Bio Paper 1

• How do bacteria reproduce

  binary fission
• 4 methods of preventing spread of pathogens

  - being hygienic

  - vaccinations

  - isolating infected individuals

  - destroying vectors that carry pathogens
• what are the symptoms of measles

  Fever and a red skin rash
• how is TMV spread

  Direct contact between plants
• how can farmers reduce the spread of TMV

  - Grow TMV-resistant strains of crops.

  - Good field hygiene and good pest control.
• how does skin prevent microorganims getting into your body

  - acts as a barrier to prevent pathogens reaching the tissue beneath

  - produces antimicrobial substances to kill pathogens
• what does HIV do to the immune system


  weakens the immune system so that the body cannot effectively fight infections
• what drug can treat HIV

  antiretroviral
• How id the respiratory system adapted to reduce the entry of microorganisms

  - lining of nose produces mucus and is full of hairs to trap particles that may contain pathogens

  - the lining of the trachea and bronchi produce mucus which is wafted up to the back of the throat by cilia so that it can be swallowed
• what 3 ways can WBCs destroy pathogens

  - phagocytosis

  - producing antibodies

  - producing antitoxins
• what is an antibody

  a blood protein produced in response to and counteracting a specific antigen, destroying them
• where does digitalis (drug for heart conditions) come from

  foxgloves
• where does aspirin (painkiller) come from

  willow
• where does penicillin come from and who discovered it

  penicillium mould

  alexander fleming
• where do most new drugs now come from

  synthesised chemicals in the lab
• what 3 things are found during drug testing

  efficacy

  dose

  toxicity
• what are nitrates used for in plants

  needed to make proteins, therefore growth

  -> lack of nitrates causes stunted growth
• what are magnesium ions used for in plants

  making chlorophyll, which is needed for photosynthesis
• what do plants without enough magnesium suffer from


  - chlorosis

  - have yellow leaves
• what are symptoms of plant disease

  - stunted growth

  - abnormal growths

  - spots on the leaves

  - malformed stems/leaves

  - patches of decay

  - discolouration
• how can different diseases in plants be identified

  - using a gardening manual/website

  - taking infected plants to a lab so scientists can identify the pathogen

  - using testing kits that identify the pathogen using monoclonal antibodies
• physical plant defences

  - wavy cuticle with acts as a barrier

  - plant cells are surrounded by cell walls made from cellulose

  - layers of dead cells around their stems act as a barrier
• chemical plant defences

  - some produce antibacterial chemicals which kill bacteria

  - some produce poisons which deter herbivores
• mechanical plant defences

  - Thorns and hairs deter animals.

  - Leaves which droop or curl when touched, knocking insects off, preventing them from eating them

  - Mimicry to trick animals
• nucleus - contains genetic material that controls the activities of the cell

  cytoplasm - where most the chemical reactions happen, contains enzymes that control these chemical reactions

  cell membrane - holds the cell together and controls what goes in and out

  mitochondria - where most of reactions for aerobic respiration take place

  ribosomes - where proteins are made

  cell wall - made of cellulose, supports and strengthens the cell

  permanent vacuole - stores cell sap

  chloroplasts - where photosynthesis occurs, contains chlorophyll which absorbs the light needed for photosynthesis
• bacteria...

  don't have chloroplasts or mitochondria

  have a single strand of DNA that floats freely in the cytoplasm

  may contain one or more small rings of DNA called plasmids
• Light microscopes use light and lenses to form an image of a specimen and magnify it.

  electron microscopes use electrons instead of light to form an image. they have a much higher magnification and resolution. allows us to see smaller things in more detail
• differentiation is the process in which a cell changes to become specialised for a job
• The Cell Cycle

  Growth - before it divides, the cell has to grow and increase the amount of subcellular structures such as mitochondria and ribosomes

  DNA Replication - the cell duplicates it's DNA. It forms X-shaped chromosomes, where each 'arm' of the chromosome is the same as the other

  Mitosis
• Mitosis - the chromosomes line up at the centre of the cell and cell fibres pull them apart. the two arms of each chromosome go to opposite ends of the cell. Membranes then form around each of the sets of chromosomes. The nucleus divides, then the cytoplasm and cell membrane divide, producing two identical daughter cells
• Stem cells (undifferentiated cells) can divide to produce lots more undifferentiated cells. They can differentiate into different types of cell, depending on what instructions they're given.

  They can be grown in the lab to produce clones and made to differentiate into specialised cells to use in medicine or research. However, there are risks involved with using stem cells in medicine. For example, stem cells grown in the lab may become contaminated with a virus that is then passed on to the patient, making them sicker
• stem cells are found in early human embryos. They have the potential to turn into any cell at all. They could be used to replace faulty cells in sick people. In a type of cloning called therapeutic cloning, an embryo could be made to have the same genetic information as the patient. This means that the stem cells produced would carry the same genes and wouldn't be rejected from the patients body
• adult stem cells can be found in certain places, such as bone marrow. They can only turn into certain types of cell, such as blood cells. They're used to cure disease, for example, stem cells transferred from the bone marrow pf a healthy person can replace faulty blood cells in the patient who receives them
• Some are against embryonic stem cells as the embryos are a potential for human life. They believe scientists should concentrate on developing another source of stem cells so that people can be helped without using embryos. Others think curing existing patients that are suffering is more important than the rights of embryos, and embryos used in research are usually unwanted ones from fertility clinics that would've been destroyed anyway
• in plants, stem cells are found in meristems. Throughout the plants life, cells in the meristem tissues can differentiate into any type of plant cell. These cells can be used to produce clones of whole plants quickly and cheaply. They can then be used to grow more plants of rare species to prevent them being wiped out. They can also be used by farmers to grow crops of identical plants that have desired features
• diffusion is the movement of particles from an area of higher concentration to an area of lower concentration

  osmosis is the movement of water molecules across a partially permeable membrane from an area of higher water concentration to an are of lower water concentration

  active transport is the movement of substances against a concentration gradient. It requires energy from respiration to work
• the inside of the small intestine is covered in millions of villi. They increase the surface area of the small intestine so that digested food is absorbed much quicker into the blood. They have a single layer of surface cells and a very good blood supply to assist quick absorption
• Cells -> tissues -> organs -> organ systems
• amylase is a type of carbohydrase made in the pancreas, the small intestine and the salivary glands. It breaks down starch into simple sugars
• Protease is made in the stomach, the pancreas and the small intestine. It breaks down proteins into amino acids