Water and Organisms Water makes up between 60 - 95% of weight of organisms

Why is water important to organisms? Water is an important substance for maintaining life. Organisms cannot live without water. Water is a major cell component.

Importance of Water It acts as: solvent / reaction medium medium for transport (e.g. blood) metabolite (e.g. photosynthesis) others like act as cooling agent (e.g. sweating in hot weather) as supporting agent (e.g. turgidity in young plant) for sexual reproduction

Water as a Solvent dissolve most organic and inorganic substances needed for all biochemical reactions remove excretory products such as urea and excess salts in plants, root hairs absorb mineral salts present in soil in solution form

As a solvent Inside an alveolus of the lung: O2 dissolves in water film for diffusion Inside a leaf : CO2 dissolves in the water for diffusion to mesophyll cells

Water as a Medium of Transport human blood plasma consists mainly of water (90%) carry many dissolved substances like excretory wastes, hormones and gases around the body in plants, sugar and mineral salts are transported in solution in vascular bundles

As a medium for transport Human blood plasma consists mainly of water (90%)

Water as a Metabolite in plants during photosynthesis, carbohydrates are synthesized from carbon dioxide and water essential in hydrolytic reactions, e.g. digestion

As a metabolite photosynthesis: water + carbon dioxide --> carbohydrates + oxygen

To provide support and to keep shape water keeps plant cells turgid and provides a means of support in plants

For sexual reproduction Sperms need water to swim to the eggs.

Ways of Gaining Water in Animals drinking eating from respiration occurs in cells which the water formed is called metabolic water

Ways of Losing Water in Animals evaporation from body surfaces sweating exhalation urination defaecation

Ways of losing water in plants: Evaporation from body surface, Transpiration.

Hypotonic, Hypertonic and Isotonic Solutions Hypotonic solution - a solution has a higher water potential than the reference solution

Hypertonic solution - solution has a lower water potential than the reference solution Isotonic solution - a solution has the same water potential as the reference solution

Water relations of organisms in the cells Osmosis in cells water will enter the cells if the surrounding fluid is hypotonic ( of higher water potential) water will leave the cells if the surrounding fluid is hypertonic ( of lower water potential) No net water movement will occur when the surrounding fluid is isotonic ( of equal water potential)

Osmosis The net movement of water from a region of higher water potential to a region of lower water potential through a selectively permeable membrane.

Osmosis in animal cell Concentrated saline solution Water Cell swells and eventually burst Cell shrinks

What will happen when water enters and leaves cells? In animal cells water enter, the cells swell burst water leaves, the cells shrink.

Animal Cells Response to Different Solutions water move in by osmosis Cells swell and burst in hypotonic solution tissue cells

Animal Cells Response to Different Solutions tissue cells in hypertonic solution water move out by osmosis cells shrink

Investigation 11.1 Investigation of the Effects of Different Salt Concentrations on Red Blood Cells

Tube A: 0.2% sodium chloride solution In A to E 5 test tubes, transfer a drop of the blood sample and different concentrations of sodium chloride solution to each of the test tubes. Tube A: 0.2% sodium chloride solution Tube B: 0.6% sodium chloride solution Tube C: 0.8% sodium chloride solution Tube D: 1.6% sodium chloride solution Tube E: 3.2% sodium chloride solution

Withdraw a drop of liquid from each tube and examine it under the microscope.

red blood cell swells and is about to burst red blood cell shrinks red blood cell remains unchanged in appearance In hypotonic saline solution In hypertonic saline solution In isotonic saline solution Which of the five saline solutions most closely resembles the blood plasma in salt concentration ? Ans: The one in 0.8% saline solution is the most resembles the blood plasma concentration.

What evidence supports your answer ? red blood cell swells and is about to burst red blood cell shrinks red blood cell remains unchanged in appearance In hypotonic saline solution In hypertonic saline solution In isotonic saline solution What evidence supports your answer ? Ans: Red blood cells in 0.8% saline solution remain unchanged in appearance indicating that the solution is isotonic to blood plasma …

What evidence supports your answer ? red blood cell swells and is about to burst red blood cell shrinks red blood cell remains unchanged in appearance In hypotonic saline solution In hypertonic saline solution In isotonic saline solution What evidence supports your answer ? Ans: Fewer red blood cells can be observed in 0.6% saline solution and even fewer in 0.2% saline solution. This shows the two solution are hypotonic to the red blood cells …

What evidence supports your answer ? red blood cell swells and is about to burst red blood cell shrinks red blood cell remains unchanged in appearance In hypotonic saline solution In hypertonic saline solution In isotonic saline solution What evidence supports your answer ? Ans: The 1.6% and 3.2% saline solutions are hypertonic to the red blood cells as a net movement of water out of the red blood cells into the saline solution is noticed.

Importance of Osmoregulation osmoregulation is the maintenance of correct levels of water in the body any excessive gain or loss of water will upset the proper functioning of cells in an organism metabolic reactions are affected and organisms may die

The importance of osmoregulation for animal cells Osmoregulation: The process of regulating body fluid to keep it at a constant concentration. In mammals, osmoregulation is achieved by controlling the amount of water and the amount of dissolved substances in the blood. The major organ responsible are the kidneys

The kidney’s role in osmoregulation

Human Urinary System kidney ureter urinary bladder urethra

Human Urinary System Inferior vena cava aorta left kidney renal vein renal artery right kidney ureters sphincter muscle urinary bladder urethra Human Urinary System

Human Urinary System - Location of Kidneys mammals have two kidneys which are reddish and bean-shaped they are situated at one on each side of the vertebral column, below the ribs and are not protected by any part of the skeletal system renal artery brings blood to kidney while renal vein takes blood away from it

Human Urinary System - Ureter carries urine from kidney down to urinary bladder where stores urine temporarily valves are present in ureter to prevent urine from flowing upwards back flow of urine may happen when urinary bladder empties if valves do not close properly.This may lead to infection and damage of kidney

Human Urinary System - Urinary Bladder a muscular bag situated towards the bottom of the abdominal cavity urethra is led out from it on the top of urethra is surrounded by ring of sphincter muscle

Urination normally, the sphincter muscle is tightly contracted, so no urination occurs Adults can control the sphincter muscle but children cannot, it relaxes automatically when the bladder is full when urinary bladder is full sphincter muscle relaxes + wall of urinary bladder contracts urination occurs

Structure of Mammalian Kidney cortex medulla nephron renal artery pelvis renal vein ureter

Structure of Mammalian Kidney made up of three parts: - a light outer region - cortex - a dark inner region - medulla - a whitish central region leads to ureter - pelvis contain numerous tiny tubules called nephrons

Structure of Nephron consists of a swollen end called Bowman’s capsule which is connected to a narrow tubule the tubule begins in cortex after leaving the capsule, it coils up (proximal convoluted tubule)

It is then descends into the medulla and becomes U-shaped (loop of Henle) It goes back into the cortex and coils up again (distal convoluted tubule) Finally, it drains into a collecting duct which goes through the medulla and down to pelvis

Nephron Bowman’s capsule glomerulus efferent arteriole afferent arteriole distal convoluted tubule (second convolution) renal artery proximal convoluted tubule (first convolution) capillaries around nephron renal vein collecting duct Loop of Henle

…... How Nephron is Connected with Blood Vessel afferent arteriole (branches from renal artery) renal artery enters Bowman’s capsule Glomerulus (a tightly bunched group of capillaries) efferent arteriole (capillaries join up) …...

How Nephron is Connected with Blood Vessel leaves Bowman’s capsule capillaries (spread out and wrap around tubule) venule (capillaries join up) renal vein

Structure of Nephron first & second convolution Bowman’s capsule (with glomerulus) afferent arteriole efferent arteriole venule loop of Henle collecting duct

How Nephron Works ? By two ways, one is ultrafiltration and the other is reabsorption

Capillaries Diffusion It is the smallest blood vessels It is the site of exchange (by diffusion) Thin wall (one cell) Nutrients O2 Diffusion CO2 Waste

Ultrafiltration diameter of tiny artery leading to the glomerulus is larger than the leaving one so increase in pressure is resulted as blood tries to force its way out of the smaller tube the high hydrostatic pressure forces small molecules through the walls of capillaries and Bowman’s capsule into the capsular space

fluid which filtered into the nephron is glomerular filtrate glomerular filtrate has the same composition as that of blood except that it hasn’t got red blood cells, blood proteins & blood platelets

Reabsorption reabsorption is the process of absorbing useful substances into capillaries which wrapped around tubule as in glomerular filtrate, some substances like glucose and amino acid are useful to human so they are absorbed back while fluid travels along the tubule

those urea which remains in the fluid pass the whole nephron and finally drains into collecting duct which leads to pelvis and form urine urine contains mostly water, with urea and excess mineral salts

reabsorption of glucose, amino acids and some salts begins in the first convolution and finished when the fluid reaches loop of Henle

useful substances are reabsorbed by diffusion down the concentration gradient and active transport against concentration gradient in collecting duct, water is mainly reabsorbed by osmosis but the first convolution actually reabsorbs the largest amount of water

Functions of Kidney kidney mainly has three functions: osmoregulation removal of excess salt excretion

Functions of Kidney - Osmoregulation drink a lot of water blood becomes diluted small proportion of water is reabsorbed More dilute urine produce Amount of water in blood: CONSTANT

Functions of Kidney - Osmoregulation after sweating blood becomes concentrated large proportion of water is reabsorbed Less concentrate urine produce Amount of water in blood: CONSTANT

Functions of Kidney - Removal of Excess Salt after eating a salty meal concentration of urine is higher salt enters blood, concentration of salt in blood increase volume of urine increase man feels thirsty drink water

Functions of Kidney - Excretion protein cannot be stored in human body, excess protein are broken down in liver removing of amino groups from amino acids is called deamination amino groups are incorporated into urea molecules and then excreted in urine

Kidney Failure and Artificial Kidney some kidney diseases can lead to kidney failure which kidney can no longer function properly toxic substances will accumulate in blood and patient will die

artificial kidney is a bulky machine attached to patient which is used to filter and clean patient’s blood artificial kidney make use of the principle of dialysis. It has a filter made of cellophane which acts as a selectively permeable membrane

along one side of the membrane is the patient’s blood while the other side is dialysis fluid which has the same contain as plasma except urea only urea diffuses from patient’s blood into dialysis fluid through cellophane filter blood without urea will return to patient through his vein

dialysis fluid flows in direction opposite to that of blood flow to increase the efficiency of diffusion of urea into dialysis fluid other than using artificial kidney, kidney transplant is another possible method but only few people are willing to donate their kidneys after death

Excretion in Human metabolism are reactions take place inside cells of an organism most of the by-products of metabolism are toxic and should be removed once they are produced by excretion there are four major excretory organs in human body: Lungs, Kidneys, Liver and Skin

Excretory Organs - Lungs excrete carbon dioxide which is produced by cells during respiration and is carried by blood to lungs carbon dioxide diffuses out of the blood capillaries surrounding the lungs and passes into the air sac it is excreted when people breathe out. Water is lost during respiration, too

Excretory Organs - Kidneys deamination (break down of excess amino acids) in liver forms urea and uric acid urea and uric acid are called nitrogenous wastes the wastes are carried by blood to kidneys which excrete them from the body in form of urine

Excretory Organs - Liver old red blood cells are destroyed in liver and haemoglobin are released haemoglobin will turned into bile and excreted with bile into small intestine finally, haemoglobin will expel with faeces and leave the body

Excretory Organs - Skin skin is the largest excretory organ in human body it carries out its function through sweating sweat contains water, salts and urea, and sweating can excrete these substances from the body

Plants Cell cell wall cytoplasm vacuole cell membrane

freely permeable so it lets most of molecules to go through osmosis does not occur cell membrane beneath cell wall selectively permeable cell wall

 Water Relations of Plant - Turgor plant cell put in distilled water net water movement into the cell by osmosis  plant cell contains solutes water potential lower than pure water vacuole and cytoplasm swells

cytoplasm is pushed against cell wall turgor turgor is present because: cell wall is rigid and strong, cell bursting is prevented hydrostatic pressure develops inside the cell

When water potential of cell = water potential of water tendency of the cell to give out water increases water potential increases When water potential of cell = water potential of water Turgor occur (cell cannot take in any water) the cell is turgid

Water Relations of Plant - Plasmolysis plant cell in concentrated solution The whole phenomenon is called plasmolysis and cell is plasmolysed net water movement out of the cell by osmosis flaccid vacuole and cytoplasm shrink cytoplasm is torn away from cell wall

Plasmolysed cells

Turgidity of Plant Cells cell membrane separated from cell wall cell wall cytoplasm vacuole enlarged vacuole very small solution here is the same as the external solution plasmolysed cell (in hypertonic sol) turgid cell (in hypotonic sol.)

What will happen when water enters and leaves cells? In plant cells water enter, the cells become turgid. water leaves, the cells become less turgid flaccid plasmolyzed

Cells in Different Solutions Solution Concentration hypotonic hypertonic animal cells (e.g. RBC) haemolysis shrink plasmolysis (cell is flaccid) plant cells turgid

Investigation 11.2 To Investigate the Effects of Sucrose Solution and Tap Water on Epidermal Cells of Red Onion Scale Leaf or Rhoeo Discolor Leaf

fleshy scale leaf of red onion bulb forceps filter paper epidermis What do you observe when the epidermal strip is placed in the concentrated sucrose solution ? Ans: The coloured cytoplasm shrinks.

Plasmolysis of red onion epidermal cells (400X)

fleshy scale leaf of red onion bulb forceps filter paper epidermis Explain your observation. Ans: When the piece of epidermis is placed in concentrated solution, cells lose water by osmosis as the cells have a higher water potential than the sugar solution.

fleshy scale leaf of red onion bulb forceps filter paper epidermis What has happened to the cells in tap water ? Ans: The coloured cytoplasm swells and cells become turgid.

Fully turgid red onion epidermal cells (400X)

fleshy scale leaf of red onion bulb forceps filter paper epidermis Explain your answer. Ans: When the piece of epidermis is placed in tap water, cells gain water by osmosis as the surrounding tap water has a higher water potential than the cells.

Investigation 11.3 Effects of Concentrated Sucrose Solution and Tap Water on Raw Potato Strips

What has happened to the potato strips ? petri dish water 20% surcose solution raw potato strips A B What has happened to the potato strips ? Ans: Potato strip A increases in both weight and length while potato strip B decreases in both weight and length.

petri dish water 20% surcose solution raw potato strips A B Explain your answer. Ans: For potato strip A, it gains water by osmosis so both of its weight and length increase but for potato strip B, it loses water by osmosis so its weight and length decrease.

Experiment to Show that Water is Given Off During Transpiration Investigation 11.4 Experiment to Show that Water is Given Off During Transpiration

What do you observe in the polythene bags ? Ans: The one enclosing plant A becomes misty while nothing can be noticed in the one enclosing plant B.

How can you show that it is water ? polythene bag A B How can you show that it is water ? Ans: We can use anhydrous cobalt chloride paper to test it. It will turn the paper from blue to pink or we can use anhydrous copper sulphate. Water will turn it from white to blue.

What conclusions can you draw from the results ? polythene bag A B What conclusions can you draw from the results ? Ans: We can conclude that a leafy shoot gives off water during transpiration.

Transpiration an evaporation of water in form of water vapour from the surface of plant to atmosphere

it mainly takes place in leaves where there are some openings called stomata more water loses from the lower surface of the leaf than the upper one as more stomata present on the lower surface it also happens in lenticels and cuticle

How does transpiration take place? How transpiration pull is formed How transpiration occurs 2. Eventually, water is pulled from the xylem, pulling water up the plant. 1. Water evaporates into sub-stomatal air space 1. Water is lost from the cell surface, this is replaced by water in the cell. Each cell then pulls water from its neighbouring cells ( through cell wall through cytoplasm and vacuoles) 2. Water diffuses out through stoma Lower concentration of water vapour Substomatal air space with higher concentration of water How water lost from leaves causes transpiration and how the transpiration pull is formed.

Transpiration in Leaves a thin film of moisture is covered with each mesophyll cell the moisture evaporates from mesophyll cells into intercellular spaces and diffuses out of stomata into atmosphere

water potential of cells losing water decreases so they draw water from deeper cells in the leaf by osmosis. This in turn, draws water in xylem vessels into leaf to replace the loss

To Measure the Rate of Transpiration by Using a Simple Potometer Investigation 11.5 To Measure the Rate of Transpiration by Using a Simple Potometer

graduated capillary tube air/water meniscus graduated capillary tube reservoir leafy shoot tap What are the environmental conditions under which transpiration occurs quickly ? Ans: It is under dry, warm and windy conditions.

graduated capillary tube air/water meniscus graduated capillary tube reservoir leafy shoot tap Does this apparatus give you an accurate measurement of the rate of transpiration ? Ans: No. It is because it only measures the rate of water uptake by the leafy shoot … Ans: In addition, it is too small to fit the whole root system and this may affect the rate of water uptake.

graduated capillary tube air/water meniscus graduated capillary tube reservoir leafy shoot tap Sometimes you may introduce an air bubble into the capillary tube. State the advantage of this method. Ans: Movement of the air bubble is easier to observe than that of air/water meniscus.

graduated capillary tube air/water meniscus graduated capillary tube reservoir leafy shoot tap Sometimes you may introduce an air bubble into the capillary tube. State the disadvantage of this method. Ans: Friction between the capillary wall and the bubble may affect the movement of bubble.

Environmental Factors Affecting the Rate of Transpiration There are five environmental factors which affect the rate of transpiration. They are: (I) Light Intensity (II) Temperature (III) Humidity (IV) Wind Speed (V) Water Supply

Light Intensity stomata open in light, so plants can get enough carbon dioxide from atmosphere for carrying out photosynthesis light will increase temperature so increases the rate of transpiration

Temperature rate of evaporation of water from mesophyll cells relative humidity of air outside leaf rate of diffusion of water vapour from intercellular space in leaf to outside

 Humidity humidity outside rate of transpiration it makes the diffusion gradient of water vapour from moist intercellular space of a leaf to the external atmosphere steeper 

Wind Speed & Water Supply wind blows lack of water water vapour around the leaf sweeps away soil dries, plant wilts and stomata close transpiration rate transpiration rate INCREASES DECREASES

Stomata stomata are pores in the epidermis which gaseous exchange takes place during photosynthesis (or respiration) find mainly in lower epidermis of dicotyledonous leaves and stems

Guard Cells each stoma is surrounded by two guard cells which possess chloroplasts its inner wall is thicker than outer wall it is kidney-shaped stoma guard cell

Distribution of Stomata in Leaves normal plants mainly on the lower surface of leaves floating plants mainly on the upper surface leaves may also have air sacs to keep them afloat so they can carry out gaseous exchange

submerged aquatic plants no stomata (not required since gaseous exchange can be carried out by diffusion through the leave surface) no cuticle (the primary function of cuticle is to prevent excess water transpiration which is not present in aquatic plants)

Investigation 11.6 Experiment to Investigate Stomatal Distribution in a Leaf by Using Cobalt Chloride Paper

Obtain a potted plant. Using sellotape stick a small square cobalt chloride paper sellotape Obtain a potted plant. Using sellotape stick a small square of anhydrous cobalt chloride paper onto each surface of a leaf of the plant. Record the time taken for the cobalt chloride paper on each surface of the leaf to turn pink.

Which piece of cobalt chloride paper turns pink first? sellotape Which piece of cobalt chloride paper turns pink first? Ans: The piece of cobalt chloride paper attached to the lower epidermis of the leaf turns pink first.

Ans: It is because more stomata are present in the lower epidermis. cobalt chloride paper sellotape Explain your answer. Ans: It is because more stomata are present in the lower epidermis.

Why is it important to handle cobalt chloride paper with forceps? sellotape Why is it important to handle cobalt chloride paper with forceps? Ans: It is because there is moisture on human fingers so the paper may turn pink before sticking onto the surfaces of leaves.

To Observe the Release of Air Bubbles from Leaves placed in Hot Water Investigation 11.7 To Observe the Release of Air Bubbles from Leaves placed in Hot Water

Which surface has more air bubbles coming off? forceps hot water leaf Which surface has more air bubbles coming off? Ans: There are more air bubbles appear on the lower surface of the leaf.

Where does the air come from? forceps hot water leaf Where does the air come from? Ans: It is in the air spaces between the mesophyll cells in leaf which expands on heating and passes out through stomata of the leaf.

What does the result show? forceps hot water leaf What does the result show? Ans: The result shows that more stomata are present on the lower epidermis of the leaf.

Structure of Root

Structure of Root Root Cap a protective layer at the very tip of root to protect the delicate cells of root from being damaged as the root grows down through the soil Epidermis cover the rest of root absence of cuticle so water can enter

Growing Point behind root cap cells are capable of active division Region of Elongation more elongated than cells in growing point and have large vacuoles

Region of Root Hair little way behind root tip root hair are thin-walled extension of epidermal cells of root increase surface area for uptake of water and mineral salts

Vascular Tissue further from the tip of root contain xylem and phloem xylem transport absorbed water to every part of plant

Absorption of Soil Water by Root Hairs soil water is a dilute solution of salts which is more dilute than cell sap and cytoplasm in root hair water will pass by osmosis into root hair through cell wall and cell membrane

Transverse Transport of Water to Xylem cytoplasm and cell sap have higher water potential than neighbouring cortical cells epidermal cells gain water by osmosis NOTE: some water may travel inwards along or between cell walls without entering cytoplasm or vacuole of each cortical cell water travels by osmosis inwards from cell to cell

reduction of effective pressure at the top of xylem vessel transpiration occurs in leaves so water is continuously removed from the plant reduction of effective pressure at the top of xylem vessel water flows upwards from roots continuously flow of water through plant: transpiration stream tension produced to draw up water: transpiration pull

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