Mod 1: 1.1.3 Cell Division, Cell Diversity, Cellular Organisation

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Explain why mitosis only occupys a small percentage of the cell cycle and what the remaining percentage involves.
Most of the cell cycle consists of interphase, when the genetic material (DNA) is copied and checked for any errors. Most important stage, as, if there are errors, the cell will kill itself (apoptosis).
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What are the main stages of mitosis?
The main stages of mitosis are: Prophase (chromosomes thicken, become visible); Metaphase (chromosomes line up on the equator); Anaphase (chromatids separate); and Telophase (each set of chromatids forms a new nucleus).
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What happens during interphase and prophase?
Interphase- Cell prepares to divide, DNA unravelled & replicated (double), organelles also replicated, ATP content increased. Prophase- chromosomes condense, centrioles move to opposite ends, spindle fibres form. Nucluear envelope breaks down.
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What happens during metaphase and anaphase?
Chromosomes (2 chromatids) line up along middle of cell, become attatched to spindle by their centromere. Anaphase- centromeres divide, separating each pair of sister chromatids, spindles contract and pull chromatids to ends, centromere 1st.
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What happens in the final stage of mitosis?
Telophase- chromatids reach opposite poles on spindle, they uncoil & become chromosomes again. Nuclear envelope forms around each group of chromosomes, now 2 nuclei. Cytoplasm divides, 2 new daughter cells that are identical to the original.
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What is meant by a homologous pair of chromosomes?
A pair of the same chromosomes or a chromosome with the same gene sequence as another E.g. our DNA
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Describe the process of cell division by budding in yeast.
Bud forms at surface of cell. Cell undergoes interphase- DNA/organelles are replicated ready to be divided. Cell undergoes mitosis. After nuclear division, the budding cell has a nucleus with an identical copy of the parent cell's DNA. Bud separates.
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Why are cells produced as a result of meiosis not genetically identical?
Each new cell ends up with a different combination of chromosomes. Chromosomes swap bits during meiosis and each gamete gets a combination of half of them, at random.
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Define the term stem cell.
Unspecialised cells that can develop into any type of cell.
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Define the term differentiation.
When stem cells divide and become new cells which then become specialised for a particular function.
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Give some examples of cells that differentiate.
Adult stem cells in bone marrow- differentiate to replace worn out blood cells, erythrocytes and neutrophils. Stem cells in the cambium differentiate into xylem and phloem tissue.
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Describe and explain how red & white blood cells are specialised for their functions.
Neutrophils- defend body, flexible shape allows engulfment of foreign material or pathogens, many lysosomes (digestive enzymes) to break down engulfed material. Erythrocytes- carry 02 in blood, biconcave disc shape, increases S/A, no nucleus.
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Describe and explain how epithelial cells and sperm cells are specialised for their functions.
Epithelial cells cover surfaces of organs- cells joined by interlinking membranes. Cilia beat to move particles away. Microvilli folds in cell membrane, increase cell's S/A. Sperm- flagella, to swim to egg, many mitochondria and acrosome.
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Describe and explain how palisade and root hair cells are specialised for their functions in plants.
Palisade mesophyll cells in leaves-photosynthesis, many chloroplasts, thin walls. Root hair cells- absortb water/mineral ions, large S/A, thin permeable cell wall, extra mitochondria (active transport of ions).
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How are guard cells specialised for their function?
Line the stomata, tiny pores in surface of leaf, used for gas exchange. In light, they take up water, become turgid. Thin outer walls, thick inner walls, force cell to bend outwards, open stomata. Leaf can then exchange gases for photosynthesis.
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Explain the meaning of tissue, organ and organ system.
Tissue- group of cells. Organ- group of tissues. Organ system- organs work together, form organ system. All cooperate with each other to keep organisms alive and functioning. Transport & Communication systems.
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Give examples of cells that are organised into tissues.
Squamous epithelium tissue- single layer of flat cells, line surface, found in alveoli. Xylem tissue- transports water, supports plant. Ciliated epithelium- cells with cilia, found in trachea. Phloem- transports sugars, sieve tubes, companion cells.
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Give examples of tissues that make up an organ.
Lungs- contain squamous epithelium tissue & ciliated. Also have elastic connective tissue & vascular tissue. Leaves- contain palisade tissue for photosynthesis, epidermal tissue, xylem & phloem tissues.
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Give examples of organs that make up an organ system.
Respiratory system- made up of organs involved in breathing (lungs, trachea, larynx, nose, mouth & diaphragm). Circulatory system- organs involved in blood supply (heart, arteries, veins, capillaries).
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What is the importance of cooperation between cells, tissues, organs and organ systems.
Specialised cells function more efficiently than unspecialised cells. Each cell depends on another cell for the functions it can't do. Must cooperate to keep organism alive. E.g. muscles rely on blood to supply 02.
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Card 2

Front

What are the main stages of mitosis?

Back

The main stages of mitosis are: Prophase (chromosomes thicken, become visible); Metaphase (chromosomes line up on the equator); Anaphase (chromatids separate); and Telophase (each set of chromatids forms a new nucleus).

Card 3

Front

What happens during interphase and prophase?

Back

Preview of the front of card 3

Card 4

Front

What happens during metaphase and anaphase?

Back

Preview of the front of card 4

Card 5

Front

What happens in the final stage of mitosis?

Back

Preview of the front of card 5
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