T.W.C Teaching With Caffiene

The emulsion test looks for the presence of fats in a substance, by adding ethanol, an organic solvent. 

Ethanol emulsifies fats and discolours the solution a cloudly/white colour. 

If the solution remains colourless, fats are not present. 

Lipids: Phospholipids

- One of the main two types of lipids

- Made of fatty acids, glycerol and phosphate molecules. 

- has a hydrophobic (water hating) tail and hydrophilic (water loving) head

- naturally forms a lipid bilayer.

Lipids: Triglycerides

characteristics:

 - One of the two main forms of Lipids.

 - Formed from three fatty acids and a single glycerol molecule. 

 - The R-group of a fatty acid refers to the long chain in the centre. This can be either saturated or unsaturated and varies. 

example: https://en.wikipedia.org/wiki/Fatty_acid

 - fatty acids bind with glycerol molecules, via condensation reaction forming an ester bond and then a triglyceride. 

 - Form fats in plants and animals

 - insoluble in water, but soluble in other lipids and organic solvents (ethanol) 

have many uses in the body:

 - Energy storage: stores double the energy of a carbohydrate. 

- Heat Insulation: e.g. whales & seals have blubber. 

- Also assists with buoyancy: e.g. larger aquatic animals and aquatic micro-organisms produce oil droplets. 

 - Shock absorption: forms a protective layer around your kidneys.

 - Digestion of triglycerides produces fatty acids. 

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Saturated bonds: All the available carbon bonds on the fatty acid are “Saturated” with Hydrogen atoms. These are generally thought to be more unhealthy an associated with higher calorie diets and diseases. Such as cardiovascular diseases and diabetes. Have a higher melting point and are more likely to be solid at room temperature. 

Unsaturated bonds: have double bonds between some of the carbon atoms, reducing the number of places where hydrogen atoms can bond to carbon atoms. Have a lower melting point and are moor likely to be liquid and room temperature. 

Polysaccharide: Cellulose

Cellulose is formed by the condensation of Beta glucose.

 - Forms cell walls of plants. Structural strength comes from the many hydrogen bonds formed between chains. 

- Can only be digested by ruminants, as it is hard to break down, with microorganisms that produce cellulase.

Polysaccharide: Starch

 - Starch is a compact molecule used for storage in plants

 - Formed by the condensation of Alpha glucose

 - not as branched as glycogen, therefore less soluble and denser. 

 - Held in plastids (organelles in plants)– either chloro-plasts or amylo-plasts (like in tubers)

Polysaccarides: Gylcogen

 - formed by the condensation of many monosaccharides. 

 - made from lots of glucose molecules joined together by glycosidic bonds to form long, branched chains surrounding a core protein of glycogenin. 

- A storage molecule particularly in liver and muscle cells (see above) 

 - Like starch formed by the condensation of αlpha glucose

 - More branched than starch and therefore less dense and more soluble

Disaccharides: Formed from a hydrolysis reaction between two monosaccharides to form a glycosidic bond. 

 - maltose (malt sugar) is two glucose molecules

 - sucrose (table sugar) is a glucose molecule and a fructose molecule

Glucose has two Isomers: Alpha and Beta glucose. 

Isomers are molecules with the same chemical formula but a different chemical structure. 

Alpha Glucose is used to form Starch. Long chain structure, but with branches formed by glycosidic bonds.  

Beta Glucose is used to form Cellulose in Plants. Long chain structure, but no branches. Formed weak bonds with neighbouring chains. 

Starch and Glucose is formed by glycosidic bonding. 

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Starch:( https://en.wikipedia.org/wiki/Starch )

Cellulose: ( http://www.joostdevree.nl/shtmls/cellulose.shtml )

Monosaccarides: are monomers from which larger carbohydrates are made from.

Condensation reactions - monomers to polymers, which then release water molecule. 

e.g. Glucose + Fructose -> Sucrose + water molecule.

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Hydrolysis reactions - polymers to monomers reaction, uses up a water molecule. 

e.g. Sucrose + water molecule -> Glucose + Sucrose

link to website:

“AS and A-level Biology Specification Specifications for first teaching in 2015 Life depends on continuous transfers of energy. In photosynthesis, light is absorbed by chlorophyll and this is linked to the production of ATP. In respiration, various substances are used as respiratory substrates. The hydrolysis of these respiratory substrates is linked to the production of ATP. In both respiration and photosynthesis, ATP production occurs when protons diffuse down an electrochemical gradient through molecules of the enzyme ATP synthase, embedded in the membranes of cellular organelles. The process of photosynthesis is common in all photoautotrophic organisms and the process of respiration is common in all organisms, providing indirect evidence for evolution. In communities, the biological molecules produced by photosynthesis are consumed by other organisms, including animals, bacteria and fungi. Some of these are used as respiratory substrates by these consumers. Photosynthesis and respiration are not 100% efficient. The transfer of biomass and its stored chemical energy in a community from one organism to a consumer is also not 100% efficient.”

5.1 Photosynthesis (A-level only)

5.2 Respiration (A-level only)

5.3 Energy and ecosystems (A-level only)

“AS and A-level Biology Specification Specifications for first teaching in 2015 All life on Earth shares a common chemistry. This provides indirect evidence for evolution. Despite their great variety, the cells of all living organisms contain only a few groups of carbon-based compounds that interact in similar ways. Carbohydrates are commonly used by cells as respiratory substrates. They also form structural components in plasma membranes and cell walls. Lipids have many uses, including the bilayer of plasma membranes, certain hormones and as respiratory substrates. Proteins form many cell structures. They are also important as enzymes, chemical messengers and components of the blood. Nucleic acids carry the genetic code for the production of proteins. The genetic code is common to viruses and to all living organisms, providing evidence for evolution. The most common component of cells is water; hence our search for life elsewhere in the universe involves a search for liquid water.” 

1.1 Monomers and polymers

1.2 Carbohydrates

1.3 Lipids

1.4 Proteins

1.4.1 General properties of proteins

1.4.2 Many proteins are enzymes

1.5 Nucleic acids are important information-carrying molecules

1.5.1 Structure of DNA and RNA

1.5.2 DNA replication

1.6 ATP

1.7 Water

“All life on Earth exists as cells. These have basic features in common. Differences between cells are due to the addition of extra features. This provides indirect evidence for evolution.

All cells arise from other cells, by binary fission in prokaryotic cells and by mitosis and meiosis in eukaryotic cells.

All cells have a cell-surface membrane and, in addition, eukaryotic cells have internal membranes. The basic structure of these plasma membranes is the same and enables control of the passage of substances across exchange surfaces by passive or active transport.

Cell-surface membranes contain embedded proteins. Some of these are involved in cell signalling – communication between cells. Others act as antigens, allowing recognition of ‘self’ and ‘foreign’ cells by the immune system. Interactions between different types of cell are involved in disease, recovery from disease and prevention of symptoms occurring at a later date if exposed to the same antigen, or antigen-bearing pathogen.”

2.1 Cell structure

2.1.1 Structure of eukaryotic cells

2.1.2 Structure of prokaryotic cells and of viruses

2.1.3 Methods of studying cells

2.2 All cells arise from other cells

2.3 Transport across cell membranes

“ AS and A-level Biology Specification Specifications for first teaching in 2015 Biological diversity – biodiversity – is reflected in the vast number of species of organisms, in the variation of individual characteristics within a single species and in the variation of cell types within a single multicellular organism. Differences between species reflect genetic differences. Differences between individuals within a species could be the result of genetic factors, of environmental factors, or a combination of both. A gene is a section of DNA located at a particular site on a DNA molecule, called its locus. The base sequence of each gene carries the coded genetic information that determines the sequence of amino acids during protein synthesis. The genetic code used is the same in all organisms, providing evidence for evolution. Genetic diversity within a species can be caused by gene mutation, chromosome mutation or random factors associated with meiosis and fertilisation. This genetic diversity is acted upon by natural selection, resulting in species becoming better adapted to their environment. Variation within a species can be measured using differences in the base sequence of DNA or in the amino acid sequence of proteins. Biodiversity within a community can be measured using species richness and an index of diversity.”

4.1 DNA, genes and chromosomes

AS and A-level Biology Specification Specifications for first teaching in 2015

4.2 DNA and protein synthesis

4.3 Genetic diversity can arise as a result of mutation or during meiosis

4.4 Genetic diversity and adaptation

4.5 Species and taxonomy

4.6 Biodiversity within a community

“AS and A-level Biology Specification Specifications for first teaching in 2015

A stimulus is a change in the internal or external environment. A receptor detects a stimulus. A coordinator formulates a suitable response to a stimulus. An effector produces a response.

Receptors are specific to one type of stimulus.

Nerve cells pass electrical impulses along their length. A nerve impulse is specific to a target cell only because it releases a chemical messenger directly onto it, producing a response that is usually rapid, short-lived and localised.

In contrast, mammalian hormones stimulate their target cells via the blood system. They are specific to the tertiary structure of receptors on their target cells and produce responses that are usually slow, long-lasting and widespread.

Plants control their response using hormone-like growth substances.”

6.1 Stimuli, both internal and external, are detected and lead to a response (A-level only)

6.1.1 Survival and response (A-level only)

6.1.2 Receptors (A-level only)

6.1.3 Control of heart rate (A-level only)

6.2 Nervous coordination (A-level only)

6.2.1 Nerve impulses (A-level only)

6.2.2 Synaptic transmission (A-level only)

6.3 Skeletal muscles are stimulated to contract by nerves and act as effectors (A-level only)

6.4 Homeostasis is the maintenance of a stable internal environment (A-level only)

6.4.1 Principles of homeostasis and negative feedback (A-level only)

AS and A-level Biology Specification Specifications for first teaching in 2015

6.4.2 Control of blood glucose concentration (A-level only)

“AS and A-level Biology Specification Specifications for first teaching in 2015 The theory of evolution underpins modern Biology. All new species arise from an existing species. This results in different species sharing a common ancestry, as represented in phylogenetic classification. Common ancestry can explain the similarities between all living organisms, such as common chemistry (eg all proteins made from the same 20 or so amino acids), physiological pathways (eg anaerobic respiration), cell structure, DNA as the genetic material and a ‘universal’ genetic code. The individuals of a species share the same genes but (usually) different combinations of alleles of these genes. An individual inherits alleles from their parent or parents. A species exists as one or more populations. There is variation in the phenotypes of organisms in a population, due to genetic and environmental factors. Two forces affect genetic variation in populations: genetic drift and natural selection. Genetic drift can cause changes in allele frequency in small populations. Natural selection occurs when alleles that enhance the fitness of the individuals that carry them rise in frequency. A change in the allele frequency of a population is evolution. If a population becomes isolated from other populations of the same species, there will be no gene flow between the isolated population and the others. This may lead to the accumulation of genetic differences in the isolated population, compared with the other populations. These differences may ultimately lead to organisms in the isolated population becoming unable to breed and produce fertile offspring with organisms from the other populations. This reproductive isolation means that a new species has evolved. Populations of different species live in communities. Competition occurs within and between these populations for the means of survival. Within a single community, one population is affected by other populations, the biotic factors, in its environment. Populations within communities are also affected by, and in turn affect, the abiotic (physicochemical) factors in an ecosystem.”

7.1 Inheritance (A-level only)

7.2 Populations (A-level only)

7.3 Evolution may lead to speciation (A-level only)