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Cells and organelles
Cells can be Eukaryotic or Prokaryotic
1)Eukaryotic cells are complex and include all animal and plant cells
2) Prokaryotes are smaller and simpler
Structure and function of organelles

Organelle Description Function
Nucleus A large organelle surrounded Chromatin is made from
by a nuclear…

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is the matrix, which contains are very active and require lots
enzymes involved in respiration of energy.

Prokaryotic cells are simpler than eukaryotic cells (they include bacteria and blue green algae).

Larger cells 2-200µm diameter Extremely small (less than 2.0µm diameter)
DNA is linear DNA is circular

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2) Fibrous connective tissue ­ helps to force air back out of the lungs when exhaling
3) Blood vessels ­ capillaries surround the alveoli.
Organs are in systems
Organs work together to form organ systems ­ each system has a particular function.
For example, the respiratory system is made up…

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Root tips can be stained to observe mitosis

1. Cut the tip from a growing root (e.g. from a broad bean or garlic). Your root tip should be
about 5mm long.
2. Place the root tip in watch glass (a small shallow bowl) and add a few drops of hydrochloric…

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Egg cells are much larger than sperm cells

Cell division by meiosis

Meiosis is a type of cell division that happens in the reproductive organs to produce
Cells that divide by meiosis have the full number of chromosomes to start with, but the cells
formed have half the number.…

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4. The sperm head fuses with the cell membrane of the egg cell. This triggers a cortical
reaction ­ the egg releases the contents of vesicles called cortical granules into the
space between the cell membrane and the zone pellucida.
5. These chemicals from the cortical granules make the zona…

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organism and extraembryonic (cells of the placenta and umbilical cord)
2) Pluripotency ­ ability of a stem cell to produce all the specialised cells in an organism but
not extraembryonic cells.
Totipotent stem cells in humans are only present in the early life of an embryo ­ they
differentiate into…

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Stem cells in medicine
Stem cells can be used to treat some diseases

Stem cells can develop into any specialised cell, so scientists think they could be used to
replace damaged tissue in a range of diseases
Some stem cell therapies already exist. For example, treatment for leukaemia ( cancer…

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embryos aren't viable , they cannot survive past a few days and cannot produce a foetus if
placed in the womb
Some people think only adult stem cells should be used as this doesn't involve the
destruction of life but they cannot develop into any cell.
The decision makers must…

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most are influenced by both genotype and the environment

Height is polygenic and affected by environmental factors, especially nutrition. E.g. tall parents
usually have tall children, but if the children are undernourished they won't grow to the maximum
Monoamine Oxidise A (MAOA) is an enzyme that breaks down monoamines…





Aniso Osman


such good info thank youuu 

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