Key Concepts - Biology triple GCSE

• A cell is the smallest unit of life that can replicate
• A eukaryotic cell has a nucleus while a prokaryotic cell has no nucleus
• Bacteria is a prokaryotic cell that is uni-cellular and has a cell wall, cell membrane, ribosome, plasmid DNA, Chromosal DNA and a flagella
• What is the job of the flagella - to make the cell swim and move around
• A chromosal DNA controls cell activity and freely floats around the cell in a circular chromosome
• Plasmid DNA is simply extra DNA that is found in bacteria.
• An animal cell has a nucleus, cytoplasm, cell membrane, mitochondria, ribosomes.
• A plant cell has a cell wall, cell membrane, cytoplasm, nucleus, mitochondria and chloroplasts, large vacuole, ribsomes
• The cell wall is rigid and made of cellulose that supports and strengthens the cell.
• The cell membrane controls what enters and leaves the cell
• The cytoplasm is where the chemical reactions occur
• Ribosome is where protein synthesis happens
• The nucleus contains the genetic material of the cell and controls the activities of the cell.
• The mitochondria provides the cell energy and where respiration reactions occur
• A large vacuole contains cell sap, which is a weak solution of sugar and salt, that supports the cell and adds structure
• The chloroplasts are green and are where photosynthesis occurs as they contain chlorophyll
• A specialised cell is a haploid which only contains half the nymber of chromosomes
• An egg cell contains cytoplasm to feed embryo and a nucleus to store genetic information. Straight after fertilisation the eggs membrane changes structure to stop any further sperm entering
• Sperms have a long tail to swim towards an egg cell and a head with acrosome containing enzymes to penetrate the egg cell's membrane. The mid section contains lots of mitochondria to provide energy to the sperm to swim to the egg.
• Ciliated epithelial cells line the surfaces of organs and the human airways to move substances such as mucus with the small hairs called cilia
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• How does the immune system respond to pathogens. -pathogen makes immune system kick into destroy -lymphocytes, a type of white blood cell make antibodies that are specifically made for a specific pathogen and antibodies attack the pathogen -memory lymphocytes are made when a pathogen enters the body once so if the same pathogen enters the body send the antibody to kill it
• A stem cell is an undifferentiated cell that is very important for growth and developmen.
• Stem cells divide by mitosis to become new cell which then differentiate
• Stem cells found in: early human embryo - stem cells can divide and produce any kind of cell in this type of cell. adults - have stem cells in bone marrow but they can’t produce any cell type only certain ones. adult animals - replace damaged cells and make new skin and blood cells
• Meristem contain plant stem cells. It’s a cell that divides by mitosis and it found at the tips of roots and shoots. They produce unspecialised cell that can divide to form any cell type in plant. They can form specialised cells such as xylem and phloem
• Stem cells can replace faulty cells

  1. Doctors can use adult stem cells to cure diseases (sickle cell anaemia can sometimes be cured with bone marrow transplant)
  2. experimenting with extracting cells from very early human embryo and growing them in labs - cells can be conditioned and stimulate and differentiate into specialized cells
  3. create specific cells to replace damaged cells due to disease - new cardiac muscle cells could be transplanted into someone with heart disease
• The risks of stem cells in medicine.

  1. tumors developing - stem cells divide quickly and if doc can’t control late tumor could develop
  2. disease transmission- viruses live inside cells, if donar cells are infected they can pass onto patient
  3. rejection - if transplanted cells aren’t grown using patients own cells the patients blood will label it as forgein and attack it
  4. Ethical reasons - some people say using human embryo is wrong as it is potentially a human