B1

• Animals and plants

  • They are eukaryotes
• Eukaryotic cells

  • Contain their genetic material enclosed in a nucleus
  • Have a cytoplasm and a cell membrane
• Prokaryotes

  • Their genetic material is not enclosed in a nucleus
  • Their genetic material consists of a single loop and plasmids
  • They may have a cell wall and cell membrane
  • They contain a cytoplasm
• Most animal cells

  • They are specialized - they have adaptations that allow them to carry out a specific function
• Sperm cell

  • Only contain half of the genetic information
  • Have a long tail
  • Streamline
  • Packed full of mitochondria
  • Enzymes
• Nerve cell

  • Sends electrical impulses around the body
  • Have a long axon
  • Covered in myelin which insulates the axon and speeds up the transmission of nerve impulses
  • Dendrites increase the surface area so that other nerve cells can connect more easily
• Muscle cells

  • Can contract and relax
  • Contain protein fibers that can change their length
  • Packed full of mitochondria
  • Work together to form muscle tissue
• Root hair cells

  • Hairs increase surface area
  • Don't contain chloroplasts
• Xylem

  • Have very thick walls containing lignin, causes xylem to die
  • The ends between the cells completely break down so that water and dissolved minerals can flow easily
  • They have no internal structures at all
• Phloem

  • Contain phloem vessel cells
  • No nucleus
  • End walls have pores called sieve plates, allows dissolved sugars to move
  • Each phloem vessel cell has a companion cell that provides it with energy from the mitochondria
• Bacteria

  • Multiply by simple cell division (binary fission)
  • Can carry this out once every 20 minutes
  • They can reproduce rapidly
• Stem cell

  An undifferentiated cell
• Where stem cells can be found

  • Bone marrow
  • Embryos
• Treating leukemia

  1. Patient's existing bone marrow is destroyed using radiation

  2. Patient then receives a transplant of bone marrow from a donor

  3. Stem cells in the bone marrow now divide and form new bone marrow

  4. They also differentiate and form blood cells
• Therapeutic cloning

  1. An embryo is produced with the same genes as the patient

  2. Stem cells from the embryo can be transplanted into the patient without being rejected by the patient's immune system

  3. Once inside the patient, the stem cells can then differentiate to replace cells which have stopped working correctly
• Meristem tissue

  Can differentiate into any type of plant tissue
• Digestive system

  1. In the mouth, enzymes break down food into smaller molecules - amylase carbohydrates - sugars

  2. The food then passes down the esophagus into the stomach where enzymes begin the digestion of proteins. Protease

  3. The stomach also contains hydrochloric acid to provide the correct conditions for the enzymes

  4. The churning of the stomach also turns the food into fluid, increasing the surface area for digestion

  5. Chemicals are released into the small intestine from the liver and the pancreas. The pancreas releases enzymes which continue the digestion of starch and protein. They also start the digestion of lipids

  6. The liver produces bile which helps to speed up the digestion of lipids. Bile also neutralizes the acid released from the stomach

  7. In the small intestine the small food molecules produced by digestion are absorbed into the bloodstream either by diffusion or by active transport

  8. The fluid makes its way through the large intestine where water is absorbed to the bloodstream
• Enzymes

  • Large protein molecules with a substrate specific active site - lock and key theory
  • Enzyme breaks down substrates into products
• Proteins

  Broken down by protease into amino acids
• Starch

  Broken down by amylase into simple sugars
• Lipids

  Broken down by lipase into glycerol and fatty acids
• Cardiovascular diseases

  • Non communicable
  • Coronary arteries provide oxygen to the muscle cells of the heart
  • In CHD layers of fatty deposits build up in the coronary arteries and block the flow of blood which results in a lack of oxygen for the heart muscle
  • Statins are drugs which reduce the level of cholesterol in the blood. Effective but can cause liver problems
  • Stents are inserted to keep the arteries open, blood can flow normally, will not prevent other arteries from blocking and doesn't treat the underlying problem
  • Faulty valves can be replaced with mechanical or animal valves
• Mitosis


  Tightly controlled by genes, if changes occur in these genes, growth can get out of hand leading to tumors
• Benign tumors


  • Usually contained within a membrane, and don't invade other parts of the body
• Malignant tumor cells


  • Invade other tissues and move into the bloodstream
• Causes of cancer

  • Genetic
  • Linked to lifestyle
  • Environmental
• Leaf


  A plant organ
• Upper epidermis and lower epidermis


  • Protect the surface of the leaf, it is transparent so that light can pass through, has a waxy cuticle to prevent water loss
• Stomata


  Allow carbon dioxide to enter and oxygen to leave
• Guard cells


  Open and close the stomata
• Palisade mesophyll


  • Contains palisade cells which are packed with chloroplasts
• Spongy mesophyll


  • Full of air spaces for carbon dioxide to effectively diffuse
• Xylem tissue


  Transports water to the leaves for photosynthesis
• Phloem tissue


  Transports dissolved sugars from photosynthesis in the leaves to the rest of the plants (translocation)
• Meristem tissue


  Found in growing tips which contain stem cells
• Transpiration


  1. Water is constantly evaporating from the leaves

  2. Water passes from xylem into leaf to replace the lost water to be used in photosynthesis

  3. Water comes from the roots, also transports mineral ions

  4. Transpiration of water also cools the leaf
• Factors affecting transpiration rate

  • Higher temperatures
  • Dry conditions
  • Windy conditions
  • High light intensity
• Communicable diseases


  Spread from person to person by pathogens
• Pathogens


  Microorganisms that cause infectious disease
• Types of pathogens


  • Bacteria
  • Viruses
  • Protists
  • Fungi