Biology 2A - cells, organs and populations

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  • Created by: shona
  • Created on: 26-12-12 12:00
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  • Biology 2A - cells, organs and populations
    • cells
      • plant and animal cells have similarities and differences
        • animal cell
          • a nucleus- contains genetic material that controls the activities of the cell
          • cytoplasm- gel like substance where most of the chemical reactions happen
            • contains enzymes that control the chemical reactions
          • cell membrane- hold the cell together and controls what goes in and out
          • mitochondria- these are where most of the reactions of the respiration take place
            • respiration releases energy that the cell needs to work
          • ribosomes- these are where proteins are made in the cell
        • plant cell
          • usually has all the bits that the animal cell has but with a few extras
          • rigid cell wall- made of cellulose it supports the cell and strengthens it
          • permanent vacuole- contains cell sap a weak solution of sugar and salts
          • chloroplasts- these are where photosynthesis occurs which makes the food for the plant they contain a green substance called chlorophyll
      • yeast is a single celled organism
        • yeast is a microorganism
        • the cell has a nucleus, cytoplasm and a cell membrane surrounded by a cell wall
      • bacterial cells have no nucleus
        • bacteria is a single cell microorganism
        • the cell has cytoplasm and a cell membrane surrounded by a cell wall
        • the genetic material floats in the cytoplasm because there is no nucleus
    • diffusion
      • diffusion is the gradual movement of particles from places where there are lots of them to where there are fewer of them
        • just the natural tendency for things to move around
      • DIFFUSION IS THE SPREADING OUT OF PARTICLES FROM AN AREA OF HIGH CONCENTRATION TO AN AREA OF LOW CONCENTRATION
      • happens in both solutions and gases- this is because the particles in these substances are free to move about randomly
      • the simplest type is when different gases diffuse through each other- this is whats happening when the smell of perfume diffuses through the air in a room
      • the bigger the difference is concentration the faster the diffusion rate
    • specialised cells
      • cells are specialised for specific functions so their structure can vary
        • palisade cells are adapted for photosynthesis
          • packed with chloroplasts more of them are crammed at the top so they are nearer to the light
          • tall shape means a lot 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 in at the top of the leaf
        • guard cells are adapted to open and close pores
          • 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 go plump
            • this makes the pores open so gases can be exchanges for photosynthesis
          • when the plant is short of water the guard cells lose water making the pores close
            • this helps stop too much water vapour escaping
          • thin outer walls and thickened inner walls make the opening and closing work
          • sensitive to light and close at night to save water without losing photosynthesis
        • red blood cells are adapted to carry oxygen
          • concave shape gives a big surface area for absorbing oxygen also helps them pass smoothly through capillaries to reach body cells
          • they are packed with haemoglobin the pigment that absorbs the oxygen
          • they have no nucleus to leave more room for the haemoglobin
        • sperm and eggs cells are specialised doe reproduction
          • the main function of the egg cells is to carry the female DNA and to nourish the developing embryo in the early stages
            • the egg cells contain huge food reserves to feed the embryo
          • when the sperm fuses with the egg the eggs membrane instantly changes its structure to stop any more sperm getting in
            • this makes sure that the offspring end up with the right amount of DNA
          • the function of the sperm is to get the male DNA to the female DNA
            • it has a long tail and a streamline head to help it swim to the egg there are a lot of mitochondria in the cell to provide the engery needed
          • sperm also carries enzymes in their head to digest through the egg cell membrane
    • cell organisation
      • specialised cells
        • cells are specialised for specific functions so their structure can vary
          • palisade cells are adapted for photosynthesis
            • packed with chloroplasts more of them are crammed at the top so they are nearer to the light
            • tall shape means a lot 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 in at the top of the leaf
          • guard cells are adapted to open and close pores
            • 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 go plump
              • this makes the pores open so gases can be exchanges for photosynthesis
            • when the plant is short of water the guard cells lose water making the pores close
              • this helps stop too much water vapour escaping
            • thin outer walls and thickened inner walls make the opening and closing work
            • sensitive to light and close at night to save water without losing photosynthesis
          • red blood cells are adapted to carry oxygen
            • concave shape gives a big surface area for absorbing oxygen also helps them pass smoothly through capillaries to reach body cells
            • they are packed with haemoglobin the pigment that absorbs the oxygen
            • they have no nucleus to leave more room for the haemoglobin
          • sperm and eggs cells are specialised doe reproduction
            • the main function of the egg cells is to carry the female DNA and to nourish the developing embryo in the early stages
              • the egg cells contain huge food reserves to feed the embryo
            • when the sperm fuses with the egg the eggs membrane instantly changes its structure to stop any more sperm getting in
              • this makes sure that the offspring end up with the right amount of DNA
            • the function of the sperm is to get the male DNA to the female DNA
              • it has a long tail and a streamline head to help it swim to the egg there are a lot of mitochondria in the cell to provide the engery needed
            • sperm also carries enzymes in their head to digest through the egg cell membrane
      • the process in which cells become specialised is called differentiation
        • this occurs during the development of multicellular organism
          • these specialised cells form tissues which form organs which form organ system
          • large multicellular organisms(squirrels) have different systems inside them for exchanging and transporting materials
      • similar cells are organised in to tissues
        • these work together to carry out a particular function
        • muscular tissue
          • contracts to move whatever its attached to
        • glandular tissue
          • makes and secretes chemicals like enzymes and hormones
        • epithelial tissue
          • covers some parts of the body( inside the gut)
      • tissues are organised into organs
        • different tissues work together to perform a certain function
        • muscular tissue
          • moves the stomach wall to churn up foo
        • glandular tissue
          • makes digestive juices to digest the food
        • epithelial tissue
      • organs are organised in to organ systems
        • organ systems are groups of organs working together to perform a particular function
        • glands(pancreas and salivary glands) produce digestive juices
        • stomach and small intestine digest food
        • liver produces bile
        • small intestine absorbs soluble food molecules
        • large intestine absorbs water from undigested food
    • plant structure and photosynthesis
      • plant cells are organised into tissues and organs too
        • plants are made of organs like stems roots and leaves these organs are made of tissues
        • mesophyll tissue
          • this is where most of the photosynthesis in a plant occurs
        • xylem and phloem
          • they transport things like water mineral ions and sucrose around the plant
        • epidermal tissue
          • this covers the whole plant
      • carbon dioxide+ water---> sunlight chlolorphyll--> glucose+oxygen
      • photosynthesis produces glucose using sunlight
        • photosynthesis is the process that produces food in plants and algae the food produces is glucose
        • happens in the chloroplasts
          • chloroplasts contain a green substance called chlorophyll which absorbs sunlight and uses its energy to convert co2 and water into glucose oxygen is also produced as a by-product
        • photosynthesis happens in the leaves of all green plants this is largely what leaves are for
  • palisade leaf cells are grouped together at the top of the leaf where most of the photosynthesis happens
  • guard cells are therefore adapted to there function of allowing gas exchange and controlling water loss within a leaf
  • red blood cells are an important part of blood
  • sperm and eggs are very important cells in reproduction
  • the digestive system exchanges material with the environment by taking in nutrients and releasing substances such as bile

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