ENZYMES AND HOMEOSTASIS UNIT TEST Flashcards
Characteristics of enzymes (3):
- Proteins with a 3-degree level of structure
- Biological catalysts. Catalysts are substances that increase rate of chemical reaction without undergoing any permanent chemical change
- Recycled or reused even after chemical reactions
Naming structure of enzymes and examples
Always ends with “ASE”. Ex. Maltase works on maltose, sucrase works on sucrose, ATPase works on ATP
Significance of enzymes
Speeds up chemical reactions by up to 100,000 times faster by lowering energy of activation of chemical reaction
Enzyme catalase
Breaks down hydrogen peroxide into hydrogen and oxygen gas
Activation energy/energy of activation
Barrier to chemical reactions. Minimum amount of energy required to start a reaction
How do catalysts work to speed up chemical reactions
Lowering the energy of activation
Non-catalyzed/no enzyme
Higher energy of activation needed to activate the reactants. Therefore, the rate of reaction is slower
Catalyzed/with enzyme
Lower energy of activation needed to activate the reactants. Therefore, the rate of reaction is faster
Protein portion of enzyme
Apoenzyme. Inactive on its own
Cofactor
Enzymes require a cofactor (helper molecule) which can be either an inorganic ion or vitamin molecule so that an enzyme can properly function
Examples of inorganic co factors
Metals such as copper, zinc, iron, magnesium, selenium, etc. MINERALS
Examples of organic non-protein factors
Vitamins, such as riboflavin, niacin. COENZYMES
Active site
Where the substrate attaches to enzyme to create a product
How is an active site created
When an apoenzyme is attached with a cofactor
What is it called when a cofactor is attached with apoenzyme
Holoenzyme, a functional enzyme
Simple equation in word form of enzyme composition
Apoenzyme (protein portion) + Co factor (in organic minerals or organic vitamin) = Holoenzyme (active enzyme)
Lock and key theory
Theory where an enzyme has a specific shape which allows the substrate to fit. Believed that an active enzyme substrate complex holds a substrate that fits like a lock and key to active site.
What reactions do enzymes work in
Hydrolysis or synthesis reactions
What happens when a random collusion occurs with an active site and substrate
Creates reaction and produces new product
Induced fit model
Some active sites are known to undergo a slight change in shape in order to accommodate a substrate. Enzyme is induced to a slight alteration to achieve a fit of substrate
Metabolism
Series of chemical reactions occurring in body
What chemical reactions do not occur haphazardly in cells and
Cellular respiration, photosynthesis, protein, and lipid synthesis digestion, etc. It is because they are usually part of a metabolic pathway which is a series of reactions
Metabolic pathways
Begin with substrate/reactant and terminate with an end product. Specific enzymes control each step of metabolic pathway so if an enzyme is missing then no reaction occurs
Easiest way to gain metabolic energy
In small increments rather than all at once
Example of simplified metabolic pathway
Starch – E1 (Analase) Maltose – E2 (Hactase) Glucose
8 things that affect enzyme activity:
- Heavy metal
- Surface area
- Temperature
- pH
- Concentration of enzyme
- Concentration of substrate
- Concentration of product
- Presence/absence of inhibitors
Heavy metal
Things like lead or mercury can attach to allosteric site of enzyme which disrupts normal distribution of electrons affecting the ionic bonds on active site. Enzyme becomes denatured
Surface area
Increasing the surface area of a solid will increase the amount of reactant that can react
Temperature (3):
- Heat increases kinetic energy which increases reaction rate. For every 10 degrees Celsius, the reaction rate doubles
- Proteins denature if temperature is above optimal temp (37). It will lose the level 3 shape and function of protein. High fever can also kill someone
- If temp is cool, the protein will not denature but molecules will move slower and have less kinetic energy = less collisions with enzymes and substrates
Temperature of denaturation in animal enzymes
40-44 degrees Celsius
pH
Enzymes have a pH for optimum activity. Most enzymes are best near pH 7 (neutral)
Stomach pH
2-3
Small intestine pH
8-9
Mouth pH
7
Blood pH
7.2-7.4
Substrate concentration in enzyme activity (3):
Adding substrate to an enzyme-catalyzed reaction will increase reaction rate until all..
B. All active sites on enzymes are saturated with substrates
- C. More enzymes are added to increase rate of activity and give more opportunities for enzymes to attach with substrates and active site
- D. Until it has denatured, and no active sites collude with substrate
How to increase rate of activity
Add more enzymes to increase opportunity for enzymes to attach with substrate and active site
Concentration of enzymes (4):
Increasing ENZYMES will result in products being made until…
- A. All substrates are acted upon
- B. Have enzymes and many active sites but limited substrates for enzymes active sites to collide with = productivity shows no progress
- C. Add more substrate = productivity increases
- D. Number of products produced decreases because no more substates added
Inhibitors
Substance that slows down a chemical reaction or reduces activity of particular reactant, catalyst, or enzyme
Two types of inhibitors
Competitive inhibitors (irreversible) and non-competitive inhibitors (reversible)
Reversible inhibitors
Binds to enzyme non-covalently. Does not form chemical bonds or reaction with enzyme so they can be easily removed
Irreversible inhibitors
Binds to enzyme covalently. They form a chemical bond and cannot be removed. The inhibitor out competes the substrate to attach to active site
2 examples of irreversible inhibitors:
- Poisons such as cyanide which inhibits essential enzyme called cytochrome c oxidase involved in cellular respiration
- Penicillin, an antibiotic derived from fungi. They inhibit enzyme needed for bacteria to build cell wall during growth and cell division
Significance of genes with enzymes
Genes are necessary to increase or to decrease concentration of enzyme (gene expression)
Another way to control enzyme activity
Inhibiting or deactivating an enzyme
When does enzyme inhibition occur
When an active enzyme is prevented from combining with its substrate.
Feedback inhibition
Something that regulates every activity of an enzyme in a cell
Negative feedback inhibition
When the concentration of an end-product in a metabolic pathway increase, the end product binds to an enzyme in pathway
Significance of negative feedback
Mechanism involved in maintaining equilibrium/homeostasis (EQUAL)
Why does a negative feedback have that name
The binding of the end product to an allosteric (non-active site) causes change in tertiary shape of enzyme’s active site
How to determine if it is a reversible inhibitor
If it can unbind from allosteric site and follow the active site to be used again
What is activation energy
Minimum amount of energy required to activate molecules to which then they can undergo a chemical reaction
How does activation energy determine reaction rate
Higher the activation energy, the slower the chemical reaction because molecules can only complete reaction once they reached the top of activation energy barrier
How do catalysts work to speed up chemical reactions
Catalysts increase the reaction rate by lowering the activation energy needed
What do all enzymes names end with
ASE
What components make up a holoenzyme
An apoenzyme (protein part) and a cofactor
Apoenzyme
Protein portion of an enzyme
Co enzyme
Substance that enhances action of an enzyme. They are organic non-proteins (vitamins) that bind with active site of enzyme for substrate recruitment
Cofactor
Non-protein like vitamins or minerals that attach to apoenzyme and are necessary for enzyme function to work as catalyst. Co factors are inorganic while co enzymes are organic
Co enzyme examples
Vitamins like riboflavin, or niacin
Co factor examples
Inorganic stuff like metals, copper, zinc, iron, magnesium, selenium, or vitamins
Metabolism
Series of chemical reactions occurring in body that change food to energy
Metabolic pathway
Set of actions or interactions between genes and their products that result in change of some component of system that is essential for correct functioning
Metabolic energy
Process of generating energy (ATP) from nutrients
Allosteric site
Non-active site that causes change in tertiary shape of enzyme’s active site
Lock and key theory
Theory that explains how enzymes are specific for their substrate. Each enzyme is specific for its substrate like a key for its lock
Induced fit theory
Theory that the binding of a substrate to an enzyme causes change in shape of enzyme to enhance its activity
Negative feedback inhibition
When too much of a substance results in decreased production of the same or different substance
Body reaction when too hot (3):
- Sweat
- Blood dilates
- SA increases to release heat
Homeostasis
Maintenance of equilibrium of the body’s internal environment in the fact of changing conditions
Examples of homeostasis (5):
- Body temperature
- Blood pressure
- Blood pH
- Blood glucose levels (0.1%)
- Blood salt level (0.9%)
Body reaction when too cold (3):
- Shiver
- Goosebumps
- blood vessel constriction
Body when blood pressure is too high
Arteries can dilate and lower the heart rate
Body when blood pressure is too low
Arteries can constrict and increase heart rate
How is blood pH maintained
Buffer which absorbs excess acid or base
How is blood glucose levels maintained
Insulin and glucagon (hormones)
How is blood salt level maintained
Kidney
Importance of constant environment (2):
- Chemical reactions occur within a narrow range of pH, temperature, and concentration
- Cells need constant supply of nutrients
What types of nutrients do cells constantly need
O2, amino acid, glucose, vitamin/minerals
What needs to be constantly removed from cell
Nitrogenous wastes such as ammonia, urea
What is toxic for a cell
Nitrogenous waste
What do humans and animals have that eliminate urea from the blood
Kidneys
Where was urea produced
Liver from nitrogenous waste
Maintaining homeostasis
Feedback mechanisms
Why is homeostasis important
Important because chemical reactions in cells occur within fine temp, pH, and concentration ranges
Examples of stimuli (5):
- Chemicals
- Light
- Sound waves
- Motion
- Touch
4 main types of receptors:
- Chemoreceptor
- Photoreceptor
- Mechanoreceptor
- Thermoreceptor
Chemoreceptor
Responds to chemical substances including taste, smell, blood pH, and pain
Pain receptors in relation to chemoreceptors
Pain receptors are a type of chemoreceptors because they respond to chemicals released by damaged tissue
Photoreceptor
Respond to light energy
Mechanoreceptor
Respond to mechanical forces which result in pressure change
Example of mechanoreceptor
Soundwaves converted to fluid-pressure to be detected by mechanoreceptor in the inner ear
Pressure receptor in relation to mechanoreceptor
Certain arteries detect changes in blood pressure
Stretch receptor in relation to mechanoreceptor
Stretch receptors in the lungs detect the degree of lung inflation, bladder, stomach, and rectum
Thermoreceptor
Respond to warm and cold and are in skin and hypothalamus
Sensory receptor significance
Respond to environmental stimuli by generating nerve impulses to the nervous system. Then the appropriate part of your body will generate impulses to the appropriate part of body for a response
Negative feedback
Decreases the effect of stimulus
Negative feedback mechanisms in blood
Blood pressure, blood pH, blood glucose levels are all maintained by negative feedback
Hypothalamus
Thermostat for body temperature located in part of brain and maintains/controls homeostasis
Positive feedback
Mechanism that makes the original stimulus more intense and does not restore homeosis so it takes it further away from equilibrium
2 examples of positive feedback
Women giving birth and nursing a baby
Positive feedback (women giving birth) in DETAIL steps (3):
- Head of baby presses against cervix and stimulates mechanoreceptors
- When nerve impulses reach brain, the brain causes pituitary gland to secrete oxytocin (hormone)
- Oxytocin travels in blood to uterus and causes uterus to contract and push fetus
How is the cervix stimulated when giving birth
Mechanoreceptors sends nerve impulses to brain and stimulates posterior pituitary glands to secrete oxytocin
Positive feedback (nursing a baby) in DETAIL steps (3):
- Sucking on a nipple cause nerve impulses to travel to hypothalamus
- Oxytocin released by posterior pituitary gland
- The lobules in mammary glands to contract, releasing milk
What works with the nervous system to maintain homeostasis
Hormones and proteins
Where are hormones secreted
Can be directly secreted into blood or into the ducts
Endocrine glands
Glands that secrete hormones directly into blood
Examples of endocrine glands (9):
- Hypothalamus
- Pituitary
- Thyroid
- Parathyroid
- Thymus
- Adrenal gland
- Pancreas
- Ovaries
- Testes
Exocrine glands
Glands that secrete hormones into ducts
Examples of exocrine glands (2)
Hypothalamus and pancreas (The two are both endocrine and exocrine glands)
Peptide hormones
Binds to specific receptor protein in plasma membrane
When does protein relay end
Protein relay in plasma membrane ends when enzyme converts ATP to cAMP, which activates an enzyme cascade. Therefore, a metabolic pathway is activated
Examples of peptide hormones (4):
- Oxytocin
- Insulin
- Glucagon
- Thyroxin
Steroid hormone
After passing through cell membrane, a steroid hormone binds to receptor protein in nucleus
Hormone-receptor complex
Binds to DNA. Activates certain genes and protein synthesis. Transcription and translation are also activated
How is transcription and translation activated
When the hormone-receptor complex binds to DNA
Where is the thyroid gland situated
In the neck in front of the trachea
Examples of negative feedback loop in hormones
Thyroid gland producing peptide hormones called thyroxin which affects body cells. It increases rate of cellular respiration and metabolic rate
What is needed to make thyroxin
Iodine
Concentration of thyroxin compared to blood
Thyroxin is 25x greater than blood
Good sources of iodine
Seaweed, seafood, ionized table salt
Thyroxin level STIMULUS
Thyroxin level drops below set-point concentration, detected by osmoreceptors
Thyroxin level REGULATORY CENTER
Hypothalamus releases Thyrotropin-RELEASING HORMONES (TRH) and it travels to anterior pituitary gland through a duct
Thyroxin level ADAPTIVE RESPONSE
Anterior pituitary gland releases THYROID-STIMULATING HORMONE (TSH) in bloodstream. The TSH binds to receptors on plasma membrane of thyroid gland.
If there are sufficient iodine in thyroid gland, what happens
Thyroxin is made and secreted into blood scream which causes an increase in thyroxin levels
How long does negative feedback mechanism continue for
Continues until thyroxin levels are at/above set point and the stimulus is not detected by the hypothalamus
Condition where you have too little thyroxin
Hypothyroidism
Symptoms of hypothyroidism (9)
- Fatigue
- Weight gain
- Low body temp
- Hair loss
- Slower pulse
- Thick/puffy skin
- Depression
- Sensitive to cold temp
- High risk of marriage if pregnant
- Poor digestion
Simple goiter
Enlargement of thyroid gland caused by lack of iodine in diet
Why does the thyroid gland enlarge when you suffer from simple goiter
The anterior pituitary gland is constantly releasing TSH. The thyroid gland is stimulated to produce more thyroxin but since they don’t have iodine, thyroxin cannot be made.
How is simple goiter treated
Iodized table salt, or eating more iodine-rich foods
Cretinism
Condition when the thyroid gland fails to develop during infancy or early childhood
Side effects or cretinism
Short and stocky due to skeletal growth usually inhibited and mental retardation occurs unless thyroid therapy begins in the first 2 months
Condition where you have too much thyroxin
Hyperthyroidism
What happens when you have hyperthyroidism
Thyroid gland becomes enlarged and overactive which causes a goiter to form and the eyes to protrude (tissue fluid increases and causes double vision)
Symptoms of hyperthyroidism (8):
- Hyperactivity
- Nervousness
- Irritability
- Insomnia (sleep disorder)
- Weight loss
- Anxiety
- Fast heart rate
- Overheating
How is enlarged thyroid gland treated in hyperthyroidism
Radiation or surgery
