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Phospolipid bilayer

This diagram shows a phospholipid bilayer. Two sets of phospholipids are arranged such that the hydrophobic tails are facing each other and the hydrophilic heads are facing the extracellular environment.
The phospholipid bilayer consists of two adjacent sheets of phospholipids, arranged tail to tail. The hydrophobic tails associate with one another, forming the interior of the membrane. The polar heads contact the fluid inside and outside of the cell.

Membrane proteins

The lipid bilayer forms the basis of the cell membrane, but it is peppered throughout with various proteins. Two different types of proteins that are commonly associated with the cell membrane are the integral proteins and peripheral protein ( [link] ). As its name suggests, an integral protein    is a protein that is embedded in the membrane. A channel protein    is an example of an integral protein that selectively allows particular materials, such as certain ions, to pass into or out of the cell.

Cell membrane

This image shows a lipid bilayer with different types of proteins, lipids and cholesterol embedded in it.
The cell membrane of the cell is a phospholipid bilayer containing many different molecular components, including proteins and cholesterol, some with carbohydrate groups attached.

Another important group of integral proteins are cell recognition proteins, which serve to mark a cell’s identity so that it can be recognized by other cells. A receptor    is a type of recognition protein that can selectively bind a specific molecule outside the cell, and this binding induces a chemical reaction within the cell. A ligand    is the specific molecule that binds to and activates a receptor. Some integral proteins serve dual roles as both a receptor and an ion channel. One example of a receptor-ligand interaction is the receptors on nerve cells that bind neurotransmitters, such as dopamine. When a dopamine molecule binds to a dopamine receptor protein, a channel within the transmembrane protein opens to allow certain ions to flow into the cell.

Some integral membrane proteins are glycoproteins. A glycoprotein    is a protein that has carbohydrate molecules attached, which extend into the extracellular matrix. The attached carbohydrate tags on glycoproteins aid in cell recognition. The carbohydrates that extend from membrane proteins and even from some membrane lipids collectively form the glycocalyx. The glycocalyx    is a fuzzy-appearing coating around the cell formed from glycoproteins and other carbohydrates attached to the cell membrane. The glycocalyx can have various roles. For example, it may have molecules that allow the cell to bind to another cell, it may contain receptors for hormones, or it might have enzymes to break down nutrients. The glycocalyces found in a person’s body are products of that person’s genetic makeup. They give each of the individual’s trillions of cells the “identity” of belonging in the person’s body. This identity is the primary way that a person’s immune defense cells “know” not to attack the person’s own body cells, but it also is the reason organs donated by another person might be rejected.

Peripheral proteins are typically found on the inner or outer surface of the lipid bilayer but can also be attached to the internal or external surface of an integral protein. These proteins typically perform a specific function for the cell. Some peripheral proteins on the surface of intestinal cells, for example, act as digestive enzymes to break down nutrients to sizes that can pass through the cells and into the bloodstream.

Questions & Answers

what are the characteristics of blood
yeboah Reply
they are red in colour
Tawoi
Me phone no petandi meku doubt vunte nenu phone chesi cheputhanu
Mohan Reply
What is respiratory disease
Rita Reply
What are the importance of homeostasis in human body?
Pablo Reply
homeostasis
Abena
it help to keep our salt and water balance
Husna
Homeostasis regulates and mentain internal equilibrium (ie temperature and pH) of the body.
Edmund
maintain temp and ph so our enzyme works properly
Husna
The inability of the body regulating and maintaining the temp. and pH results in disease affection.
Edmund
formation of the bone
Ali Reply
.
mohamed
عاوز ايه يعني من الفورمايشن
Doctor
notes on cell theory and discovery
Masika Reply
Cell theory are a set of rules for overall knowledge on cells. The most famous set of rules include: All cells arise from other cells. The cell is the functional unit of life. The structure (organelles) and morphology of the cell indicates it's main functions.
Carmelo
Antonie Van L. was the first to actually observe alive microorganisms (such as protist and bacteria) in a microscope in the 1600s.
Carmelo
electro phisiology meand
aparna Reply
rouleaux formation factors
Hridya Reply
can anyone suggest me how to learn forearm and hand topic of anatomy?
Anjali Reply
can anyone suggest me how to learn forearm and hand anatomy topic?
Anjali
can anyone suggest me how to learn forearm and hand topic of anatomy? pls pls tell
Anjali
check out youtube videos for trickss and while learning the boness part keep the bone wid u and learn ..... hope it helps u
Subuhi
ohk
Anjali
formation of the bone
Ali
what is the space between d dura mater and pia mater
Uwakwe Reply
Subdural space
Juveriya
Actually sub dural space is space between dura and arachnoid mater And sub arachnoid space is space between arachnoid and pia mater
Juveriya
the smallest bone in the body
Bahja Reply
stapes is the smallest bone in human Body
dipayan
Yeah
Ridwan
what is cell membrane
Hajara
cell membrane is like a protective cover of a cell and it's cytoplasm
dipayan
thanks
Hajara
list two adpitive mechanism that control homeostasis condition
Hajara
positive and negative feedback Mechanism
dipayan
@Dipayan, a cell membrane encloses and surrounds the cytoplasm of the cell. It's structure varies between species of life (eukaryotes, archaea, bacteria), but it is mostly composed of phospholipid, arachidonic acid, proteins, glycoproteins, glycolipids, and cholesterol.
Carmelo
and the glycoprotein and polysaccharides of the cell membrane forms the glycocalyx which has several functions especially in a bacteria.
Norom
can we stain sputum samples?
Apai Reply
Yes
Dorcas
wat do we use in staining them?
Apai
gram stain
Mawuli
Hello
bona
zeel Nelson stain
bona
why the ganglion cyst bumps?
dipayan Reply
i think fats gather under the skin
Matthew
but there were some tissue is present
dipayan
plz Matthew clearly present your answer
dipayan
appilied physiology of umn and lmn lesion
Ananthan Reply
what is umn and imn
dipayan
I don't know
bona
saaa
Patricia
Upper motor neurons (UMN) are responsible for conveying impulses for voluntary motor activity through descending motor pathways that make up the upper motor neurons. UMN send fibers to the LMN, and that exert direct or indirect supranuclear control over the LMN of the cranial and spinal nerves.
Amit
What is your doubt
Mohan
Anatomy of functions of the skeletal system
Tobokwa Reply

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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