cell signalling

Question 1

homeostasis

Answer 1

all living organisms need to be able to respond to their changes in their internal or external environment
it is the tendency of an organism or cell to maintain a relatively constant internal environment within tolerance limits, despite changing conditions
internal equilibrium is maintained by adjusting physiological processes such as body temperature, pH, co2 concentration, water balance, blood glucose concentration

Question 2

stimulus responce model (draw it)

Answer 2

1. stimulus - 2. receptors. - 3. modulator or control center - 4. effector - 5. responce —-(feedback)—- back to stimulus

all positive feedback is to do with birthing
all negative feedback is to do with reversing the stimulus message (turning off)

Question 3

negative feedback

Answer 3

homeostatic control mechanisms operate through a negative feedback loop. when a specialised receptor detect a change to an internal condition, the response generated will be the opposite of the change that occurred.
when the levels have returned to equilibrium, the effector will cease to generate a response

Question 4

draw glucose regulation

Answer 4

look at powerpoint for answer

Question 5

what are the types of signalling molecules

Answer 5

steroid hormone, peptide hormone, neurotransmitter, neurohormones, cytokines, pheromones, plant growth regulators

Question 6

hormones

Answer 6

produced in endocrine glands (ductless glands)
travels through the circulatory system to the receptors on the target cell
steroid hormone are hydrophobic (water hating)
peptide hormones are hydrophilic (water loving, cannot cross the membrane)

Question 7

neurotransmitters

Answer 7

produced by neurons
diffuse locally to neighbouring target cells
neurotransmitters carry an action potential (wave of chemical energy) across the synapse (in electrical energy) to the post synaptic neuron.

Question 8

neurohormones

Answer 8

hormones secreted by specialised neurones (neurosecretry cells) in hypothalamus which diffuse into the bloodstream

Question 9

cytokines

Answer 9

produced by immune cells (white blood cells)

Question 10

pheromones

Answer 10

chemicals are released into the external environment snd influence another organism, typically of the same species. e.g. trail, sex, alarm, territorial pheromones

Question 11

plant growth regulators

Answer 11

produced by plant cells and cause a response (tropism)

• note: plant hormones are different from animal hormones as plant hormones don’t travel in general circulation (as plants lack a circulatory system (vascular system): plant hormones are not produced in specialised endocrine glands; are not biomacromolecules (plant hormones are simple)
• plant and animal hormones are both organic
• both use signalling molecules to communicate
• in both organisms signalling molecules travel to target tissue which is often a distance a way

Question 12

autocrine signalling and diagram

Answer 12

secreted molecules diffuse locally and trigger a response in the cells that secrete them

Question 13

paracrine signalling and diagram

Answer 13

secreted molecules diffuse locally and trigger a response in neighbouring target cells

Question 14

endocrine signalling and diagram

Answer 14

secreted molecules diffuse into the bloodstream and trigger a response in target cells anywhere in the body

Question 15

cell junctions

Answer 15

cells can communicate via direct contact

cell junctions allow molecules to readily pass between adjacent cells without crossing the membrane

Question 16

what the purpose of signalling molecules

Answer 16

a signalling molecule is one that enables communication between cells. when a signalling molecule binds to the receptor of the target cell, it causes the target cell to carry out a response

Question 17

what are the five types of receptors, what do they detect and where are they located

Answer 17

• thermoreceptors: detect temperature, located on the skin and the hypothalamus
• mechanoreceptors: detects pain vibration, touch pressure, located on skin, muscles, lungs
• osomoreceptors: water, located in the hypothalamus
• chemoreceptors: detects chemicals, located all throughout the body
• photoreceptors: detects light, in the retinas

Question 18

intrinsic (mitochondrial) pathway

Answer 18

signal for the cell produced inside of damaged/ stressed cell –> signalling molecule ruptures mitochondrial membrane —> activates caspase cascade (apoptosome) —> cell death (apoptosis) initiated

Question 19

extrinsic (death receptor)

Answer 19

signal for cell death is produced outside of the cell (death ligand) —> death ligand/ signalling molecule bends to death receptor on cell membrane —> procapase is activated (caspase cascade)
—> cell death apoptosis initiated

Question 20

characteristics of cell undergoing apoptosis

Answer 20

• caspase enzymes are activated
• cells begin to shrink
• ‘blebbing’ at surface of plasma membrane
• nucleus/mitochondria/cytoskeleton are broken down
• DNA is fragmented

these characteristic are packages into neat membrane bound vesicles (apoptotic bodies) are engulfed by phagocytosis without trigger an immune response

Question 21

what are the two types of apoptosis

Answer 21

intrinsic and extrinsic pathways