt.googleusercontent.com/docsz/AD\_4nXcw1G4EZQswpvikW5F0FcFKh24\_S-UPdIM875-8sI70TB0UVNE7CuaXAbogav7bGvZbk9hVnU6zFEpa8i8LLFg3ssvZESPPmo7XKGwoevxPNoXDAHZLriEzM0OCxcutQGDLwoQa5Z7GL4PGr0jgzA1uxGg?key=eP1gM\_5SxdjNygDKkSKp5Q - Anchor cell to its substrates  - Attach the cell to the extracellular matrix - Signal Transduction - Receptors that receive information from other cells in chemical forms or electric signals - Cell-to-Cell Recognition - Serves as identification tags that other cells recognizehttps://lh7-rt.googleusercontent.com/docsz/AD\_4nXcAZgLrfNDRKTvqzUTpA17h6NZsa08WShwEFPmjlq\_PtPZIqwlVb6bwo8KAI3wNEv6bbFDZoj8A-hAG2TGdF68F7u40z\_7eKpu-CsjJIHWJpbjea9UBjfwfdaJOVFCO445100vRsKA0d1UYfAMopiEoGOc?key=eP1gM\_5SxdjNygDKkSKp5Q - Enzymatic Activity - Catalyze reactions near the cell surface - - - - - - **RELATIONSHIP OF CELL MEMBRANE STRUCTURE TO ITS FUNCTION** 1. **Phospholipids form bilayers in water** - Phospholipids are amphipathic molecules, consisting of two hydrophobic fatty acid chains linked to two of the three carbons of a glycerol molecule. - The bilayer arrangement allows the hydrophilic heads of the phospholipids to be in contact with the aqueous medium, while their oily tails are buried in the interior of the structure. 2. **The *[Fluid-Mosaic Model]* explains Membrane Structure** - Fluidity - membrane structures can be likened to icebergs in a fluid sea since they are in constant motion or changing position - Mosaic - composed of various components from phospholipids, proteins, carbohydrates, and cholesterol. 3. **Biological Membranes are two-dimensional fluid** - Movement of structures are side-by-side. It cannot jump. https://lh7-rt.googleusercontent.com/docsz/AD\_4nXff39r9gC9zHlz2WfeBCh5De-iVBCwlcMZmxf1ggm1M-NvCC8oMoef6TYQrH4lxPj1mQcrFoV2lyZ0g1j8\_PxYjJW08eiNwNDIy6iwH7A8YrKh0VD8ybiKjsU\_ddAk1JVNZOdyn0EYyt7fdkIKABESIAw?key=eP1gM\_5SxdjNygDKkSKp5Q 4. **Biological Membranes fuse and form closed vesicles** - Bilayers tend to resist forming free ends; as a result, they are self-sealing spontaneously round up to form closed vesicles. - Lipid bilayers are also flexible, allowing cell membranes to change shape without breaking, and under appropriate conditions lipid bilayers fuse with other bilayers **CELLULAR TRANSPORT**  **PASSIVE TRANSPORT** - Movement of molecules or substances across membranes without the use of energy - Moves from a high concentration to low concentration gradient - Multidirectional - **Three types:** Diffusion, Osmosis, Facilitated diffusion - **DIFFUSION** - Movement of molecules from high to low concentration gradient - Spontaneous and does not need energy - **OSMOSIS** - Movement of water molecules from high to low concentration gradient - A process water moves from a hypotonic solution to a hypertonic solution through a selectively permeable membrane - Hypotonic and Hypertonic characteristics of cells are dangerous - Hypertonic -- cells [shrivel and die (plasmolyzed)] - Hypotonic -- cells [bulge and burst (turgid)] - To survive, cells must be in an isotonic state where equilibrium is present https://lh7-rt.googleusercontent.com/docsz/AD\_4nXfr0KEqNZASBLfhZxb-p1ahDIevvjIhTeNivKaOI9pHAB4EsU5NddtgUTCtG1HsEDJtK1oZCp-fDnTVA0MeP28SqDYfqro93vV-INbK2yRRS4NGBQcibtluW8oOuHv0WQB05o9soe6N18ANmNj5qyF1xTU?key=eP1gM\_5SxdjNygDKkSKp5Q - - - - - - - - - - - - - - - - -  **ACTIVE TRANSPORT** - Movement of molecules or substances across membranes with the use of energy - Moves against the concentration gradient from low to high concentration - Also use carrier proteins - Unidirectional - **ACTIVE TRANSPORT: HOW IT WORKS** - Carrier proteins in the cell membrane help move substances across by using energy from ATP. - The terminal phosphate group from ATP attaches to the carrier protein, changing its shape and allowing it to transport a specific molecule (or solute) across the membrane. - **ACTIVE TRANSPORT: RELEVANCE** - Nutrient Uptake - Waste Removal - Ion Balance - Type: Primary, Secondary, and Bulk transport - **PRIMARY ACTIVE TRANSPORT** - Uses energy directly from ATP to transport molecules against their concentration gradient.  - Example: Sodium-potassium pump (Na⁺/K⁺-ATPase), which moves sodium ions out of the cell and potassium ions into the cell. - **SECONDARY ACTIVE TRANSPORT** - Utilizes the energy from the electrochemical gradient created by primary active transport - **Symport** (Cotransport): Molecules move in the same direction.  - **Antiport** (Countertransport): Molecules move in opposite directions.  - **BULK TRANSPORT** - Movement of large molecules such as proteins and polysaccharides in group - Two processes: Endocytosis and Exocytosis - **BULK TRANSPORT: EXOCYTOSIS** - Process of *removing materials* from the cell through the vesicles base with the plasma membrane, subsequently releasing their contents outside the cell - **BULK TRANSPORT: ENDOCYTOSIS** - Cells engulf materials - The substance is then enclosed in a vesicle and brought into the cytoplasm. - Either phagocytosis or pinocytosis - **PHAGOCYTOSIS vs PINOCYTOSIS** - Phagocytosis (cellular-eating) occurs when undissolved materials enter the cell. - Pinocytosis (cellular-drinking) occurs when dissolved substances enter the cell.