SCIENCE 1ST TERM
Chemical equation - represents a chemical reaction using chemical symbols and formulas.
General form: Reactants → Products
• Reactants – substances present before the reaction
• Products – new substances formed
• Arrow (→) – means “produces” or “yields”
Types of Chemical Reactions
1.) Synthesis: A + B → AB
2.) Decomposition: AB → A + B
3.) Substitution: AB + C → AC + B
4.) Metathesis: AB + CD → AD + CB
Word equations - A chemical equation can be written using the names of the substances.
1) P₄ + 10Cl₂ → 4PCl₅ Phosphorus reacts with chlorine to produce phosphorus pentachloride
2) 2SO₂ + O₂ → 2SO₃ Sulfur dioxide reacts with oxygen to produce sulfur trioxide
3) AgNO₃ + NaCl → AgCl + NaNO₃ Silver nitrate reacts with sodium chloride to produce silver chloride and sodium nitrate
4) BaCl₂ + Na₂SO₄ → BaSO₄ + 2NaCl Barium chloride reacts with sodium sulfate to produce barium sulfate and sodium chloride
Law of Conservation of Mass - Matter cannot be created or destroyed during a chemical reaction. Therefore, a chemical equation must have the same number of atoms of each element on both sides.
Coefficient – number placed before a chemical formula.
Example: 2H₂O.
Subscript – small number within a chemical formula.
Example: H₂O.
Reaction Rate - The rate of reaction describes how quickly reactants are converted into products.
Collision Theory - Chemical reactions occur when particles collide. For a successful reaction, particles must collide with enough energy and have the proper orientation. These are effective collisions.
Activation energy is the minimum energy required for a chemical reaction to occur.
Factors Affecting the Rate of Reaction
1. Temperature - Increasing temperature generally increases reaction rate because particles move faster and have more kinetic energy, resulting in more effective collisions.
2. Concentration - Increasing the concentration of reactants generally increases reaction rate because there are more reactant particles in a given space, increasing collision chances.
3. Surface Area - Increasing surface area generally increases reaction rate. Crushed sugar reacts faster than a large sugar cube because it has a larger surface area exposed for collisions.
4. Catalysts - A catalyst increases the rate of a chemical reaction by helping the reaction occur more easily through lower activation energy
Applications:
1. Food and Pharmaceutical Preservation - Often involves slowing chemical reactions and the growth of microorganisms. Lower temperature generally slows reactions. Ex. vaccines, gulay
2. Preservation or Decomposition of Specimen - Cryopreservation - The preservation of cells or biological materials at a very low temperature. Ex. freezing egg cells for future use
3. Medication or Poison Effects on the Body - Its concentration determines how quickly and effectively it reacts in the body. Ex. dosage of antibiotics
4. Fire Control - Combustion is a rapid chemical reaction involving fuel and oxygen that releases heat and light. Removing oxygen can help slow or stop a fire.
5. Dating, Restoration, Preservation of Artifacts - Corrosion of Metals - Scientists can help protect historical metal artifacts by slowing the chemical reaction responsible for corrosion.
6. Combustion of Coals - Rapid chemical reaction between a fuel and oxygen that releases heat and light. The total surface area of an object increases as it is crushed to a powder. The concept is applied in companies that burn coal.
Glands - make or release substances like hormones, sweat, or saliva.
1. Exocrine glands secrete nonhormonal substances such as sweat, tears, and saliva through their ducts.
Ex: Salivary glands, sweat glands, lacrimal glands (tears)
2. Endocrine glands secrete hormones that are long-distance chemical messengers that travel through the bloodstream and initiate responses from the cells. These glands are referred to as "ductless glands."
Endocrine System - composed of all the glands that secrete hormones.
Types of Endocrine glands:
1. Pituitary gland - known as the "master gland" because it regulates the activity of the other glands.
*Posterior pituitary gland - located at the back of the anterior pituitary gland. It releases the neurohormones that are synthesized in the hypothalamus.
*Anterior pituitary gland - releases several hormones
2. Hypothalamus - regulates the hormone production of the pituitary gland via a bundle of axons. The hypothalamus synthesizes the hormones oxytocin and vasopressin. Once synthesized, it will be transported to the posterior pituitary for storage and will be released if a stimulus is received by the posterior pituitary.
3. Pineal gland, which is located in the midline of the brain, releases the hormone melatonin, which regulates the circadian rhythm of the body. The circadian rhythm refers to the changes (physical, mental, and behavioral) an organism experiences in a day. The diurnal (daily) cycle of this hormone peaks at night and troughs around noon.
4. Thyroid gland is located in the neck region. It releases the thyroid hormone (TH), which regulates the body's metabolism, and calcitonin, which is responsible for regulating the blood calcium level by lowering it.
5. Parathyroid gland - releases the parathyroid hormone, which also regulates the blood calcium level by increasing it.
6. Adrenal glands - are situated atop the kidneys, release hormones responsible for regulating metabolism, as well as the fight-or-flight response of the body. The fight or flight response refers to your body's reaction to an event or circumstance that is considered stressful or frightening.
7. Pancreas - produces the hormone insulin and glucagon, which regulate the blood sugar levels. Insulin decreases the blood sugar level into normal levels whereas glucagon increases blood sugar levels. Because they have opposite effects on one another, these hormones are known to be antagonistic.
8. Gonads (testes for males and ovaries for females) - secretes sex hormones.
Hormones are chemical messengers produced by endocrine glands that travel through the bloodstream to control key body functions like growth, metabolism, and mood.
Hormones and their Functions:
* Oxytocin: Stimulates uterine contractions, initiates labor, and initiates milk lactation. Positive feedback
* Antidiuretic Hormone (ADH): Stimulates kidney tubule cells to reabsorb water back into the blood.
* Growth Hormone (GH): Promotes body growth and metabolism; acts as an anabolic hormone in bones and cartilages.
* Thyroid-Stimulating Hormone (TSH): Stimulates the thyroid gland to produce its hormones.
* Adrenocorticotrophic Hormone (ACTH): Stimulates the adrenal cortex to release glucocorticoids and androgens.
* Follicle-Stimulating Hormone (FSH): Stimulates ovarian follicle maturation and estrogen production in females, and spermatogenesis in males.
* Luteinizing Hormone (LH): Triggers ovulation and hormone production (estrogen/progesterone) in females, and testosterone production in males.
* Prolactin: Stimulates lactation (milk production) in mammary glands.
* Glucocorticoids: Promotes fat and protein metabolism; inhibits immune response.
* Gonadocorticoids: Contributes to the growth of female axillary and pubic hair (no evident effects in males).
* Mineralocorticoids: Regulates electrolyte (sodium and potassium) excretion in the kidneys.
* Epinephrine and norepinephrine: Stimulates the stress response of the body.
* Estrogen - Initiates the development of the female reproductive system in females during puberty, along with the development of secondary sex traits. May occur in males and women
* Progesterone - Prepares the endometrium for the implantation of a fertilized egg.
* Testosterone - Initiates the development of the male reproductive system in males and the emergence of secondary sex traits in males.
Homeostasis is the process by which the body maintains a stable internal environment even when external conditions change.
Stimulus (plural: Stimuli) - is any change, inside or outside the body, that triggers a response from a living organism.
Response - refers to any action or change that takes place in an organism.
Feedback Mechanisms - a physiological regulation system in a living body that works to return the body to its normal internal state, or commonly known as homeostasis.
Main Components of a Feedback Mechanism
1. Receptor - the sensor that will detect the changes in the environment. Once it detects a change in the environment, it will send the information to the control center. This is called the afferent pathway.
2. Control center - is in charge of determining the normal levels that the body should maintain and determines appropriate action. The action will be relayed to the effector from the control center. This is the efferent pathway.
3. Effector - perform the feedback mechanism, which is the control center's response to the change.
Two types of feedback mechanisms:
1. Negative feedback mechanism - mostly maintains homeostasis because it shuts off or decreases the effect of the stimulus. This will result in stabilizing the system and ensuring that homeostasis is maintained. Ex. Thermoregulation, Blood glucose level
a) Thermoregulation - homeostatic activity that maintains the body temperature in contrast with external conditions. This process is mediated by a gland known as the hypothalamus.
Normal human body temperature - 37°C
When the Body Gets Too Hot
* Stimulus- Body temperature increases above the normal range.
* Receptor - Thermoreceptors in the skin and hypothalamus detect the increase in temperature. Sensory nerve signals carry information toward the hypothalamus (afferent pathway).
* Control Center- The hypothalamus detects that the body is too warm and coordinates a response. Autonomic nerve signals travel from the hypothalamus to the effectors (efferent pathway).
* Effectors- Sweat glands produce more sweat while skin blood vessels undergo vasodilation (the blood vessels widen).
* Response- more blood flows near the skin, sweating, sweat evaporates and removes heat. Body temperature decreases toward normal.
When the Body Gets Too Cold
* Stimulus- Body temperature decreases below the normal range.
* Receptor - Thermoreceptors detect the decrease in temperature. Sensory nerve signals carry information toward the hypothalamus (afferent pathway).
* Control Center- The hypothalamus detects that the body is too cold and coordinates a response. Autonomic nerve signals travel from the hypothalamus to the effectors (efferent pathway).
* Effectors- Skeletal muscles contract rapidly while skin blood vessels undergo vasoconstriction (the blood vessels narrow).
* Response-reduces blood flow near the skin, less heat is lost to the surroundings and shivering. Body temperature increases toward normal.
b) Blood glucose level
Glucose (C6H1206) is primarily the main sugar which is found in blood.
Pancreas is a pear-shaped gland that releases hormones (glucagon and insulin) to regulate blood sugar.
Glucagon is a hormone that increases blood glucose levels.
Insulin is a hormone that decreases blood glucose levels.
Normal Blood Glucose Level: 70 mg/dL - 130 mg/dL
When Blood Glucose Gets Too High
* Stimulus - Blood glucose increases above the normal range, such as after eating a carbohydrate-rich meal.
* Receptor - Beta cells of the pancreas detect the increase in blood glucose.
* Afferent pathway - The increased blood glucose level is detected by the pancreatic beta cells.
* Control Center - The pancreas responds by releasing the hormone insulin into the bloodstream.
* Efferent pathway - Insulin travels through the bloodstream to target cells, including liver, muscle, and fat cells.
* Effectors - Target body cells take up glucose, while the liver and muscles convert excess glucose into glycogen.
* Response - Glucose is removed from the bloodstream, causing blood glucose levels to decrease toward the normal range.
Diabetes mellitus (DM) is a disease of inadequate control of blood levels of glucose. It develops when your pancreas doesn't make enough insulin or any at all.
Type 1 Diabetes- body cannot produce insulin
Type 2 Diabetes- insulin resistance, where the body cannot use insulin effectively.
2. Positive feedback is a homeostatic mechanism in which the response amplifies or strengthens the stimulus rather than reversing it. Ex. Childbirth, Blood clotting, Menstrual cycle
a) Childbirth
* Stimulus -The baby's head pushes against the cervix.
* Receptor- Receptors in the cervix detect the stretching, Sensory nerve signals travel to the hypothalamus (afferent pathway).
* Control center - The hypothalamus signals the posterior pituitary gland. The hormone oxytocin is released into the bloodstream (efferent pathway).
* Effector - Uterine muscles.
* Response - Uterine contractions become stronger, the cervix become more stretch until the baby will be delivered.
b) Blood clotting
* Stimulus- A blood vessel is damaged.
* Receptor - Platelets detect the damaged area and attach to the exposed tissue. Activated platelets release chemical signals. Effector - Nearby platelets are activated and recruited.
* Response - More platelets gather and release more signals. A platelet plug and blood clot form, helping stop the bleeding.
Photosynthesis reaction allows plants to produce their own food using sunlight?
Metathesis is the type of reaction involving the exchange of ions between two compounds, resulting in the formation of two new compounds
Synthesis is the type of chemical reaction that occurs when two or more substances combine to form a single compound
Cellular respiration is the process that occurs in plants, animals, and microorganisms in which glucose is broken down in the presence of oxygen to produce carbon dioxide, water, and energy
Ozone depletion is the chemical reaction is described by the breakdown of ozone molecules in the ozone layer due to chlorofluorocarbons
Biogeochemical cycle refers to the continuous movement and recycling of nutrients such as carbon, nitrogen, and phosphorus between living organisms and the environment
Substitution is the type of reaction involving the breakdown of a single compound into two or more simpler substances