what does diffusion lead to?
equilibrium of concentrations
how do you maintain a concentration gradient?
molecules must be moved UP the conc. gradient at a rate faster than they diffuse DOWN the conc. gradient
what is active transport?
movement of molecules or ions across a cell membrane from lower to higher conc. AGAINST/ UP conc. gradient
is active transport selective or non selective?
selective - specific shape of pore
what does ‘pump’ mean?
that what’s happening is always an active process
what happens if substrate molecules are moving from lower to higher concentration? (active transport)
- specific transmembrane proteins are required
- these proteins have receptor sites that bind to specific molecules and transport them across cell membrane
- energy for this supplied by ATP
where does active transport often take place?
internal lining of small intestine
which proteins does active transport use?
carrier proteins
what do plants need to absorb from the soil, and where do these things exist?
- absorbs mineral salts
- only exist in very dilute solutions in soil water
what does active transport enable for the cells in the plant?
enables them to take up salts from dilute solution against direction of conc. gradient
what is the possible mechanism for active transport?
- molecule binds to receptor site on inner wall of the pore on the carrier protein
- ATP cytoplasm side of carrier protein, then hydrolysed into ADP +Pi, energy is transferred, and Pi is bound, to carrier protein
- carrier protein changes shape to open the pore to other side of membrane, molecule is released to inside of cell
- Pi released from carrier protein, carrier protein changes shape again do adopt original shape
what are the two types of bulk transport?
- endocytosis
- exocytosis
what is endocytosis?
substances moving from out of the cell to in
what processes does endocytosis involve?
- phagocytosis
- pinocytosis
- receptor-mediated endocytosis
what does phagocytosis form?
phagosome (vacuole)
what does pinocytosis form?
vesicles
what does receptor-mediated endocytosis form?
coated vesicles
what is exocytosis?
substances moving from in the cell to out of it
- also a mechanism where cells are able to insert membrane proteins, lipids etc. into cell membrane
what happens during exocytosis?
- membrane-bound secretory vesicles are carried to plasma membrane
- vesicle contents are secreted into extracellular environment
- secretion possible because the vesicle TRANSIENTLY FUSES with plasma membrane
- vesicles containing these membrane components FULLY FUSE & become part of cell surface membrane
what is bulk transport?
the movement of WHOLE cell substances, not selective
how are vesicles attached to cytoskeleton?
by proteins
what is another type of active transport?
bulk transport
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module 2 - 2.1 microscopy20
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module 2 - 2.2 magnification and calibration6
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module 2 - 2.3 more microscopy12
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module 2 - 2.4 eukaryotic cell structure & 2.5 the ultrastructure of plants24
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module 2 - 2.5 continued - cytoskeleton of eukaryotic cells6
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module 2 - 3.8 nucleic acids57
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module 2 - 3.9 DNA replication and the genetic code44
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module 2 - 3.10 protein synthesis51
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module 2 - 3.11 ATP31
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module 2 - 5.1 structure and function of membranes67
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module 2 - 5.2 factors affecting membrane structure18
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module 2 - 5.3 diffusion and passive transport29
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module 2 - 5.4 active transport22
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module 2 - 5.5 osmosis26
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module 2 - 6.1 the cell cycle39
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module 2 - 6.2 mitosis25
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module 2 - 6.3 meiosis20
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module 2 - 6.4 organisation and specialisation of specialised cells & 6.5 stem cells30
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module 3 - 7.1 specialised exchange surfaces13
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module 3 - 7.2 mammalian gaseous exchange system41
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module 3 - 7.3 measuring the process of breathing17
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module 3 - 7.4 ventilation and gas exchange in other organisms50
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module 3 - 8.1 transport systems in multicellular organisms9
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module 3 - 8.2 blood vessels35
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module 3 - 8.3 blood, tissue fluid and lymph30
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module 3 - 8.4 transport of oxygen and carbon dioxide in the blood42
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module 3 - 8.5 the heart27
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module 4 - 10.1 classification15
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module 4 - 10.2 the 5 kingdoms10
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module 4 - 10.3 phylogeny8
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module 4 - 10.4 evidence for evolution23
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module 4 - 10.5 types of variation29
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module 4 - 10.6 representing variation graphically17
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module 5 - 10.7 adaptations22
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module 4 - 10.8 changing populations characteristics11
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module 5 - 13.1 coordination18
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module 5 - 13.2 neurones23
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module 5 - 13.3 sensory receptors12
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module 5 - 13.4 nervous transmission33
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module 5 - 13.5 synapses24
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module 5 - 13.6 organisation of the nervous system18
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module 5 - 13.7 structure and function of the brain18
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module 5 - 13.8 reflexes12
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module 5 - 13.9 voluntary and involuntary muscles14
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module 5 - 13.10 the sliding filament model25
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module 5 - 14.1 hormonal communication26
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module 5 - 14.2 structure and function of the pancreas11
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module 5 - 14.3 regulation of blood glucose concentration18
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module 5 - 14.4 diabetes and its control11
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module 5 - 14.5 coordinated responses16
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module 5 - 14.6 controlling heart rate10
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15.1 the principles of homeostasis0
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15.2 thermoregulation in ectotherms0
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15.3 thermoregulation in endotherms0
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15.4 exctretion, homeostasis and the liver0
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15.5 structure and function of the mammalian kidney0
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15.6 the kidney and osmoregulation0
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15.7 urine and diagnosis & 15.8 kidney failure0
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module 5 - 16.1 plant hormones and growth in plants25
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module 5 - 16.2 and 16.3 plant responses to abiotic stress and herbivory18
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module 5 - 16.4 tropisms in plants & 16.5 the commercial uses of plant hormones18
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module 5 - 17.1 energy cycles & 17.2 ATP synthesis25
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module 5 - 17.3 photosynthesis (1)26
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module 2 - 17.3 photosynthesis (2)7
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module 5 - 17.4 factors affecting photosynthesis26
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module 5 - 18.1 glycolysis & 18.2 linking glycolysis and the Krebs cycle27
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module 5 - 18.3 the krebs cycle22
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module 5 - 18.4 oxidative phosphorylation25
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module 5 - 18.5 anaerobic respiration15
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module 5 - 18.6 respiratory substrates20
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BIOLOGY MODULE 2 (papers 1,2, & 3)242
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BIOLOGY MODULE 3 (papers 1 & 3)109
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BIOLOGY MODULE 4 (papers 2 & 3)1
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BIOLOGY MODULE 5 (papers 1 & 3) incomplete - add plant hormone PAGs and kidney stuff after mocks176
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BIOLOGY MODULE 6 (papers 2 & 3)4
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A LEVEL BIOLOGY KEY TERMS83
