Cellular Biology Flashcards
Cell Membrane
Selective permeability
Readily permeable to small, nonpolar hydrophobic molecules and small polar molecules
Small charged particles are able to cross through protein channels
Charged ions and larger charged molecules cross by carrier proteins
Fluid Mosaic Model: Phospholipid bi-layer with proteins embedded
Endoplasmic Reticulum
Transport of materials throughout cell, especially materials destined to be secreted by cell.
Smooth ER is involved in metabolism and production of lipids.
Rough ER is involved in protein production.
Nucleus
Controls the activities of the cell, including cell division.
Contains DNA which is complexed with histone (protein) to from chromosomes.
The nucleolus is a dense structure in the nucleus where rRNA is synthesized.
6 Kingdoms
Bacteria Archaea Protista Fungi Plantae Animalia
Cell Theory
All living things are composed of cells.
Cell is basic functional unit of life.
Cells can only arise from pre-existing cells.
Cells carry genetic info in the form of DNA.
Ribosomes
Site of protein production.
Synthesized by nucleolus.
Golgi Apparatus
Receives vesicles and their contents from the smooth ER and then modifies them, repackaging them into vesicles and distributes them to the cell surface by exocytosis.
Mitochondria
Sites of aerobic respiration.
Supply ATP.
Composed of outer and inner phospholipid bilayer.
Cytoplasm
Where most of the cell’s metabolic activity occurs.
Includes cytosol (cellular fluid) and organelles.
Cyclosis: streaming movement within cell (transport).
Vacuoles / Vesicles
Membrane-bound sacs involved in the transport and storage of materials that are ingested, secreted, processed or digested by the cell.
Vacuoles are larger and more likely to be found in plant cells.
Centrioles
Involved in spindle organization during cell division.
Plant cells do not have centrioles.
Lysosomes
Membrane-bound vesicles that contain hydrolytic enzymes involved in intracellular digestion.
Break down material ingested by the cell.
Autolysis: injured or dying tissue may “commit suicide” by rupturing its lysosomes membrane and releasing the hydrolytic enzymes.
Cytoskeleton
Supports cell, maintains shape, and aids in cell motility.
Composed of microtubules, microfilaments, and intermediate filaments.
1. Microtubules: hallow tubes made of polymerized tubulin and provide cell with support.
Provide framework for organelle movement within cell.
2. Microfilaments: solid rods of actin, important for cell movement and support.
Move materials across plasma membrane , i.e., in contraction phase of cell division and in amoeboid movement.
Cellular Transport: Simple Diffusion
Net movement of dissolved particles down their concentration gradients- from a region of higher concentration to a region of lower concentration.
Passive - does not require external source of energy.
Cellular Transport: Osmosis
Simple diffusion of water from a region of lower solute concentration to a region of higher solute concentration.
Hypertonic: cytoplasm of cell has a lower solute concentration than the extracellular medium, the medium is hypertonic to cell and water will flow out of cell (plasmolysis –>cell will shrivel).
Hypotonic: extracellular environment is less concentrated than the cytoplasm of the cell, the extracellular medium is hypotonic to cell and water will flow into cell, causing it to swell and lyse.
Isotonic: extracellular environment has the same concentration of solutes as the cell cytoplasm, the cell is isotonic to the environment and water will move back and forth equally.
Cellular Transport: Facilitated Diffusion
Net movement of dissolved particles down their concentration gradient through special channels or carrier proteins in the membrane.
Passive transport.
Cellular Transport: Active Transport
Net movement of dissolved particles against their concentration gradients with the help of transport proteins.
Requires energy.
Aid in regulation of cell’s internal content of ions and large molecules.
Carrier molecules:
1. Energy-independent Carriers: facilitate movement of compounds along a concentration gradient.
2. Symporters: move 2+ ions or molecules in the same direction across the membrane.
3. Antiporters: exchange one or more ions/molecules for another across the membrane.
4. Pumps: energy dependent carriers (require ATP).
Endocytosis
Process in which the cell membrane invaginates, forming a vesicle that contains extracellular medium.
Allows cell to bring large volumes of extracellular material inside cell.
Pinocytosis: ingestion of fluids or small particles.
Phagocytosis: engulfing of large particles.
Exocytosis
Vesicle within cell fuses with cell membrane and releases a large volume of contents to the outside.
Can play a role in cell growth and intercellular signaling (synapse).
Intracellular Circulation
Material move about within cell in a number of ways:
- Brownian Movement: kinetic energy spreads small suspended particles throughout the cytoplasm of the cell.
- Cyclosis/Streaming: circular motion of cytoplasm around the cell transports molecules.
- ER: the ER forms a network of channels throughout the cytoplasm and provides a direct continuous passageway from the plasma membrane to the nuclear membrane.
Extracellular Circulation
A number of systems deal with the movement of materials on a larger scale through the body of an organism.
- Diffusion: if cells are in direct or close contact with external environment, transports food and oxygen. In larger, more complex animals, transports materials between cells and interstitial fluid.
- Circulatory System: complex animals require a circulatory system, the cells are too far from external environment. Includes vessels and a pump.
Interphase
Period of growth and chromosome replications.
90% of cell life.
Sister Chromatids
After replication, 2 identical chromosomes held together at centromere.
Chromatin
Uncoils DNA that is not visible during Interphase.
Phases of Interphase
G1: initiates interphase, active growth phase, increases in size and synthesizes proteins.
S: period of DNA synthesis.
G2: cell prepares to divide, grows and synthesizes proteins.
M: mitosis or meiosis occurs
Mitosis
The division and distribution of the cell’s DNA to its 2 daughter cells.
Occurs in somatic cells
Nuclear division (karyokinesis) is followed by cell division (cytokinesis).
Prophase, Metaphase, Anaphase, Telophase (PMAT)
Prophase
Chromosomes condense.
Centriole pairs (animals) separate and move toward opposite poles of cell.
Spindle apparatus forms between them, and nuclear membrane dissolves.
Metaphase
Centriole pairs are now at opposite poles of cell.
Fibers of spindle apparatus attach to each chromatid at its corresponding kinetochore (protein located on centromere).
Spindle fibers align chromosomes at the equator forming the metaphase plate.
Anaphase
Centromeres split, allowing sister chromatids to separate.
Sister chromatids are pulled toward the opposite poles of the cell by shortening spindle fibers.
Telophase
Spindle apparatus disappears.
Nuclear membrane forms around each set of newly formed chromosomes.
Diploid (2N)
Chromosomes uncoil.
Cytokinesis
Near the end of telophase the cytoplasm divides into 2 daughter cells, each with a complete nucleus and its own set of organelles
Animals: a cleavage furrow forms and the cell membrane indents along the equator of the cell, pinching through the cell and separating the 2 nuclei.
Plants: a cell plate forms between the 2 nuclei, splitting the plant cell in half and allowing the cell to divide.
Meiosis
Process by which sex cells are produced.
Like mitosis, the cell duplicated its chromosomes before undergoing the process.
Unlike mitosis, meiosis results in haploid cells (1N).
First Meiotic Division
Produces 2 intermediate daughter cells with N chromosomes and sister chromatids.
Prophase I
Homologous chromosomes come together and intertwine in a process called synapsis.
Each synaptic pair of homologous chromosomes contains 4 chromatids and is called a tetrad.
Crossing Over
Sometimes chromatids of homologous chromosomes break at corresponding points and exchange equivalent pieces of DNA.
Chiasmata: points of contact between homologous chromosomes where crossing over can occur.
Does not occur between sister chromatids of the same chromosomes (bc they are identical, no genetic variation).
Occurs in Prophase I.
Metaphase I
Homologous pairs (tetrads) align at the equatorial plane, and each pair attaches to a separate spindle fiber at the kinetochore.
Anaphase I
Homologous pairs separate and are pulled to opposite poles of cell (disjunction).
Each chromosome of paternal origin separates from its homologous of maternal origin, and either chromosome can end up in either daughter cell.
Each daughter cell will have a unique pool of genes from a random mixture of maternal and paternal origin.
Nondisjunction
Occurs when cells do not separate appropriately during meiosis.
Occurs during anaphase
Telophase I
Nuclear membrane forms around each new nucleus.
Each chromosome still consists of sister chromatids joined at the centromere.
Second Meiotic Division
Meiosis II is not preceded by chromosomal replication.
The chromosomes align at the equator, separate and move to opposite poles, and are surrounded by a reformed nuclear membrane.
The new cells have a haploid number of chromosomes.
In women, only one of these daughter cells becomes a functional gamete, the others are destroyed by the body.
