Additional Biology (Unit 2)-Specialised Cells

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Palisade Leaf cells- adapted for photosynthesis.

Packed with chloroplasts for photosynthesis. More of them are crammed at the top of the cell, this is so that they are neare to the light.

Tall shape means alot of surface area exposed down the side for absorbing CO2 from the air in the leaf.

Thin shape means that you can pack loads of them at the top of the leaf, these Palisade leaf cell are packed at the top of the leaf where photosynthesis happens.

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Guard Cells- adapted to open and close pores.

These are a special kidney shape which opens and closes the stomata in the leaf.

When the plant has lots of water the guard cells fill with it and go plump and turgid. This makes the stomata open so gases can be exchanged for photosynthesis.

When the plant is short of water the guard cells lose water and become flaccid, making the stomata close. This helps stop too much water vapor escaping.

Thin outer walls and thickened inner walls make the opening and closing of the stomata work.

They are also sensitive to light and close at night to save water without losing out on photosynthesis.

Guard cells are adapted to their function of allowing gas exchange and controlling water loss within the leaf.

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Red Blood cells- adapted to carry oxygen

Concave shape gives a big surface area for absorbing oxygen. It also helps them pass smoothly through capillaries to reach body cells.

Packed with haemoglobin, the pigment that absorbs oxygen.

They have no nucleus, to leave more room for haemoglobin,

Red blood cells are an important part of the blood.

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Sperm and Egg cells- specialised for reproduction

The main function of the egg cell are to carry the female DNA and to nourish the developing embryo in the early stages. The egg cell contains huge food reserves to feed the embryo.

When a sperm fusses with the egg, the egg's membrane instantly changes its structure to stop more sperm getting in. This makes sure the offspring ends up with the right amount of DNA.

The function of a sperm is basically to get male DNA to the female DNA. It has a long tail and a streamlined head to help it swim to the egg. There are a lot of mitochondria in the cell to provide the energy needed.

Sperm also carry enzymes in their heads to digest through the egg cell membrane.

Sperm and egg cells are very important in reproduction.

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