Aqa biology stuvia 2024 - Study guides, Class notes & Summaries

Describe how oxygen in the air reaches capillaries surrounding alveoli in lungs - ANSWERTrachea and bronchi and bronchioles; Down pressure gradient; Down diffusion gradient; Across alveolar epithelium; Across capillary endothelium/epithelium; Difference between species richness and index of diversity - ANSWERSpecies richness measures only number of (different) species / does not measure number of individuals; Explain how cellulose molecules are adapted for their function in plant cells...

Describe how you would use a biochemical test to show that a solution contained a non-reducing sugar, such as sucrose. [3] - ANSWER,first reducing sugars test; boil with dilute HCl acid then Neutralise with NaHCǑ, add benedict and heat to 95 degrees C brick red ppt forms if reducing sugar is present Describe a chemical test you could carry out to show that a piece of coconut contains lipids. [3] - ANSWER(Crush in) ethanol / alcohol; Add (to) water (Order of adding is critical for this point)...

Benedict's test - ANSWERWhich food test is heated in a water bath? Sucrose - ANSWERWhich disaccharide is not a reducing sugar? Test for non-reducing sugars - ANSWERAdd acid. Neutralise. Add Benedicts. Heat. Hydrolysis - ANSWERReaction performed by dilute HCl in the non reducing sugar test. Glucose + fructose - ANSWERDuring the non-reducing sugar test what is sucrose hydrolysed into? Alpha - ANSWERWhich type of glucose makes up starch? amylose and amylopectin - ANSWERNames of t...

large molecules often contain carbon. why? - ANSWERthey can readily form bonds with other carbon atoms. this forms a 'backbone'. other atoms can then attach. describe benedicts test for reducing sugars - ANSWERadd equal volumes of the sugar sample and benedicts reagent. heat the mixture in a water bath for 5 minutes. brick red precipitate will form. what is a reducing sugar? - ANSWERa sugar that can reduce (give electrons to) another chemical. describe the benedicts test for non red...

Describe the relationship between the size of an organism and its SA:V ratio - ANSWERSmaller organisms have high SA:V ratios Larger organisms have low SA:V ratios What adaptations do some organisms have for exchange (in terms of SA:V ratio)? - ANSWERThe flattened shape so that no cell is ever far from the surface. The specialised exchange surfaces with large areas to increase the SA:V ratio ---> lungs in animals, gills in fish etc. What is the relationship between SA:V ratio and metabo...

What kind of receptors are changes in blood pH and pressure detected by? - ANSWERchemoreceptors and pressure receptors in the aorta or carotid artery Two types of photoreceptors in the eye? - ANSWERrods and cones What colour do rods detect and why? - ANSWERBlack and white ONLY - because they can't distinguish between wavelengths of light What kind of light intensity do rods detect and why? - ANSWER- Rods detect low light intensity - because many rods connect to one sensory neurone (R...

Many different substances enter and leave a cell by crossing its cell surface membrane. Describe how substances can cross a cell surface membrane. (5) - ANSWER1 (Simple / facilitated) diffusion from high to low concentration / down concentration gradient; 2 Small / non-polar / lipid-soluble molecules pass via phospholipids / bilayer; OR Large / polar / water-soluble molecules go through proteins; 3 Water moves by osmosis / from high water potential to low water potential / from less to mo...

aerobic respiration - ANSWERan exothermic reaction in which glucose is broken down using oxygen to produce carbon dioxide and water and release energy for the cells anaerobic respiration - ANSWERan exothermic reaction in which glucose is broken down in the absence of oxygen to produce lactic acid in animals and ethanol and carbon dioxide in plants and yeast. A small amount of energy is transferred for the cells exothermic reaction - ANSWERa reaction that transfers energy to the environment...

Polysaccharide - ANSWERMany monosaccharides joined together by a condensation reaction Activation energy - ANSWERenergy required to bring about a reaction, it is lowered by presence of enzyme active site - ANSWERa group of amino acids that make up a region of the enzyme where a substrate binds to catalyse a reaction enzyme - ANSWERa protein that acts as a biological catalyst tertiary structure (protein) - ANSWERfolding of a polypeptide chain and contains disulfide bridges, hydrogen +...

Describe the role of a ribosome in the production of a polypeptide. /3 - ANSWER1. mRNA binds to ribosome; 2. Idea of TWO codons/binding sites; 3. tRNA with ANTICODONS binds; 4. (Catalyses) formation of PEPTIDE bond between AMINO ACIDS (held by tRNA molecules); 5. Moves along (mRNA to the next codon); Describe the structure of glycogen. /2 - ANSWER1. Polysaccharide of α-glucose; OR polymer of α-glucose; 2. (Joined by) glycosidic bonds OR Branched structure; NHE3 actively transp...