BIOLOGY ASSIGMENT SEM 1 NABIHA (1)

MOLECULES OF LIFE & CELL STRUCTURES
AND FUNCTIONS FLIP BOOK

NAME : SITI NUR NABIHA BT ABDUL JABAR
MATRIC NO : MS2213201587
PRACTICUM : H6T01A

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Set C Questions

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I ) STAIT THE MAIN TYPES OF
MOLECULES

WATER CARBOHYDRATES

LIPIDS PROTEINS

DNA AND RNA MOLECULS 3

ii)Classify lipids into three main
types based on their structure
and characteristic

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Three main type of lipids is triglycerides , phospholipid and steroids.

Firsty , triglycerides is also known as triacylglycerol . Triglycerides structure is consisting a glycerol bound to three
fatty acid molecules . Triglycerides are esters in which three molecules of one or more different fatty acids are
linked to the alcohol glycerol; they are named after the fatty acid components; for example, tristearin contains
three molecules of stearic acid, while oleo distearin contains one molecule of oleic acid and two molecules of

stearic acid . Triglycerides character is the most common lipids found in the body . Other than that , altought

similar in structure to the phospholipids that build cell membranes , triglycedrides are completely hydrophobic ,
meaning they cannot mix with water , so they cannot integrate into membranes . In fat , tryglycerides is solid at
room temperature while in oil triglycerides is liquid at room temperatu

Second , Phospholipid . Phospholipid are mostly made from glycerides by substituting one of the three fatty
acids by a phosphate group with some other molecule attached to its end .The structure of a phospholipid
molecule contains two hydrophobic tails of fatty acids and one hydrophilic head of phosphate moiety, jointed

together by an alcohol or glycerol molecule The head for phospholipids has an electric charge, and is
attracted to water (hydrophilic). The other end which is the tail , consists of the fatty acids, is
neutral and it is hydrophobic and water-insoluble but is fat-soluble. One of the phospholipids
characteristic are the major components of cell membranes . Molecules that can pass through
phospholipids are water , urea , gases such as oxygen , carbon dioxides and lipids soluble substance
. Molecules that cannot pass through phospholipids are ions ( Na + , K+ , Ca 2+ ) , polar and large 5
moleculs such as glucose .

Lastly is steroids . Steroids serve as chemical messengers and have other roles . All steroids are
related to a characteristic molecular structure composed of 17 carbon atoms—arranged in four rings

conventionally denoted by the letters A, B, C, and D—bonded 28 hydrogen atoms. Steroids vary by

the functional groups attached to this four-ring core and by the oxidation state of the rings. Steroids
can also be more radically modified, such as by changes to the ring structure, for example, cutting one
of the rings. Cutting Ring B produces secosteroids one of which is vitamin D3. Steroid characteristic
is steroid are found in animal , fungi , plant and else where are many steroids are necessary
to life at al levels . They include cholesterol , sex hormone , extradiol and testosterone , bile
acids , and drugs such as anti – inflammatory agent dexamethasone . Steroids also helps to
control metabolism , inflammation , immune function , salt and water balance , and
development of sexual characteristic

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iii) Plasma membrane of
cells consists lipids and

some other organic
molecules . With the aid of
labelled diargram , briefly

describe the structure of
plasma membrane

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COMPONENT FUNCTION
1. Glycolipids
Glycolipids are lipids with a
carbohydrate attached by a 8
glycosidic (covalent) bond. Their
role is to maintain the stability of
the cell membrane and to
facilitate cellular recognition,
which is crucial to the immune
response and in the connections
that allow cells to connect to one
another to form tissues.

2. Glycoprotein a type of protein molecule that has had
3. Cholestrol a carbohydrate attached to it. They enable cells to
4.Channel protein recognize another cell as familiar or foreign,
which is called cell-cell recognition. They also
help cells attach to and bind other cells, which
is called cell adhesion.

Cholesterol plays has a role in membrane fluidity
but it's most important function is in reducing the
permeability of the cell membrane. Cholesterol
helps to restrict the passage of molecules by
increasing the packing of phospholipids.

Channel protein is to transport the ions and
water molecules quickly through the
membrane. Channel proteins are transmembrane
proteins, which are involved in the movement of
substance both entry and exit in the cell.

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5. Carbohydrates the third major component of plasma membranes. In
general, they are found on the outside surface of
7. a-helix protein cells and are bound either to proteins
8. Integral protein (forming glycoproteins) or to lipids
(forming glycolipids). These carbohydrate chains
may consist of 2-60 monosaccharide units and can
be either straight or branched

α-helical membrane proteins are responsible for
interactions between most cells and their
environment.

Integral membrane proteins are, as their name
suggests, integrated into the membrane: they have
at least one hydrophobic region that anchors them to
the hydrophobic core of the phospholipid bilayer.
Some stick only partway into the membrane, while
others stretch from one side of the membrane to the
other and are exposed on either side.

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9. Phospholipids Phospholipids, arranged in a bilayer, make up
the basic fabric of the plasma membrane.
They are well-suited for this role because they
are amphipathic, meaning that they have
both hydrophilic and hydrophobic regions.
The hydrophilic, or “water-loving,” portion of
a phospholipid is its head, which contains a
negatively charged phosphate group.
The hydrophobic, or “water-fearing,” part of
a phospholipid consists of its long, nonpolar
fatty acid tails

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iv) Explain how certain type
of lipid ensures the fluidity of

the
plasma membrane while
some other type if lipids may

reduce its fluidity

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Certain type of lipids ensures the fluidity of then plasma membrane also by the degree of
saturation of fatty acids tails . Unsaturated tails have double bonds and, as a result, have
crooked, kinked tails. Unsaturated fatty acids, on the other hand, have more distance between the
tails and thus fewer intermolecular interactions and more membrane fluidity.

Besides that , the temperature also ensures fluidity of the membrane plasma. At high
temperatures the opposite process occurs, phospholipids have enough kinetic energy to
overcome the intermolecular forces holding the membrane together, which increases membrane
fluidity.

Certain type of lipid reduce fluidity of the plasma membrane by The degree of saturation
of fatty acids tails . Phospholipid tails can be saturated. The terms saturated or no double bonds
are present between the carbons in the fatty acid tails. Saturated tails have no double bonds and
as a result have straight, unkinked tails. As we know `, saturated fatty acids tails are arranged in a
way that maximizes interactions between the tails. These interactions decrease bilayer fluidity.

Other than that temperature also reduce fluidity of the plasma membrane . As temperature
increases, so does phospholipid bilayer fluidity. At lower temperatures, phospholipids in the
bilayer do not have as much kinetic energy and they cluster together more closely, increasing
intermolecular interactions and decreasing membrane fluidity.

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REFERENCE :

01 02 03

https://www.healthline https://www.khanacad https://byjus.com/neet
.com/health/is- emy.org/science/ap- -questions/what-is-the-
cholesterol-a-steroid biology/cell-stru purpose

04 05 06

https://www.ncbi.nlm. http://www.msrblog.c https://study.com/aca
nih.gov/books/NBK268 om/science/biology/fu demy/lesson/glycolipid
71/ s-definiti

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“BIOLOGY IS THE SCIENCE .
EVOLUTION IS THE CONCEPT

THST MAKES BIOLOGY
UNIQUE”

—SOMEONE FAMOUS

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THANK YOU

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