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| 1312883902 | What is the structure of microtubules? | Hollow tubes made of globular proteins (alpha and beta tubulin). They are dynamic as they can lengthen and shorten by adding and removing tubulin subunits at the ends. | |
| 1312883903 | What is the function of microtubules? | maintaining the cell shape and attaching to chromosomes during cell division to pull the chromosomes apart. They can also be used as tracks along which special motor proteins propel organelles and move them from one part of the cell to another. They enable movement through cilia and flagella. | |
| 1312883904 | What is the structure of cilia and flagella of eukaryotes? | A ring of 9 microtubule doublets surrounding a pair of central microtubules giving a "9+2" pattern. | |
| 1312883905 | What is the structure of microfilaments? | Much thinner than microtubules. They consist of a double chain of polymers of actin (a globular protein) | |
| 1312883906 | What is the function of microfilaments? | Maintaining cell shape, but are less rigid than microtubules (tension bearing), muscle contraction, cell division and cell motility. | |
| 1312883907 | What is the structure of intermediate filaments? | Intermediate in diameter between microtubules and microfilaments. They are cables made from fibrous proteins (keratin) and are long - not globular. There are many different types. | |
| 1312883908 | What is the function of intermediate filaments? | Maintaining cell shape, anchorage and they are the major component of the nucelar lamina. | |
| 1312883909 | How are there connections between plant cells? | Plants thick cell wall prevents the transfer of molecules so cell walls between adjacent cells are perforated to form plasmodesmata. These membrane lined channels allow the flow of cytosol. | |
| 1312883910 | How are there connections between animal cells? | Animal cells are held together by tight junctions (glue) and desmosomes (rivets) and have channels called gap junctions which provide a cytoplasmic connection between cells and allow small molecules to pass from one cell to another. | |
| 1312883911 | What are examples of signal molecules? | Growth factors and hormones (e.g testosterone) which send instructions to cells about whether to undergo cell division, or about which set of genes to switch on. | |
| 1312883912 | What are the two ways in which cells can communicate? | By sending signals by direct contact between cells or signal molecules can be secreted out of cells by exocytosis and diffused to other cells in the vicinity (local signalling) or cells further away (long-distance signalling). | |
| 1312883913 | What is the first step in the process that leads to activation of cellular response? | Reception - The signal must be detected by binding to a protein receptor. The binding is usually specific so only certain receptors will respond to specific signal molecules. Receptors are sometimes located inside the cell but most are located in the plasma membrane. When a signal molecule binds to a receptor this triggers a change in the shape of the receptor, either directly activating it or allowing it to interact with other molecules. | |
| 1312883914 | What is the second step in the process that leads to activation of cellular response? | Transduction - signals are transducted from an activated receptor to another molecule in the cell. Often these are a whole series of molecules that pass the message on from one to another. Signal transduction involves many steps that each activate the next step in the path way. This is an important way to amplify a signal, so that even a weak signal can lead to a strong cellular response. | |
| 1312883915 | What is the third step in the process that leads to activation of cellular response? | Response - The cellular response sometimes involves converting a specific enzyme from an inactive to an active form, or vice versa. Often it involves switching on genes that encode for particular proteins required to produce a response. |
