Hydrophobic interactions

Some molecules just don’t play nicely with water. Because water is a polar molecule, it tends to stick to itself via hydrogen bonds. Other polar molecules also stick to water molecules and can mix right in, dissolv ing into the water. However, nonpolar molecules have evenly shared covalent bonds and lack the slight negative and positive charges of polar molecules. Because they’re uncharged, nonpolar molecules don’t mix well with water.

Nonpolar molecules are also called hydrophobic molecules because “hydro” means water and “phobic” means to fear.

When nonpolar molecules are placed in a watery environment, the polar mol ecules will all stick to each other and push the nonpolar molecules away. You can think of the scenario as if the polar molecules all belong to a clique that refuses to hang out with the nonpolar molecules. (The name of this clique, by the way, is the hydrophilic molecules.) Because the nonpolar molecules all get pushed together, they become associated with each other.

The interaction between nonpolar molecules is called a hydrophobic interaction.

You can easily demonstrate a hydrophobic interaction to yourself. Just go into your kitchen, put some water in a cup, and then add a little oil. Even if you stir the mixture vigorously to mix the oil into the water, as soon as you stop stirring, all the oil will gather together on top of the water.

The water molecules all stick to each other and push the oil molecules away. Hence the saying, “They get along like oil and water!”

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How viruses get into cells

Viruses attach to cells when viral proteins successfully bind to receptors on the host cell. If the viral protein has the right shape, it will tuck into the cor responding shape on the host cell receptor. You can think of viral attachment as a virus having the right key to fit into the lock on the host cell.

After the virus is attached, it may force itself into the cell by digging a hole through a cell wall slip in by fusing its envelope with the membrane of the host cell, or trick the cell into bringing it inside.

The ability of a virus to infect a host cell depends on a match between pro teins on the surface of the virus and receptors on the surface of the host cell.

The type of cells a particular virus can infect is called the host range of the virus. Because viruses can infect only cells that they can attach to with their proteins, each virus has a very specific range of hosts it can infect. In other words, each virus can infect only the host cells for which it has keys.

Some viruses have a key that works in the lock on many types of cells. These viruses have a broad host range. For example, the rabies virus can infect humans and many other mammals. On the other hand, some viruses have a key that fits into the lock on only a few cells. These viruses have a narrow host range. The HIV virus, which infects only certain cells of the human immune system, is a good example of a virus with a very narrow host range.

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The structure of viruses

The simplest viruses have just two components: a nucleic acid core and protein capsid. The nucleic acid core, which may be DNA or RNA, contains the instructions for taking over cells and making more virions, or viral par ticles. The nucleic acid is surrounded by the capsid, a protective protein coat. Each individual protein that makes up the capsid is called a capsomere.

All viruses have at least a capsid and a nucleic acid core. The core consists of one of four types of nucleic acid:

*Double-stranded DNA

*Single-stranded DNA

*Double-stranded RNA

*Single-stranded RNA

One difference between cells and viruses is that cells contain DNA and RNA. However, a single viral particle contains only DNA or RNA. Also, single stranded DNA and double-stranded RNA are commonly found in viruses, but not in cells.

In addition to the capsid and the core, some viruses have an outer membrane layer called an envelope. It’s no coincidence that the envelope of a virus is similar to the plasma membrane of a cell viruses that have envelopes steal them from their cellular victims as they leave the cell! Viral envelopes aren’t exactly the same as plasma membranes because they’ve been changed to suit the needs of the virus by the addition of viral proteins.

Once modified and adopted, the envelope helps the virus enter and exit from host cells. Viruses may also have proteins that stick out of the envelope or off the sur face of the capsid. These proteins, called spikes, help the virus attach to host cells.

Viruses come in three common shapes:

*Helical viruses have a capsid that forms a twisting helix around the nucleic acid core.

*Polyhedral viruses have a regular geometric shape. The most complex polyhedral viruses are icosahedrons with 20 faces.

*Complex viruses have separate patches of proteins, often forming unique structures or extensions on the virus.

Under the microscope, enveloped viruses appear irregular in shape. However, a helical or polyhedral capsid may be located underneath the envelope.

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FOOD WEB

Food webs
Energy passes from one animate thing to a different within the sort of food. Food webs show however living things go after each other. At very cheap of a food cycle are plants, that build their own food, taking energy from the Sun. At the highest ar predators, that go after alternative animals.

Food chain
Food webs are created from totally different, many various, many alternative food chains that have different levels. In a very organic phenomenon, plants are referred to as producers as a result of they create their own food. Animals that eat plants are referred to as primary customers. Primary customers are ingested by alternative animals referred to as secondary customers, or predators. Once all living things die they become the food of organisms referred to as decomposers.


Food pyramid
As we have a tendency to go up a organic phenomenon, the number of food offered decreases. This is often as a result of living things use most of the energy within the food they eat respiration. A organic phenomenon shows however energy is lost at every level. close to the highest, there ar simply many predators, whereas at very cheap there are more producers.

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ENDOCRINOLOGY

ENDOCRINOLOGY in short and if we get more information then we’ll update this post.

1) ADRENAL GLAND

HORMONE

  1. Adrenaline hormone
  2. Cortisol hormone
  3. Steroid hormone

Adrenaline –

Action of the adrenalin include increasing the heart rate ,increasing blood pressure , expending the air passage of the lunge entering of the pupil in the eye.

CORTISOL 

         Increases the gluconeogenesis in the liver.

Inhibitory effect on insulin which stop transport of glucose into the cells

Cortisol has diurnal variation.

No diurnal change In cushings syndrome.

STEROID HORMONES-

Steroid hormones play an important role in    –

Carbohydrate regulation (glucocorticoids)

Mineral balance (mineralocorticoide)

Reproductive function (gonadal steroids)

Steroid play a important role in inflammatory responses stress responses bone metabolism, cardiovascular fitness, behavior

2) THYMUS GLAND

A pink gland with two lobes located in the thoracic cavity posterior to the sternum.

It is large during the child hood and puberty but shrinks during adulthood.

FUNCTION

         Its primary function is to stimulate the production of T Cells which are an important part of the immune system.

Thymosin also assists in the development of B Cells to plasma cell to produce antibodies.

 Over production of thymosin- Lymphocytosis

3) PANCREAS

HORMONE     Insulin 

FUNCTION-

           Insulin is the only hormone that reduce blood glucose levels and it does this by activating the glucose transport mechanism and glucose utilizing metabolic pathway in different tissues of the body.

    GONADS

4) Testes

Hormone -androgen (testosterone)

Function

  1. Growth development and maintenance of male reproductive organs.
  2. Sexual differentiation and secondary sexual characteristics.
  3. Spermatogenesis
  4. Male pattern of aggressive behavior.
  5. pubertal transformation.
  6. Enlargement of testes ,penis and scrotum.
  7. Pubic and axillary hair.
  8. Bone growth
  9. RBC mass increase
  10. Skeletal muscle mass increase
  11. Larynx enlarges -deeping increase
  12. Development of beard.

5) Ovaries-

Hormone – Estrogens  and progesterone

Function

  1. Maturation growth and development of the reproductive organs
  2. Stimulation of normal physiological process of the tubular reproductive tract.
  3. Growth of the uterine tube
  4. Development of the endometrial lining of the uterus
  5. Increase the vascularity of the uterus
  6. Induction of the behavioral estrus
  7. Dilation of the cervix liquefaction of mucous plug.
  8. Under the influence of the estrogens the uterus is less susceptible to infection.

6) THYROID GLAND

Function of thyroid gland-

  1. Role in growth
  2. It has role in development
  3. It stimulate heart rate and contraction.
  4. Stimulate synthesis of proteins and carbohydrates
  5. It encreases vit. Requirements.

Function of thyroid hormone

  1. Maturation of bone
  2. Maturation of skeletal system
  3. Maturation of nerves in CNS
  4. Regulation of growth hormone
  5. Regulation of body temperature
  6. Generation of heat
  7. Metabolic function
  8. It  influence mood and behaviour

Disorders of thyroid gland – Hypothyroidism

PARATHYROID HORMONE

Hormone  Calcitonin

Function of PTH

             Bone  Parathyroid hormone stimulates the release of calcium from large calcium stores in the bone into the bloodstream.

This increases bone destruction and decreases the formation of new bone.

Kidney Pth reduces loss of calcium in urine.

Pth stimulate the production of active vitamin D in the kidney.

Intestine  pth indirectly increases calcium absorption from food in the intestine via its effects on vitamin D metabolism.

7) PITUITARY GLAND

Posterior pituitary

Hormone     ADH

Function        Stimulate water reabsorption by kidney.

Hormone   Oxytocine

Function   Stimulate uterine muscle contraction release of milk by mammary gland.

Anterior pituitary

Hormone   TSH

Function     Stimulate thyroid gland.

Hormone    ACTH

Function      Stimulate adrenal cortex.

Hormone    PRL

Function      Milk production

Hormone   GH

Function      Cell division , protein synthesis ,and bone growth.

Hormone   MSH

Function Unknown function in humans regulates skin color in lower vertebrates.

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Inflorescence

The reproductive organs of flowering plants are the flowers. Flowers are produced after a period of vegetative growth. The flowers may be borne singly or in clusters.

Flowers when borne singly are said to be solitary (eg) Hibiscus rosa sinensis (shoe flower), if in clusters they form an inflorescence. Inflorescence When several flowers arise in a cluster on a common axis, the structure is referred to as an inflorescence.

The common axis is the inflorescence axis which is also called as rachis or peduncle. Several single flowers are attached to the inflorescence axis. In case of plants possessing underground rhizomes, the rachis or peduncle arises directly from the rhizome. Such a rachis is referred to as scape. In the case of lotus, the scape gives rise to a solitary flower.

In plants like onion, the scape gives rise to an inflorescence. Based on the location, the inflorescence may be classified into 3 types.

(i) Terminal Inflorescence

(ii) Intercalary Inflorescence and

(iii) Axillary Inflorescence.

In plants like Callistemon the inflorescence is found in between the stem. This is called intercalary inflorescence. Generally, based on the arrangement, structure and organisation of flowers on the axis, inflorescences are classified into various types.

There are four major types. i) Racemose

ii) Cymose

iii) Mixed and

iv) Special types

PLASTIDS

Plastids are the largest cytoplasmic organelles bounded by double membrane. These are found in most of the plant cells and in some photosynthetic protists. These are absent in prokaryotes and in animal cells. Plastids are of three types namely chloroplasts, Chromoplasts and leucoplasts. Chromoplasts are coloured plastids other than green. They are found in coloured parts of plants such as petals of the flower, pericarp of the fruits etc.

Leucoplasts are the colourless plastids. These colourless plastids are involved in the storage of carbohydrates, fats and oils and proteins.

The plastids which store carbohydrates are called amyloplasts. The plastids storing fats and oils are called elaioplasts. The plastids storing protein are called proteinoplasts.

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RIBOSOMES

Ribosomes are small subspherical granular organelles, not enclosed by any membrane. They are composed of ribonucleoproteins and they are the site of protein synthesis. They occur in large number. Each ribosome is 150-250A in diameter and consists of two unequal sub units, a larger dome shaped and a smaller ovoid one. The smaller sub unit fits over the larger one like a cap. These two sub units occur separately in the cytoplasm and join to form ribosomes only at the time of protein synthesis.

At the time of protein synthesis many ribosomes line up and join an mRNA chain to synthesise many copies of a particular polypeptide.

Such a string of ribosomes is called polysome. Ribosomes occur in cytoplasmic matrix and in some cell organelles. Accordingly, they are called cytoplasmic ribosomes or organelle ribosomes.

The organelle ribosomes are found in plastids and mitochondria. The cytoplasmic ribosomes may remain free in the cytoplasmic matrix or attached to the surface of the endoplasmic reticulum.

The attached ribosomes generally transfer their proteins to cisternae of endoplasmic reticulum for transport to other parts both inside and outside the cell. Depending upon size or sedimentation coefficient(s), ribosomes are of two types. 70s and 80s. 70s type of ribosomes are found in all prokaryotic cells and 80s type are found in eukaryotic cells. S is Svedberg unit which is a measure of particle size with which the particle sediments in a centrifuge. In eukaryotic cells, synthesis of ribosomes occurs inside the nucleolus.

Ribosomal RNA are synthesized in the nucleolus. The ribosomal proteins are synthesized in the cytoplasm and shift to the nucleolus for the formation of ribosomal sub units by complexing with rRNA. The sub units pass out into the cytoplasm through the nuclear pores. In prokaryotic cells, both ribosomal RNAs and proteins are synthesized in the cytoplasm. Thus the ribosomes act as the protein factories of the cell.

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CELL THEORY

In the year (1839) Schleiden and Schwann have jointly proposed the “Cell Theory” It states that all living organisms are made up of cells and cells are the structural and functional units of all organisms.

Development of Cell Theory

If we study the step by step development of cell theory we will understand how scientific methodology operates. It includes the following steps

1. observation

2. Hypothesis

3. Formulation of theory

4. modification of theory ( if it warrants). Observations were made by Schleiden (1804 -1881) a German botanist.

He examined a large variety of plants and found that all of them were composed of cells. In 1838 he concluded that cells are the ultimate structural units of all plant tissues. Schwann a German Zoologist studied many types of animals and found that animal cells lack a cell wall and they are covered by a membrane. He also stated that animal cells and plant cells were basically identical but for the cell wall.

He observed that both contain nucleus and a clear substance around it. He defined the cell as a membrane bound nucleus containing structure. He proposed a hypothesis that the bodies of animals and plants are composed of cells and their products. Schleiden and Schwann both together discussed Schwann’s hypothesis and they formulated cell theory.

The important aspects of cell theory are:

1. All living organisms are made up of minute units, the cells which are the smallest entities that can be called living.

2. Each cell is made up of protoplasm with a nucleus and bounded by plasma membrane with or without a cell wall.

3. All cells are basically alike in their structure and metabolic activities.

4. Function of an organism is the sum total of activities and interaction of its constituent cells.

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SOIL WATER

Soil water is of paramount importance in the physiology of plants. It occurs in various forms, such as gravitational, capillary, hygroscopic and combined water. Rain is the principal source of water for the soil.

Water which flows down due to the force of gravity is known as gravitational water. The gravitational water is not available to the plants.

However, it is a big soil water reservoir and is trapped out through tube wells. A certain amount of rain water is retained within the intercellular spaces of the soil particles in the form of a capillary network.

It is called capillary water and is used by the plants. Some water molecules form a thin sheet of water around soil particles. It is called hygroscopic water (water of imbibition). The hygroscopic water is also not absorbed by the plants.

The water, which is bound up in chemicals is called combined water or crystalline water. (e.g. MgSo4.7H2O). It is not available to plants. The total water present in the soil is called as field capacity.

Addition of water beyond field capacity causes water logging. It excludes soil air and thus inhibits plant growth. The soils that have poor water holding capacity, cannot afford luxuriant vegetation. In such soils, the plants generally show wilting of their leaves.

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