Biology AS AQA
-
1-1-biological-molecules-carbohydrates11 主题
-
1-1-1-biological-molecules-key-terms
-
1-1-2-biological-molecules-reactions
-
1-1-3-monosaccharides
-
1-1-4-glucose
-
1-1-5-the-glycosidic-bond
-
1-1-6-chromatography-monosaccharides
-
1-1-7-disaccharides
-
1-1-8-starch-and-glycogen
-
1-1-9-cellulose
-
1-1-10-biochemical-tests-sugars-and-starch
-
1-1-11-finding-the-concentration-of-glucose
-
1-1-1-biological-molecules-key-terms
-
1-2-biological-molecules-lipids3 主题
-
1-3-biological-molecules-proteins5 主题
-
1-4-proteins-enzymes12 主题
-
1-4-1-many-proteins-are-enzymes
-
1-4-2-enzyme-specificity
-
1-4-3-how-enzymes-work
-
1-4-4-required-practical-measuring-enzyme-activity
-
1-4-5-drawing-a-graph-for-enzyme-rate-experiments
-
1-4-6-using-a-tangent-to-find-initial-rate-of-reaction
-
1-4-7-limiting-factors-affecting-enzymes-temperature
-
1-4-8-limiting-factors-affecting-enzymes-ph
-
1-4-10-limiting-factors-affecting-enzymes-enzyme-concentration
-
1-4-11-limiting-factors-affecting-enzymes-substrate-concentration
-
1-4-12-limiting-factors-affecting-enzymes-inhibitors
-
1-4-14-control-of-variables-and-uncertainty
-
1-4-1-many-proteins-are-enzymes
-
1-5-nucleic-acids-structure-and-dna-replication8 主题
-
1-5-2-nucleotide-structure-and-the-phosphodiester-bond
-
1-5-3-dna-structure-and-function
-
1-5-4-rna-structure-and-function
-
1-5-5-ribosomes
-
1-5-6-the-origins-of-research-on-the-genetic-code
-
1-5-8-the-process-of-semi-conservative-replication
-
1-5-9-calculating-the-frequency-of-nucleotide-bases
-
1-5-10-the-watson-crick-model
-
1-5-2-nucleotide-structure-and-the-phosphodiester-bond
-
1-6-atp-water-and-inorganic-ions4 主题
-
2-1-cell-structure7 主题
-
2-2-the-microscope-in-cell-studies4 主题
-
2-3-cell-division-in-eukaryotic-and-prokaryotic-cells8 主题
-
2-4-cell-membranes-and-transport9 主题
-
2-4-1-the-structure-of-cell-membranes
-
2-4-3-the-cell-surface-membrane
-
2-4-4-diffusion
-
2-4-5-osmosis
-
2-4-7-osmosis-in-animal-cells
-
2-4-9-required-practical-investigating-water-potential
-
2-4-10-active-transport-and-co-transport
-
2-4-11-adaptations-for-rapid-transport
-
2-4-13-required-practical-factors-affecting-membrane-permeability
-
2-4-1-the-structure-of-cell-membranes
-
2-5-cell-recognition-and-the-immune-system7 主题
-
2-6-vaccines-disease-and-monoclonal-antibodies6 主题
-
3-1-adaptations-for-gas-exchange6 主题
-
3-2-human-gas-exchange14 主题
-
3-2-5-the-alveolar-epithelium
-
3-2-1-the-human-gas-exchange-system
-
3-2-2-dissecting-the-gas-exchange-system
-
3-2-3-microscopy-and-gas-exchange-surfaces
-
3-2-4-investigating-gas-exchange
-
3-5-5-investigating-heart-rate
-
3-5-6-blood-vessels
-
3-5-7-capillaries-and-tissue-fluid
-
3-5-8-cardiovascular-disease-data
-
3-2-10-risk-factor-data
-
3-2-11-correlations-and-causal-relationships
-
3-2-6-ventilation-and-gas-exchange
-
3-2-8-the-effects-of-lung-disease
-
3-2-9-pollution-and-smoking-data
-
3-2-5-the-alveolar-epithelium
-
3-3-digestion-and-absorption5 主题
-
3-4-mass-transport-in-animals6 主题
-
3-5-the-circulatory-system-in-animals4 主题
-
3-6-mass-transport-in-plants6 主题
-
4-1-dna-genes-and-chromosomes10 主题
-
4-2-dna-and-protein-synthesis3 主题
-
4-3-genetic-diversity-mutations-and-meiosis7 主题
-
4-4-genetic-diversity-and-adaptation6 主题
-
4-5-species-and-taxonomy4 主题
-
4-6-biodiversity9 主题
1-1-5-the-glycosidic-bond
Exam code:7401
Forming the glycosidic bond
-
To make monosaccharides more suitable for transport, storage and to have less influence on a cell’s osmolarity, they are bonded together to form disaccharides and polysaccharides
-
Disaccharides and polysaccharides are formed when two hydroxyl (-OH) groups (on different saccharides) interact to create a strong covalent bond called the glycosidic bond
-
Each glycosidic bond is catalysed by enzymes specific to which OH groups are interacting
-
-
Every glycosidic bond results in one water molecule being removed, thus, glycosidic bonds are formed by condensation
-
As there are many different monosaccharides, this results in different types of glycosidic bonds forming (e.g. maltose has an α-1,4 glycosidic bond and sucrose has an α-1,2 glycosidic bond)
Glycosidic bond in maltose
-
Maltose is a disaccharide formed by the condensation reaction of two glucose molecules
Glycosidic bond in sucrose
-
Sucrose is a disaccharide formed by the condensation of a glucose molecule and a fructose molecule
Glycosidic bond in lactose
-
Lactose is a disaccharide formed by the condensation of a glucose molecule and a galactose molecule
Glycosidic bond in a polysaccharide
-
Polysaccharides are formed by the condensation of many glucose units
-
E.g. Glycogen and starch are formed by the condensation of α-glucose
-
E.g. Cellulose is formed by the condensation of β-glucose
-
Examiner Tips and Tricks
Make sure you can identify where the glycosidic bond is in a carbohydrate. You need to know the specific examples discussed on this page.
Breaking the glycosidic bond
-
The glycosidic bond is broken when water is added in a hydrolysis (meaning ‘hydro’ – with water and ‘lyse’ – to break) reaction
-
Hydrolytic reactions are catalysed by enzymes, these are different to those present in condensation reactions
-
-
Disaccharides and polysaccharides are broken down into smaller molecules in hydrolysis reactions
-
Examples of hydrolytic reactions include the digestion of food in the alimentary tract and the breakdown of stored carbohydrates in muscle and liver cells for use in cellular respiration
Examiner Tips and Tricks
Remember that disaccharides hydrolyse to two monosaccharides, whereas polysaccharides must undergo many hydrolytic reactions until they form monosaccharides.
Responses