4.Plasma membrane structure
The cell membrane (or plasma membrane) surrounds all living cells. It controls how
substances can move in and out of the cell. Membranes are composed of
phospholipids, proteins and carbohydrates arranged in a fluid mosaic structure, as
shown in this diagram.
The plasma membrane is formed by two layers of lipids - bilipid layer, or bilayer.
Each lipid molecule consists of a hydrophilic head and a hydrophobic tail, the lipids
are located outward, with tails inward. Proteins are embedded in this double layer of
lipids.
There are:
-peripheral proteins - located on the outer or inner surface of the membrane, can
convert signals from the external and internal environment,
-semi-integral proteins - immersed in bilayer at different depths, support the structure
of the membrane,
-transmembrane proteins - penetrate the membrane through, contacting with the
external and internal environment of the cell, catalyze metabolic reactions provide the
transport of cations and anions, form pores.
Outside, the membrane is covered with glycocalyx Glycocalyx (3-4 nm thick) is
represented by the outer, carbohydrate sections of complex proteins, glycoproteins
and glycolipids, which are part of the membrane. These carbohydrate chains play the
role of receptors, which ensure recognition of the neighboring cells and intercellular
substance by the cell and interaction with them. The glycocalyx contains receptors
for many hormones and neurotransmitters.
The presence of glycocalyx is characteristic of animal cells.
New terms
two layers of lipids
Phospholipids
Proteins
Carbohydrates
hydrophilic head
hydrophobic tail
Двойной слой липидов
фосфолипиды
Белки
Углеводы
Гидрофильная голова
Гидрофобный хвост
Practical work
2. Сollect hexagons in a logical mosaic
Нydrophobic
tail
Нydrophilic
head
Glycocalyx
lipids - bilipid
laye
(3-4 nm thick)
Function of
receptors
recognition of
neighboring cells
peripheral
proteins
Transmembrane
proteins
Can convert
signals from
the external
and internal
environment
Provide the
transport of
cations and
anions, form
pores
Test 1
1. Protects the internal contents of the cell from the effects of the environment
а) nucleus
b) cytoplasm
c) chloroplast
d) plasma membrane
2.Plasma membrane form
a) lipids and proteins
d) proteins and carbohydrates
c) nucleic acids and proteins
d) lipids and carbohydrates
3. What is the structure of the plasma membrane?
a) formed by a bimolecular lipid layer
b) closer to the cytoplasm - a bimolecular layer of lipids, outside - protein molecules
c) closer to the cytoplasm - a bimolecular layer of lipids, outside - carbohydrate
molecules
d) a bimolecular lipid layer, proteins penetrate its entire thickness and are located on
its outer and inner surface
4.Glycocalyx in the cell is formed
a) lipids and nucleotides
b) Fat and ATP
c) carbohydrates and proteins
d) nucleic acids
5.The head of a phospholipid is...
a) Made of carbohydrates
b) Made of proteins
c) Made of nucleic acids
d) Hhydrophilic
6.The tail of a phospholipid is...
a) Made of carbohydrates
b) Made of proteins
c) Made of nucleic acids
d) Hydrophobic