Mark my biology essay please

The importance of water and regulation of water in organisms
Water is a essential biological molecule which acts as the foundation for many metabolic processes. Water is polar, with a slightly negative charge around the oxygen molecule, allowing water to have properties such as being cohesive, having a high specific heat capacity and latent heat of evaporation. Water is required in the splitting of polymers to monomers and building up of polymers from monomers through hydrolysis and condensation reactions.
Water is crucial in the formation of tissue fluid in the capillaries. In the arteriole end , contraction of the left ventricle creates an increase in hydrostatic pressure above oncotic pressure in the blood plasma. This forces tissue fluid containing water with dissolved solutes including glucose, amino acids and urea out of the capillary bed via pores into fluid surrounding cells. Large plasma proteins remain in blood, decreasing the water potential in the capillary bed, causing water to be reabsorbed at the venule end via osmosis down a water potential gradient. Water is an important medium here for respiratory substrates like oxygen (the final electron acceptor in oxidative phosphorylation) and glucose which are vital for glycolysis and oxidative phosphorylation in respiration. If water wasn’t reabsorbed by osmosis in the venule end, tissue fluid would accumulate surrounding cells leading to oedema. If there was a decreased volume of water in the blood plasma, less fluid would be forced out of the capillaries, reducing respiration (as less oxygen provided to cells for oxidative phosphorylation).Therefore, water is vital as a solvent which provides nutrients and also its selective reabsorption ensures normal volumes of fluid surrounding cells, preventing oedema and other issues.
Water aids in the digestion of proteins in organisms. Membrane bound dipeptidase enzymes use addition of water to hydrolyse peptide bonds between polypeptides. Endopeptidases hydrolyse peptide bonds between amino acids inside a polypeptide chain, whilst exopeptidases hydrolyse terminal peptide bonds. Both of these enzymes require the use of a water molecule to split these polypeptides into amino acids. This allows the diffusion of amino acids into the cell lining of epithelial cells in the small intestine. As polypeptides are too large to simply diffuse through the phospholipid bilayer, the hydrolysis of polypeptides into amino acids allows the simple diffusion of amino acids into the ileum cell lining of epithelium. Without this digestion, amino acids wouldn’t be able to enter the epithelial cells, and wouldn’t be able to be used in metabolic processes such as in times of glucose depletion, glucagon converts amino acids into glucose for glycolysis to continue. Therefore, water is imperative for the digestion of proteins into amino acids which are able to be used in bodily processes.
In the light dependent reaction, chlorophyll undergoes photoionisation where an electron is excited and lost for chemiosmosis to occur. Water is crucial in the LDR, as it is split into its protons electrons and oxygen, replacing the electrons lost by the chlorophyll molecule. This replacement of electrons by water is crucial as it allows continual photoionisation. Without this, electron supply would be exhausted and thus less would be transferred down the ETC, decreasing the electrochemical gradient used to pump protons into the thylakoid. So less protons are able to diffuse down ATP synthase and phosphorylate ADP and Pi. And also less protons are able to reduce NADP. Therefore, water is imperative to ensure enough electron for the electron transport chain to allow chemiosmosis, so that there is continual production of the products of the light dependent reaction (NADPH and ATP) required in the light independent reaction. Water replenishing lost electrons in photoionisation thus allows the continual production of hexose sugars and other useful organic compounds which ensure productivity of biomass transferred along trophic levels.
Water contents in the blood plasma requires regulation to ensure no osmotic lysis of cells. A decrease in blood water potential below average is detected by osmoreceptors in the hypothalamus. These cells shrink when blood water potential is too low, stimulating the secretion of antidiuretic hormone from the posterior pituitary gland. ADH binds to specific tertiary structure receptors on the collecting duct and distal convoluted tube. This stimulates vesicles to fuse with the membrane, inserting aquaporins which increase the collecting ducts permeability for water. Therefore, more water diffuses into the blood from the nephron down a water potential gradient. This results in higher solute concentrated urine, and more water concentrated in the blood plasma. If low water potential of blood wasn’t detected, Cells would thus shrink, losing water via osmosis as it moves down a water potential gradient out of cells.
Water is cohesive, which means it is held by hydrogen bonds and its polarity means that molecules of water tend to stick together in a continuous column. This is crucial for the mass transport of water and mineral ions in plants via the xylem. When water diffuses into roots via osmosis, it causes a high hydrostatic pressure which causes a forced upwards pressure which draws water up the xylem in a continuous column. The water also contains dissolved nutrients in the form of nitrates and phosphates. The movement of water as a cohesive column up the xylem is thus crucial in allowing nutrients from the soil to be uptaken to cells all over the plant via the central stem. For example nitrate ions from the soil are incorporated into plants biomass, by synthesising the nitrogenous base in ATP, DNA and RNA. This movement of water thus allows the semiconservative replication of DNA in cells as well as the synthesis of proteins from mRNA in ribosomes, using tRNA molecules which are also composed of a nitrogenous base. Water is also vital in the mass transport of assimilates in a plant. Decreased water potential in the phloem due to active transport of assimilates causes water from the xylem to diffuse into the phloem down a water potential gradient. This creates a high hydrostatic pressure in the sieve tube elements of the phloem, causing a mass flow of assimilates from the source to sink. Without water, there would be less of a hydrostatic pressure created in the phloem, so less assimilates would be transported to respiring tissues and storage organs in the sink. For example, less sugars transported to respiring cells could cause anaerobic respiration and the build up of ethanol as a waste product, which could damage cell phospholipid membranes by hydrolysing lipids. Therefore, water has an essential role in the mass transport of nutrients in plants- ensuring movement of water, mineral ions and hexose sugars throughout the plant, as well as preventing build up of waste products by anaerobic respiration.

The importance of water and regulation of water in organisms
Water is a essential biological molecule which acts as the foundation for many metabolic processes. Water is polar, with a slightly negative charge around the oxygen molecule, allowing water to have properties such as being cohesive, having a high specific heat capacity and latent heat of evaporation. Water is required in the splitting of polymers to monomers and building up of polymers from monomers through hydrolysis and condensation reactions.
Water is crucial in the formation of tissue fluid in the capillaries. In the arteriole end , contraction of the left ventricle creates an increase in hydrostatic pressure above oncotic pressure in the blood plasma. This forces tissue fluid containing water with dissolved solutes including glucose, amino acids and urea out of the capillary bed via pores into fluid surrounding cells. Large plasma proteins remain in blood, decreasing the water potential in the capillary bed, causing water to be reabsorbed at the venule end via osmosis down a water potential gradient. Water is an important medium here for respiratory substrates like oxygen (the final electron acceptor in oxidative phosphorylation) and glucose which are vital for glycolysis and oxidative phosphorylation in respiration. If water wasn’t reabsorbed by osmosis in the venule end, tissue fluid would accumulate surrounding cells leading to oedema. If there was a decreased volume of water in the blood plasma, less fluid would be forced out of the capillaries, reducing respiration (as less oxygen provided to cells for oxidative phosphorylation).Therefore, water is vital as a solvent which provides nutrients and also its selective reabsorption ensures normal volumes of fluid surrounding cells, preventing oedema and other issues.
Water aids in the digestion of proteins in organisms. Membrane bound dipeptidase enzymes use addition of water to hydrolyse peptide bonds between polypeptides. Endopeptidases hydrolyse peptide bonds between amino acids inside a polypeptide chain, whilst exopeptidases hydrolyse terminal peptide bonds. Both of these enzymes require the use of a water molecule to split these polypeptides into amino acids. This allows the diffusion of amino acids into the cell lining of epithelial cells in the small intestine. As polypeptides are too large to simply diffuse through the phospholipid bilayer, the hydrolysis of polypeptides into amino acids allows the simple diffusion of amino acids into the ileum cell lining of epithelium. Without this digestion, amino acids wouldn’t be able to enter the epithelial cells, and wouldn’t be able to be used in metabolic processes such as in times of glucose depletion, glucagon converts amino acids into glucose for glycolysis to continue. Therefore, water is imperative for the digestion of proteins into amino acids which are able to be used in bodily processes.
In the light dependent reaction, chlorophyll undergoes photoionisation where an electron is excited and lost for chemiosmosis to occur. Water is crucial in the LDR, as it is split into its protons electrons and oxygen, replacing the electrons lost by the chlorophyll molecule. This replacement of electrons by water is crucial as it allows continual photoionisation. Without this, electron supply would be exhausted and thus less would be transferred down the ETC, decreasing the electrochemical gradient used to pump protons into the thylakoid. So less protons are able to diffuse down ATP synthase and phosphorylate ADP and Pi. And also less protons are able to reduce NADP. Therefore, water is imperative to ensure enough electron for the electron transport chain to allow chemiosmosis, so that there is continual production of the products of the light dependent reaction (NADPH and ATP) required in the light independent reaction. Water replenishing lost electrons in photoionisation thus allows the continual production of hexose sugars and other useful organic compounds which ensure productivity of biomass transferred along trophic levels.
Water contents in the blood plasma requires regulation to ensure no osmotic lysis of cells. A decrease in blood water potential below average is detected by osmoreceptors in the hypothalamus. These cells shrink when blood water potential is too low, stimulating the secretion of antidiuretic hormone from the posterior pituitary gland. ADH binds to specific tertiary structure receptors on the collecting duct and distal convoluted tube. This stimulates vesicles to fuse with the membrane, inserting aquaporins which increase the collecting ducts permeability for water. Therefore, more water diffuses into the blood from the nephron down a water potential gradient. This results in higher solute concentrated urine, and more water concentrated in the blood plasma. If low water potential of blood wasn’t detected, Cells would thus shrink, losing water via osmosis as it moves down a water potential gradient out of cells.
Water is cohesive, which means it is held by hydrogen bonds and its polarity means that molecules of water tend to stick together in a continuous column. This is crucial for the mass transport of water and mineral ions in plants via the xylem. When water diffuses into roots via osmosis, it causes a high hydrostatic pressure which causes a forced upwards pressure which draws water up the xylem in a continuous column. The water also contains dissolved nutrients in the form of nitrates and phosphates. The movement of water as a cohesive column up the xylem is thus crucial in allowing nutrients from the soil to be uptaken to cells all over the plant via the central stem. For example nitrate ions from the soil are incorporated into plants biomass, by synthesising the nitrogenous base in ATP, DNA and RNA. This movement of water thus allows the semiconservative replication of DNA in cells as well as the synthesis of proteins from mRNA in ribosomes, using tRNA molecules which are also composed of a nitrogenous base. Water is also vital in the mass transport of assimilates in a plant. Decreased water potential in the phloem due to active transport of assimilates causes water from the xylem to diffuse into the phloem down a water potential gradient. This creates a high hydrostatic pressure in the sieve tube elements of the phloem, causing a mass flow of assimilates from the source to sink. Without water, there would be less of a hydrostatic pressure created in the phloem, so less assimilates would be transported to respiring tissues and storage organs in the sink. For example, less sugars transported to respiring cells could cause anaerobic respiration and the build up of ethanol as a waste product, which could damage cell phospholipid membranes by hydrolysing lipids. Therefore, water has an essential role in the mass transport of nutrients in plants- ensuring movement of water, mineral ions and hexose sugars throughout the plant, as well as preventing build up of waste products by anaerobic respiration.

Hi would be able to look over mine too? My teacher never really bother with the essay so I am unsure I’m on the right path. It’s only three paragraphs, obviously i would write two more but I just want to know if it’s okay so far. Thanks
Importance of proteins in control of processes and responses in organisms
Proteins are polymers formed by a sequence of amino acids joined by peptide bonds, where folding occurs due to hydrogen bonds between the NH and C=O groups in the polypeptide chain. The 3D folding involves more hydrogen bonds, disulfide bridges, and ionic bonds, creating the specific structure of enzymes. Enzymes have active sites where substrates bind with complementary shapes to form an enzyme-substrate complex. An example is ATPase, which is essential for the hydrolysis of ATP into ADP and inorganic phosphate during muscle contraction. When the myosin head with ADP attaches to the binding site on actin, it forms a crossbridge, causing a power stroke that pulls the actin filament along the myosin using energy from ATP hydrolysis. ATP hydrolysis also re-energises the myosin head, allowing it to detach and repeat the cycle. Without ATPase, the myosin head would be unable to change shape and pull actin, so muscles would not contract or produce movement. This would prevent mammals from escaping predators, reducing their chances of survival and reproduction. Therefore, proteins are crucial for forming enzymes that control processes like muscle contraction, enabling organisms to respond effectively to their environment.
Quaternary structure of proteins involve more than one polypeptide chain joined together by interactions such as hydrogen bonds between polypeptides. An example of this are antibodies, which are secreted by B lymphocytes during humoral immune response, where B cells differentiate into plasma cells and memory cells. Antibodies bind specifically to antigens, forming an antigen antibody complexes. Each antibody can bind complementary to two pathogens at the same time causing agglutination. This allows phagocytes to easily engulf pathogens and hydrolyse them. Antibodies can be produced from vaccines to provide immunity, if there is a change in protein structure due to gene mutation,then primary structure of antibody alters affecting the foldings of tertiary and quaternary structures.This results in antibodies no longer complementary antigens and can not bind, so organisms are no longer immune to infection.
Another crucial protein that controls a process is transcription factors (TF) found in cytoplasm and regulate transcription of specific target genes in eukaryotes. This happens by TF binding to a specific DNA base sequence on the promoter region of the gene when entering the nucleus, TF can stimulate transcription by helping RNA polymerase to bind and produce mRNA that then undergoes splicing to remove introns. Environmental factors can lead to epigenetic changes that can either stimulate or inhibit TF binding to the promoter region. Increased methylation of DNA allows chromatin to condense making nucleosomes pack more tightly together and prevents TF and RNA polymerase from binding to promoter regions inhibiting transcription. Similarly this occurs with decreased acetylation of histones, increasing positive charge and binding more tightly to DNA. This leads to uncontrolled transcription and cell division that can form tumours that can either be malignant or benign. Thus, the protein TF is important to regulating gene expression and ensuring mitosis is controlled to prevent the mass of abnormal cells from forming.

The importance of water and regulation of water in organisms
Water is a essential biological molecule which acts as the foundation for many metabolic processes. Water is polar, with a slightly negative charge around the oxygen molecule, allowing water to have properties such as being cohesive, having a high specific heat capacity and latent heat of evaporation. Water is required in the splitting of polymers to monomers and building up of polymers from monomers through hydrolysis and condensation reactions.
Water is crucial in the formation of tissue fluid in the capillaries. In the arteriole end , contraction of the left ventricle creates an increase in hydrostatic pressure above oncotic pressure in the blood plasma. This forces tissue fluid containing water with dissolved solutes including glucose, amino acids and urea out of the capillary bed via pores into fluid surrounding cells. Large plasma proteins remain in blood, decreasing the water potential in the capillary bed, causing water to be reabsorbed at the venule end via osmosis down a water potential gradient. Water is an important medium here for respiratory substrates like oxygen (the final electron acceptor in oxidative phosphorylation) and glucose which are vital for glycolysis and oxidative phosphorylation in respiration. If water wasn’t reabsorbed by osmosis in the venule end, tissue fluid would accumulate surrounding cells leading to oedema. If there was a decreased volume of water in the blood plasma, less fluid would be forced out of the capillaries, reducing respiration (as less oxygen provided to cells for oxidative phosphorylation).Therefore, water is vital as a solvent which provides nutrients and also its selective reabsorption ensures normal volumes of fluid surrounding cells, preventing oedema and other issues.
Water aids in the digestion of proteins in organisms. Membrane bound dipeptidase enzymes use addition of water to hydrolyse peptide bonds between polypeptides. Endopeptidases hydrolyse peptide bonds between amino acids inside a polypeptide chain, whilst exopeptidases hydrolyse terminal peptide bonds. Both of these enzymes require the use of a water molecule to split these polypeptides into amino acids. This allows the diffusion of amino acids into the cell lining of epithelial cells in the small intestine. As polypeptides are too large to simply diffuse through the phospholipid bilayer, the hydrolysis of polypeptides into amino acids allows the simple diffusion of amino acids into the ileum cell lining of epithelium. Without this digestion, amino acids wouldn’t be able to enter the epithelial cells, and wouldn’t be able to be used in metabolic processes such as in times of glucose depletion, glucagon converts amino acids into glucose for glycolysis to continue. Therefore, water is imperative for the digestion of proteins into amino acids which are able to be used in bodily processes.
In the light dependent reaction, chlorophyll undergoes photoionisation where an electron is excited and lost for chemiosmosis to occur. Water is crucial in the LDR, as it is split into its protons electrons and oxygen, replacing the electrons lost by the chlorophyll molecule. This replacement of electrons by water is crucial as it allows continual photoionisation. Without this, electron supply would be exhausted and thus less would be transferred down the ETC, decreasing the electrochemical gradient used to pump protons into the thylakoid. So less protons are able to diffuse down ATP synthase and phosphorylate ADP and Pi. And also less protons are able to reduce NADP. Therefore, water is imperative to ensure enough electron for the electron transport chain to allow chemiosmosis, so that there is continual production of the products of the light dependent reaction (NADPH and ATP) required in the light independent reaction. Water replenishing lost electrons in photoionisation thus allows the continual production of hexose sugars and other useful organic compounds which ensure productivity of biomass transferred along trophic levels.
Water contents in the blood plasma requires regulation to ensure no osmotic lysis of cells. A decrease in blood water potential below average is detected by osmoreceptors in the hypothalamus. These cells shrink when blood water potential is too low, stimulating the secretion of antidiuretic hormone from the posterior pituitary gland. ADH binds to specific tertiary structure receptors on the collecting duct and distal convoluted tube. This stimulates vesicles to fuse with the membrane, inserting aquaporins which increase the collecting ducts permeability for water. Therefore, more water diffuses into the blood from the nephron down a water potential gradient. This results in higher solute concentrated urine, and more water concentrated in the blood plasma. If low water potential of blood wasn’t detected, Cells would thus shrink, losing water via osmosis as it moves down a water potential gradient out of cells.
Water is cohesive, which means it is held by hydrogen bonds and its polarity means that molecules of water tend to stick together in a continuous column. This is crucial for the mass transport of water and mineral ions in plants via the xylem. When water diffuses into roots via osmosis, it causes a high hydrostatic pressure which causes a forced upwards pressure which draws water up the xylem in a continuous column. The water also contains dissolved nutrients in the form of nitrates and phosphates. The movement of water as a cohesive column up the xylem is thus crucial in allowing nutrients from the soil to be uptaken to cells all over the plant via the central stem. For example nitrate ions from the soil are incorporated into plants biomass, by synthesising the nitrogenous base in ATP, DNA and RNA. This movement of water thus allows the semiconservative replication of DNA in cells as well as the synthesis of proteins from mRNA in ribosomes, using tRNA molecules which are also composed of a nitrogenous base. Water is also vital in the mass transport of assimilates in a plant. Decreased water potential in the phloem due to active transport of assimilates causes water from the xylem to diffuse into the phloem down a water potential gradient. This creates a high hydrostatic pressure in the sieve tube elements of the phloem, causing a mass flow of assimilates from the source to sink. Without water, there would be less of a hydrostatic pressure created in the phloem, so less assimilates would be transported to respiring tissues and storage organs in the sink. For example, less sugars transported to respiring cells could cause anaerobic respiration and the build up of ethanol as a waste product, which could damage cell phospholipid membranes by hydrolysing lipids. Therefore, water has an essential role in the mass transport of nutrients in plants- ensuring movement of water, mineral ions and hexose sugars throughout the plant, as well as preventing build up of waste products by anaerobic respiration.

The importance of water and regulation of water in organisms
Water is a essential biological molecule which acts as the foundation for many metabolic processes. Water is polar, with a slightly negative charge around the oxygen molecule, allowing water to have properties such as being cohesive, having a high specific heat capacity and latent heat of evaporation. Water is required in the splitting of polymers to monomers and building up of polymers from monomers through hydrolysis and condensation reactions.
Water is crucial in the formation of tissue fluid in the capillaries. In the arteriole end , contraction of the left ventricle creates an increase in hydrostatic pressure above oncotic pressure in the blood plasma. This forces tissue fluid containing water with dissolved solutes including glucose, amino acids and urea out of the capillary bed via pores into fluid surrounding cells. Large plasma proteins remain in blood, decreasing the water potential in the capillary bed, causing water to be reabsorbed at the venule end via osmosis down a water potential gradient. Water is an important medium here for respiratory substrates like oxygen (the final electron acceptor in oxidative phosphorylation) and glucose which are vital for glycolysis and oxidative phosphorylation in respiration. If water wasn’t reabsorbed by osmosis in the venule end, tissue fluid would accumulate surrounding cells leading to oedema. If there was a decreased volume of water in the blood plasma, less fluid would be forced out of the capillaries, reducing respiration (as less oxygen provided to cells for oxidative phosphorylation).Therefore, water is vital as a solvent which provides nutrients and also its selective reabsorption ensures normal volumes of fluid surrounding cells, preventing oedema and other issues.
Water aids in the digestion of proteins in organisms. Membrane bound dipeptidase enzymes use addition of water to hydrolyse peptide bonds between polypeptides. Endopeptidases hydrolyse peptide bonds between amino acids inside a polypeptide chain, whilst exopeptidases hydrolyse terminal peptide bonds. Both of these enzymes require the use of a water molecule to split these polypeptides into amino acids. This allows the diffusion of amino acids into the cell lining of epithelial cells in the small intestine. As polypeptides are too large to simply diffuse through the phospholipid bilayer, the hydrolysis of polypeptides into amino acids allows the simple diffusion of amino acids into the ileum cell lining of epithelium. Without this digestion, amino acids wouldn’t be able to enter the epithelial cells, and wouldn’t be able to be used in metabolic processes such as in times of glucose depletion, glucagon converts amino acids into glucose for glycolysis to continue. Therefore, water is imperative for the digestion of proteins into amino acids which are able to be used in bodily processes.
In the light dependent reaction, chlorophyll undergoes photoionisation where an electron is excited and lost for chemiosmosis to occur. Water is crucial in the LDR, as it is split into its protons electrons and oxygen, replacing the electrons lost by the chlorophyll molecule. This replacement of electrons by water is crucial as it allows continual photoionisation. Without this, electron supply would be exhausted and thus less would be transferred down the ETC, decreasing the electrochemical gradient used to pump protons into the thylakoid. So less protons are able to diffuse down ATP synthase and phosphorylate ADP and Pi. And also less protons are able to reduce NADP. Therefore, water is imperative to ensure enough electron for the electron transport chain to allow chemiosmosis, so that there is continual production of the products of the light dependent reaction (NADPH and ATP) required in the light independent reaction. Water replenishing lost electrons in photoionisation thus allows the continual production of hexose sugars and other useful organic compounds which ensure productivity of biomass transferred along trophic levels.
Water contents in the blood plasma requires regulation to ensure no osmotic lysis of cells. A decrease in blood water potential below average is detected by osmoreceptors in the hypothalamus. These cells shrink when blood water potential is too low, stimulating the secretion of antidiuretic hormone from the posterior pituitary gland. ADH binds to specific tertiary structure receptors on the collecting duct and distal convoluted tube. This stimulates vesicles to fuse with the membrane, inserting aquaporins which increase the collecting ducts permeability for water. Therefore, more water diffuses into the blood from the nephron down a water potential gradient. This results in higher solute concentrated urine, and more water concentrated in the blood plasma. If low water potential of blood wasn’t detected, Cells would thus shrink, losing water via osmosis as it moves down a water potential gradient out of cells.
Water is cohesive, which means it is held by hydrogen bonds and its polarity means that molecules of water tend to stick together in a continuous column. This is crucial for the mass transport of water and mineral ions in plants via the xylem. When water diffuses into roots via osmosis, it causes a high hydrostatic pressure which causes a forced upwards pressure which draws water up the xylem in a continuous column. The water also contains dissolved nutrients in the form of nitrates and phosphates. The movement of water as a cohesive column up the xylem is thus crucial in allowing nutrients from the soil to be uptaken to cells all over the plant via the central stem. For example nitrate ions from the soil are incorporated into plants biomass, by synthesising the nitrogenous base in ATP, DNA and RNA. This movement of water thus allows the semiconservative replication of DNA in cells as well as the synthesis of proteins from mRNA in ribosomes, using tRNA molecules which are also composed of a nitrogenous base. Water is also vital in the mass transport of assimilates in a plant. Decreased water potential in the phloem due to active transport of assimilates causes water from the xylem to diffuse into the phloem down a water potential gradient. This creates a high hydrostatic pressure in the sieve tube elements of the phloem, causing a mass flow of assimilates from the source to sink. Without water, there would be less of a hydrostatic pressure created in the phloem, so less assimilates would be transported to respiring tissues and storage organs in the sink. For example, less sugars transported to respiring cells could cause anaerobic respiration and the build up of ethanol as a waste product, which could damage cell phospholipid membranes by hydrolysing lipids. Therefore, water has an essential role in the mass transport of nutrients in plants- ensuring movement of water, mineral ions and hexose sugars throughout the plant, as well as preventing build up of waste products by anaerobic respiration.

The importance of water and regulation of water in organisms
Water is a essential biological molecule which acts as the foundation for many metabolic processes. Water is polar, with a slightly negative charge around the oxygen molecule, allowing water to have properties such as being cohesive, having a high specific heat capacity and latent heat of evaporation. Water is required in the splitting of polymers to monomers and building up of polymers from monomers through hydrolysis and condensation reactions.
Water is crucial in the formation of tissue fluid in the capillaries. In the arteriole end , contraction of the left ventricle creates an increase in hydrostatic pressure above oncotic pressure in the blood plasma. This forces tissue fluid containing water with dissolved solutes including glucose, amino acids and urea out of the capillary bed via pores into fluid surrounding cells. Large plasma proteins remain in blood, decreasing the water potential in the capillary bed, causing water to be reabsorbed at the venule end via osmosis down a water potential gradient. Water is an important medium here for respiratory substrates like oxygen (the final electron acceptor in oxidative phosphorylation) and glucose which are vital for glycolysis and oxidative phosphorylation in respiration. If water wasn’t reabsorbed by osmosis in the venule end, tissue fluid would accumulate surrounding cells leading to oedema. If there was a decreased volume of water in the blood plasma, less fluid would be forced out of the capillaries, reducing respiration (as less oxygen provided to cells for oxidative phosphorylation).Therefore, water is vital as a solvent which provides nutrients and also its selective reabsorption ensures normal volumes of fluid surrounding cells, preventing oedema and other issues.
Water aids in the digestion of proteins in organisms. Membrane bound dipeptidase enzymes use addition of water to hydrolyse peptide bonds between polypeptides. Endopeptidases hydrolyse peptide bonds between amino acids inside a polypeptide chain, whilst exopeptidases hydrolyse terminal peptide bonds. Both of these enzymes require the use of a water molecule to split these polypeptides into amino acids. This allows the diffusion of amino acids into the cell lining of epithelial cells in the small intestine. As polypeptides are too large to simply diffuse through the phospholipid bilayer, the hydrolysis of polypeptides into amino acids allows the simple diffusion of amino acids into the ileum cell lining of epithelium. Without this digestion, amino acids wouldn’t be able to enter the epithelial cells, and wouldn’t be able to be used in metabolic processes such as in times of glucose depletion, glucagon converts amino acids into glucose for glycolysis to continue. Therefore, water is imperative for the digestion of proteins into amino acids which are able to be used in bodily processes.
In the light dependent reaction, chlorophyll undergoes photoionisation where an electron is excited and lost for chemiosmosis to occur. Water is crucial in the LDR, as it is split into its protons electrons and oxygen, replacing the electrons lost by the chlorophyll molecule. This replacement of electrons by water is crucial as it allows continual photoionisation. Without this, electron supply would be exhausted and thus less would be transferred down the ETC, decreasing the electrochemical gradient used to pump protons into the thylakoid. So less protons are able to diffuse down ATP synthase and phosphorylate ADP and Pi. And also less protons are able to reduce NADP. Therefore, water is imperative to ensure enough electron for the electron transport chain to allow chemiosmosis, so that there is continual production of the products of the light dependent reaction (NADPH and ATP) required in the light independent reaction. Water replenishing lost electrons in photoionisation thus allows the continual production of hexose sugars and other useful organic compounds which ensure productivity of biomass transferred along trophic levels.
Water contents in the blood plasma requires regulation to ensure no osmotic lysis of cells. A decrease in blood water potential below average is detected by osmoreceptors in the hypothalamus. These cells shrink when blood water potential is too low, stimulating the secretion of antidiuretic hormone from the posterior pituitary gland. ADH binds to specific tertiary structure receptors on the collecting duct and distal convoluted tube. This stimulates vesicles to fuse with the membrane, inserting aquaporins which increase the collecting ducts permeability for water. Therefore, more water diffuses into the blood from the nephron down a water potential gradient. This results in higher solute concentrated urine, and more water concentrated in the blood plasma. If low water potential of blood wasn’t detected, Cells would thus shrink, losing water via osmosis as it moves down a water potential gradient out of cells.
Water is cohesive, which means it is held by hydrogen bonds and its polarity means that molecules of water tend to stick together in a continuous column. This is crucial for the mass transport of water and mineral ions in plants via the xylem. When water diffuses into roots via osmosis, it causes a high hydrostatic pressure which causes a forced upwards pressure which draws water up the xylem in a continuous column. The water also contains dissolved nutrients in the form of nitrates and phosphates. The movement of water as a cohesive column up the xylem is thus crucial in allowing nutrients from the soil to be uptaken to cells all over the plant via the central stem. For example nitrate ions from the soil are incorporated into plants biomass, by synthesising the nitrogenous base in ATP, DNA and RNA. This movement of water thus allows the semiconservative replication of DNA in cells as well as the synthesis of proteins from mRNA in ribosomes, using tRNA molecules which are also composed of a nitrogenous base. Water is also vital in the mass transport of assimilates in a plant. Decreased water potential in the phloem due to active transport of assimilates causes water from the xylem to diffuse into the phloem down a water potential gradient. This creates a high hydrostatic pressure in the sieve tube elements of the phloem, causing a mass flow of assimilates from the source to sink. Without water, there would be less of a hydrostatic pressure created in the phloem, so less assimilates would be transported to respiring tissues and storage organs in the sink. For example, less sugars transported to respiring cells could cause anaerobic respiration and the build up of ethanol as a waste product, which could damage cell phospholipid membranes by hydrolysing lipids. Therefore, water has an essential role in the mass transport of nutrients in plants- ensuring movement of water, mineral ions and hexose sugars throughout the plant, as well as preventing build up of waste products by anaerobic respiration.