Hormones/Signal Transduction Flashcards
What two hormones does the pancreas produce?
Insulin and Glucagon
What is the role of insulin and glucagon
Control glucose in the blood
What does insulin control
Insulin is produced when blood glucose levels needs decreasing
What does glucagon control
Glucagon acts if there is too little glucose in the body
Where is insulin produced??
Beta cells of the pancreas
Where is glucagon produced??
Alpha cells of the pancreas
Explain negative feedback if there is an increase in blood glucose
Stimulus- Increase in blood glucose
Receptor-Chemorecptor
Control Centre-Pancreas
Effector- Pacreatic beta cells will release insulin
Response-Liver and muscle cells uptake glucose and store as glycogen
Feedback- Blood sugar levels decrease
Explain negative feedback in regards to, too little glucose in the blood
Stimulus- decrease in blood glucose
Receptor-Chemorecptor
Control Centre-Pancreas
Effector- Pacreatic alpha cells will release glucagon
Response-Liver and muscle cells will break down glycogen and release as glucose
Feedback- Blood sugar levels increase
Explain how insulin promotes the uptake of glucose
Changes the permeablity of the cell membrane to glucose
Why do cells need to communicate
Control and regulation of systems
What are signalling molecules also known as??
Ligands
What are receptors and hormones
Specific
What are the three types of signals??
Autocrine signals
Paracrine Signals
Endocrine Signals
Define Autocrine Signals
A cell secretes a hormone into extracellular fluid and binds to its own receptors
Define Paracrine Signals
Signals being released by cells into extracellualr medium acts on nearby target cells, so this type of signal is a local signal.
Define Endocrine Signals
Signals that are produced in the endocrine gland are secreted in the blood stream, therefore distributed throughout the whole body, but only stimulate those with specific receptors
Defintion for Hormone
An organic molecule produced in a cell, either acting within the cell or diffusing or being transported to other cell. Hormones travel via extracellular fluid and act on specific target cells.
Where do hormones usually travel
In the blood stream of tissue fluid
What are the three different classification of hormones?
- Steroid
- Protein/peptide
- Amino acid derivative
Explain steroid hormones
- Tend to have a long life span
- Created on demand from precursors in the cell
- Made from chloesterol therefore lipophilic and hydrophobic
- Steroids pass through the cell membrane via simple diffusion
- Need a carrier protein when travelling through blood
Example of a steroid hormone
testoesterone
Explain Protein/Peptide Hormones
- Made in advance and stored in cells secretory vesciles
- Cannot pass through the membrane so they leave via exocytosis
- Short life span
- They are hydrophilic and can easily travel through the blood stream but need assistance when passing through the membrane
example of protein/peptide hormones
Adrenaline
Explain Amino Acid Dervative Hormones
- Small molcules that have the same structure as an amino acid
- Made in advance and stored in the secretory vescilces, leave via exocytosis.
- Short Life span
- Water soluble so they can travel through the blood stream easily but need assitance when passing through the cell membrane
Are hormones slow or fast
Slow
Do they work for a long period or time or short?
Generally long
Where are steriod receptors in regards to the cell?
Lipid based hormones are able to pass through the membrane easily and therefore their receptor is located on the inside of the cell in the cytosol.
Where are the peptide and amino hormones located?
- Situated on the outside of the cell.
- This is due to not being able to pass through the membrane
- The receptors then activate a protein on the inside of the membrane
Define Signal Transdution
Refers to the cascade of events originating outside the cell in leading to a specific cellular response. This is the process in which a cell converts one kind of kind into another by a series of relay molecules.
Explain the steps in signal transduction
- Signal is recieved
- Signal is amplified
- Transduction
- Response
- Feedback (possible)
What is the first messenger
The extracellular molecule that binds to the receptor is he first messenger.
What is the second messenger?
Molecules that relay signals received at the receptors on the cell surface.
What are some potential responses to the signal transduction pathways?
May lead to activation of genetic material (DNA)
-This can lead to the production of proteins
Explain the signal transduction of steroids
- Lipid soluble hormone passes through the cell membrane and binds to a receptor in the cytosol
- Then forms a hormone-receptor complex
- Then the complex enters the nucleus
- Then the complex will act on genes
Discuss hormone longevity
Hormones do not last forever
Once they have delivered their message they are degraded by enzymes
Excreted the body via kidneys or faeces
Explain the steps o the negative feedback model if there is an increase in temperature
Stimulus-Increase in temperature Receptor-Thermoreceptor Control Center- CNS Effector- Sweat glands and blood vessels Response- Sweating and blood vessels dilate Feedback- Decrease in body temperature
Explain extracellular fluid
Fluid on the outside of the cell
e.g tissue fluid and plasma
Explain intracellular fluid
Located on the inside of cells
e.g cytosol
Define Homeostasis
Processes which are responsible for maintaining a constant internal environment.
What are some aspects of internal environment that need to be kept stable?
- Temp
- pH
- ion concentration and nutrient levels
What is the external environment for unicellular organisms?
Water or air
What are some ways that unicellular organisms maintain their own internal environment
- Regulate the composition of the cytosol by the cell membrane
- Use flagella to move away from undesired stimuli
What are the two main systems involved in coordiniation and regulation of internal environments of multi cellular organisms
Nervous System
Hormonal
Steps in stimulus response model
- Stimulus
- Receptor
- Control Centre
- Effector
- Response
Explain the two steps in negative feedback
- Stimulus is dectected and a response is produced
- The response will either oppose the stimulus or bring back the original stimulus to normal levels
What organisms are chemical messengers found in?
Plants and Animals
What are the main groups of hormones?
Steroids
Protein/peptide
Amino acid derivatives
Explain why hormones act on specific cells?
They only act on cells that have a specific cell receptor site that is only found within the target cell. IF the cell does not have that specific receptor site then it will not bind to it. `
Where are protein based hormones receptors located?
Outside of the cell
Where are lipid based hormones receptors located?
Within the cytoplasmic
Briefly explain cell junctions
Allow molecules to readily pass through adjacent cells wwithout crossing cell membranes.
-Occurs in both plant and animal cells
What are the two broad groups that hormones are placed in?
- Water soluble
- Lipid Soluble
What are the three steps in cell signalling?
- Signal reception
- Signal Transduction
- Cell’s Response
What does each step in signal transduction lead to the molecule becoming?
Amplified
Explain the process of signal transduction when a g protein-linked receptor is involved
- A protein or peptide hormone will activate a membrane receptor
- May activate G protein
- G protein causes a cascade and therefore signal transduction
- Leading to cells response
Explain signal transduction in regards to steroid hormone receptors
- Lipid soluble hormone passes through the cell membrane
- Binds to a receptor protein found inside of the cells
- Hormone-receptor complex enters the nucleus
- Binds to s specific regulator site for the targeted gene
- Simtulating the gene to produce mRNA
- Then read by ribosomes to produce a specific protein
(essentally activates gene expression)
Explain the role of auxins in plant cells
Cause growth and elongation of plant cells
What do auxins cause
Positive phototropism (plant grows in the direction of the light)
Where are auxins most commonly found in the plant?
In the dark side as they move away from the light
hence the elongate more due to the unevenness in the shoot.
Explain cytokinins
Cause growth and divison of plant cells
explain ethlyene
Promotes ripening of fruit
abscisic acid
prohibits plant growth and prevents excess loss of water
gibberellins
promotes growth and development of plant cells
What are pheromones
a chemical substance produced and released into the environment by an animal, especially a mammal or an insect, affecting the behaviour or physiology of others of its species.
