Enzymes Flashcards
(37 cards)
1
Q
What is metabolism?
A
-describes all the chemical reactions occuring constantly in the cell that maintain homeostasis`
2
Q
What are metabolic pathways?
A
- the orderly step-wise series of chemical reactions from the initial reactants to the final products
- one reaction leads to the next
- controlled by enzymes; each step requires a specific enzyme
3
Q
Why do metabolic pathways exist?
A
- it’s impossible to have a single reaction that could produce complex molecules from simple reactants
- one pathway can lead to several others(intermediate products of one pathway can be starting reactant for another pathway)
- having more than one step means that there are more places where the overall reaction can be controlled
4
Q
What is an enzyme?
A
- a globular protein that acts as a catalyst of chemical reactions
- sites of chemical reactions but aren’t used up in the reaction or permanently changed by the reaction
- can hold reactant molecules together long enough for them to react
- highly specific; each enzyme speeds up only one reaction
- enzymes names usually end with the suffix “ase” or “sin”
5
Q
What is the equation for an enzyme-catalyzed reaction?
A
E + S –> ES –> E + P
“E” = enzyme
“S” = the reactant(s) in an enzyme’s reaction
“ES” = enzyme substrate complex(chemical reaction occurs)
“P” = product
6
Q
What is the active site?
A
- a region on the surface of an enzyme to which substrates bind and which catalysts a chemical reaction involving the substrates
- allows related molecules to bind but possibly preventing undesirable substrates from binding
- the shape of the active site only corresponds to the shape of the substrate when the substrate binds
7
Q
Describe the structure of an enzyme
A
- a protein part called an apoenzyme that gives it its specificity(i.e. exactly what reaction it will catalyze)
- a non-protein group called a coenzyme which may help out the reaction by accepting or donating atoms(eg H)
8
Q
What is coenzyme?
A
- large non-protein molecules
- many are vitamins(nicotonic acid, vitamin B2, vitamin H, vitamin B1)
- may help reaction by participating in reaction by accepting or donating atoms to the reaction
9
Q
What is apoenzyme?
A
- protein part of enzyme
- gives specificity to particular reaction
10
Q
What are the factors that change the shape of the enzyme?
A
- pH
- temperature
- concentration
11
Q
What happens when pH is too low or high?And what is the most ideal pH for enzyme
A
- pH 6-8(except for stomach acid)
- if the pH is too low or high, the enzyme denatures(the structure of the enzyme changes in which it can no longer carry out its function
12
Q
What happens when the temperature changes?
A
- decreasing temperature will slow rate of reaction; the lower the temperature, the lower the rate of reaction
- low temperatures don’t normally denature the enzyme
- increasing the temperature will at first increase the rate of reaction, but when temperature gets too high(above 45 degrees)the enzyme will denature
13
Q
What happens when the concentration of substrates change?
A
- if the concentration of substrate increases, the amount of product increases as well; however after a certain concentration the rate won’t increase anymore as all the enzymes are already being used
- if the concentration of substrate decreases the rate of product formation will decrease as well
14
Q
What happens when the concentration of enzyme change?
A
- limits the overall rate of reaction
- if concentration of enzyme increases, rate of product formation increases
- if concentration of enzyme decreases, the rate of product formation decreases as well
15
Q
How do enzymes work?
A
When substrates bind to the active site, the enzyme changes shape slightly to bind the substrate more tightly. This is due to changes in the R groups of amino acids as they interact with the substrate. And when the product is produced, the enzyme changes back to its original shape.
16
Q
Lock and key vs induced fit
A
- lock and key is the original model; it was believed that E and S fit together perfectly from the very beginning like a lock and key
- the model now we believe is called induced fit in which the enzyme changes shape slightly when it binds the substrates in order to get a tighter “grip” on the reactants. This is due to the changes in the R groups of amino acids as they interact with the substrate
17
Q
What are inhibitors?
A
-molecules that bond to the enzyme in some way to prevent the rate of substrate to enzyme
18
Q
What is competitive inhibition?
A
- occurs when a molecule that looks like the substrate can compete for space at the active site
- slows down the reaction rate
- can be reversible or irreversible
19
Q
What is non-competitive inhibition?
A
- occurs when the inhibitor binds to another place on enzyme(instead of the active site)
- may look completely different from the substrate
- when the inhibitor binds, it causes the enzyme to change shape at the active site so the substrate cannot bind
- can reversible or irreversible
- aka “allosteric” inhibition
20
Q
What is end product inhibition?
A
- when a substrate binds to an enzyme, a series of reactions occur involving many enzymes(metabolic pathway)and the end product is produced
- once there is enough end product, some binds allosterically with the first enzyme and that changes the shape of the active site of the first enzyme and so no more end product is produced
- this is how cell is able to regulate itself from overproducing
21
Q
What is homeostasis?
A
- the maintainence of the body’s equilibrium
- the attempt to balance the body’s internal enviornment in the face of changing conditions
22
Q
What are some examples of homeostasis?
A
- when the body is too hot, sweat develops and surface blood vessels become dilated so blood can get closer to the surface of the skin and release heat
- when the body is too cold, it will start to shiver and form goosebumps, constricting the blood vessels for the opposite effect
23
Q
Why is homeostasis so important?
A
- chemical reactions occur within a narrow range of temperature, pH, and concentration
- cells need a constant supply of nutrients and constant removal of nitrogenous wastes which are toxic to the cell
24
Q
What are stimuli?
A
- chemical
- light
- sound waves
- motion
- touch
25
What are the receptors that detect stimuli?
- chemoreceptors(respond to taste, smell, blood pH,and pain)
- photoreceptors(respond to light)
- mechanoreceptors(respond to mechanical forces or pressure change of some sort, such as sound waves, blood pressure, and degree of lung inflation
- thermoceptors(respond to temperature)
26
How do receptors work?
- they respond to enviornmental simuli by generating nerve impulses to the nervous system
- then the regulatory center(part of the brain)will generate impulses to the appropriate parts of the body for an adaptive response
27
What are feedback loops?
- the body determines the simuli and maintains itself through feedback mechanisms
- the 2 types of feedback loops are negative and feedback and positive feedback
28
What is negative feedback?
- act to decrease the effect the stimulus
- blood pressure, blood pH, blood glucose and body temperature are all maintained by negative feedback mechanisms
- when a stimulus is perceived as too low, the negative feedback will elevated the levels to normal and maintain
- e.g. the furnace in the house automatically turns on when it's too cold and it will stay on until the heat reaches the set temperature at which the thermostat will turn off
29
What is positive feedback?
- mechanisms take the system further away from equilibrium as this is a mechanism that makes the original stimulus more intense
- rare feedback loop
- eg. giving birth, breastfeeding
30
What do hormones do?
- act as chemical signals to affect the metabolism of cells
- serve as means of communication in between cells and the different parts of the body
- can be secreted directly into ducts or into the blood
31
Endocrine glands vs exocrine glands
- endocrine glands secrete hormones into blood; hypothalamus, pituitary, thyroid, thymus, pancreas, ovaries, and testes
- exocrine glands secrete hormones into ducts; hypothalamus & pancreas
32
What is thyroxin?
- a hormone produced by the thyroid gland(which is found in the neck in front of the trachea & is an example of a negative feedback loop)by using iodine
- thyroxin increase cellular respiration and thus one's metabolic rate
- the negative feedback mechanism continues until thyroxin levels are at/above set point and the stimulus is not detected by the hypothalamus
33
What is the process for releasing thyroxin?
- thyroxin levels drop below set point concentration
- hypthalamus releases HRH(hypthalamus releasing hormones)
- anterior pituitary gland releases TSH(thyroid stimulating hormone)into bloodstream
- TSH binds to receptors on the plasma membrane of the thyroid gland
- if there is sufficient iodine in the thyroid gland, thyroxin is made and secreted into bloodstream
34
What is hypothyroidism?
- hypothyroidism develops if thyroxin levels are not maintained and has too little thyroxin
- symptoms include lack of energy, weight gain, decreased body temperature, hair loss, slow pulse rate, thickness and puffiness of skin, goiter, or cretinism
35
What is goiter?
- develops due to lack of iodine in the diet
- thyroid gland enlarges because the anterior pituitary gland constantly release TSH
- the thyroid gland is stimulated to produce more thyroxin but since the person lacks iodine, thyroxin can't be made
- treatable with iodized salt and iodine-rich foods
36
What is cretinism?
- occurs when the thyroid gland fails to develop during infancy or early childhood
- result is inhibition of skeletal growth and therefore individuals are super short
37
What is hyperthyroidism?
- occurs when thryroxin levels are too high
- thyroid gland is enlarged and overactive causing a goiter to form and the eyes to protrude
- symptoms include hyperactivity, nervousness, irritability, insomnia, and weight loss
- can be treated with radiation or surgery
