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Unit 1-Chapter 3
Cells
| Question | Answer |
|---|---|
| What unit of measurement is used in describing cell size? | measure in units called micrometers (μm) |
| What is a differentiated cell? | Cells that have developed specialized characteristics |
| Name the major parts of a cell. | The major parts of a cell are the nucleus, cytoplasm, cell membrane. |
| Name at least three cellular organelles composed of membranes. | Nucleus (nuclear envelope) mitochondria, lysosomes, vesicles, endoplasmic reticulum, cell membrane, Golgi apparatus |
| State the general functions of the cytoplasm and nucleus. | The cytoplasm consists of organelles and the fluid in which they are suspended (the cytosol). Each type of organelle performs a specific function for the cell, and the cytosol keeps the cell hydrated |
| What is a selectively permeable membrane? | A selectively permeable membrane is one that regulates which substances enter or leave the cell. |
| Describe the chemical structure of a cell membrane. | The cell membrane consists of a double layer, or bilayer, of phospholipids. |
| What are some functions of cell membrane proteins? | Some cell membrane proteins function as enzymes or receptors |
| What happens in cellular adhesion? | cellular adhesion molecule (CAM) called a selectin binds a moving white blood cell, coating it and slowing it down, so it can bind to carbohydrates on the inner surface of a capillary. |
| What are the functions of the endoplasmic reticulum? | Endoplasmic reticulum provides a transportation system for molecules in the cell, and also performs protein and lipid synthesis. |
| Describe how the Golgi apparatus functions. | Golgi apparatus modifies proteins produced on the ribosomes of the rough endoplasmic reticulum, packages them, and transports them in vesicles to other organelles or to the cell membrane for export. |
| Why are mitochondria nicknamed the “powerhouses” of cells? | Mitochondria break down food molecules in the chemical reactions of cellular metabolism to produce energy and heat. The energy is stored mainly in a molecule called ATP (adenosine triphosphate) |
| How do lysosomes and peroxisomes function? | Lysosomes contain over 40 types of enzymes that degrade specific cellular components. |
| Describe the functions of microfilaments | Microfilaments: • Tiny rods of actin; have the smallest diameter of the cytoskeletal filaments • Provide cellular movement, such as muscle contraction |
| Describe the functions of microtubules. | Microtubules: • Larger tubes of tubulin; have the largest diameter of the cytoskeletal filaments • Rigidity maintains cell shape • Make up cilia, flagella, and centrioles • Help move organelles |
| How are the nuclear contents separated from the cytoplasm? | The nuclear envelope (membrane) separates the nuclear contents from the cytoplasm |
| What is the function of the nucleolus? | The nucleolus produces ribosomes. |
| What is chromatin? | Chromatin is composed of DNA and protein in a loose array of coiled fibers. This is the form in which DNA exists when the cell is at rest. |
| List the types of substances that most readily diffuse through a cell membrane. | Lipid-soluble substances diffuse most readily through a cell membrane |
| Diffusion | passive random movement of a substance from a region of higher concentration to a region of lower concentration. |
| Facilitated diffusion | is similar to diffusion, but requires the help of a membrane protein, such as an ion channel, to help transport the substance across the cell membrane. |
| Osmosis | the movement of water molecules across a cell membrane, into a region containing a dissolved substance (solute) that cannot cross the membrane. |
| Isotonic | have the same osmotic pressure; cells in an isotonic extracellular fluid neither gain nor lose water. |
| Hypertonic | is one with a higher osmotic pressure (higher solute concentration and lower water concentration) than that of the cells or another solution; cells in a hypertonic solution lose water by osmosis and shrink. |
| Hypotonic | is one with a lower osmotic pressure (lower solute concentration and higher water concentration) than that of the cells or another solution; cells in a hypotonic solution will gain water by osmosis and swell. |
| Explain how filtration occurs in the body | During diffusion, molecules pass through a membrane due to random molecular movement. During filtration, molecules are forced to move across a membrane due to pressure. |
| How does a cell maintain unequal concentrations of ions on opposite sides of a cell membrane? | The cell uses ATP (adenosine triphosphate) energy |
| How are facilitated diffusion and active transport similar? | Facilitated diffusion and active transport both use membrane proteins to transport substances across cell membranes. |
| How are facilitated diffusion and active transport different? | Facilitated diffusion moves substances from higher to lower concentration, and does not require ATP. Active transport moves substances from lower to higher concentration, and requires ATP |
| What is the difference between pinocytosis and phagocytosis? | Pinocytosis moves liquids across the cell membrane inside a vesicle, and phagocytosis engulfs solid matter. |
| Describe receptor-mediated endocytosis. | membrane engulfs specific substances, which have bound (specific molecules) to receptor proteins on the membrane in order to transport them across the membrane into the cell. |
| What does transcytosis accomplish? | Transcytosis transports a substance across a cell, by bringing the substance into one side of the cell by endocytosis, and releasing it on the other side of the cell by exocytosis. |
| Why is precise division of the genetic material during mitosis important? | It ensures that both new daughter cells receive a complete copy of the DNA (genetic material), so they can grow into normal, functional cells. |
| Mitosis consists of 4 stages. | Prophase/Metaphase/Anaphase/Telophase |
| Prophase | chromatin changes in chromosomes, the nuclear envelope disassembles, the centriole pairs migrate to opposite sides of the cell, and microtubules begin organizing into spindle fibers. |
| Metaphase | the spindle fibers stretch between the centriole pairs, and the chromosomes attach to them and line up along the midline of the cell. |
| Anaphase | the chromosome pairs split; one chromatid from each pair migrates along the spindle fibers to opposite sides of the cell. |
| Telophase | the chromatids, now called chromosomes, reach the vicinity of the centrioles, and change back to their chromatin form. The spindle fibers disassemble, and a nuclear envelope forms around each newly forming nucleus. |
| How do cells vary in their rates of division? | Skin cells and intestinal cells divide very rapidly cells that become neurons only divide a few times, and then they stop dividing. Most cells divide 40 – 60 times, and then stop. |
| Which factors control the number of times and the rate at which cells divide? | The DNA at the ends of the chromosomes, called telomeres, shortens in many cells every time the cell divides |
| How can too infrequent or too frequent cell division affect health? | Too infrequent cell division in an embryo, fetus, or child causes a lack of growth and slow wound healing. Too frequent cell division can cause an abnormal growth, such as a tumor. |
| What is the difference between a benign and a malignant tumor? | A malignant tumor invades and metastasizes (invades other organs); a benign tumor enlarges but stays in place. |
| What are two ways that genes cause cancer? | • Oncogenes: Abnormal forms of genes that control cell cycle, but are overexpressed • Tumor Suppressor Genes: Normally limit mitosis, but if inactivated/removed, cannot regulate mitosis |
| Distinguish between a stem cell and a progenitor cell. | A stem cell has the ability to divide over and over without specializing. A progenitor cell can produce daughter cells that differentiate into a limited number of cell types. |
| Distinguish between totipotent and pluripotent. | A totipotent cell can give rise to any cell type. A pluripotent cell can give rise to daughter cells that can specialize into many cell types, but not all. |
| Explain how cells differentiate. | Cells differentiate by activating and suppressing the functions of many specific genes. |
| What is apoptosis? | Apoptosis is a form of programmed cell death, which is part of normal development. It does not result from disease or injury. |
| List two general functions of apoptosis. | It sculpts organs so they will not overgrow, and destroys defective, injured or extra cells. |
| List the steps of apoptosis. | Activated caspases inside the cell dismantle cellular contents, destroy DNA replication enzymes, abolish the cytoskeleton and the ability to adhere to other cells, degrade mitochondria, and change the cell membrane in ways that attract phagocytes. |
| Mitochondria | small organelles found within cells, often referred to as the "powerhouse of the cell," |
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