Functions of Life | Cell Biology


In this video we are going over some of the
basic functions essential for life. Based on cell theory all living things have
a cellular structure, they are made up of one or more cells. All forms of life from unicellular bacteria
to the large blue whale all share the same functional characteristics of life. These characteristics can be remembered by
the Mnemonic MR H GREN. This stands for: Metabolism, Response, Homeostasis,
Growth, Reproduction, Excretion and Nutrition. One of the essential functional characteristic
of life is metabolism. All cells carry out many chemical reactions
that are essential for life, metabolism is the web of all these chemical reactions occurring
within cells and organisms. These include chemical reactions that are
catabolic, those that break down compounds, such as the breaking down of glucose into
energy in cellular respiration. These chemical reactions can also be anabolic,
those that are building up and are involved in the synthesis of compounds, such as the
production of proteins and lipids. Viruses lack metabolism, this is one of the
reasons they are not considered living, as metabolism is considered a characteristic
of life. Another essential functional characteristic
of life is response to stimuli, sometimes referred to as sensitivity. All living things, whether unicellular bacteria
or multicellular complex organisms, are able to respond to internal and external stimuli. There is a range of stimuli organisms can
respond to such as light, chemical, pressure and temperature. In small invertebrates like slaters, the stimulus
could invoke a movement that leads them out of the light. In plants it can invoke growth towards the
light. In unicellular organisms such as cyanobacteria
it can cause movement towards better light conditions. These are all examples of a response to the
stimulus: light. Homeostasis is another essential functional
characteristics of life. Living things are able to maintain and regulate
their internal environments within a certain range, such as water levels, pH levels or
internal temperature despite changes in their external environment. Another essential functional characteristic
of life is Growth. All living things are able to grow and develop. Growth means that they are able to increase
in size over time. Develop means they are able to transform over
time, this allows the young of a species to develop to have the same features as the adult
form. Reproduction is another essential functional
characteristic of life. All living things produce offspring, this
may be through asexual or sexual reproduction. Asexual reproduction through binary fission
or mitosis involves just one parent creating offspring that are genetically identical to
the parent. Sexual reproduction involves the fusion of
sex cells from two parents creating offspring that are genetically unique. Excretion is another essential functional
characteristic of life. Living organisms excrete waste products. In unicellular organisms this occurs through
the cell membrane, in plants it can be through the leaves and roots. Nutrition is another essential functional
characteristic of life. Living organisms require a source of energy
to fuel the metabolic activities also required for life. This can be through absorption of organic
matter, or by synthesising organic molecules which is what occurs in photosynthesis. Unicellular organisms are organisms that consist
in their entirety of a single cell, where with this single cell are able to live an
independent life carrying out all the functions of life. Paramecium is an example of a heterotrophic
unicellular organism, that carries out all the functions required for life. Paramecium contain enzymes within their cytoplasms
that enable them to digest food particles. They are heterotrophic and eat smaller uncellular
organisms by engulfing them through the oral groove. Solids are then excreted through an anal pore,
liquids through contractile vacuoles. Paramecium are covered in small hairs called
cilia, these cilia allow them to move around in response to changes in the environment,
this is an example of their responsiveness. Homeostasis in Paramecium is maintained by
the movement of materials through the cell membrane, such as the diffusion in and out
of gases like O2 and CO2, or to maintain water levels, excess fluid is removed via the cell
membrane through vacuoles. Paramecium grow until they reach a size that
affects their surface area to volume ratio where they divide via asexual reproduction
into two smaller unicellular paramecium (reproduction). Two individuals can also fuse before splitting,
in a form of sexual reproduction. Chlamydomonas is an example of a unicellular
autotroph, in other worlds a single-celled photosynthetic organism, that is able to carry
out all the functions of life. Chlamydomonas have chlorophyll pigments within
the chloroplast that produce organic molecules (sugars) through the chemical reactions involved
in photosynthesis. This is also how they get their nutrition,
as they are making their own food through the process of photosynthesis. Diffusion allows the excretion of waste products
such as oxygen from photosynthesis through the cell membrane out into the environment
around them. They have a pigment eye spot that can detect
bright light, and they have flagella that enable them to move towards the light. They have contractile vacuoles that are able
to move water out through the cell membrane to maintain stable water levels within the
cell. They grow by absorbing minerals from the environment
around them and through photosynthesis. They continue to grow until they reach a size
that affects their surface area to volume ratio where they divide via asexual reproduction
into two smaller unicellular Chlamydomonas. The nuclei can also fuse and then divide in
a form of sexual reproduction. Thank you for watching, if you found this
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