Biology

• The Nucleus controls all activities in the cell and contains the DNA of the cell.
• An example of a prokaryotic cell is a bacterial cell.
• Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration.
• Active transport moves substances from a more dilute solution to a more concentrated solution (against the concentration gradient)
• Active transport requires energy from respiration.
• An example of Active transport is the lumen of the small intestine. The sugars cannot diffuse into the cell and so they are carried in by active transport. Once they are in the cell, they can be transported into the blood and carried around the body.
• An example of active transport is that it is used to move ions into root hair cells.
• Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.
• Dilute solutions contain a high concentration of water and concentrated solutions contain a low concentration of water.
• The cytoplasm of cells is a relatively concentrated solution. If this cell is placed in water then osmosis will take place. Water will move from outside to inside a cell.
• What will happen to an animal cell if it is placed in a very concentrated solution?

  It will shrink.
• Body cells contain two of each chromosome. They are paired.
• Human body cells contain 23 pairs of chromosomes.
• chromosomes carry a large number of genes
• Gametes have chromosomes that are not paired.
• Animal and plant cells contain a large number of cells. This means that cells have to be able to divide. This is called the cell cycle.
• In the 1st stage of the cell cycle, the DNA replicates to form two copies of each chromosome. In the 2nd stage of the cell cycle mitosis takes place. One set of chromosomes is pulled to each end of the cell. The nucleus also divides. In the 3rd stage of the cell cycle, the cytoplasm and the cell membrane divide to form two identical cells.
• Mitosis is essential for growth and development of multicellular organisms.
• Mitosis takes places when an organism repairs itself. Mitosis happens during asexual reproduction.
• Sperm cells are specalised for reproduction.
• Nerve cells are specalised for rapid signalling. They carry electrical signals to different parts of the body
• Sperm cells have a long tail to help it swim to the egg and they contain lots of mitochondria to provide the energy needed.
• Nerve cells are long to help it carry more distance.
• Muscle cells function is to contract quickly. They are long so they have space to contract and contain lots of mitochondria to generate energy.
• Root hair cells are specailsed by having a large surface area for absorbing water and minerals from the soil. They also have long hairs so they can stick into the soil.
• Stem cells are found in early human embryos.
• Stem cells can be grown in labs to produce clones and to be used for medicine and research.
• Adults have stem cells which can be found in bone marrow
• Stem cells from a healthy human can replace faulty blood cells in a patient.
• Thrapeautic cloning is a process that produces an embryo with genes that are identical to the patients. However there are some risks. The cells grown in the lab could become contaminated with a virus, which could be passed onto the patient.
• The larger the concentration gradient, the faster the diffusion.
• The aveoli are specalised by having good blood supply and very thin walls
• Magnification = image size/size of real object
• What is lime water used to test for and what happens?

  Used to test for carbon dioxide and goes cloudy if present
• Stem cells are unspecialised cells which can become any type of cell needed
• List the levels of organastion of multicellular organisms

  cells, tissues, organs, organ systems, organism
• An iodine test is used to detect the presence of starch. It goes yellow to blue if present
• Biuret test is used to detect the presence of protein. It goes blue to purple if present
• A catalyst increases the rate of chemical reactions without changing chemically themselves
• Enzymes are biological catalysts