4 Flashcards
Why is the plasma membrane a phospholipid bilayer
phosphlipid bilayer is composed of hydrophilic head which faces outwards to form the bilayer BECAUSE they attract water and hydrophiobic tails which face inwards away from the intra nad extracelluar fluid because they repel water
Why are so many cells needed
to exchange more materials and for better survival of the cell
Fluid mosaic model
A model that describes the structure of cell membranes
what is constantly moving in the fluid mosaic model
phospholipids, sterols and proteins
Difference between hydrophilic head and hydrophobic tail
hydrophilic head-attracted to water
hydrophobic tail-repels water
what is the cell memrbane structured as
phospholipid bilayer
what is the head and tail of the fluid mosaic model composed of
head is made of hydrophilic phosphate
the tail is made of hydrophobic fatty acid
what can fatty acids be in phospholipids
be saturated (form straight chains) or unsaturated (kinked chains)
Why is it called the fluid mosaic model
phospholipids are constantly moving around like a liquid, hence the term fluid
The phospholipids, proteins, and cholesterol and the other substances that make the lipid bilayer create a mosaic like pattern hence, the term mosiacc
Therefore, it is known as the term fluid mosiac model
some proteins are bound onto the membrane surface whilst others are…
embedded in the phospholipid bilayer
Receptor protein
protein molecule that has receptor sites at the end of carb chains that bind with ligands to trigger a series of chemical reactions
ligands
specific signal molecules eg. lips, ions and carbohydrates
Transport proteins
Allows speficifc substances to move across a membrane eg. channel and carrier proteins
Extracellular fluid
liquid that supplies nutrients and removes waste found on the outside of cell memrbaen
factors that effect the permeability of the membrane
heat
PH
ethanol
how does heat, PH and ethanol effect the permeability of cell membrane
high temperatures and change in PH levels cause proteins to denature, hecneincreasing permeability
the permeability of the cell membrane also increases when ethanol dissolves lipid components of the membrane which creates holes in the membrane
what do kinked chains do
prevent the phospholipids from being stacked together hence, increasing and maintaining fluidity even in cold climates
what organelles are composed of a phosplipid bilayer
cell membrane and vesicle
why does the cell membrane get larger when a vesicle is added
both organelles are made up of a phopslipid bilayer which means when these 2 organelles fuse, the cell membrane becomes larger
what is the process of translation
mRNA is read by ribosomes to create a polypeptide chain of amino acids (protein)
what do receptor sites do
receive signals
Messenger rna
a copy of DNA that carries out instructions to ribosomes for translations
Transfer rna
carries a specific amino acid to the ribosome for translation
surface protein
proteins that are attached to the surface of the membrane that play a role in cell communication
Transmembrane proteins
proteins that are embedded in the phospholipid bilayer that only allow specific substances across the membrane
Integral proteins
protein that is permanently attached to the cell membrane membrane
Peripheral proteins
temparoolty attached to the cell membrane
4 main types of proteins in cell membrane
Surface proteins –
Transmembrane proteins
Integral proteins
Peripheral proteins
Types of transmembrane proteins
Receptor protein
Transport proteins
each receptor-ligand pair bind with a lock-and-key fit- to do what?
to allow receptor proteins to become either activated or inactivated leading to an intercellular response
WHAT IS THE LOCK AND KEY MODEL?
the lock and key model explains that the ligand (signalling molecule) is shaped complementarily to the receptor protein so that they can fit in each other.
The ligand acts as a key whilst the receptor acts a lock and this binding causes a celluar response
what does the lock and key model result in
causes the receptor protein to either become activated or deactivated creating a response inside the cell.
channel protein
type of transport protein that causes ions and water to flow through cell membrane
examples of polar substances and whether they are hydrophilic or hydrophobic
water and ions
hydrophilic
what do non non polar substances attract and whether they are hydropholic or hydrophobic
eg, fats
hydrophobic
what diffuses through the cell membrane easily and why
Small non-polar substances because non polar substances attract fat and the cell membrane is made of fat, Also, Small hydrophobic substances because they repel water and attract fat as well.
what else besides polar substances are unable to cross through the cell membrane
Really large substances eg. glucose
in what form is the genetic material found
chromatin
areboic respiration
the exchange of oxygen and carbon dioxide
carrier proteins
A
type of transport protein that allows water and ions to flow through the membrane. However, unlike a channel protein when a substance enters one side of the carrier protein closes and another opens continuously.
what is the cell membrane made of
lipids such as phospholipids and proteins
What is the plasma membrane
a secelectvitley permable membrane that controls the movement of substances, in and out of the cell.
Transcription
Dna is replicated into an mRNA
difference between transcription and translation
transcription occurs first- a copy of DNA is made(mRNA)
Translation:
occurs after transcription
mRNA is read by ribosomes to create proteins
what factors increase perambilty
steeper concentration graident
higher temperatures
PH
