A2 Biology Unit 5 Control in Cells and in Organisms BIOL 5

The black mamba’s toxin kills prey by preventing their breathing. It does this by inhibiting the enzyme acetylcholinesterase at neuromuscular junctions. Explain how this prevents breathing.

Acetylcholine not broken down / stays bound to receptor; 2. Na+ ions (continue to) enter / (continued) depolarisation / Na+ channels (kept) open / action potentials/impulses fired (continuously)3.(Intercostal) muscles stay contracted / cannot relax

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People who have McArdle’s disease produce less ATP than healthy people. As a result, they are not able to maintain strong muscle contraction during exercise. Use your knowledge of the sliding filament theory to suggest why.

(Idea ATP is needed for:) 1. Attachment/cross bridges between actin and myosin; 2. ‘Power stroke’ / movement of myosin heads / pulling of actin; 3. Detachment of myosin heads; 4. Myosin heads move back/to original position / ‘recovery stroke’

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Explain how Implanon(contains progesterone) prevents fertilisation from taking place.

1. FSH inhibited; 2. Follicle not stimulated / ripened / does not grow; 3. LH inhibited; 4. Ovulation prevented / egg/ovum not released

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Suggest one advantage of using Implanon rather than an oral contraceptive.

Will not forget to take Implanon / may forget to take an oral contraceptive / does not have to be taken daily / not affected by illness/vomiting

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ncreased intensity of exercise leads to an increased heart rate. Explain how.

1. (Oxygen/carbon dioxide) detected by chemoreceptors / (pressure) detected by baroreceptors; 2. Medulla/cardiac centre involved; 3. More impulses to SAN/along sympathetic nerve;

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Name the type of enzyme that is used to cut the gene for Factor IX from human DNA

Restriction / endonuclease

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Suggest one reason why very few live births result from the many embryos that are implanted.

. Mutation / nucleus/ chromosomes/DNA may be damaged / disrupts genes; 2. May interfere with proteins (produced)/gene expression/ translation; OR 3. Embryo/antigens foreign; 4. Embryo is rejected/attacked by immune system

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Adrenaline binds to receptors in the plasma membranes of liver cells. Explain how this causes the blood glucose concentration to increase.

1. Adenylate cyclase activated / cAMP produced / second messenger produced; 2. Activates enzyme(s) (in cell); 3. (So) glycogenolysis/ gluconeogenesis occurs / glycogenesis inhibited

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Selective breeding can be used to produce cows with desirable features. This involves mating cows with bulls. Suggest how a bull is selected to increase the probability of producing cows with a high milk yield.

Select a bull whose mother/offspring produced a high milk yield

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Explain the difference between pre-mRNA and mRNA

(pre-mRNA) contains introns / mRNA contains only exons

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Describe how hormones are different in the cells they affect

Hormones have widespread effect / affect different organs / affect different parts of the body / affect distant organs / only affect cells with right receptor;

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Describe how hormones and local chemical mediators reach the cells they affect

1. Hormones in blood; 2. Local chemical mediators spread by diffusion / spread directly

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Synapses are unidirectional. Explain how acetylcholine contributes to a synapse being unidirectional

1. (Acetylcholine) released from/in presynaptic side; 2. Diffusion from higher concentration/to lower concentration; 3. Receptors in postsynaptic (side) / binds on postsynaptic (side);

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Name the process by which IAA moves from the growing regions of a plant shoot to other tissues.

Diffusion

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Farmers sometimes give progesterone to sheep to prevent ovulation. Explain how progesterone prevents ovulation.

1. Progesterone has negative feedback effect / inhibits secretion of FSH/LH; 2. (FSH) stimulates follicle development / ( LH) stimulates ovulation

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Scientists can separate fragments of DNA using electrophoresis. Suggest how they can use electrophoresis to estimate the number of base pairs in the separated fragments.

Give one mark for answer confined to smaller fragments move further/faster; Give two marks for comparing with distance/speed moved by fragments of known size/markers / DNA ladder

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Transcriptional factors are important in the synthesis of particular proteins. Describe how

1. Bind to DNA/gene; 2. At specific region/base sequence/promoter sequence; 3. Stimulate transcription / prevents transcription / turn on gene / turn off gene

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Hydrolysis and condensation are important in the formation of new adult proteins. Explain how.

1. Hydrolysis breaks proteins / hydrolyses proteins / produces amino acids (from proteins); 2. Protein synthesis involves condensation; 3. Hydrolysis of polysaccharides/lipids linked to energy source (for synthesising proteins)

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Give two characteristic features of stem cells.

Will replace themselves/keep dividing/replicate; Undifferentiated/can differentiate/develop into other cells/totipotent/multipotent/pluripotent

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When viruses infect cells, they pass their RNA and two viral enzymes into the host cells. One of the viral enzymes makes a DNA copy of the virus RNA. Name this enzyme.

Reverse transcriptase

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Diabetic people who do not control their blood glucose concentration may become unconscious and go into a coma. A doctor may inject a diabetic person who is in a coma with glucagon. Explain how the glucagon would affect the person’s blood [glucose]

Glycogen to glucose/glycogenolysis; By activating enzymes; Gluconeogenesis

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Multicellular organisms are able to control the activities of different tissues and organs within their bodies. They do this by detecting stimuli and stimulating appropriate effectors.How to plants and animals do this?

Plants use specific growth factors.Animals use hormones,nerve impulses or both.By responding to internal & external stimuli, animals ⬆ chances of survival by avoiding harmful environments & by maintaining optimal conditions for their metabolism

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what are Tropisms?

responses to directional stimuli that can maintain the roots and shoots of flowering plants in a favourable environment.

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what general factors help control heart rate?

chemoreceptors and pressure receptors, the autonomic nervous system and effectors

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wha does the Pacinian corpuscle tell us about receptors (2)

eceptors only respond to specific stimuli Stimulation of receptor membranes produces deformation of stretch-mediated sodium channels, leading to the establishment of a generator potential

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Homeostasis is ........

the maintenance of a constant internal environment

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Negative feedback helps maintain an optimal internal state in the context of a dynamic equilibrium. Positive feedback also occurs. What is the difference?

Negative feedback restores systems to their original level.Positive feedback results in greater departures from the original levels. Positive feedback is often associated with a breakdown of control systems, e.g. in temperature control

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Multicellular organisms are able to control the activities of different tissues and organs within their bodies. They do this by detecting ……….. and stimulating appropriate …………….:

stimuli effectors

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To do this plants use specific …………… ………...

growth factors;

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To do this animals use…………….. , or ………….. …………..or a combination of both.

hormones nerve impulses

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By responding to internal and external stimuli, animals increase their chances of survival by (2)

avoiding harmful environments and by maintaining optimal conditions for their metabolism.

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What are responses to directional stimuli that can maintain the roots and shoots of flowering plants in a favourable environment called?

Troprisms

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Mammalian hormones are substances that stimulate their target cells via …………………...

the blood system.This results in slow, long-lasting and widespread responses.

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………………..and ……………..are local chemical mediators released by some mammalian cells and affect only cells in their immediate vicinity.

Histamine and prostaglandins

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Different substances are involved in coordinating responses in animals. Hormones are different from local chemical mediators such as histamine in the cells they affect. Describe how hormones are different in the cells they affect.

Hormones have widespread effect / affect different organs / affect different parts of the body / affect distant organs / only affect cells with right receptor;

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Describe how hormones and local chemical mediators reach the cells they affect.

1. Hormones in blood; 2. Local chemical mediators spread by diffusion / spread directly;

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Synapses are unidirectional. Explain how acetylcholine contributes to a synapse being unidirectional.

1. (Acetylcholine) released from/in presynaptic side; 2. Diffusion from higher concentration/to lower concentration; 3. Receptors in postsynaptic (side) / binds on postsynaptic (side);

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IAA is a specific growth factor. Name the process by which IAA moves from the growing regions of a plant shoot to other tissues.

Diffusion

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When a young shoot is illuminated from one side, IAA stimulates growth on the shaded side. Explain why growth on the shaded side helps to maintain the leaves in a favourable environment.

1. Causes plant to bend/grow towards light / positive phototropism 2. (Light) required for photosynthesis;

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Explain the effect of temperature on the rate at which NAA is taken up by the lower surface of the leaf.

1. More kinetic energy; 2. Faster movement of molecules; 3. More diffusion;

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Suggest how these differences in the cuticle might explain the differences in rates of uptake of NAA by the two surfaces.

1. Thick cuticle on upper surface / thin cuticle on lower surface / few stomata on upper surface / no stomata on upper surface; 2. More diffusion / shorter diffusion pathway (on lower surface);

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Transcriptional factors are important in the synthesis of particular proteins. Describe how.

1. Bind to DNA/gene; 2. At specific region/base sequence/promoter sequence; 3. Stimulate transcription / prevents transcription / turn on gene / turn off gene

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At high temperatures, a desert iguana keeps its mouth wide open and breathes in and out rapidly. This is called panting. Explain how panting helps to reduce the body temperature of an iguana.

1. Evaporation (of water from lining of mouth); 2. Heat transferred from blood;

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Hydrolysis and condensation are important in the formation of new adult proteins. Explain how.

1.Hydrolysis breaks proteins/hydrolyses proteins/produces amino aa's (from proteins); 2.Protein synthesis involves condensation; 3.Hydrolysis of polysaccharides/lipids linked to energy source (for synthesising proteins)

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what enzyme is use in the transcription of DNA?

RNA polymerase

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Oestrogen is a hormone that affects transcription. It forms a complex with a receptor in the cytoplasm of target cells. Explain how an activated oestrogen receptor affects the target cell.

(Receptor/transcription factor) binds to promoter; Stimulates RNA polymerase/enzyme X; Transcribes gene/increase transcription;

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Oestrogen only affects target cells. Explain why oestrogen does not affect other cells in the body.

Other cells do not have the/oestrogen/ ERα receptors

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Give two characteristic features of stem cells.

Will replace themselves/keep dividing/replicate; Undifferentiated/can differentiate/develop into other cells/totipotent/multipotent/pluripotent

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Diabetic people who do not control their blood glucose concentration may become unconscious and go into a coma. A doctor may inject a diabetic person who is in a coma with glucagon. Explain how the glucagon would affect the person’s blood glu conch

Glycogen to glucose/glycogenolysis; By activating enzymes; Gluconeogenesis;

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A2 Biology Unit 5 Control in Cells and in Organisms BIOL 5

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