Cell Biology

• All plant and animal cells are eukaryotic
• Bacteria are prokaryotic cells
• Nucleus contains genetic material
• Cytoplasm is where most chemical reactions happen
• Cell membrane controls what goes in and out of the cell
• Mitochondria is where most aerobic respirations happens. Respirations transfers energy that the cell needs to work.
• Ribosomes are where proteins are made in the cell.
• Plants cells have a cell wall that is made of cellulose. It supports and strengthens the cell.
• A plant cell has a permanent vacuole which contains cell sap.
• A plant cell has chloroplasts where photosynthesis happens. Photosynthesis makes food for the plant.
• Specialised cells are cells that carry out a specific function.
• The process by which cells change to become specialised is called differentiation.
• Some cells are undifferentiated, these are called stem cells.
• Sperm Cells take the male DNA to the egg. A sperm cell has a tail to help it swim to the egg. It has a lot of mitochondria. These provide energy for swimming.
• Nerve cells carry electrical signals around the body. Nerve cells are long to cover more distance of the body. They have branches at the end to connect tot other nerve cells.
• Muscle cells are long so they have space to contract. They have lots of mitochondria. These provide energy for contracting.
• Roots hair cells absorb water and minerals. They grow into long hairs that stick out of the soil. This gives the plant a big surface area for absorbing water and mineral ions from the soil.
• Phloem cells transport food. Xylem cells transport water. Xylem cells are hollow and phloem cells have very few sub cellular structures so there is lots of space inside the cells for stuff to flow through them.
• Chromosomes contain genetic information.
• The nucleus of a cell contains chromosomes.
• Chromosomes are coiled up lengths of DNA molecules.
• There are 23 pairs of chromosomes in a human cell
• Stem cells can differentiate into different types of cells
• Cells differentiate (change) to become specialised at their job.
• Stem cells found in early human embryos are called embryonic stem cells. Embryonic stem cells can
• Adult stem cells can only produce certain types of specialised cell eg. blood cells
• Embryonic stem cells could be used to replace faulty cells in sick people
• There are risks involved using stem cells in medicine.
• Some people think that feel that embryos shouldn't be used for research because each one could be a human life. Others think that curing patents who are suffering is more important than the right of embryos.
• Plants have tissues called meristems.
• Meristems are where growth occurs - in the tips of shoots and roots.
• Meristems contain stem cells that can differentiate into any type of plant cell. They can do this all through the plant's entire life. These stems cells can be used to make clones of plants quickly and cheaply. Clones can be made of rare species or crop plants.
• Diffusion is the spreading out of particles from an area of high concentration to an area of lower concentration.
• The difference in concentration is called the concentration gradient. The bigger the difference in concentration, the fast the rate of diffusion.
• Molecules can flow through the cell membrane from where there is higher concentration to where there is lower concentration.
• Osmosis is the diffusion of water molecules across a partially permeable membrane from an area of less concentrated solution to a more concentrated solution.
• Active transport is the movement of molecules from an area of low concentration to an area of high concentration against a concentration gradient.
• Roots hair cells take in minerals using active transport. The concentration of minerals is usually higher in the root hair cell that in the soil around them.
• Cells use diffusion to take in substances from the environment such as oxygen. They also use diffusion to get rid of waste products such as carbon dioxide and urea.
• Gas exchange happens in the lungs. Oxygen and carbon dioxide are exchanged in the lungs. The lungs contain millions of little air sacs called alveoli. This is where gas exchange happens.