Category: BIOLOGY

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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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.

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.

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.

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.