Week 9

Question 1

What is a signal transduction pathway?

Answer 1

A series of steps by which a signal on a cell’s surface is converted into a specific cellular response.

Question 2

What are the types of chemical signal?

Answer 2

Autocrine
Paracrine
Neural
Neuroendocrine
Pheromones

Question 3

What is an autocrine signal?

Answer 3

The signalling mechanism acts on the same cell it has been secreted by.

Question 4

What is a paracrine signal?

Answer 4

Acts on locally neighbouring cells and moves by diffusion.

Question 5

What are neuroendocrine signals?

Answer 5

Released from neurones but act on distant cells.

Question 6

What are pheromones ?

Answer 6

Released into the environment and act on a different individual.

Question 7

What type of signalling molecules are used in endocrine signalling?

Answer 7

Hormones

Question 8

Give an example of a type go signalling molecule used in paracrine signalling.

Answer 8

Neurotransmitter

Question 9

What methods do animals use for local signalling?

Answer 9

By cellular direct contact or by using local messenger molecules which only travel short distances.

Question 10

What methods do animals use for long distance signalling?

Answer 10

Hormones - endocrine system

Question 11

How do steroid hormones reach receptors in the cytoplasm or nucleus?

Answer 11

Diffuse across the plasma membrane

Question 12

Where are the receptors found that steroid hormones bind to?

Answer 12

Cytoplasm or nucleus

Question 13

What are all steroid hormones synthesised from?

Answer 13

Cholesterol

Question 14

What are the 2 categories of steroid hormones?

Answer 14

Sex steroids

Coricosteroids

Question 15

What are corticosteroids?

Answer 15

Steroids produced in the adrenal Cortex

Question 16

Where are sex steroids produced?

Answer 16

Gonads

Question 17

Give examples of sex steroids

Answer 17

Oestrogen, progesterone, testosterone

Question 18

Give examples of cortiocosteroids

Answer 18

Glucocorticoids and mineralcorticoids

Question 19

Which steroid hormones have a different structure and function to most steroids?

Answer 19

Vitamin D3, Retionic Acid and Thyroid hormone

Question 20

Although thyroid hormone has a different structure and function to most steroids, what is its similarity to most steroids?

Answer 20

The mechanisms it uses

Question 21

How do steroids acts as signalling molecules?

Answer 21

Steroids are soluble in plasma membrane so can readily enter the cell cytosol by diffusion and bind to mobile receptors.

The hormone-receptor complex formed then enters the nucleus of the cell by diffusion and binds to specific genes, acting as a transcription factor.

mRNA is transcribed and leaves the nucleus to be translated into specific proteins by ribosomes.

The specific proteins produced then carry out functions or produce structures in target cells

Question 22

What is the overall purpose of steroid hormones?

Answer 22

Protein synthesis

Question 23

Describe the solubility of steroid hormones in plasma membrane

Answer 23

soluble

Question 24

Describe the time it takes steroid hormones to produce a response

Answer 24

Slow

Question 25

Describe how long the effects of steroid hormones last

Answer 25

A long Tim

Question 26

How do nitric oxide and carbon monoxide reach receptors when acting as target molecules.

Answer 26

Use simple diffusion to cross membranes.

Question 27

How do nitric oxide and carbon monoxide affect cells when act as signalling molecules?

Answer 27

They alter the activity of intracellular target enzymes.

Question 28

How wide spread are the effects of nitric oxide and carbon monoxide when they act as signalling molecules?

Answer 28

Localised effects

Question 29

What is of the main bodily effects that NO and CO have when act as signalling molecules?

Answer 29

Vasodilation

Question 30

What are the stages of cell signalling?

Answer 30

Reception Transduction Response

Question 31

Who discovered the steps of cell signalling?

Answer 31

Earl W. Sutherland

Question 32

What happens in step 1 (reception) of cell signalling?

Answer 32

A signal molecule binds to a receptor protein, causing a conformational change. The signalling ligand molecule and the receptor then form a complex.

Question 33

where are intracellular receptors found?

Answer 33

Cell cytosol or nucleus of target cells

Question 34

What are the hydrophobic signalling molecules used by animals?

Answer 34

Steroid and thyroid hormones

Question 35

What type of molecules mainly bind to receptor molecules on the plasma membrane?

Answer 35

Water soluble signalling molecules

Question 36

What are the 3 main types of receptors in the plasma membrane?

Answer 36

G-protein linked receptors Receptor Thyrosine Kinase Ion channels

Question 37

How does the G protein receptor affect activity of GDP?

Answer 37

If a G-protein is bound to GDP, it is inactive.

Question 38

What type of molecules do receptor throne kinases bind to ?

Answer 38

Phosphates and Thyrosines

Question 39

What is step 2 of cell signalling?

Answer 39

Transduction

Question 40

What are the possible methods of transduction in cell signalling?

Answer 40

Phosphorylation Cascade Second messenger methods Cytoplasmic and nuclear responses

Question 41

What are the benefits of a multiple step transduction cell signalling pathway?

Answer 41

Amplify cellular signals and create a large cellular response.

Question 42

What are the most common type of signalling molecules?

Answer 42

Proteins

Question 43

Outline the use of a phosphorylation cascade in the transduction process of cell signalling.

Answer 43

Phosphatase enzymes are used to remove phosphate groups and kinases are used to add phosphate groups. Protein kinases each activate the next in a series by phosphorylating the inactive precursor.

Question 44

What type of molecules are second messengers?

Answer 44

Small, non-protein, water-soluble molecules or ions

Question 45

What is the 'first messenger' in a second messenger model?

Answer 45

The single molecule that binds to the membrane

Question 46

How do second messengers spread through a cell?

Answer 46

By diffusion

Question 47

Name a widely used second messenger

Answer 47

cAMP

Question 48

What enzyme in the plasma membrane converts ATP to cAMP?

Answer 48

Adenyl cyclase

Question 49

What is the purpose of the enzyme Adenyl Cyclase?

Answer 49

coverts ATP to cAMP

Question 50

What does cAMP activate?

Answer 50

Protein kinases

Question 51

Why are calcium ions important as second messengers?

Answer 51

They can regulate their own concentration.

Question 52

What second messengers are used when Ca2+ is used as the first messenger?

Answer 52

Inositol triphosphate and diaculglycerol

Question 53

What is usually the final outcome of cellular signalling transduction via a cytoplasmic or nuclear pathway ?

Answer 53

To synthesise enzymes or proteins by selectively transcribing genes and using signalling molecules as transcription factors.

Question 54

What do signalling molecules often act as to regulate protein synthesis ?

Answer 54

Transcription factors

Question 55

What fine tuning methods are used in the response of cell signalling methods?

Answer 55

Amplification Making the response specific Enhancing response efficiency Terminating the signal

Question 56

How are cell signalling responses amplified?

Answer 56

Enzyme cascades amplify the signal. The number of activated products at each step is greater than at the previous step.

Question 57

By what method are cell signal often coordinated?

Answer 57

"Cross-talk" between branching pathways

Question 58

What type of proteins are often used to enhance the responses of cell signalling?

Answer 58

Scaffolding proteins

Question 59

How are cell signalling mechanisms terminated?

Answer 59

When signalling molecules leave the receptor and cause it to become inactive.

Question 60

What causes target organ specificity ?

Answer 60

Specific receptor molecules for hormones either on the plasma membrane surface or in the cytoplasm of cell of the target organ.

Question 61

What is a Kinase?

Answer 61

An enzyme that transfers phosphate groups from high-energy donor molecules such as ATP, to a specific substrate via phosphorylation.

Question 62

In terms of local signalling, how do animal cells interact?

Answer 62

By direct contact or by local regulators which are messenger molecules that only travel a short distance.

Question 63

What is used for long distance signalling in plants and animals ?

Answer 63

Hormones

Question 64

How do steroid hormones travel across the plasma membrane?

Answer 64

By diffusion

Question 65

Where do steroid hormones bind to receptors in cells?

Answer 65

In the cytoplasm or in the nucleus.

Question 66

What are steroid hormones synthesised from?

Answer 66

Cholestrol

Question 67

What are the 2 categories of steroids used for cellular communication?

Answer 67

Sex steroids and Corticosteroids

Question 68

Name some steroids which have a different structure to the rest but perform the same function.

Answer 68

Thyroid hormone Vitamin D3 Retinoic Acid

Question 69

What are the purpose of the steroid receptor superfamily and what feature allows them to do this?

Answer 69

They have transcription factors that function as activators or repressors of transcription.

Question 70

Can calcium be produced by cells on demand?

Answer 70

No

Question 71

Where is calcium stored?

Answer 71

In the endoplasmic reticulum and sarcoplasmic reticulum.

Question 72

Where is calcium bound in the sarcoplasmic reticulum?

Answer 72

Bound to specialised proteins.

Question 73

What happens in terms of calcium when the sperm penetrates the egg ?

Answer 73

Calcium which is previously sequestered in the organelles is spread across the surface f the egg from the point of sperm entry.

Question 74

What is calcium used for during fertilisation?

Answer 74

It triggers complete meiosis of the egg which must occur before the sperm and egg pronuclei can fuse.