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50 Cards in this Set
- Front
- Back
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What are the two main phases of the cell cycle |
Interphase and mitotic (division phase) |
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What is the interphase |
Consists of G1, S and G2 In interphase, DNA is replicated and is checked for errors in the nucleus. Protein synthesis occurs in the cytoplasm Mitochondria grow and divide In plants, chloroplasts grow and divide Normal metabolic processes, cell respiration. |
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What is G1 |
This is the first growth phase, proteins from which organelles are synthesised are produced and organelles replicate. The cell increases in size. |
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What is the S phase |
DNA is replicated, known as the synthesis phase. |
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What is G2 |
This is the second growth phase, the cell continues to grow, energy stores are increased, replicated DNA is checked for errors. |
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What are the phases in the mitotic division phase |
Mitosis - the nucleus divides Cytokinesis - the cytoplasm divides and two cells produced. |
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What is the G0 phase |
The cell will leave the cycle, either permanently or temporarily. Differentiaion, a cell becomes specialised, it cannot divide anymore. And so it cant enter the cycle again. Ageing, number of cells increase DNA is damaged, it can no longer divide (G0) and enters a period of permanent cell arrest. |
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Why is it necessary to check the DNA |
Checks for DNA to be error free and in the correct position of chromosomes. Ensures the fidelity of cell division - two identical daughter cells are created from the parent cell |
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What are the checkpoints |
Control mechanisms of the cell cycle. They monitor and verify the processes at each phase of the cell cycle have been cmolpeted. G1 checkpoint - At the end of the G1 phase, and just before S phase. Checks for cell size, nutrients, DNA damage, growth factors. If it fails it enters the G0 phase, resting state. G2 checkpoint - At the end of the G2 phase and before the start of the mitosis phase. It will check for cell size, DNA replication, and DNA damage. It needs to the pass this to go into mitosis. If it fails it will go to G0. Spindle assembly checkpoint - metaphase checkpoint. It checks that the chromosomes are attached to the spindle and have aligned. Mitosis cant continue until this checkpoint is done. |
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What is mitosis |
Nuclear division, and ensures that the daughter cells are genetically identical. Asexual reproduction, produce genetically identical offsprings. |
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How do prokaryotes reproduce asexually |
Binary fission |
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What are the four stages of mitosis |
PMAT Prophase, Metaphase, Anaphase and Telophase. |
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Why do you stain to see mitosis |
They bind to the DNA and makes chromosomes more visible. |
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What are chromatin fibres |
Complex made up of various proteins, DNA and RNA. |
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What happens in prophase |
Chromatins coil and condense, become a stain. Nuclear membrane break down, and nucleolus will disappears. Microtubules form the fibress that link the cell, the fibres are important as they move chromosomes into their positions, before division In some plant and animal cells, that the centrioles migrate to opposite poles of the cell. Spindle fibres attach to the centromere and move the chromosomes to the centre of the cell. At the end of prophase the nuclear envelope will disappear. |
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What is the metaphase |
During metaphase, the chromosomes are moved by the spindle fibres to form a plane in the centre of the cell. This is called the metaphase plate, and it holds them in position. |
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What is Anaphase |
The centromeres holding together the pairs of chromatids in each chromosome divide during anaphase. The chromatids are separated - pulled to opposite poles of the cell, this is done by the spindle fibres shortening. V shape is the chromatids being dragged by their centromeres through the liquid cytosol. |
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What is Telophase |
Chromatids are now chromosomes and have reached the poles. Two new sets of chromosomes are assembled around each pole, and the nuclear envelope reforms around them. The chromosomes start to uncoil and the nucleolus is formed. |
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What is cytokinesis |
The actual division of the cell into two separate cells. Animals cells - a cleavage furrow forms around the middle of the cell. The cell surface membrane is pulled inwards by the cytoskeleton and it fuses around the middle |
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How would plant cells differ in cytokinesis. |
Plant cells have cell walls, so it is not possible for a cleave furrow to be formed. Vesicles come from the Golgi Apparatus and assemble at the metaphase plate. The vesicles fuse with each other and divide the cell into two. |
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What is meiosis |
Sexually reproduction to produce haploid cells (each gamete contain half the number of chromosomes). Reduction division Nucleus divides twice to give 4 daughter cells |
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What are homologus chromomes |
A pair of same chromosomes, one from each parent, have the same genes, but different versions of the same genes(alleles) |
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What are alleles |
Different versions of the same gene. |
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What are the stages of Meiosis |
Meiosis 1 the first divsion and it is a reduction division. Pairs of homologous chromosomes are separated into two two cells. Each cell will contain one full set of genes, instead of two, so cells are haploid. Meiosis 2-similar to mitosis, the pairs of chromatids in each daughter cells are separated to form two more cells. Four haploid daughter cells. |
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What happens in prophase 1 |
Chromosomes condense, and nuclear envolope disintegrates and nucleolus disappears. Spindle form. Homologous chromosomes pair up, forming bivalents. Chromsomes cross over as they are dragged through. |
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What happens in metaphase 1 |
Similar to mitosis, but the homologous pairs of chromosomes line up along the metaphase plate. Independent assortment - this happens because of the way the pairs line up, many different combinations of alleles facing the poles. This process allows genetic variation. |
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What happens in Anaphase 1 |
When the homologous chromosomes are pulled to the opposite poles, the chromatids stay together. Sections of the DNA cross over and break off and rejoin. The points at which this happens, the chromatids break and rejoin are called chiasmata. The chromatids are now called recombinat. |
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What is telophase 1 |
Same as mitosis. chromosomes assemble at each pole and the nuclear membrane reforms. Chromosomes uncoil. Cell undergoes cytokinesis and divides into two cells. The reduction of chromosome number from diploid to haploid is complete. |
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What happens in prophase 2 |
The chromosomes will condense and become visible again. The nuclear membrane breaks down and spindle will form again. |
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What happens in metaphase 2 |
Individual chromosomes assemble on the metaphase plate. Independent assortment happens again and there is even more genetic variation produced. |
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What happens in anaphase 2 |
Chromatids of the individual chromosomes are pulled to opposite poles after division of the centromeres. Anaphase in mitosis |
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What is telophase 2 |
Chromatids assemble at the poles at telophase 2. The chromosomes uncoil and form chromatin agains. The nuclear envelope refroms and the nucleolus becomes visible. Cytokinesis divdes the cells to form 4 daughter cells. Haploid due to reduction division. |
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What are the levels of organisation in multicellular organisms |
Specialised cells -> tissues -> organs -> organ stystems -> whole organsims. |
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How are erythrocytes have specialised |
No nucleus, increases space for haemoglobin, and are flexible so they can squeeze through narrow capillaries. Bioconcave shape, increases surface area to volume ratio. |
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How are neutrophils have specialised |
They have a role in the immune system. They have a multi lobed nucelus, so they can squeeze through gaps to get to sites of infection. The cytoplasm have lysosomes - engulf pathogens. |
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How are sperm cells specialised |
Tail to swim and many mitochondria. Acrosome on the head of the sperm contains digestive enzymes that are released to digest the protective layers around the ovum. The sperm penetrate and lead to fertilisation |
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How are palisade cells specialised |
Contain many chloroplasts which can move within the cytoplasm in order to absorb more light. |
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How are root hair cells specialised |
They have long extensions of root hairs, which increase the surface area of the cell and maximises the uptake of water and mineral ions from the soil. |
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How do guard cells work |
They form an opening called stomata. They are necessary for CO2 to enter for photosynthesis. When guard cells lose water, they become less swollen, and can change shape and stoma close to prevent further water loss from the plant. The cell wall of a guard cell is thicker on one side so the cell does not change shape symmetrically. |
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What is a tissue |
A collection of differentiated cells that work together to perform a particular function. Each tissue is adapted for a particular function within the organism. |
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What are the four main categories of tissues in animals |
Nervous tissues - adapted to support the transmission of electrical impulses Epithelial tissue - adapted to cover the body surfaces, internal and external Muscle tissue, adapted to contract Connective tissue - adapted either to hold the tissues together or as a transport medium. |
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What is squamous epithelium |
They are made of specialised squamous epithelial cells, are very flat and thin, one cell thick. Allow for rapid diffusion, its found in the lining of lungs and allows rapid diffusion of oxygen into the blood. |
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What is the ciliated epithelium |
Hair like structures, move in rhytmic manner. They line the trachea, sweep away mucus. Goblet cells release mucus to trap any unwanted particles present in the air. This prevents bacteria reaching the alveoli. |
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What is the cartilage |
Connective tissue, contains elastin and collagen. Cartilage is firm, and flexible connective tissue. |
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What is muscle |
This is tissue that can shorten in length to move bones. There are different types of muscle fibres, skeletal muscle fibres and contain myofibrils. |
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What is the epidermis layer |
Single layer of closely packed cells that cover the surfaces of plants. Is covered by a waxy cuticle, and this prevents water loss. Stomata, controls what goes oin and out. CO2 in and out. Water vapour and O2 in and out. |
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What is the xylem tissue |
Vascular tissue, transport of water and minerals throughout plants. Tissue is made of vessel elements which are elongated dead cells. Lignin is placed on the walls and provides structural support for plants. Waterproofs the wall. |
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What is the phloem tissue |
Vascular tissue in plants, transports organic nutrients. such as sucrose, from the leaves and stems, where it is made by photosynthesis to the parts of the plant where it is needed. Made of columns of sieve tube cells, and they separated by perforated walls called sieve plates. |
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What is an organ |
A collection of tissues that are adapted to perform a particular function in an organism. Mammalian heart is an organ, adapted for pumping blood around the body. Made up of muscle tissue and connective tissue. Leaf is adapted for photosynthesis, epidermis and vascular tissue. |
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What are the organ systems of large multicellular organisms |
Each organ system is composed of a number of organs working together to carry out a major function in the body Digestive system - takes in food, breaks down the |
