8481864
Descripción
Fichas por Lucy Frances, actualizado hace más de 1 año
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Creado por Lucy Frances
hace más de 7 años
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| Pregunta | Respuesta |
| High blood pressure can lead to an accumulation of tissue fluid. Explain how | High blood pressure=high hydrostatic pressure Increased outward pressure from arteriole end of capillary Decreased inward pressure from venule end more tissue fluid formed/less reabsorbed |
| Describe how bacteria are destroyed by pathogens | Phagocyte engulfs bacteria to form phagosome Lysosomes in phagocyte release lysozymes Lysozymes hydrolyse the bacterium in the phagosome |
| Describe and explain the mechanism that causes forced expiration | Contraction of internal intercostal muscles Relaxation of diaphragm/external intercostal muscles Decrease in volume of thorax External pressure lower than internal pressure Air pushed down pressure gradient |
| Describe the appearance and behaviour of chromosomes during mitosis | Prophase - Shortening and thickening - Attach to spindle fibres Metaphase - Line up along the equator of the cell Anaphase - Spindle fibres contract - Splitting of the centromere - Chromosomes split in half - Half go to each pole |
| Compare and contrast the processes by which water and inorganic ions enter cells | Both move down concentration gradients Both move through (protein) channels in the membrane Ions can move against a concentration gradient by active transport |
| Give two properties of water that are important in the cytoplasm of cells | Polar - Solvent Solvent - Speeds up metabolic reactions Reactive - Hydrolysis/condensation reactions |
| Cells lining the ileum of mammals absorb the monosaccharide glucose by co-transport with sodium ions. Explain how | Sodium is actively transported out the epithelial cells Sodium-potassium pump Lower concentration of sodium ions inside epithelial cells Sodium enters from lumen Enters via sodium-glucose co-transport channel Must be in association with glucose to enter Glucose enters blood capillaries via facilitated diffusion |
| Homologous chromosomes carry the same genes but are not genetically identical. Explain why | (Homologous chromosomes) carry different alleles |
| Explain why meiosis is important in sexual reproduction | Produces gametes that are genetically different Chromosome number halved (haploid) When fertilisation occurs the embryo has the correct number of chromosomes (diploid) |
| Explain the advantage of peptidases being secreted in an inactive form | Cell membranes contain protein Active peptidases may digest these proteins |
| Amylase is not secreted in an inactive form. Explain why this is not a disadvantage | Amylase digests starch Starch is not present in animal cells |
| Describe the reaction catalysed by a peptidase enzyme | Hydrolysis reaction Water is added (to a large soluble molecule) Breaking the peptide bond |
| Explain how water enters a bacterial cell | Water potential lower/more negative in cell Water enters by osmosis |
| Explain -(i) The shape of the curve at 55C after 20 minutes -(ii) Why the curves for 27C and 37C level off that the same value | (i) Causes detnaturation H+/ionic bonds break Shape of active site changed Substrate can no longer bind (ii) All substrates changed into product Same amount of product formed Same initial substrate concentration |
| Describe how the Golgi apparatus is involved in the secretion of enzymes | Modifies protein Put into Golgi vesicles Transport to cell surface/vacuole |
| Describe how two amino acids differ from one another | Different R groups |
| Give structural differences between mRNA and tRNA | tRNA - Folded shape mRNA - No hydrogen bonds |
| Describe how phospholipids are arranged in a plasma membrane | Bilayer Hydrophobic (lipid) (tails) to inside Hydrophillic (polar) (phosphate) (heads) to outside |
| Describe and explain the processes that occur during meiosis that increase genetic variation | Crossing over - Bivalents overlap - Break off at chiasmata - Recombination - Different alleles Independent assortment/segregation - Homologous chromosomes are independent of each other |
| When a vaccine is given to a person it leads to the production of antibodies against a disease causing organism. Describe how | Vaccine contains antigen from pathogen Macrophage presents antigen on its surface T cell with complementary receptor protein binds to antigen T cell stimulates B cell with complementary antibody B cell secretes large amount of the antibody B cell divides by mitosis Memory cell formed producing the same antobody |
| How do mutations lead to non-functional proteins? | Base deletion/substitution Frame shift - changes codons after that point - Base deletion Different amino acids coded for Change in hydrogen/ionic/disulfide bonds Change in tertiary structure Can no longer bind to substrate as it is no longer complementary |
| Describe the difference between passive and active immunity | Active - Memory cells - Production of antibody by plasma/memory cells - Long term - antibody production - Takes time to develop Passive - Antibody introduced into body from outside source - Short term - Antibody given is eventually broken down |
| Explain how the structures of the walls of arteries and arterioles are related to their function | Elastic fibres - Stretch under pressure/during systole - Recoil during diastole - Maintain constant blood pressure Muscle - Contracts -Reduces diameter of lumen/vasoconstriction - changes pressure to maintain a constant Epithelium - smooth - Reduces friction/blood clots/resistance |
| Compare and contrast the structure of starch and cellulose | Both - Polysaccarides - Contain glucose - Contain hydrogen bonds within the structure Starch - Contains alpha glucose - Helical structure - No hydrogen bonds between molecules Cellulose - Contains beta glucose - Straight molecule |
| When comparing variation it is often considered more useful to compare standard deviations rather than ranges. Explain why | Range influenced by a single outlier (anomaly) Standard deviation shows dispersion around the mean Range only shows extremes Standard deviation allows statistical use |
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