Chapter 3 Cell division and cellular organisation

  • Created by: Chloesn
  • Created on: 03-01-14 02:48
The four stages of the cell cycle?
G1, S-Phase, G2, Mitosis
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The stages of mitosis?
Prophase, Metaphase, Anaphase, Telophase
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What is cytokinesis?
The cytoplasm now divides, forming two new cells, each with a nucleus containing a complete set of chromosomes and a centriole.
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How long is the cell cycle, what percent is spent in interphase and approximately how long is mitosis?
The cell cycle is 24 Hours, 95% is spent in interphase and approximately 80 minutes in mitosis.
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What happens during G1?
During G1 the cell grows to nearly full size and performs many of its specific biochemical functions.
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What happens during the S-phase?
S-phase (synthesis phase) is the stage which DNA in the nucleus is replicated.
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What happens in G2?
During G2 the cell finishes growing with duplicated DNA and two centrosomes in the cytoplasm mitosis can begin.
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Describe interpahse
In this stage doing normal cell activities such as respiration and protein synthesis. The DNA that makes up the chromosomes is duplicated - a perfect copy is made, so that the DNA can be divided up equally into the two new cells when it divides.
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Describe prophase
The chromosomes become visible the DNA molecules coil and supercoil As it proceeds the nucleolus disappears as well as this the spindle begins to form at this stage. The centrioles move away from each other - organizing formation of microtubles
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Describe metaphase?
The nuclear membrane breaks down room for maneuvering the chromosomes. The microtubules attach to the centromeres of their chromosomes each is grabbed by one microtubule on either side. Pull in opposite directions bring the chromosomes to the equator
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Describe anaphase
The centromeres split and the microtubules are still pulling so the centromeres and chromatids are pulled apart to each pole.
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Describe telophase
The 2 groups of chromatids have now arrived at the poles each contains a complete set of chromatids can now be called chromosomes. Microtubules making up the spindle fibres break down. Nuclear envelopes form around each group of chromosomes- uncoil
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How ,any chromosomes does a human have?
In a human cell there are 46 chromosomes - each made up of one enormously long molecule of DNA.
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What is the centromere and chromatids?
It is copied and the pair of identical DNA molecules that are now contained in each chromosome remain attached at a point called the centromere. The two identical strands of DNA are called chromatids.
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Errors and checking?
It’s important that the DNA molecules are the same, a small error - mutation - could have harmful effects.So there’s a ‘checking’ process - special proteins work along the DNA molecules, checking for errors and correcting them where possible.
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Mitosis and damage?
It also comes into play when the body is damaged and needs repair - if you cut yourself cells in the skin will produce new cells which will spread across the wound.
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Asexual reproduction and budding?
In some organisms, mitosis is used for reproduction - strawberry plants. Asexual reproduction, does not involve gametes or fertilisation. Single celled organisms can also reproduce by mitosis - yeast - reproduces by budding.
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The body contains a lot of cells all developing from the single cell - zygote - formed by the fusion of an egg and sperm cell. The zygote divided to form a tiny ball - blastocyst continuing to divide to form an embryo.
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Stem cells?
Once a human cell has differentiated it cannot usually change to another kind of cell, different to the abilities of the blastocyst with the potential to become any of many different cells - they are stem cells.
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Differentiation - specialization of a cell to carry out a particular function.
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Define totipotent
totipotent - (of an immature or stem cell) capable of giving rise to any cell type or (of a blastomere) a complete embryo.
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Adult stem cells?
Adults have some stem cells though those found can only differentiate into a limited range of cells. Bone marrow stem cells - can form red blood cells but cannot differentiate into neurones or any other cell.
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Stem cell uses?
They could cure parkinsons disease - death of a particular group of cells in the brain - could be used to replace these.
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They destroy bacteria and other foreign material by phagocytosis. The cytoplasm contains small granules - some of these are lysosomes containing digestive enzymes and some are glycogen stores.
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There is no nucleus to allow for more haemoglobin. The cell is very small to allow it to travel through capillaries and so get very close to body tissues. The cytoplasm is packed with a protein haemoglobin Has a biconcave shape large SA:V
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Plasma membrane, containing receptors that bind with the egg cell membrane to allow fertilisation. Acrosome - a specialised lysosome containing hydrolytic digestive enzymes Mitochondria Microtubules nucleus with a haploid no. chromosomes
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Plant stem cell?
Plants do not have stem cells - most retain the ability to differentiate. However parts of a plant that are able to divide and places that this occurs at a high rate - meristems.
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Xylem vessels
Thick, strong cell walls containing cellulose and lignin help support the plant. Pits (thin sections in the wall) allow lateral water movement. They are dead and have no cytoplasm, so all the space inside can be used to transport water and minerals.
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Phloem sieve tube
Cells are connected to each other through sieve plates that have many pores allowing sugars to be transported. Have a modified cytoplasm with few organelles, so the tube can transport sugars. Sugar transport in sieve tubes requires energy. Companion
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A collection of cells, together with any intercellular secretion produced by them, that is specialised to perform one or more particular functions. The cells are often of the same type, such as palisade tissue in a plant leaf or squamous epithelium
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is a part of the body which forms a structural and functional unit and is composed of more than one tissue. A leaf is an example of a plant organ and the brain is an example of an animal organ.
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is a collection of organs with particular functions, such as the excretory, reproductive, cardiovascular and digestive systems in humans.
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It is essential there is communication and cooperation between cells within tissue, and tissues, organ etc. All the activities work together and do the appropriate things at the appropriate times essential for multicellular organisms survival.
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A type of division that is needed in a stage of sexual reproduction.
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Chromosomes 23 and sets?
In the nucleus of the cell there are 46 chromosomes - two sets one set of 23 and another of 23.
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Diploid cell?
Cells with two complete sets of chromosomes are called diploid cells.
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The two chromosomes are of the same kind - homologous - meaning same position, genes for the same feature in the same position though unlikely to be the same.
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Haploid cell?
Haploid cells only have one set of chromosomes. Gametes are therefore genetically different.
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What is cytokinesis?


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Card 5


What happens during G1?


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