Term
| Describe the structure of the plasma membrane: |
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Definition
| It is described by a fluid-mosaic model-- membrane is primarily composed of a phospholipid bilayer; it also contains proteins, most of which span its entire width. |
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Term
| Describe the structure of cilia and flagella: |
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Definition
| They are minute cytoplasmic projections that extend from the cell's surface. They are composed of 9 pairs of microtubules, with 1 pair in the middle (9+2 arrangement, except non-motile cilia, with a 9+0 arrangement). |
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Term
| Describe amoeboid movement: |
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Definition
| Certain cells can extend pseudopods (false feet) which involves extending parts of its cytoplasm which pulls the cell through the extracellular matrix. This process aids in phagocytosis. |
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Term
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Definition
| "Cell eating" Cells use pseudopods to surround and engulf particles of organic matter. This protects the body from invading microorganisms and extracellular debris. |
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Term
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Definition
| "Cell drinking" A form of endocytosis in which the plasma membrane furrows inward the membrane near the surface fuses, and a small vesicle containing extracellular fluid is pinched off and enters the cell. It can also be a receptor-mediated process. |
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Term
| Describe receptor-mediated endocytosis: |
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Definition
| It involves a smaller area of cell membrane, and the interaction of a specific molecule in the exracellular environment with a specific receptor protein in the cell membrane. |
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Term
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Definition
| The reverse of endocytosis. It is a process that allows the cell to secrete its products |
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Term
| Describe the structure and function of the cytoskeleton: |
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Definition
| It is composed of microfilaments and microtubules. It aids in the movement of organelles within a cell. |
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Term
| Describe the structure and function of lysosomes: |
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Definition
| They are membrane-bound organelles that contain digestive enzymes. They fuse to phagocytotic food vacuoles and digest the contents, as well as structures and molecules within the cell |
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Term
| Describe the structure and function of peroxisomes: |
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Definition
| They are membrane-enclosed organelles that contain enzymes that promote oxidative reactions. They remove hydrogen from certain orgainc molecules, transferring it to O2, which oxidises it and forms hydrogen peroxide. This detoxifies toxic molecules. |
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Term
| Describe the structure and function of mitochondria: |
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Definition
They are bean-shaped with an outer membrane with a smooth contour and an inner membrane with infoldings called cristae. They are the site of ATP production, and they have their own DNA. |
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Term
| Describe the structure and function of ribosomes: |
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Definition
| They are composed of rRNA and protein arranged in two subunits. They can be free-floating or attached to rough ER. They are "protein factories" responsible for protein synthesis. |
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Term
| Describe the structure and function of the ER: |
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Definition
They are a system of membranous tubules in the cell. Rough ER- It is covered in ribosomes and is involved in protein synthesis Smooth ER- Provides a site for many enzymatic reactions and in skeletal muscles, is a site for Ca2 storage. |
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Term
| Describe the structure and function of the Golgi apparatus: |
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Definition
| It is a series of membranous sacs that receives products from the rough ER, modifies those products amd releases those products within vesicles. |
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Term
| Describe the structure of the nucleus: |
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Definition
| It is surrounded by a double-layered nuclear envelope. At some points, the two layers are fused by nuclear pore complexes, which allow for the passage of molecules. |
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Term
| Describe the structure of nucleosomes: |
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Definition
| DNA is wound like a spool around regulatory proteins called histones, which form particles called nucleosomes. |
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Term
| Distinguish between the different types of RNA: |
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Definition
rRNA- ribosomal RNA- forms part of the structure of ribosome. "workbench" tRNA- transfer RNA- decodes the genetic message contained in mRNA; carries amono acids to ribosomes. "taxi" mRNA- messenger RNA- contains the code for synthesis of specific proteins |
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Term
| How does DNA direct the synthesis of RNA in genetic transcription? |
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Definition
| The enzyme RNA polymerase causes separation of the two strands of DNA along the region of the DNA that constitutes a gene. One of the two strands of DNA serves as a template for the production of RNA. This occurs by complimentary base pairing between the DNA and ribonucleic bases. |
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Term
| Explain how RNA directs the synthesis of proteins in genetic translation: |
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Definition
| mRNA leaves the nucleus and attaches to ribosomes. Each tRNA with a specific base triplet in its anticodon , binds to a specific amino acid. As the mRNA moves through the ribosomes, complimentary base pairing between tRANA anticodons and mRNA codons occurs. As each successive tRNA molecule binds to its complimentary codon, and the amino acid it carries is added to the end of a polypeptide chain. |
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Term
| How may proteins be modified after genetic translation? |
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Definition
| Enzymes in the ER may remove certain amino acids from the polypeptide chains changing its structure so it can be secreted. In the Golgi apparatus, carbohydrates may be added to some proteins (glycoproteins) for secretion. |
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Term
| What is the role of ubiquitin? |
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Definition
| It tags regulatory proteins that are targeted for destruction. |
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Term
| What is the role of proteasome? |
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Definition
| Regulatory proteins tagged by ubiquitin are degraded by proteaseome, and organelle consisting of several protease enzymes (those that digest proteins). |
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Term
| Explain the semiconservative replication of DNA in DNA synthesis: |
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Definition
| The strands of the original DNA molecule gradually seperate along their entire length, and through complimentary base pairing form a new complimentary strand. This way each DNA molecule consists of one old and one new strand. |
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Term
| Identify the phases of mitosis, and give a short description of each phase: |
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Definition
Interphase- chromosomes are in extended form and nucleus is visible Prophase- chromosomes are seen to consist of 2 chromatids joined by a centromere Metaphase- chromosomes are lined up at equator of cell, nucleus dissapears Anaphase- centromere split and the sister chromatids are pulled to opposite poles of cell Telophase- chromosomes become thinner, longer and less distinct, new nuclear membranes form, cleavage furrow forms |
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Term
| Identify the phases of meiosis: |
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Definition
Prophase I, metaphase I, anaphase I, telophase I (seperate into 2 daughter cells) Prophase II, metaphase II anaphase II telophase II (original 2 daughter cells divide, and 4 daughter cells are formed) |
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Term
| Distinguish between mitosis and meiosis: |
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Definition
In mitosis, homologous chromosomes line up single file in the middle and are pulled apart, resulting in two cells with one pair of 23 chromosomes in each (equaling in 46 chromosomes in each). In meiosis, homologous chromosomes line up side by side in the middle and are pulled apart, so that only one of each pair is pulled to each pole, resulting in two cells with 23 chromosomes. |
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Term
| Describe the function of cilia: |
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Definition
| Cilia aid in motility, they beat like rowers and project from the apical surface of epithelial cells. ex. In respiratory airways they transport strands of mucus to the pharynx. Almost every cell has a single non-motile cilium, which is believed to serve sensory functions. |
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Term
| Describe the function of flagella: |
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Definition
| Only found in sperm cells, it is a whiplike structiure tha propels sprem through its environment. |
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Term
| Describe the structure of microvilli: |
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Definition
| They are tiny, fingerlike projections found in areas specialized for rapid diffusion. They increase the surface area of the cell membrane. |
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Term
| Explain why microfilaments and microtubules can be thought of as a skeleton and musculature of a cell: |
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Definition
| Although it is not rigid, it forms a latticework within the cell, giving it structure and shape (like a skeleton). They also contain contractile proteins- including actin and mysosin, which aid in movement such as in amoeboid movement (like a muscle) |
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Term
| How can mitochondia provide a genetic inheritance derived from only the mother? |
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Definition
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Term
| What is the significance of histone proteins? |
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Definition
| They are positively charged and organized to form spools about which the negatively charged strands of DNA are wound. They allow for unwinding and winding when chromatin is extended (during RNA synthesis) or condensed. |
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Term
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Definition
| DNA combined with a protein, forming the threadlike material which makes up chromosomes. |
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Term
| How is pre-cursor mRNA modified to form mRNA? |
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Definition
| pre-mRNA is much larger than mRNA, and it contains excess bases within it. The genetic code for a particular protein is split up by stretches of base pairs that are useless (introns). The coding portions are called exons, and are used to form mRNA. These exons can be cut and spliced (alternative splicing) so a gene can form several different mRNA molecules (3 on average) which can code for several different proteins. |
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Term
| How does processing of secretory proteins differ from the processing of proteins that remain in the cell? |
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Definition
| Secretory proteins are produced in the rough ER and sent to the Golgi apparatus for packaging and modification, and sent off in vesicles for secretion. Proteins to be used in the cell are likely to be produced by polyribosomes, which float freely in the cytoplasm. |
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Term
| What is genetic recombination? |
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Definition
The events of "shuffling the deck" and "crossing over" |
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Term
| Describe "shuffling the deck" |
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Definition
| At metaphase I, pairs of homologous chromosomes can line up with either member facing a given pole of the cell (keeping in mind, each member of a pair came from a different parent). Maternal and paternal members of homologous pairs are thus randomly shuffled. So when the 1st meiotic division occurs, each daughter cell will obtain a complement of 23 chromosomes, randomly derived from the maternal or paternal contribution of to the homologous pairs of chromosomes from the parent cell. |
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Term
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Definition
| In prophase I, pieces of one chromosome of a homologous pair can be exchanged with the other homologous chromosome. |
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Term
| Decribe the function of microvilli: |
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Definition
| They aid in rapid diffusion or digestion due to the increased surface area they provide. |
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