Банк рефератов содержит более 364 тысяч рефератов, курсовых и дипломных работ, шпаргалок и докладов по различным дисциплинам: истории, психологии, экономике, менеджменту, философии, праву, экологии. А также изложения, сочинения по литературе, отчеты по практике, топики по английскому.
Полнотекстовый поиск
Всего работ:
364139
Теги названий
Разделы
Авиация и космонавтика (304)
Административное право (123)
Арбитражный процесс (23)
Архитектура (113)
Астрология (4)
Астрономия (4814)
Банковское дело (5227)
Безопасность жизнедеятельности (2616)
Биографии (3423)
Биология (4214)
Биология и химия (1518)
Биржевое дело (68)
Ботаника и сельское хоз-во (2836)
Бухгалтерский учет и аудит (8269)
Валютные отношения (50)
Ветеринария (50)
Военная кафедра (762)
ГДЗ (2)
География (5275)
Геодезия (30)
Геология (1222)
Геополитика (43)
Государство и право (20403)
Гражданское право и процесс (465)
Делопроизводство (19)
Деньги и кредит (108)
ЕГЭ (173)
Естествознание (96)
Журналистика (899)
ЗНО (54)
Зоология (34)
Издательское дело и полиграфия (476)
Инвестиции (106)
Иностранный язык (62791)
Информатика (3562)
Информатика, программирование (6444)
Исторические личности (2165)
История (21319)
История техники (766)
Кибернетика (64)
Коммуникации и связь (3145)
Компьютерные науки (60)
Косметология (17)
Краеведение и этнография (588)
Краткое содержание произведений (1000)
Криминалистика (106)
Криминология (48)
Криптология (3)
Кулинария (1167)
Культура и искусство (8485)
Культурология (537)
Литература : зарубежная (2044)
Литература и русский язык (11657)
Логика (532)
Логистика (21)
Маркетинг (7985)
Математика (3721)
Медицина, здоровье (10549)
Медицинские науки (88)
Международное публичное право (58)
Международное частное право (36)
Международные отношения (2257)
Менеджмент (12491)
Металлургия (91)
Москвоведение (797)
Музыка (1338)
Муниципальное право (24)
Налоги, налогообложение (214)
Наука и техника (1141)
Начертательная геометрия (3)
Оккультизм и уфология (8)
Остальные рефераты (21692)
Педагогика (7850)
Политология (3801)
Право (682)
Право, юриспруденция (2881)
Предпринимательство (475)
Прикладные науки (1)
Промышленность, производство (7100)
Психология (8692)
психология, педагогика (4121)
Радиоэлектроника (443)
Реклама (952)
Религия и мифология (2967)
Риторика (23)
Сексология (748)
Социология (4876)
Статистика (95)
Страхование (107)
Строительные науки (7)
Строительство (2004)
Схемотехника (15)
Таможенная система (663)
Теория государства и права (240)
Теория организации (39)
Теплотехника (25)
Технология (624)
Товароведение (16)
Транспорт (2652)
Трудовое право (136)
Туризм (90)
Уголовное право и процесс (406)
Управление (95)
Управленческие науки (24)
Физика (3462)
Физкультура и спорт (4482)
Философия (7216)
Финансовые науки (4592)
Финансы (5386)
Фотография (3)
Химия (2244)
Хозяйственное право (23)
Цифровые устройства (29)
Экологическое право (35)
Экология (4517)
Экономика (20644)
Экономико-математическое моделирование (666)
Экономическая география (119)
Экономическая теория (2573)
Этика (889)
Юриспруденция (288)
Языковедение (148)
Языкознание, филология (1140)

Реферат: Viruses Complex Molecules Or Simple Life Forms

Название: Viruses Complex Molecules Or Simple Life Forms
Раздел: Топики по английскому языку
Тип: реферат Добавлен 00:53:48 12 ноября 2010 Похожие работы
Просмотров: 2 Комментариев: 12 Оценило: 2 человек Средний балл: 5 Оценка: неизвестно     Скачать

Viruses: Complex Molecules Or Simple Life Forms? Essay, Research Paper

Viruses: Complex Molecules or Simple Life Forms?

Viruses have been defined as “entities whose genomes are elements of

nucleic acid that replicate inside living cells using the cellular synthetic

machinery, and cause the synthesis of specialised elements that can transfer the

genome to other cells.” They are stationaryand are unable to grow. Because of

all these factors, it is debatable whether viruses are the most complex of

molecules or the simplest life forms. While the definition of living organisms

must be adapted, the majority of evidence leads to the classification of viruses

as living organisms.

Viruses are composed of a nucleic acid core, a protein capsid, and

occasionally a membraneous envelope. The nucleic acid core is composed of

either DNA or in the case of retroviruses, RNA, but never both. In retroviruses,

the RNA gets transcribed to DNA bye the enzyme reverse transcriptase. The

protein capsid is a protein layer that wraps around the virus. There are four

basic shapes of viruses. The tobacco mosiac, adenovirus, influenza virus, and

t-even bacteriophage are each examples of a different virus structure. Each

individual protein subunit composing the capsid is a capsomere.

The tobacco mosiac virus has a helical capsoid and is rod shaped. The

adenovirus is polyhedral and has a protein spike at each vertex. The influenza

virus is made of a flexible, helecal capsid. It has an outer membranous

enevelope that is covered with glycoprotein spikes. The T-even bacteriophage

consists of a polyhedral head and a tail. The tail is used to inject DNA into a

bacterium while the head stores the DNA.

Basic life is defined as the simplest form capable of displaying the

most essential attributes of a living thing. This makes the only real criterion

for life the ability to replicate. Only systems containing nucleic acids are

capable of this phenomenon. With this reasoning, a better definition is the

unit element of a continuous lineage with an individual evolutionary history.

Because of viruses inability to survive when not in a host, they must have

evolved from other forms of life. The origin of viruses is an easy thing to

theorize about so many hypothesese have been made.

One such hypothesis is that viruses were once complete living parasites.

Over time they have lost all other cellular components. This is backed up by

the idea that all cells degenerate over time.

Some people think along very similar lines that viruses are

representatives of an early “nearly living” stage of life. This goes along with

the first hypothesis in that it accounts for a loss of components. All

creatures that become parasitic can be seen losing their obsolete functions and

structures. An example of this is the flea. Fleas are eveolved from flies but

have discarded their unneeded wings.

This theory when applied suggests that atleast some branches of

viruses have evolved from bacteria because of their similar natures.

Scientists say that at one point viruses could have been independant

organisms. As they slowly became parasitic, the unsed structures for protein

and energy synthesis were lost, along with the inhibiting cell wall. While

viruses do need a host cell to complete many important functions of living

organisms, the should still be considered living themselves.

The ability to replicate is important to the classification of an

item as living. Within the host, viruses are able to replicate, evolve, and

even mutate. They are deeply intertwined in the life process by this

dependancy on a host.

Viruses are very specific to what they can use as a host. Despite

the specificness, many viruses can host withmembers of different species,

genus, and even phylums. A lock and key fit determines the host, or host

range. This works vert similar to that of an enzymes active site.

Once the virus has found a host cell, the virus uses the host’s

nucleotides and enzymes to replicate it’s DNA. Other materials and machinery

of the host cell produce the virus’s capsid proteins. The viral DNA and

proteins then join to make a new copy of the virus.

While viruses are inactive when in transport between hosts, the

arguements are overwhelmingly in favor of considering viruses living organisms.

Through their parasitic nature, they are able to fulfill most qualities of

living organisms. Their behavior and complexness also lead to this

classification. While they are not the text book example of living organisms,

is has been in agreement that there always will be exceptions to the rules.

Viruses deserve to take their rightful place among the ranks of living organisms.

.

Оценить/Добавить комментарий
Имя
Оценка
Комментарии:
Привет студентам) если возникают трудности с любой работой (от реферата и контрольных до диплома), можете обратиться на FAST-REFERAT.RU , я там обычно заказываю, все качественно и в срок) в любом случае попробуйте, за спрос денег не берут)
Olya03:20:41 27 августа 2019
.
.03:20:40 27 августа 2019
.
.03:20:39 27 августа 2019
.
.03:20:38 27 августа 2019
.
.03:20:38 27 августа 2019

Смотреть все комментарии (12)
Работы, похожие на Реферат: Viruses Complex Molecules Or Simple Life Forms

Назад
Меню
Главная
Рефераты
Благодарности
Опрос
Станете ли вы заказывать работу за деньги, если не найдете ее в Интернете?

Да, в любом случае.
Да, но только в случае крайней необходимости.
Возможно, в зависимости от цены.
Нет, напишу его сам.
Нет, забью.



Результаты(258516)
Комментарии (3480)
Copyright © 2005-2020 BestReferat.ru support@bestreferat.ru реклама на сайте

Рейтинг@Mail.ru