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Flashcards by blueaweiss, updated more than 1 year ago
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Created by blueaweiss
almost 10 years ago
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| Question | Answer |
| What are unicellular organisms? | Living organisms that are made up of one cell. All seven life processes take place in one cell |
| What is a multicellular organism? and in a multicellular organism name the things the cells form from smallest to largest ? | A multicellular organism that is made of many cells. The different cells share the work of the whole organism. Each cell is specialised for a specific job. tissues --> organ --> organ systems |
| What is a zygote? | A fertilised egg cell. It then grows through mitosis to form two daughter cells. This then continues until the group of cells form an embryo |
| How do cells differentiate? And give an of a specialised cell? | By turning on or off genes / making some genes active and other inactive. Red blood cells have large surface area which allows efficient absorption of oxygen. |
| What is special about the 8 cell stage? | All the cells are embryonic stem cells |
| What are embryonic and adult stem cells? | Embryonic stem cells are cells that can differentiate into any cell in the body. Adult stem cells can only differentiate into cells within a specific organ or tissue. For example an adult stem cell in bone marrow can become any blood cell. |
| Why are stem cells important? in terms of within the body and within medicine? | In the body adult stem cells are used to replace dead or damaged cells. In medicine - stem cells could be grown to create organs and could replace damaged cells in patients. They could also help us understand birth defects and test new drugs. |
| What are palisade cells where are they found and give two features? | Cells designed to collect sunlight. They are found near the tops of leaves. Two features : 1) Many chloroplasts 2) rectangular |
| What are xylem cells and give features? | Are adapted to carry water and mineral salts to where they are needed. Features : 1) Long tubes 2) thick walls 3) A one way flow 4) dead xylem cells join to form long tubes of xylem tissue. |
| What are phloem cells where are they found and give features? | Cells that carry dissolved substances like sugars and amino acids to every part of the plant. Features: 1) 2 way flow 2) Walls have holes like a sieve 3) They join with other phloem cells to form long tubes |
| What is a vascular bundle? | A bundle of xylem and phloem cells |
| What are meristems, what is their purpose, how do they divide and where are they found? | Meristems are unspecialised cells in plants that can differentiate into any cell. Their purpose is to grow whole organs or replace damaged cells or help plant growth. They divide by mitosis and form two daughter cells separated by a cell plate which later become a cell wall. They are found in the tips of shoots and roots and flowers. |
| Explain the process of tissue culture and the 4 stages? | 1) Take cells from the plants root or stem 2) Use enzymes to separate the cells 3) Place the cells in a nutrient jelly containing plant hormones 4) Plantlets are transferred to soil to form clones of the original plant |
| Explain making clones from cuttings? | Cut the ends of shoots and put them into water or moist earth and a clone will be created. Often prior to this the cuttings are dipped in root powder to encourage the creation of roots from the end of the stem. |
| What are the advantages of using tissue culture over cuttings? | Creating clones from cuttings is : lengthy, expensive and can only be done is some seasons whereas cloning from tissue culture is: cheaper, quicker and can be done throughout the year |
| What is tissue culture with meristems and what are the advantages? | If a plant is particularly novel or desirable we use meristems as this creates an exact clone of the parent. Tissue culture can sometimes create irregularities whereas meristems do not. |
| What are auxins? | A plant hormone that promotes growth. Auxin effects cells by causing changes on cell division and the elongation of the cell. In the shoots it causes the growth of cells whereas in the roots it slows down growth. |
| What is phototropism and how does it work in plants? | When a plant rows toward light (the growth response toward light). Shoots growing towards light are said to be positively phototrophic. It works as when a shoot tip gets light the auxin is found in the shaded side. Auxin then enables the cell walls to be stretched more easily be yet pressures developed in the vacuole. This makes the cells on the shaded sided elongate and expand more than on the sunny side causing the shoot to curve toward the light. Also in the roots it slows down growth when roots are exposed to light which are thus said to be negatively phototrophic. |
| What is mitosis? and give the stages | When a cell divides to create to identical daughter cells. 1) Within a cell each cel makes a copy of itself. 2) The cell then divides in two to create two daughter cells with identical genes and chromosomes (one of each of the cloned chromosomes) |
| What is the 'cell cycle'? | First a cell grows, accumulates nutrients, makes copies of its chromosomes and increases the number of organelles (the specialised structures within the cell) that are going to take place in the process of mitosis. The second phase is mitosis when the original chromosomes and their copies divide into two nuclei. This is followed immediately be a process in which the nuclei, cytoplasm, organelles and cell membrane are divided into two cells containing equal parts of each of the components. Once the parent cell has divided completely each daughter cell enters the first phase. |
| What is meioses outline the stages and its importance? | Meioses is a type of cell division which take splice in the male testes and female ovaries. Meioses is the division that creates gametes (males produce sperm cells and women are ova which mature to form egg cells). Gametes have half the chromosomes as another cell so when they join they have 46 chromosomes. Stage 1) All the chromosomes in a cell divide an are copied like in mitosis. 2) The cell the divides in two 3) The cell then immediately divides again It is important as it means that a zygote does not have 92 chromosomes (46 + 46) which would not work. |
| Describe the structure of DNA? | Phosphate - sugar - base are the three units that make it up A DNA molecule is two strands of molecules facing each other like a ladder. The sugar and phosphate are the uprights and the bases are the rungs. The strands of the DNA molecule are twisted into a double helix. |
| Outline the genes and base pairs? | DNA has four bases A,C,G and T. Each unit is called a nucleotide. Each base is heeled together in a base pair. A pairs with T C pairs with G Genes are sections of a DNA molecule .These genes determine the proteins that are needed for a cell. This is called the genetic code. |
| How are proteins made? | MRNA copies a particular section of the DNA. This MRNA takes the copy to a ribosome in the cytoplasm. The MRNA copy then tells the ribosome which amino acids to make which then form proteins. TRNA (a molecule that gives up the amino acid that is carries) is attracted to MRNA and when it reaches the ribosome it's amino acid is used to build the protein. A set of three bases carries the code for one amino acid each combination of amino acids form different proteins. |
| After the 8 cell stage what two things could happen to a cell? | The cell may divide again to form identical daughter cells or the cells may undergo differentiation |
| What are ethical issues with stem cell research? | Using embryonic stem cells means that the embryo is not able to develop into a foetus. MAny think the destruction of life is wrong. |
| What is therapeutic cloning? and what are some ethical issues? | Where they remove the nucleus of an egg cell which they replace with the nucleus from a body cell. This is advantageous as the new cell will have identical genes to the body cell used. Issues - who should donate the eggs, the eggs could form life etc |
| What can scientists now do in terms of active and inactive genes and what are the ethical issues? | Scientist can now re activate all the genes in a cell to recreate embryonic stem cells which can then be re -specialised (what happened with the mouse with the ear on the back) Ethical issues - these cells could become a human embryo producing a clone of the donor which many feel is wrong . |
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