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116 Cards in this Set
- Front
- Back
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What is the cell cycle? |
The process that all body cells in multicellular organisms use to grow and divide.
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When does the cell cycle start? |
When a cell has been produced by cell division.
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When does the cell cycle end? |
With the cell dividing to produce identical cells.
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What does the cell cycle consist of? |
A period of cell growth and DNA replication (metaphase) and a period of cell division (M phase) |
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What does M phase involve? |
Mitosis (nuclear division) and cytokineses (cytoplasmic division) |
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What is interphase? |
Cell growth. Subdivided into three separate growth stages (G1, S, G2) |
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How is the cell cycle regulated? |
By checkpoints. They occur at key points during the cycles to make sure its ok for the process to continue. |
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What happens in the gap 1 phase? |
Cells grow and new organelles and proteins are made. |
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What happens in the G1 checkpoint? [2] |
- Cell check chemicals needed for replication are present - Checks for any damage to DNA before S phase |
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What happens in the S phase? |
Cell replicates DNA, ready to divide by mitosis. |
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What happens in the Gap 2 phase? |
Cell keeps growing, proteins needed for cell division made. |
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What happens in the G2 checkpoint? |
Cell checks whether all DNA has been replicated without any damage. |
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Why is mitosis needed? |
Growth of multicellular organisms and repairing damaged tissue. |
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What is mitosis a method of? |
Asexual reproduction for some plants, animals and fungi. |
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What is mitosis described as? |
A series of division stages - though it is one continuous process. |
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What is the order of the stages in mitosis? |
Prophase, metaphase, anaphase, telophase. |
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What comes before mitosis in the cell cycle? |
Interphase. |
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What is interphase? |
Where cells grow and replicate their own DNA ready for division. |
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What happens in interphase? [4] |
- Cell carries out normal functions, prepares to divide - Cells DNA unravelled and replicated to double genetic content - Organelles replicated so has spare ones - ATP content increased to provide energy for divison |
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What happens in prophase? [3] |
- Chromosomes condense, getting shorter and fatter - Centrioles start to move to opposite ends of the cell, forming the spindle - Nuclear envelope breaks down and chromosome lie free in cytoplasm |
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What are chromosomes made of as mitosis begins? |
Two strands joined in the middle by a centromere. Separate strands are called chromatids. |
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Why are there two strands in prophase? |
Each chromosome has already made an identical copy of itself during interphase. |
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What happens to the chromatids once mitosis is over? |
They end up s one strand chromosome in the new daughter cells. |
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What happens in metaphase? [2] |
- Chromosomes each with two chromatids line up along middle of the cell and become attached to spindle by centromere - Metaphase checkpoint, cell checks all chromosomes are attached to spindle before mitosis continues |
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What happens in anaphase? [2] |
- Centromeres divide, separating sister chromatids - Spindles contract, pulling chromatids to opposite ends of cell, centromere first |
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What happens in telophase? [3] |
- Chromosomes reach opposite poles on spindle - Uncoil, become long and thin again, called chromosomes again - Nuclear envelope forms around each group of chromosomes, two nuclei |
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What happens in cytokineses? [2] |
- Cytoplasm divides, in animal cells cleavage furrow forms to divide cell membrane - Two daughter cells genetically identical to original cell and each other |
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when does cytokinesis begin/end? |
Usually begins in anaphase and ends in telophase. |
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How can you see chromosomes under a microscope? |
Stain them. |
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Why is viewing chromosomes under a microscope good? |
You can see what happens during mitosis. |
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What happen in sexual reproduction? [2] |
- Two gametes (egg and sperm)join together at fertilisation to form a zygote - Zygote divides and develops into a new organism |
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What is meiosis? |
Type of cell division that happens in the reproductive organs to produce gametes. |
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What kind of division does meiosis involve? |
Reduction division. |
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How many chromosomes do cells that divide by meiosis have? |
The full number, 46. |
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How many chromosomes do cells that are formed from meiosis have? |
Half the number, 23. |
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What are haploid cells? |
cells with half the normal number of chromosomes. |
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Why are cells formed by meiosis all genetically different? |
Each new cell ends up with a different combination of chromosomes. |
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What are the two divisions in meiosis? |
Meiosis I and meiosis II.
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Which division in meiosis is the reduction one? |
Meiosis I, halves the chromosome number. |
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What happens in meiosis during interphase? |
DNA unravels, replicates to produce double armed chromosomes (sister chromatids). |
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What happens in prophase I? [3] |
- Chromosomes condense, getting shorter and fatter - Chromosomes arrange into a homologous pair and crossing over occurs - Centrioles start moving to opposite ends of cell, form spindle fibres. Nuclear envelope breaks down. |
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What are homologous pairs? |
Chromosomes that make up each pair, same size and have same genes although could have different versions of these genes (alleles). |
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What happens in metaphase I? |
Homologous pairs line up across centre of cell, attach to spindle fibres by centomeres. |
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What happens in anaphase I? |
Spindles contract, separates homologous pairs, one chromosome to each end of cell. |
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What happens in telophase I? |
Nuclear envelope forms around each group of chromosomes. |
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What happens in cytokineses after meiosos |
It occurs and two haploid daughter cells are produced. |
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What happens in meiosis II? |
Stages a lot like mitosis apart from anaphase II. |
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What happens in anaphase II? [3] |
- Sister chromatids separated -Each new daughter cell inherits one chromatid from each chromosome - Four haploid daughter cells are produced (gametes) |
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What happens in the cross over in prophase I? [2] |
- Chromatids twist around each other and bits swap over - Contain same genes but have a combination of different alleles |
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What are the two things during meiosis that lead to genetic variation? |
Crossing over of the chromatids and independent assortment of chromosomes. |
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What does the crossing over of chromatids mean? |
Each of the fur daughter cells formed contain chromatids with different alleles. |
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What is each homologous pair made up of? |
One paternal chromosome and one maternal chromosome. |
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What is independent assortment of chromosomes? [2] |
- When homologous pairs line up and separate, it is completely random which chromosome ends up in which daughter cell - Four daughter cells have different combinations of maternal and paternal chromosomes |
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What does independent assortment of chromosomes lead to? |
Genetic variation in potential offspring. |
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What are multicellular organisms made up from? |
Many different cell types that are specialised for their function. |
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What are stem cells? |
Unspecialised cells that can develop into different types of cell. |
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Where are stem cells in humans? |
Early embryos and a few places in adults. |
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What is the difference between embryo stem cells and adult ones? |
Embryo stem cells can develop into any type of human cell; adult stem cells have a limited range. |
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Why do stem cells divide? |
To become new cells, which then become specialised. |
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What is differentiation? |
The process by which a cell becomes specialised for its job. |
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What are adult stem cells used for in animals? |
To replace damaged cells. |
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Why are stem cells needed in plants? |
To make new shoots and roots throughout their lives. |
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What can stem cells in plants do? [2] |
- Differentiate into various plant tissues such as xylem and phloem - Divide to produce more undifferentiated stem cells |
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What are bones? |
Living organs, containing nerves and blood vessels. |
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What do the main bones of the body have? |
Marrow in the centres. |
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What do adult stem cells in bone marrow do? |
Divide and differentiate to replace worn out blood cells. |
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What are red blood cells called? |
Erythrocytes. |
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What are white blood cells that help fight infection called? |
Neutrophils. |
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Where are stem cells found in plants? |
In the meristems. |
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What are meristems? |
Parts of the plant where growth can take place. |
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What happens in the root and stem to the stem cells? |
Stem cells of the vascular cambium divide and differentiate to become xylem vessels and phloem sieve tubes. |
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Why might stem cells be able to treat Alzheimer's? [2] |
- With it, nerve cells in the brain die in increasing numbers, resulting in memory loss - Researchers hoping to use stem cells to regrow healthy nerve cells |
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Why might stem cells be able to treat Parkinson's? [3] |
- Suffer from tremors and causes loss of particular type of nerve cell found in the brain - Cells release dopamine, which is needed to control movement - Transplanted stem cells may help regenerate depomine producing cells |
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What are stem cells used by scientists researching? |
Developmental biology - how organisms grow and develop. |
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What can studying stem cells help us understand? |
Things like developmental disorders and cancer. |
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What do neutrophils do? |
Defend the body against disease. |
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How are neutrophils adapted to their function? [2] |
- Flexible shape allows them to engulf foreign particle or pathogens - Many lysosomes in cytoplasm contain digested enzymes to break down engulfed particles |
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What do erythrocytes do? |
Carry oxygen in the blood. |
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How are erythrocytes adapted to their function? [2] |
- Biconcave disc shape provides large surface area for gas exchange - No nucleus so more room for haemoglobin |
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What do epithelial cells do? |
Cover the surface of organs/ |
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How are epithelial cells joined? |
By interlinking cell membranes and a membrane at their base. |
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How are epithelial cells adapted to their function? [2] |
- Ciliated epithelia have cilia that beat to move particles away - Squamous epithelia are very thin to allow efficient gas diffusion |
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How are sperm cells adapted to their function? [3] |
- Have a flagellum so their can swim to the egg - Lots of mitochondria to provide energy to swim - Acrosome contains digestive enzymes so sperm can penetrate egg |
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What do palisade mesophyll cells in leaves do? |
Most of the photosynthesis. |
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How are palisade mesophyll cells adapted to their function? [2] |
- Contain many chloroplasts, can absorb a lot of sunlight - Walls are thin, CO2 can easily diffuse in |
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What do root hair cells do? |
Absorb water and minerals from the soil. |
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How are root hair cells adapted to their function? [3] |
- Large surface area for absorption - Thin, permeable cell walls for entry and water and ions - Cytoplasm contains extra mitochondria to provide energy for active transportH |
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How are guard cells found? |
In pairs, with a gap to form stoma. |
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What do stoma do? |
Tiny pores in surface of leaf for gas exchange. |
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How are guard cells adapted to their function? [3] |
- In light, guard cells take up water and become turgid - thin outer walls and thick inner walls force them to bend outwards, opening stomata - This allows leaf to exchange gases for photosynthesis |
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What is a tissues? |
A group of cells (plus any extracellular material secreted by them) that are specialised to work together to carry out a particular function. |
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What is squamous epithelium? |
A single layer of flat cells lining a surface, found in many places including alveoli in the lungs. |
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What is ciliated epithelium. |
A layer of cells covered in cilia. |
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Where is ciliated epithelium found? |
On surfaces where things need to be moved, in trachea for example. |
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What is muscle tissue? |
Made up of bundles of elongated cells called muscle fibres. |
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What are the three different types of muscle tissue? [3] |
- Smooth (lines stomach) - Cardiac (found in heart) - Skeletal (used to move) |
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What is cartilage? |
A type of connective tissue found in the joints. Shapes and supports the ears, nose and windpipe. w |
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What is xylem tissue? |
A plant tissue. |
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What does xylem tissue do? |
Transports water around the plant and supports it. |
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What does xylem tissue contain? |
Hollow xylem vessel cells which are dead and living parenchyma cells. |
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What do parenchyma cells do? |
Fill in gaps between vessels. |
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What is a xylem vessel tissue like? |
Has a thickened wall perforated by pits. |
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What does phloem tissue do? |
Transports sugars around the plant. |
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How is phloem tissue arranged? |
In tubes, made up of sieve cells, companion cells and ordinary plant cells. |
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What does each sieve cell have? |
Sieve plates. |
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What are sieve plates? |
End walls with holes in them, so sap can easily move through them. |
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What is an organ? |
A group of different tissues that work together to perform a particular function. |
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Give two examples of organs, plant and animal. |
The lungs and leaves. |
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What tissue do the lungs contain? |
Squamous epithelial tissue in the alveoli, ciliated epithelial tissue in the bronchi, elastic connective tissue and vascular tissue in the blood vessels. |
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What tissue do the leaves contain? |
Palisade tissue for photosynthesis, epidermal tissue to prevent water loss from leaf, xylem and phloem tissue in the veins. |
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What are organ systems? |
Organs working together.
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Two examples of organ systems? |
Respiratory and circulatory systems. |
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What is the respiratory system made up of? |
All the organs, tissue and cells involved in breathing. |
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What are some parts of the respiratory system? |
Lungs, trachea, larynx, nose, mouth, diaphragm. |
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What is the circulatory system made up of? |
All the organs involved in blood supply. |
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What are some parts of the circulatory system? |
Heart, arteries, veins, capillaries. |
