molecule - Biologypetesnotes.weebly.com/uploads/2/6/7/7/26772952/maintaining_a... · molecule |㷦mälə㷧kyoōl|noun Chemistry ... Maintaining A Balance - HSC Biology 2012 Notes

Metabolism

molecule |ˈmäləˌkyoōl|noun Chemistry

a group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a chemical reaction.

The molecules in cells are constantly interacting: being formed, broken down or exchanged. These chemical reactions -- in fact, all the chemical processes occurring within an organism -- are called it’s metabolism. An organism is regulated (regulate: To control or maintain the rate of speed so it operates properly), and the rate of its chemical activity is maintained by special large protein molecules called Enzymes. Enzymes are also used in the digestive system to break down energy from the food we eat - to compounds - which are then absorbed by the blood to be transported around the body to the cells.

Enzymes

Enzymes bind to one or more specific ligands, called substrates, and convert them into chemically modified ‘products’.

They work by providing an Active Surface/Site where the reaction takes place. The Substrate binds on to the active site (Chemical attraction) much like an Jigsaw puzzle. It needs to fit precisely.

Each Enzyme is highly specific, catalyzing only a single type of reaction - and no other.

Every reaction requires a catalyst. Enzymes can react without themselves being changed - they act as a catalyst for the reaction. Biological catalysts are called Enzymes.

catalyst |ˈkatl-ist|nouna substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.

Maintaining A Balance - HSC Biology 2012 Notes Peter Richardson

Reactions occur at the active site

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Effect of pH( PRAC 1 - part B )

❖ Generally, all intra-cellular enzymes (those within a cell) will show a peak activity of about pH = 7 -- very close to neutrality

❖ Digestive enzymes such as “pepsin” from the stomach will work best in much more acidic environments.

❖ CO2 can cause elevation of pH

Practical: Tested enzyme catalase (potato)Activity was inhibited at pH 5 & pH 8.5Was most effective at a relatively neutral pH of 6.5.

Effect of Substrate Concentration( PRAC 1 - part C )

❖ Initially the rate of reaction increases as the substrate concentration goes up, just as with anyreaction.

Soon though, the graph flattens out because the enzyme molecules become “saturated’’with substrateand cannot work any faster. Practical :


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An perfect enzyme - Substrate fit.

Tested enzyme catalase (potato) Concentration of substrate (Hydrogen peroxide) Optimum at 50% Hydrogen Peroxide 50% Water.

Effect of Temperature( PRAC 1 - part A )

❖ Not all enzymes will peak at the same temperature, or have exactly the same shape graph. In mammals, most enzymes will peak at around the animal’s normal body temperature.

❖ Beyond a peak temp, the enzymes 3-D shape begins to change. The substrate no longer fits the active sit so welland the reaction slows. If the temperature is changed, theenzyme may reshape and be successfully restored. But ifit has reached an extreme temperature. there will be a permanent distortion with which activity can not be restores. We say the enzyme has become ‘Denatured’

Practical: Enzyme rennin (stomach enzyme) in solidifying milk. (curdling)Most effective at 40 °c.

➡ Enzymes have a specific range of operation. Change any of the conditions and the enzyme will become denatured.

Homeostasis ❖ Enzymes are very sensitive to the conditions around them. It is vital that the “internal environment” of any organism is kept as constant as possible so that enzymes and chemistry keep operating normally. Water / Salt balance, Blood sugar levels, Ox and Carbon levels.

❖ The process of “Keeping Everything The Same” is called homeostasis.

Two homeostatic mechanism stages;

1. Detecting changes from the stable state: Detected by organs called receptors or sensors. They contain neurons, which detect information from external (somatic) and internal (Viseral) environments, and send nerve impulses appropriately. e.g Thermoreceptors, Photoreceptors, Mechanoreceptors, Baroreceptores (pressure) 2. Counteracting changes from the stable state: Detected changes are counteracted using effector organs. e.g Muscles, Glands (motor reflexes [motor: movement]

This counteracting of the Stimulus (what causes the change from stable state) is called a Negative Feedback System. Causes a reverse of the direction in which the change occurs enabling balance.

A Positive Feedback System will amplify the stimulus instead of reducing it. E.g adding fuel to fire. This does NOT result in Homeostasis.


- Autonomic (involuntary)- Somatic (voluntary)

‣ Blood Vessels - sometimes called vasodilation or vasoconstrictionDilation (Widening); When the body is too hot, blood vessels near the skin dilate and the blood is shunted toward the surface. This way, more heat is radiated away from the body. Constriction (Narrowing); When the body is cold, the surface blood vessels constrict keeping blood in the lower levels reducing the loss of heat and causing body heat to be retained. ‣Sweat Glands; Sweat glands secrete perspiration. The evaporation of this water in the external environment - has a powerful cooling effect.‣Muscles: Nerve signals can cause the skeletal muscles to begin “shivering”. This extra muscle activity generates more heat to warm the body‣Hormones: The hormone thyroxine (produced by the thyroid gland in the neck) controls the rate of metabolism. It is under the control of the hypothalamus, via another hormone. Metabolism = heat

The Human Nervous System Is made up of:❖ Central Nervous System : The brain (hypothalamus: the Homeostasis control centre) & spinal chord acting as control centre to coordinate all the organisms responses, receiving information interpreting and indicating a response. ❖ Peripheral Nervous System : nerves branching throughout the body, to and from receptors and effectors. (act as the communication network)❖ The nervous system works closely with the Endocrine System. The endocrine system produces hormones in specific glands.

• In a healthy human the internal “core temperature” is about 37°C and is maintained within 0.5°C. If temperature goes ± 4°c it is a life threatening situation.

The External Environment - TemperatureHomeostasis allows an organism to maintain its cells at a temperature close to optimum for its enzymes. This allows metabolism to run efficiently. Though homeostasis has it limits, No organism can remain active and thriving under a full range of temperatures of the biosphere of Earth. Different organisms have adapted to survive in extreme cold, or in extreme heat, but never both. e.g. Thermophilic Bacteria of volcanic springs or certain algae in very cold temps.


Dilate : Become larger - more open and wide.

Ectotherms and endotherms have similar behavioral adaptations to hot or cold conditions, but endotherms have more structural and physiological adaptions for maintaining a constant internal body temperature. ~ The responses of ectotherms are usually behavioral ~

Red Kangaroo - EndothermAdaptation or response to temperature regulation

Evaporative Heat Loss (EHL) panting, sweating, licking - evaporates water = coolingLick forearms - Kangaroos often lick their forearms in very hot weather. Their forearms have a good blood supply and very little fur; the moisture evaporates and cools the forearms, thus cooling the blood.Vasoconstriction / vasodilation ( vaso means blood vessels)Concentration of Urine to conserve water and can thus tolerate severe dehydration. Fur acts as insulate to the body - Endotherms rely heavily on body insulationBehavioral Response to seek shade.Behavioral Response to be active during later times, when temperatures are cool. Large Ears (Structural) with many blood vessels, increases the surface area for heat loss Producing your own body heat is expensive. Mammals use 70-90% of the food they eat just to maintain their body temperature, so of course they have to eat a lot.


Fun Fact: Metabolism produces heat in both Endo & Ectotherms. Ectotherms just canʼt maintain this heat.

Australian lizards in general (blue tongue / frilled neck) - EctothermAdaptation or response to temperature regulation

- Behavioral Response to seek shade / sun -- dependent upon internal body temperature.

- ‘Bask’ in the sun, in sites that are sheltered from the wind and exposed not only to direct sunlight but to the warmth reflected off rocks or logs. If the substrate has been warmed by the sun they will often flatten themselves against it to absorb as much heat as they can.

- Orientating themselves in sunlight to modify exposure. E.g. side on for most, or straight and direct for less.

Temperature Control in Plants - (Not too important)- They cannot run away or seek shade - they need structural or physiological adaptations- Some plants may be deciduous - they loose leaves in cold weather & grow again.- in hot weather w/ lots of water available (Tropical jungle) plants cool themselves by

allowing maximum evaporative cooling. Stomates open and transpiration occurs.- in hot and DRY weather = small, hard leaves reduce the surface area being hit by

sun. Also leaves are orientated so as to absorb sun at the coolest part of day. (most eucalyptus leaves hang vertically). Plants in hot dry climates, usually conserve water by reducing transpiration in the hottest part of the day.

Internal Transport ; The Human Circulatory System

‣ Composition of the Blood


‣ The solvent is made up of about 90% water ‣ Function is to transport ; - Waste materials such as Urea & Carbon Dioxide. - Products of digestion such as salts, amino acids, fats (lipids) & sugars - Certain hormones

‣ WBC’s Larger than RBC yet, less numerous.‣ There are several types & are used to fight infection.‣ Has a nucleus

‣ Platelets are used to clot the blood when necessary

‣ Donut shaped, Their function is to carry respiratory gases, particularly oxygen (carried as oxyhaemoglobin). When the blood reaches the body tissue the high concentration of dissolved CO2 lowers pH of the blood slightly. This causes the haemoglobin proteins to change shape slightly and release oxygen molecules. The haemoglobin then picks up some of carbon and takes it to the lungs.‣ Oxygen has difficulty dissolving in water. Hemoglobin molecules contain iron that easily pick up oxygen. (MUCH better than plasma)

‣ Factors effecting the Blood ; CO & the importance of removing

Pulse Oximeter


RespirationOxygen + glucose (oxygen and glucose must react) -> CO2 + H2O (waste products ) + Energy

[Fun Fact]: The flow of blood distributes heat around the body.

Red Blood Cell 7 um

White Blood Cell 11um

Side note: An acid has a low pH, a neutral solution has a pH of 7 and an alkaline solution has a high pH

2

Nutrients & Nitrogenous Wastes

As the blood circulates around the body, it’s chemical composition undergoes a series of changes.

Carbon Dioxide doesn’t just dissolve in water, it reacts! forming a weak acid. The level of carbon dioxide critically affects the pH of cells. Remember, enzymes are very sensitive to pH changes. If the carbon dioxide is not removed by the blood it will dissolve into the cells forming carbonic acid. To avoid this problem, CO2 is carried away in the blood as rapidly as it is produced in the cells. The concentration of oxygen and carbon dioxide is of much interest to doctors. The most important measurement is “Percentage Oxygen Saturation” (%SpO2). A reading of 95% -‐ 100% is indicative of good health.

• Measures %SpO2 (Percentage Oxygen Saturation) in arterial blood (blood being pumped from the heart)

• Works by emitting light from two diodes; one visible red light and the other infrared. These are directed through the tissue of the finger, and the absorption of the light into the haemoglobin is measured. This gives a direct measurement of the %SpO2 because haemoglobin with or without absorbs these light beams differently.• Non - invasive technique, useful for rapid, continuous monitoring of

blood.

~ 1 Micrometre (um) = 0.001 mm

Two important types of white blood cell:es.1. Phagocytes can actively move about by flowing their cytoplasm andcan move from the blood into the tissue fluid. They surround and ingestbacteria, foreign bodies and dead cells, and collect at areas of infection orinjury.2. Lymphocytes act specifically against foreignmaterial. They make antibodies which help the bodyʼs defence againstdisease.

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Arterial Blood Gas (ABG) Analysis


• Measures %SpO2 (Percentage Oxygen Saturation) as well as, concentration of carbon dioxide and pH

• Process is invasive (sample of blood must be taken) and there can be a delay between sampling and availability of results.

There is also a separate network, responsible for the transport of lymph & bodily/interstitial fluid. (/)


The heart consists of four chambers: the right and left atria (Singular: atrium) and the right & left ventricles.

All types of blood cells come from haematopoietic stem cell found in the marrow of all the major bones in the body.

The blood moves like this: Body - heart - lungs - heart - body

pulmonary of or relating to the lungs

Products of Blood Donation

The blood donated from blood donors is often broken apart into components, so each donation can treat many patients. Whole blood is only kept for emergency situations.

Artificial BlooOooOodReasons why research is needed: • Fresh blood cannot be stored for long, and many parts of the world lack the necessary storage

facilities.• Blood products can set off immune-responses in patients, even after correct blood typing (similar

to “rejection” of a transplanted organ)• Donated blood can carry viruses such as hepatitis or HIVDifficulties • Artificial products must be totally sterile, disease free and most importantly able to be accepted and adopted by a patient.

‣ Transport Systems in Plants

‣ Xylem tubes are dead, hollow cells that form from root to leaf. Coated with lignin - strength.‣ TRANSPIRATION ; Is the evaporation of water from the leaves. When the stomates are open, water can constantly evaporate, creating a tension or “pull”.‣ COHESION ; aka. capillarity is the tendency of water molecules to strongly cling together. So, when evaporation from the leaves creates the pull force, each water molecule pulls the one behind it because of cohesion. The flow that is created is called a “transpiration stream”‣ ADHESION : Water molecules are not only attracted to each other as in Cohesion, but also to other substances such as glass or an xylem tube. So they creep up forming a meniscus.


XYLEM The Xylem transports water & inorganic minerals

(Mineral Ions) upward only - from the roots (which absorb h20 and minerals)

Organic = Containing carbon

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‣ Food, mainly sugar, is made by photosynthesis in the leaves. This must then be transported out of the leaves to supply other parts of the plants through the phloem. This movement is called translocation.‣ The structure of phloem tubes is made up of two parts; called sieve tubes and companion cells. The sieve tubes are responsible for the actual transport. They are alive and filled with a thin cytoplasm that carries sugars through each cell. Alongside the sieve tubes are companion cells that have many mitochondria that provide ATP to the phloem cells.

in between sieve tubes are sieve plates, that are perforated so each cell is open into the next - thus forming an continuos tube.‣ The flow of nutrients through the phloem is caused by pressure difference between the “source” tissues and the “destination”. The pressure difference is osmotic pressure.

PHLOEM


The Phloem transports Organic Nutrients (FOOD) esp. Sugarsin either direction.

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Stem Cross SectionCAMBIUM ; Consists of cells which can divide to producemore cells - forming extra phloem and xylem cells.

Note: Phloem on the outside

‣Water is the Solvent of Life

‣ Homeostasis of Water & Salts Water’s concentration and the concentration of the substances dissolved in it, such as

salts, must be kept at the correct levels. If the balance is broken then osmosis may cause problems. Cells could lose water and dehydrate, or gain to much water and be damaged.

‣ The Importance of Removing Metabolic Wastes

As a result of all the metabolic processes that occur in cells, waste products particularly nitrogenous wastes are constantly being formed. If allowed to accumulate in the body, they would slow down metabolism (pH can change - enzymes) and poison cells. The excretory system is responsible for maintaining a constant blood composition and therefore maintaing a constant internal environment.


Life cannot exist without water. All the chemical reactions of metabolism take place in water solution. Water is also a reactant or product of many metabolic reactions e.g Respiration. Also, the transport of materials in the cytoplasm, blood or phloem takes place mainly in water solution.

Water regulates temperature with it’s high specific heat capacity. This means it can absorb (or loose) relatively large quantities of energy with minimal temperature change, which helps stabilize temperature.

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Isotonic environment - one in which the solute concentration is the same both inside and outside the cell.

Atom -> Molecule or Compound -> Organelle -> CELL -> Tissue -> Organ System -> Organism

FISHA fish kidneys are used not so much for excretion, but for maintaining their water balance. Fish excrete ammonia. Ammonia is toxic, but can be released continuously and is highly soluble.

Freshwater Fish Saltwater Fish

MAMMALSOn land, however, terrestrial animals need to conserve water. By converting waste into the less toxic form of urea, mammals can hold wastes in the body and excrete it periodically. It is highly soluble, much less toxic than ammonia, & can be stored in a more concentrated solution and so requires less water to remove than ammonia.

Unlike fish, the simple processes of diffusion and osmosis are not adequate to remove nitrogenous wastes - as they do not occur fast enough to maintain the required solute concentrations in cells. I. Diffusion is too slow, requires copious amounts of water to be excreted (which

terrestrial animal cannot afford to do esp. desert), and is non-selective process.II. Osmosis only deals with water. Water would exit the body and nitrogenous waste

would stay.


Maintain a higher concentration of solutes in their body than environment ( hypotonic) Because of this, water diffuses into the body by osmosis. They must continually get rid of this excess water - their kidneyʼs producing copious amounts of dilute urine in almost a continuos stream! They also absorb salts to prevent loss.

Have the opposite problem. Their internal body concentration is lower than their surroundings (hypertonic).They must drink salt water to replace any water loss, and actively excrete the salts.

The kidney has dual functions of excretion, and the regulation of proper water and salt concentrations in the body (osmoregulation)

~ Tend to loose salts, & gain water ~

~ Tend to loose water, & gain salts ~

The kidney plays a central role in homeostasis, forming and excreting urine while regulating water & salt concentrations in the blood. It maintains the precise balance between waste disposal and the animals needs for water and salts.

note :There is correlation between the type of wastes produced and the animals environment.

‣ The Kidney


Passive & Active TransportDiffusion and osmosis are passive processes because there is no expenditure of energy. When removing nitrogenous wastes, some substances must be REabsorbed against a concentration gradient (e.g. sugar, amino acids, salts). This requires energy and is called Active transport. Osmosis then occurs, which causes water to flow from the tubules back into the blood. (Passive transport - Salt moving out of the tubules will change concentration gradient for water)The Nephron The nephron is the smallest functional unit of the kidney. The nephron is a regulatory unit; it selectively reabsorbs materials required to maintain homeostasis. Approx. 1 mill in human kidney. The nephrons are arranged in the outer cortex and central medulla & are a complicated tangle of blood vessels and renal tubules (tubules=Small tubes).

‣ FiltrationFiltration is a non-selective process. The blood pressure is so high in the glomerulus that liquid from the blood is forced through the walls of the capillaries into the bowman's capsule. The liquid produced is called glomerular filtrate, consisting of blood plasma but no blood cells or large proteins (they are to large to pass)

‣ ReabsorptionAlong the tubule, the composition of the filtrate is carefully adjusted. Surrounding each nephron tubule is a large capillary network, to which materials are selectively re-absorbed (all amino acids, all glucose, all vitamins (kidneys don’t regulate these) some water, some salt) until the tubule only carries unwanted substances (urine)

‣ SecretionDeposits substances that were not removed in filtration into the proximal and distal tubules (e.g. H+, K+, poisons)

then via ureter to bladder

FILTRATION REABSORPTION SECRETION


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(hypertonic)

CO + H O -> H CO -> H + HCO2 2 2 3 3+

Carbonic Acid

* Refer to previous notes ʻforms substances are carried in bloodʼ

The amount of H in a solution determines itʼs pH. There is some secretion of H

Bicarbonate ionsare reabsorbed

+

There is a buffer system here that helps maintain a constant pH

* Nutrients like amino acids, glucose

*

- Potassium, Sodium and chloride are all electrolytes

renal of or relating to the kidneys

Side Note: Addisonʼs Disease occurs when a person cannot produce Aldosterone. This leads to osmotic imbalance. Can be treated with “Hormone Replacement Therapy (HRT)”

+

Hormonal Regulation of Salt & Water levelsThe amount of water and salts lost by the kidneys is controlled by hormones.

AldosteroneIs produced by the adrenal glands, which are situated above both kidneys. It regulates the transfer of sodium. When salt levels are low, more aldosterone is produced to encourage more reabsorption of sodium ions. Chloride ions follow passively, & so more salt is absorbed. (note also, it has effect on water due to osmosis)

ADH (Anti-Diuretic Hormone or Vasopressin)Reabsorption of water is controlled by ADH. Made by the hypothalamus but stored and released from the pituitary gland in the brain. If the body lacks hydration, ADH increases the permeability of the collecting ducts to water. (note: Collecting ducts pass through medulla which is purposely very salty)

Renal Dialysis You cannot live without you kidneys. Individuals suffering from kidney failure rely on dialysis to work for them. Similarities• Like the nephrons, dialysis selectively removes urea, and other wastes from the blood.• Both rely on movement of substances through semi-permeable membranes.Differences• The kidney is a highly complex organ. it uses both active and passive transport, dialysis only = diffusion.• Dialysis is much slower and less efficient.• Does not correct hormone producing functions of the kidney (e.g erythropoietin - that promotes growth of

RBC’s in the bone marrow)

Insects:• All insects are small, and most are adapted for flight. This means they cannot afford to carry

large amounts of water in their bodies just for the purpose of excreting urine. They excrete uric acid, which precipitates as a solid. It is thousands of times less soluble than ammonia or urea and has low toxicity, which means that little water is expended to remove it.

• It is particularly important for organisms living in estuarine environment (a point where the river meets the sea) where salinity varies greatly (due to factors such as tides and rainfall).

• Fish can swim away to evade the salt, and certain crabs can dig below into the mud - but plant’s are stuck where they are. They must find ways to cope with the salinity daily.

• Plant’s cannot cope with high levels of salt. It is toxic to the plant, accumulating in their leaves. Also, salt breaks a concentration gradient in the soil; preventing less water from entering the plant by osmosis.

Minimising water loss in Australian PlantsAdaptations of Australian xerophytes (plants adapted to dry conditions) include:

• Thick, waxy, or even reflective cuticles • Small & narrow leaves that reduce surface area. even needle

like foliage (spinifex grasses)• Hairy Leaves that reduce airflow across the leaf. (Wind increases

evaporation rates) (grevila alpina)• Hang vertically, and are oriented to avoid the heat of midday. • Open / Closed stomates Plants must negotiate a balance

between co2 intake and h20 loss. An adaptive advantage is to have stomates on the under side of a leaf, away from the evaporative heat.


Note: The length of the nephron tubules (esp. Loop of Henle) can be elongated in an animals kidneys ; An adaptionallowing greater reabsorption of water.

Enantiostasis Enantiostasis does not maintain a constant internal environment like homeostasis. Enantiostasis means the organism fluctuates with the environment (hence saving energy). Although there are mechanisms which still allow metabolic and physiological functions to continue.

The Grey Mangrove ~ Avicennia Marina

Salt Excluders: Prevent the entry of salt into their root system, by passive filtration.

Salt Excreters: Special salt glands (usually in the leaves), salt is concentrated here and then actively secreted from the plant.

Salt Accumulators: Salt is accumulated in part of the plant, such as old bark or leaves and then shed.

Spinifex GrassGrevillea Alpina

Eucalyptus

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molecule - Biologypetesnotes.weebly.com/uploads/2/6/7/7/26772952/maintaining_a... · molecule |㷦mälə㷧kyoōl|noun Chemistry ... Maintaining A Balance - HSC Biology 2012 Notes