intercellular communication and signal transduction

Question 1

what types of cell communication is there?

Answer 1

indirect and direct

Question 2

name the types of direct cell comunication

Answer 2

Gap junctions and linking of surface receptors

Question 3

name the tyoes of indirect cell communication

Answer 3

paracrines
autocrines
neurotransmitters
hormones and neurohormones

Question 4

what are Gap junctions

Answer 4

Gap junctions are specialized intercellular connections that allow direct communication between adjacent cells by forming minute tunnels, known as connexons, that bridge the cytoplasm of neighboring cells.

Question 5

What are connexons, and what is their structure?

Answer 5

Connexons are tube-like structures made of six protein subunits arranged in a circular pattern. Two connexons from adjacent cell membranes align end-to-end to form a tunnel that allows the direct passage of small ions and molecules between cells.

Question 6

What types of particles can pass through gap junctions?

Answer 6

Gap junctions allow the passage of small, water-soluble particles such as ions, glucose, and amino acids. These particles move directly between the cytoplasm of neighboring cells without entering the extracellular fluid

Question 7

what tissues are gap junctions abundant

Answer 7

cardiac and smooth muscle
non muscle- pass nutrients like glucose and AA

Question 8

What is the role of gap junctions in cardiac and smooth muscle tissues?

Answer 8

In cardiac and smooth muscle tissues, gap junctions allow the movement of ions between cells, transmitting electrical signals. This leads to synchronized contractions of the entire muscle, such as the coordinated pumping action of the heart chambers.

Question 9

How do gap junctions contribute to the development of an egg in the ovary?

Answer 9

Gap junctions in the ovary allow the transfer of nutrients like glucose and amino acids between cells, helping the developing egg store essential nutrients necessary for its growth.

Question 10

Why are gap junctions considered the most intimate means of intercellular communication?

Answer 10

allow the direct exchange of small ions and molecules between the cytoplasm of adjacent cells, bypassing the extracellular fluid

Question 11

What happens when two connexons from adjacent cells join?

Answer 11

they form a tunnel that bridges the cytoplasm of both cells, allowing small, water-soluble molecules and ions to pass directly between them.

Question 12

What is direct intercellular communication?

Answer 12

Direct intercellular communication is the process where cells communicate with each other through physical contact, allowing for the exchange of signals or molecules.

Question 13

What mechanism allows direct linking

Answer 13

The transient linking of cell surface receptors allows direct linking between cells. Cells have specialized surface markers that can recognize and bind to compatible markers on other cells, enabling temporary interactions.

Question 14

Which type of cells use direct communication, and why?

Answer 14

immune system to recognise and interact with cells- identify and respond to threats such as cancer or infected cells

Question 15

what form of communication do phagocytes use and how?

Answer 15

transient linking of cell surface receptors to recognise undesirable cells like cancer. selectively interact with these cells enabling the immune system to destroy them while sparing healthy cells

Question 16

What role do specialized surface markers play in immune system interactions?

Answer 16

specialized surface markers on immune cells help them identify and link with other cells that have compatible markers. This transient interaction allows immune cells to determine whether the target cell is healthy or should be destroyed.

Question 17

What are surface markers, and how do they function in cell communication?

Answer 17

Surface markers are proteins or glycoproteins present on the cell membrane. They help in recognizing other cells by binding to compatible markers, facilitating direct and transient interactions essential for cellular recognition and communication

Question 18

What is indirect intercellular communication?

Answer 18

cells releasing specific chemical messengers (signal molecules) into the extracellular fluid (ECF) to interact with target cells. These messengers bind to receptors on the target cells, allowing them to perform specific functions.

Question 19

How do chemical messengers communicate with target cells?

Answer 19

Chemical messengers are released into the extracellular fluid by controlling cells and bind to receptors on target cells that are specific for those messengers. This triggers specific actions in the target cells.

Question 20

What percentage of the human genome codes for the synthesis of membrane receptors, and why is this significant?

Answer 20

5% of the human genome codes for the synthesis of membrane receptors, highlighting the importance of this means of communication in regulating cellular functions.

Question 21

What are paracrines, and how do they function?

Answer 21

local chemical messengers that exert their effects only on neighboring cells in the immediate environment of the secretion site. They diffuse through the interstitial fluid and act over short distances. An example is histamine, which dilates blood vessels during an inflammatory response.

Question 22

How are paracrines different from other chemicals that influence neighboring cells?

Answer 22

Paracrines are specifically released for communication between neighboring cells, while other chemicals, like carbon dioxide (CO2) released during muscle activity, influence neighboring cells without being specifically released for that purpose. CO2 promotes blood vessel dilation in active muscle but is not classified as a paracrine.

Question 23

What are neurotransmitters, and how do they communicate between neurons?

Answer 23

short-range chemical messengers released by neurons in response to electrical signals (action potentials). They diffuse across small gaps to act on adjacent target cells such as other neurons, muscles, or glands.

Question 24

What distinguishes neurotransmitters from hormones?

Answer 24

: Neurotransmitters act over short distances, typically between adjacent cells, while hormones are long-range messengers secreted by endocrine glands and carried through the blood to distant target cells.

Question 25

how do hormones function in the body

Answer 25

They travel through the bloodstream to distant parts of the body, where they exert effects on target cells that have specific receptors for those hormones.

Question 26

How do neurohormones differ from regular hormones and neurotransmitters?

Answer 26

Neurohormones are chemical messengers released by neurosecretory neurons, which respond to electrical signals but, instead of directly acting on target cells, they release the messengers into the blood to affect distant target cells. This is different from regular neurotransmitters, which act over short distances.

Question 27

What is an example of a neurohormone, and what is its function?

Answer 27

An example of a neurohormone is vasopressin (ADH), produced by neurons in the brain. It regulates water balance in the body by promoting water conservation in the kidneys and is released in response to high osmolality or low blood volume/pressure, triggering thirst and adjusting water retention.

Question 28

How do neurosecretory neurons differ from normal neurons?

Answer 28

: Neurosecretory neurons release neurohormones into the blood to reach distant target cells, while normal neurons release neurotransmitters into confined spaces, affecting adjacent cells over short distances.

Question 29

What is signal transduction?

Answer 29

process by which an incoming signal from a chemical messenger is conveyed to a target cell and transformed into a specific cellular response.

Question 30

How does the binding of a chemical messenger influence the target cell?

Answer 30

he binding of a chemical messenger to its specific receptor on the target cell acts as a signal for the cell to perform a particular function. This signal is then converted into intracellular changes that lead to the desired response.

Question 31

What happens to the extracellular signal during signal transduction?

Answer 31

he extracellular signal (the chemical messenger) is transduced, meaning it is converted or changed into a form that modifies intracellular activity, leading to a specific outcome within the cell.

Question 32

Can you give an analogy to explain signal transduction?

Answer 32

Signal transduction can be compared to a radio receiving radio waves from a broadcast station and converting them into sound. Similarly, cells receive external signals and convert them into actions like metabolism, contraction, or division.

Question 33

How do lipid-soluble messengers (such as steroid hormones) interact with target cells?

Answer 33

r: Lipid-soluble messengers, such as cholesterol-derived steroid hormones, can easily pass through the lipid bilayer of the cell membrane. Once inside the cell, they bind to receptors within the cell to initiate a specific response.

Question 34

Why can’t water-soluble messengers enter the cell?

Answer 34

Water-soluble messengers, such as protein hormones and neurotransmitters, cannot pass through the lipid bilayer of the cell membrane because they are not soluble in lipids. Instead, they bind to specific receptors on the surface of the target cell.

Question 35

How do water-soluble messengers trigger a response in target cells if they cannot enter the cell?

Answer 35

Water-soluble messengers bind to receptors on the cell membrane. This binding triggers a series of intracellular events that ultimately control various cellular activities, such as secretion, metabolism, or muscle contraction.

Question 36

What are some of the cellular activities controlled by signal transduction?

Answer 36

ignal transduction can control a wide range of cellular activities, including membrane transport, secretion, metabolism, contraction, cell division, and differentiation.

Question 37

How do the mechanisms of signal transduction vary?

Answer 37

The mechanisms of signal transduction vary depending on the type of chemical messenger (lipid-soluble or water-soluble) and the type of receptor involved (whether the receptor is on the cell surface or inside the cell).

Question 38

What is the role of receptors in signal transduction?

Answer 38

Receptors play a crucial role in signal transduction by specifically binding to chemical messengers. This binding initiates a cascade of intracellular events that lead to the appropriate cellular response.

Question 39

Despite various possible responses, binding of messenger to matching receptor causes intracellular response by 3 mechanisms:
name them

Answer 39

1. Opening/closing chemically gated receptor channels

2.Activating receptor enzymes

3. Activating 2nd messenger pathways via G-protein-coupled receptors