Biology (B2)

1. Human cells

   Nota:

   • Use this acronym to remember what is in a human cell: Nice Chicken Curry Mild Rice
   1. Nucleus

      Nota:

      • Controls the cell's activities
   2. Cytoplasm

      Nota:

      • Many chemical reactions take place.
   3. Cell membrane

      Nota:

      • Controls the movement of materials in and out of cell.
   4. Mitochondria

      Nota:

      • Energy is released during aerobic respiration
   5. Ribosomes

      Nota:

      • Protein synthesis takes place
2. Plant cells

   Nota:

   • Contain all the things in a human cell, with these extra:
   1. Cell wall

      Nota:

      • Made of cellulose for support
   2. Chloroplasts

      Nota:

      • Contain chlorophyll for photosynthesis. The light energy is absorbed to make food.
   3. Permanent vacuole

      Nota:

      • Contains cell sap

Nota:

• -Very small and can only be seen by a microscope.

1. Bacteria

   Nota:

   • Contains a cell membrane and cytoplasm surrounded by a cell wall.
   • NO NUCLEUS - genetic material is in the cytoplasm
   • Multiplied bacteria = bacterial colony
2. Yeast

   Nota:

   • -SINGLE-CELLED organism -Have a nucleus, cytoplasm and a membrane surrounded by a cell wall.

Nota:

• -Cells are specialized to carry out a specific function. -The structure of the cell gives clues as to what it does.

1. Muscle cells

   Nota:

   • Many mitochondria to create a lot of energy.
2. Gland cells

   Nota:

   • Many ribosomes to create a lot of protein.
3. Neurons

   Nota:

   • Specialized to carry impulses from receptors to the CNS.

Nota:

• The spreading out of the particles of a gas, or of any substance in a solution.

1. Concentration

   Nota:

   • NET MOVEMENT into or out of cells depends on concentration on either side of cell membrane.
   • Difference in concentration between two areas is: CONCENTRATION GRADIENT
2. Increasing diffusion

   Nota:

   • Rate is increased when: -Distance is decreased. -Surface area is increased. -Concentration gradient is increased.
3. Examples

   Nota:

   • Diffusion of oxygen into cells of body from the bloodstream. Due to respiration of cells.
   • Diffusion of carbon dioxide into actively photosynthesizing plant cells.
   • Diffusion of simple sugars and amino acids from gut through cell membranes.

1. Tissues

   Nota:

   • A tissue is a group of cells with similar structure and function.
   1. Animal tissues

      Nota:

      • Muscle tissue - Can contract to bring about movement.
      • Glandular tissue - To produce substances such as enzymes or hormones.
      • Epithelial tissue - Covers some parts of the body.
   2. Plant tissues

      Nota:

      • Epidermal tissue - Covers the plant
      • Mesophyll - Can photosynthesize
      • Xylem and phloem - transport substances around the plant.
2. Organs

   Nota:

   • Organs are made of several tissue types.
   1. The stomach

      Nota:

      • The stomach is an organ made up of: -Muscular tissue to churn the stomach contents. -Glandular tissue to produce DIGESTIVE JUICES. -Epithelial tissue to cover the outside and the inside of the stomach.

Nota:

• Groups of organs work together in an organ system.

1. The digestive system

   Nota:

   • The digestive system in humans is adapted to exchange substances with the environment.
   • It includes: -Glands, such as the pancreas and salivary glands which produce digestive juices. -Stomach and small intestine where digestion occurs. -Liver which produces bile. -Small intestine where the absorption of soluble food occurs. -The large intestine where water is absorbed from undigested food, producing faeces. 

Nota:

• During photosynthesis, light energy is transferred to chemical energy.
• Some of the glucose is converted into insoluble starch for storage.

1. Equation

   Nota:

   • Carbon Dioxide + Water → Glucose + Oxygen
   • 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂   
2. Process

   Nota:

   • 1. CO₂ taken in by leaves, water taken in by roots. 2. Chlorophyll traps light energy. 3. Energy is used to convert the CO₂ and H₂0 to C₆H₁₂O₆
3. Testing

   Nota:

   • -Testing leaves with iodine solution, to test for starch.  -Green patches will turn solution blue-black to show starch has been made.
   1. Variegated leaves

      Nota:

      • Different patches = difference in chlorophyll. Green = Chlorophyll White = No Chlorophyll

Nota:

• 3 limiting factors: -Lack of light -Cold (enzymes slower) -Little carbon dioxide

1. Experiments

   Nota:

   • Independent variable: Concentration of Carbon Dioxide
   • Dependent Variable: Volume of Oxygen produced.
   • Control variables: Light, temperature, type of plant

Nota:

• -Converted into insoluble starch for storage. -Respiration -Converted into lipids  and oils for storage. -Produce cellulose which strengthens cell walls. -Produce proteins.

1. Ions

   Nota:

   • Plant and algal cells need a supply of mineral ions such as: -Nitrate ions to produce protein. --Plants absorb nitrate ions from soil. --Algae absorb nitrate ions from the water in which they live.

Nota:

• Plant growers can artificially control the environment to improve plant growth.
• To improve plant growth, the factors that need to be controlled are: -Light intensity -Temperature -Carbon dioxide levels

Nota:

• The distribution of organisms is affected by environmental factors.
• -Temperature -Availability of nutrients -Amount of light -Availability of water -Availability of oxygen -Availability of carbon dioxide

Nota:

• Quantitative data is used to describe how physical factors might be affecting the distribution of organisms in a habitat.
• There are two ways to obtain quantitative data: -Random quantitative sampling using a quadrat. -Sampling along a transect.

1. Quadrat

   Nota:

   • -A square from which may be subdivided into a grid.  -Several quadrats are placed randomly and the thing being investigated is counted in each one. -It can be used to estimate the number of species or plant in a field.
2. Transect

   Nota:

   • -This is not random. A line is marked between two points, and a random quadrat placed every 5 metres along the line. -Supplies a lot of information about:  --Habitat --Organisms in it.
3. Sample size

   Nota:

   • In a large field, enough random quadrats are needed so that the sample is representative of the entire field.

1. Proteins

   Nota:

   • -Made up of long chains of amino acids. -Long chains are folded to produce specific shapes, which have a specific function.
   • They can be: -Structural components of tissues -Hormones -Antibodies -Catalysts
2. Enzymes

   Nota:

   • -Biological catalysts -Large proteins and the shape is vital for its function. -The 'active site' is the area where other molecules can fit.
   • In a reaction, the substrate can: -Be held in the active site. -Be connected to another molecule. -Be broken down.
   • Enzymes can: -Build large molecules from smaller ones. --Starch from glucose molecules -Change one molecule into another -Break down large molecules into small ones.

Nota:

• -Reactions take place quicker if it is warmer. --At higher temperatures the molecules move around more quickly and so collide with each other more often, with more energy. (Learn this word for word)
• -Each enzyme works best at a particular pH value.

1. Denaturing

   Nota:

   • If the temperature gets too hot, the active site CHANGE SHAPE, causing the enzyme to stop working.
   • If the pH is too acidic or too alkaline for the enzyme, the active site could change shape.

Nota:

• -These enzymes are produced in the glands and in the lining of the gut. -Enzymes pass out of the cells and come into contact with food. -Digestion involves the breakdown of large, insoluble molecules into smaller soluble ones.

1. Special enzymes
   1. Amylase

      Nota:

      • Produced in the salivary glands, the pancreas and the small intestine.
      • Catalyses the digestion of starch into sugar in mouth and small intestine.
      • Work best when the conditions are slightly alkaline.
   2. Protease

      Nota:

      • Produced by the stomach, pancreas and small intestine.
      • Catalyses the breakdown of proteins into amino acids in the stomach and small intestine.
      • Work best when the conditions are acidic.
   3. Lipase

      Nota:

      • Produced by the pancreas and small intestine.
      • Catalyses the breakdown of lipids to fatty acids and glycerol.
      • Work best when the conditions are slightly alkaline.
2. Bile

   Nota:

   • -The liver produces bile. -Stored in the gall bladder before being released into the small intestine. -Bile neutralises the acid that was added to food in the stomach. -This provides alkaline conditions in which enzymes in the small intestine work most effectively.

1. Biological detergents

   Nota:

   • -Contain proteases and lipases that digest food stains. -Work at lower temperatures than ordinary washing powders. -Saves energy and money spent on electricity.
2. Baby foods

   Nota:

   • Proteases are used to pre-digest proteins in some baby foods.
3. Fructose syrup

   Nota:

   • -Isomerase is used to convert glucose syrup into fructose syrup.  -Fructose is MUCH SWEETER so less is needed in foods. -Foods are less fattening. 
4. Foods

   Nota:

   • Carbohydrases are used to convert starch into sugar syrup for use in foods.
5. Industry

   Nota:

   • -Used to bring about reactions at normal temperatures and pressures. -Traditional chemical processes require: --Expensive equipment. --A lot of energy (to produce high temperatures and pressures)

1. Advantages

   Nota:

   • -Enzymes in biological washing powders are very effective at removing stains. -Biological washing powders can be used at lower temperatures. -Used in medicine to diagnose, control or cure disease. -Industry, costs of equipment and energy can be reduced.
2. Disadvantages

   Nota:

   • -Misuse of washing powders can cause allergic reactions on skin. -Enzymes may enter waterways via the sewage system. -Industrial enzymes are costly. -Enzymes denature at high temperatures needed to kill pathogens in the washing. -Fabrics such a wool are digested by proteases.

Nota:

• -Takes place continually. -Chemical reactions take place in the mitochondria and are controlled by enzymes.

1. Equation

   Nota:

   • Glucose + oxygen  → Carbon dioxide + water [+ energy]
2. Uses

   Nota:

   • Energy released used to: -Build larger molecules. -Enable muscle contraction. -Maintain a constant body temperature in colder surroundings. -Build sugars, nitrates and other nutrients into amino acids and then proteins in plants.
3. Experiment

   Nota:

   • -Measure volume of carbon dioxide produced.

Nota:

• -During exercise muscles need more energy. -More glucose and oxygen need to be transported to the muscles.

1. Heart rate

   Nota:

   • Increase and the blood vessels dilate to allow more blood containing oxygen and glucose to reach the muscles.
2. Breathing

   Nota:

   • Increase in breathing rate and depth of each breath to allow a greater uptake of oxygen and release of carbon dioxide in the lungs.
3. Glycogen

   Nota:

   • Muscles store glucose at glycogen which can be converted back to glucose during exercise.

Nota:

• When muscles work hard for a long time, they may have too little oxygen and become fatigued.
• Muscles use anaerobic respiration if they are short of oxygen.
• Anaerobic respiration doesn't break down glucose fully, therefore less energy is released from the glucose.

1. Equation

   Nota:

   • glucose → lactic acid (+ energy released)
2. Oxygen debt

   Nota:

   • In anaerobic respiration, lactic acid replaces carbon dioxide and water as the waste product.
   • When the exercise is complete, the lactic acid MUST be broken down.
   • The extra oxygen you need to oxidize the lactic acid into carbon dioxide and water is called oxygen debt.

Nota:

• Necessary for the growth of an organism, or for the repair of damaged tissues.

1. Mitosis

   Nota:

   • Two identical cells being produced from the original cell. Mitosis = Making Identical Two
   • Two identical cells being produced from the original cell. 46 chromosomes (2 sets) Mitosis = Making Identical Two
   1. Chromosomes

      Nota:

      • Found in pairs and contain genes (alleles) which must be passed onto each new cell.
   2. Process

      Nota:

      • -Normal body cell has 46 chromosomes (23 pairs). -Copies of these pairs are made. -Then the cell divides once to form two genetically identical body cells.
2. Meiosis

   Nota:

   • -Cells in reproductive organs divide by meiosis to form gametes.  -23 chromosomes (one set) -Meiosis = Making Eggs
   1. Process

      Nota:

      • -Before division, a copy of each chromosome is made. -The cell now divides twice to form four gametes. -Each gamete has a single set of chromosomes with a different combination of genes. 
   2. Sexual reproduction

      Nota:

      • -Results in variation as the gametes from each parent fuse. -Half genetic information from mother, half from father. -In fertilization, a single body cell with new pairs of chromosomes form. -Individual develops through mitosis. 
3. Differentiation

   Nota:

   • Most animal cells differentiate early in development and cell division is mainly for: -Repair -Replacement
   • Plant cells can differentiate throughout the life of the plant as it continues to grow.
4. Asexual

   Nota:

   • Asexual reproduction cells are produced by mitosis from the parent cell. They contain the SAME alleles as the parents.

Nota:

• -Unspecialised. -Found in human embryo and bone marrow. -Differentiate into different types of body cell. -Adult bone marrow stem cells - can differentiate into blood cells.-Hoped that stem cells could be used to cure diseases.

1. Embryos

   Nota:

   • Embryonic stem cells can be used in medical research and treatments.
   • Found: -Spare embryos from IVF. -Created from adult cells. -Taken from the umbilical cord of newborn babies.
   1. Issues
      1. Economical

         Nota:

         • Very expensive to carry out research using embryonic cells.
      2. Ethical

         Nota:

         • -The research is experimental. -Embryos have potential to become a baby and are destroyed. -Embryo cannot give permission.
   2. Embryo screening

      Nota:

      • Involves tests to diagnose disorders before the baby is born.
      1. Results

         Nota:

         • -Sometimes parents decide to terminate the pregnancy. -Others decide it isn't ethical and keep the baby.
         • In IVF, only healthy embryos are implanted into the mother. Embryos carring FAULTY genes are destroyed, which isn't ethical.

Nota:

• A monk who worked out how characteristics were inherited.

1. Genes

   Nota:

   • -Found on chromosomes. -Control our characteristics. -Short section of DNA.
   1. Genetic code

      Nota:

      • Each genes codes for a particular combination of amino acids which make a specific protein.
2. DNA

   Nota:

   • -A very long molecule with a double helix structure (chromosomes). -Every individual (bar identical twins) has different DNA.
   1. DNA Fingerprint

      Nota:

      • Unique DNA pattern which can be used to identify people.

1. Sex chromosomes
   1. Male

      Nota:

      • An X and a Y chromosome (XY)
   2. Female

      Nota:

      • Two X chromosomes (XX)
2. Alleles

   Nota:

   • Genes controlling the same characteristic.
   1. Dominent

      Nota:

      • 'Masks' the effect of another allele.
   2. Recessive

      Nota:

      • The dominant allele 'masks' this allele, so it has no effect.
3. Genetic diagrams

   Nota:

   • Biological models which can be constructed to predict and explain the inheritance of particular characteristics.
   1. Terminology
      1. Phenotype

         Nota:

         • Physical appearance of the characteristic (dimples or no dimples)
      2. Genotype

         Nota:

         • The genetic make-up, which alleles does the individual inherit.  (DD, Dd, dd)
      3. Homozygous

         Nota:

         • Both alleles are the same DD (homozygous dominant) or dd (homozygous recessive).
      4. Heterozygous

         Nota:

         • The two alleles are different, Dd.
4. Genetic disorders

   Nota:

   • If an allele is recessive, the person must inherit two recessive alleles to have the disorder.
   • If the allele is dominant, the person has to inherit only one dominant allele to have the disorder.
   1. Polydactyly

      Nota:

      • -Caused by a dominant allele. -Where a baby is born with extra fingers or toes.
   2. Cystic fibrosis

      Nota:

      • -Caused by a recessive allele. -Affects cell membranes and causes the production of thick sticky mucus. 
   3. Carriers

      Nota:

      • People who carry a recessive allele.
5. Punnet squares

   Nota:

   • Used to predict the chances of inheriting a disorder.

Nota:

• -Believed that the Earth is 4500 million years old and that life began about 3500 million years ago. -There is DEBATE as to whether first live developed due to conditions on Earth, or whether simple life forms arrived from another planet.

1. Fossils

   Nota:

   • -Fossils are remains of organisms from many years ago which are found in rocks. -We can learn from fossils how different organisms have changed as life developed on Earth.
   • -The fossil record is INCOMPLETE.
   1. How they are formed

      Nota:

      • -From hard parts of animals that do not decay easily (teeth, claws) -From parts of organisms that have not decayed because some of the conditions for decay are absent (ice preservation). -When parts of the organism are replaced by other materials, such as minerals, as they decay. -As preserved traces of organisms (footprints, burrows).
   2. Destruction

      Nota:

      • Traces which were left are likely to have been destroyed by geological activity such as earthquakes.
   3. Soft-bodied

      Nota:

      • Soft-bodied organisms didn't leave fossils.

Nota:

• -The fossil record is incomplete. -We can learn a lot from fossils which exist. -Some organisms have changed a lot over time. -Other have changed very little. -Some have become extinct.

1. Extinction

   Nota:

   • A species which once existed has completely died out. 
   1. Factors

      Nota:

      • -A new disease may kill all members of a species. -Change in environment. -New diseases may be introduced. -A new predator may evolve or be introduced to an area that kills and eats all of a species. -A new competitor - original species may be left with little or nothing to eat. -A single catastrophic event may occur which destroys the habitat. -Natural changes in species occur over time.

Nota:

• The biggest influences on a species survival are changes in the environment.

1. Climate change

   Nota:

   • -A species which is very well adapted to a hot climate may become extinct in an Ice Age. -There could be insufficient food or it is too cold to breed.
   • -Climate change may: --Make it too cold or hot. --Make it too wet or dry. --Reduce a species food supply.
2. Fossil evidence

   Nota:

   • -Shows that there have been mass extinctions on a global scale. -Many of the species died out over a period of several million years - a short time.
   • -The habitat the species live in may be destroyed by catastrophic events such as a major volcanic eruption. -The environment can change dramatically following a collision between a giant asteroid and Earth.
3. The dinosaurs

   Nota:

   • No one knows why they have become extinct. Some ideas are: -The collision of a giant asteroid caused huge fires, earthquakes, landslides and tsunamis. The dust which rose blocked out the sun, lowering temperatures and causing darkness. Plants could not grow. -The extinction was a slower process due to sea ice melting and cooling the sea temperature by 9 degrees, therefore there was less plankton - less food available. 

Nota:

• New species can arise form existing species if a group becomes isolated from the rest.

1. Geographical isolation

   Nota:

   • -Could occur if an island separates from the mainland or if a new river separates two areas. -Mountain ranges and old craters can isolate organisms. 
2. Speciation

   Nota:

   • Logical process: Isolation → Genetic variation → alleles selected → interbreeding no longer possible → new species (speciation).
   1. Isolation

      Nota:

      • New species can occur following separation of two populations, as in geographical isolation. 
      1. Genetic variation

         Nota:

         • Each population has a wide range of alleles that control their characteristics.
         1. Natural selection

            Nota:

            • -Occurs in both populations. -The alleles that control the characteristics which help the organism to survive are selected. -The organisms with these alleles will survive and breed.
            1. Evolution

               Nota:

               • If the environment, competitors, food supply and predators are different for each population, they will evolve differently. 
               1. Interbreeding

                  Nota:

                  • SPECIATION has occurred when the two populations can no longer successfully interbreed.