Edexcel Biology Unit 2

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Name two prokaryotic cells
Bacteria and Archaea
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Name three eukaryotic cells
Animal, Plant and Fungi
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Where are membrane-bound organelles and a nucleus with an envelope found-eukaryotic or prokaryotic cells?
Only Eukaryotic (Animals and Plants)
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How does DNA differ in eukaryotic and prokaryotic cells?
It is a loop in prokaryotic cells and separate strands in eukaryotic cells
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Which cells can contain slime capsules?
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Which cells contain a flagellum?
Prokaryotic cells can have a simple flagellum and animal cells can have a complex flagellum
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Which cells have a cell wall?
Prokaryotic cells (bacterial cell wall) and Plant cells (cellulose cell wall)
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How are extracellular enzymes formed and secreted?
Animo acids made into proteins by ribosomes on rER. Proteins packaged at the end of rER and pinched off into vesicles which move to Golgi apparatus where they're modified. Vesicles move to the cell surface mem and release proteins outside the cell.
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What is tissue?
Cells of a particular type working together to perform a particular function
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What are organs?
Several different tissues which work together to carry out a particular function
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Name the stages of Mitosis
Prophase, Metaphase, Anaphase, Telophase
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Describe Prophase
The chromosomes continue to condense and become visible. The nuclear envelope breaks down and the nucleolus disappears. Spindle forms and centrioles move to opposite poles of the cell (only in animal cells)
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Describe Metaphase
Chromosomes (as paired chromatids) line up at the equator. Chromosomes attach to spindle fibres at the centromere.
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Describe Anaphase
Spindle fibres contract pulling chromatids apart leading with the centromere.
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Describe Telophase
Chromosomes decondense (and become invisible). Nuclear envelope reforms and the nucleolus reappears.
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Describe cytokinesis
The cell divides
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Describe interphase
Newly formed cell grows. Cell undertakes its normal function. Cell prepares to divide by replicating its chromosomes, chromosomes start to condense, some organelles increase in number.
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In the root tip squash practical, name a suitable stain and a suitable acid.
Orcein Stain and Hydrochloric acid
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Name the two varieties of Meiosis
Crossing over (swapping part of their genetic material) and independent assortment (changing places)
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Name the main features of a Sperm and how they're useful
Flagellum (whips back and forth to propel sperm). Nucleus (contains haploid number of chromosomes). Acrosome (contains digestive enzymes to burrow through Zona Pellucida). Mitochondria (produces ATP by aerobic respiration providing energy to move)
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Name the main features of an Egg cell and how they're useful
Zona Pellucida (a protective layer made of glycoproteins allowing only one sperm to reach the egg). Nucleus (haploid number of chromosomes). Lipid globule (provides energy for young embryo).
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Describe the structure of a pollen grain
It contains two haploid nucleus (the tube nucleus and the generative nucleus). It has a tough and waterproof exterior called the exine.
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How do pollen grains reach the stigma of a flowering plant?
Pollen grains are carried from one flower to another by insects, birds or the wind (pollination).
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How does the contents of the pollen grain reach the embryo sac?
If the stigma is the same species as the pollen grain and if it is ripe, it secretes substances that stimulate the pollen grain to germinate. An area in the exine breaks down and a tube grows out. It digests style tissue and uses it to grown further.
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What happens to the generative nucleus while the pollen tube is growing down the style?
The generative nucleus divides by mitosis to form two male gametes.
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How do the two male gametes enter the embryo sac in plant fertilisation?
The pollen tube enters the ovule through a little gap in its coverings called the micropyle. Once the tube has reached the embryo sac, the tube nucleus disintegrates and the two male games enter the embryo sac.
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What does a plants embryo sac contain?
It contains an egg cell (female gamete), two synergid cells, a primary endosperm nucleus and three antipodal cells.
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Describe double fertilisation in the embryo sac in plants
One male gamete fuses with the egg cell forming a diploid zygote which will develop into the embryo. The other fuses with the diploid nucleus forming a triploid endosperm nucleus which will divide to form tissue used as nutrients for the early embryo
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Name the three types of stem cells
Embryonic, Totipotent, Pluripotent
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Define stem cells
Cells that retain the ability to divide and produce daughter cells which can become specialised for particular functions.
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Define phenotype
The phenotype of a cell is its measurable and observable features
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Name organelles which are only found in animal cells
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Name organelles which are only found in plant cells
Chloroplasts, Amyloplasts, Vacuole
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Describe chloroplasts
Organelles surrounded by an envelope which contain chlorophyll
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Describe amyloplasts
Organelles surrounded by an envelope in which starch is stored
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Describe a vacuole in a plant cell
A space bounded by a membrane known as the tonoplast containing cell sap.
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Describe pits
A dip in the cell wall of a plant which makes it easier for substances ti diffuse across it
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What does a middle lamella connect?
The cell walls of adjacent plant cells
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What does a plasmodesmata connect?
Adjacent plant cells (connects the cells surface membrane)
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What is starch?
An energy storage compound found in many plant organs (inside amyloplasts and chloroplast). It can be hydrolysed to glucose and respire when energy is required.
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What is cellulose?
A structural compound which forms the fibres making up plant cell walls. It is difficult to hydrolyse as there are few enzymes that can break the links between the glucose molecules in the chain.
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Starch and cellulose are both polysaccharides what does this mean?
They consist of hundreds of glucose molecules linked together in long chains by 1-4 glycosidic bond.
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Name the main difference between starch and cellulose
Starch is alpha glucose, cellulose if beta glucose. In starch, hydrogen bonds form to hold spiral shape; in cellulose, hydrogen bonds form between different molecules holding them in parallel forming microfibrils.
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Name the positives of starch and cellulose
Starch is compact and good for storage. Cellulose has a high tensil strength.
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Describe a cellulose primary and secondary cell wall
Primary: fairly thin and has cellulose microfibrils running in all directions. Secondary: thicker and has several layers of cellulose microfibrils running in parallels but in different directions.
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Describe sclerenchyma fibres
Long and thin. No living content. Cell walls filled up with lignin which is hard, strong and waterproof. Helps to support plant stems.
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Describe xylem vessels
Transports H2O and mineral salts in solution. Lignin and no living content. Ends broken down so vessels are stacked to form one long tube. Contains pits to allow H2O to move sideways between vessels and into surrounding tissue. Provides support.
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In a vascular bundle, what is the position of the sclerenchyma fibres and the xylem vessels?
Sclerenchyma fibres = On the outside. Xylem vessels = On the inside.
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What do plants need water for?
Photosynthesis. Maintaining turgor (cells absorb H2O through osmosis through their cell surface membrane if the water potential on the outside of the cell is greater than inside causing swelling). Transport (aqueous solutions). Cooling (evaporation)
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What do plants need nitrate for?
Nitrate ions convert carbohydrates (made in photosynthesis) to amino acids and nucleotides. The amino acids are used to make proteins, many of which act as enzymes. Nucleotides are used to make RNA and DNA.
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What do plants need calcium ions for?
The matrix of the cell wall and the middle lamella are made of calcium pectate. Calcium ions are essential in the formation of microtubules and therefore cell division. Calcium ions are also used in signalling.
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What do plants need magnesium for?
Chlorophyll molecules contain magnesium. Magnesium ions are also essential for the activity of many enzymes including those involved with glycolysis and the Calvin cycle.
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Name the main features of William Withering's historical drug testing
Testing different methods and dosages on 156 patients then publishing the results to doctors to help them prescribe the right dose of medicine.
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Name the main features of modern drug testing
Drug tested on living cells and animals in a lab. P1:small no. of healthy volunteers to see side effects and safe doses. P2:200-400 patients to see if drug treats condition/best dose/ new side effects. P3:thousands of patients -drug in everyday life
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Define placebo
A drug treatment that looks identical in every way to the drug being tested but is chemically inactive.
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Define biodiversity
The range of habitats, communities and species in an area, and the genetic variation that exists within the population of each species
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Define community
All the different organisms and all the different species that live in the same place at the same time
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Define species richness
The number of different species in the gene pool of a species
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Define genetic diversity
The number of different alleles in the gene pool of a species
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Define population
All the individuals of a particular species that live in the same place at the same time
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Name the different adaptations
Behavioural (what an organism does). Physiological (chemical changes). Anatomical (structural changes e.g. fur on a bear)/
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Describe the classification system
Eukarya and Archaea more closely related than Bacteria
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Name the benefits of zoos
Research (behaviour/diet). Education (students/campaigns). Reintroduction programmes. Captive breeding (moving males between zoos (stud books)/IVF/surrogate mums if female numbers low)
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Describe the acrosome reaction in the fertilisation in mammals
Acrosome releases digestive enzymes when sperm head meets zona pellucida. Enzymes digest a channel in bona pellucid for sperm to burrow through to the cell surface membrane of the egg.
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Describe how the membranes fuse in the fertilisation in mammals
Cell surface membrane of sperm and egg fuse enabling haploid nucleus from sperm to enter the cytoplasm of the egg cell.
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Describe the egg cell response (cortical reaction) in the fertilisation in mammals
Special vesicles (cortical granules) move towards and fuse with the cell surface membrane. They release their contents (through exocytosis) which cause changes in the surface layers of the egg that stop other sperm from entering the egg cell.
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Describe how meiosis is restarted in the fertilisation in mammals
The presence of the sperm nucleus in the cytoplasm of the egg cell causes the second division of meiosis to occur. The chromosomes from the haploid sperm and egg nucleus combine to restore the full complement of chromosomes (the diploid number).
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Other cards in this set

Card 2


Name three eukaryotic cells


Animal, Plant and Fungi

Card 3


Where are membrane-bound organelles and a nucleus with an envelope found-eukaryotic or prokaryotic cells?


Preview of the front of card 3

Card 4


How does DNA differ in eukaryotic and prokaryotic cells?


Preview of the front of card 4

Card 5


Which cells can contain slime capsules?


Preview of the front of card 5
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