p1 - set a Flashcards
Gestational diabetes is a medical condition that affects pregnant women. It results in high levels of glucose in the blood, even though the woman produces normal levels of insulin. (i) Gestational diabetes is most similar to which other type of diabetes? Explain your answer.
- type 2 diabetes
- this is because the liver cells are not responding to the insulin
Suggest two ways a woman with gestational diabetes can manage her condition.
- excercise
- low sugar diet
- managing weight
Explain why glucose is required for the contraction of skeletal muscle.
- contraction of the muscle requires atp
- glucose, will provide atp during respiration
- the atp is used to break cross bridges between actin and myosin
- the atp is hydrolysed to reset the myosin heads
Mean oxygen uptake rate at rest in women is around 0.020dm3 s–1. Using these data, the student made the following conclusion: My data show that being pregnant reduces rate of oxygen uptake by up to 20%. Evaluate this claim, using the data in Fig. 16.1.
- involves a calculation mark
- being 36 weeks pregnant doe not represent the whole pregnancy
- this investigation only counts for one woman and not more and so may not be representative so invalid
A cell surface membrane is partially permeable. The phospholipid bilayer is important in controlling the movement of molecules through the membrane. Explain how the structure of a phospholipid molecule contributes to the partial permeability of a cell surface membrane.
- it consists of a bilayer which has hydrophobic tails facing inwards and hydrophillic heads facing outwards
- polar molecules cannot pass through the bilayer
- non polar molecules can pass through the membrane
Compare and contrast the processes of endocytosis and exocytosis.
similar-
- they both involve vesicles
- both involve the use of ATP
differences-
- exocystosis, is movement out of the cell and endocytosis is movement into the cell
- exocytosis involves the vesicle fusing with the membrane and endocytosis involves the formation of vesicles
Explain how the resting potential of –70 mV is maintained in the sensory neurone when no pressure is applied
- the membrane is more permeable to potassium ions and less to sodium ions
- sodium is pumped out and potassium in
Explain how applying pressure to the Pacinian corpuscle produces the changes in membrane potential
- pressure causes the lamelle to stretch
- sodium channels open and sodium moves in
- the greater pressure means more channels open
When the membrane potential is the same whether medium or heavy pressure is applied to the fingertip. Explain why.
- the threshold limit is reached
- and so any additional pressure wont have an effect this is known as the all nothing principle
Multiple sclerosis is a disease in which parts of the myelin sheaths surrounding neurones are destroyed. Explain how this results in slower responses to stimuli.
- neurones unable to jump between the nodes of ranvier
- more depolarisation over length of membranes
Following their formation, assimilates are transported throughout the plant by translocation in phloem. Phloem sap mainly consists of carbohydrates in the form of sucrose, but also contains other solutes. (i) Suggest why it is beneficial to the plant for the carbohydrate to be transferred throughout the plant in the form of sucrose rather than as an alternative carbohydrate.
- sucrose is soluble and so transported in the sap
but metabolically inactive so removed during transport
How is transport in the phloem similar to and different from transport in the xylem?
similar - they both carry solutes in their solution
difference - phloem carries carbohydrates and xylem does not
- phloem transport is multidirectional and xylem is unidirectional
Assimilates are loaded into the phloem at the ‘source’ and then transported to the ‘sink’. (i) Explain, with a suitable example, how some parts of the plant can act as both a ‘source’ and a ‘sink’.
- certain parts of the plants can store carbohydrates and release them when needed
- examples include roots and leafs which can act as a sink or source
19.1 is a diagram that represents the loading of sucrose into the phloem at the ‘source’. Fig. 19.1 With reference to Fig. 19.1, explain the process of the loading of sucrose into the phloem and its movement in the phloem.
- Sucrose pumped from the companion cell into the phloem sieve tube by active transport, when in the sieve tube it moves through pores in the sieve plate (point b)
- At point c, water is moving into the phloem sieve tube from the xylem
- At a, water enters the sieve tube from the companion cell
Increased pressure forces flow of sap down phloem
In the modified plants, the unloading of sucrose is increased in the tubers compared with those that were not modified. The transport of sucrose to the tubers was also increased in the modified plants. Using the data and the information given, deduce a possible mechanism to account for the increased unloading and transport of sucrose in the modified plants.
Sucrose is unloaded at the sink and invertase converts sucrose into glucose
Increases sucrose concentration gradient between phloem and sink
Causes increased unloading of sucrose from phloem
Increases solute gradient between source and sink
Removal of water from phloem increases pressure gradient between source and sink
Contributes to increased movement in phloem
