Download Secondary active transport

summary
osmosis : movement of water from lower solute concentration ( higher
water concentration )to higher solute concentration (lower water
concentraion )
 why hypotonic cause hemolysis of RBCs (red blood cells ) ?
hypotonic: it means lower concentration of solute around the cell, which
mean the amount of higher ---> so water transport to the cell and the cell
swell . this is not the only way cause hemolysis .
hypertonic : concentration of solute inside the cell is lower than cytosol
(outside ) (it mean higher concentration of water ) ---> so the water go
outside and the cell shrink . such shrinking of cells that called crenation
Active transport
_ transport that need energy to transport molecule against its
concentration gradient , energy obtained come from hydrolysis of
adenosine tri phosphate (ATP) ---> that we called primary active transport
Active transport divided into : 1- primary active transport(using energy
directly) 2- secondary active trasport (using of energy indirectly )
 primary active transport :
use hydrolysis of ATPase a source of energy , this will cause change
the shape of certain carrier protein (most common integral protein)
(pumps , because it will pump certain ion into and out of the cell )--->
pumps called sodium -potassium ATPase , why we called sodium potassium ? because it is selective to Na and K ,,, why we called
ATPase ? parts of protein (enzyme ) that hydrolyze ATP . this
hydrolysis of ATP will cause conformational changes for this protein ,
and it will expel Na ---> expel 3 ions of sodium out of the cell , and
allow to entry 2 ions of potassium inside the cell . net ion equal 1 out
of the cell . So inside the cell the charge will be negative .
ATP that we use to phosphorylate the pump ,how? ( ‫يعني الفكرة انو‬
‫االرتباط بسبب‬hydrolysis for ATP and phosphorylate for the pump
this expel sodium out of the cell and it will allowed to entry of 2ions
of potassium ,,,this what we called sodium potassium ATPase .
- Note that the hydrolysis happened from binding of integral protein since
we name it ATPase (pumps)
- Difference between channels and pumps ?
- Channel may be gated or not , It allow the entry of material ( down it
concentration gradient ) ( passive transport)
- Pumps : push something against it concentration gradient(active
transport)
- what makes membrane potential ?
1- negative ions inside the cell
2- Sodium -potassium pump
 Secondary active transport :
: ‫ وصار في‬ ‫ انه تم وضع ايونات الصوديم خارج الخيه وتركزت بالخارج طيب‬: ‫فكرتها‬
Concentration and Electrical gradient  this energy converted to another
state ( energy of motion )  stored energy converted to kinetic energy and
use to transport other substances  So this energy we use as source of
potential energy is concentrated in Na  So Sodium ions have this
potential energy  and this will be use as we  mentioned
movement of another ions against its concentration gradient .
ATP ‫ الصوديم تخزنت بداخله طاقة جايه من‬: ‫ يعني‬-
" :P ‫ اذا ً هذه الطاقه ال تنفذ (( مثل ما بتعرفو بقانون حفظ الطاقة ))" اللي جننونا فيه ايام المدرسه‬indirect ‫ وهي بيحكو عنها‬Secondary ‫ رح استعملها بشكل غير مباشر عشان هيك اسمها‬down it's concentration gradient ‫ طبعا ُ انتقال الصوديم يكون‬)against) ‫ وانتقال االيونات‬‫ رح يضطر يستخدم هاي الطاقة‬against ‫ألنه اذا الصوديوم رح ينتقل‬-
 So it will leak back in the cell and take with it ions ( against it's
concentration )(I mean against ions concentration gradient )
- Na concentrated outside the cell it’s go down its concentration gradient
(passive) , So it doesn't need energy .
I can use energy to do Job  It can transport another ions against its
concentration gradient , this ions can be Calcium ions ; for Example
( Calcium out more ) its enter the cell against its concentration gradient,
how can this happened ?
by using potential energy stored in Na ions  this is secondary  use
energy indirectly .
‫ يعني انت بتأثر بطاقة على البكرة (انو بتسحبها) من‬,,, ‫فكرة الموضوع مثال ممكن نشبهها بالبكرة‬
( ,,, ‫ جهة و ازا كان مثال في صندوق عالجهة التانية بيرتفع‬Antiporters(
‫ بس يا جماعة ما حدا يفهم انو ال‬primary , ,, ‫وال‬secondary ‫يصيرو كل واحد لحال‬
‫ال همي التنين بيحدثو بنفس الوقت‬
- secondary active transport can be
 Antiporters :moving two substances in opposite direction across
the membrane .
 Symporters :of these transport move two substances in the same
direction .
- The concentration of Ca+2 is low in the cytosol because Na+ / Ca+2
Antipater's eject calcium ions .
- Na+/ H+ Antiporters help to regulate the cytosol's PH by expelling excess
H+ .
- By contrast , dietary glucose and amino acids are absorbed into cells that
line the small intestine by Na+/glucose and Na+/amino acid Symporters .

Transport in vesicles :
- Way to transport inside the cell , needs ATP , from one organelle to
another , or one structure to another or from inside to outside or from
Extracellular fluid to inside the cell.
- which mean by = Endocytosis  into the cell .
= Exoctosis  outside the cell .
 Endocytosis : material move into the cell ‫بنجمعهم وبدخلهم كلهم مع بعض‬
- There are three type of endocytosis
1- Receptor mediated endocytosis
2- Phagocytosis
3- Bulk -phase endocytosis
- Receptor mediated endocytosis :
highly selective , cells take up , specific ligands  bind to specific
Receptor.
* Receptor protein in the plasma membrane recognise and binds to
particular in ECF (Extracellular fluid ), for instance cells take up
cholesterol containing low density of lipoproteins LDLs , tranferin
(an-iron trans porting proteins (in the blood ) ,some vitamins ,
antibodies ,and certain hormones.
- Lipoprotein (Lipid + protein)  LDL
-LDL : molecules that has low density lipoprotein we called transporter .
-main function  carry cholesterol  so I have this molecules with all
cholesterol it has transporter in the plasma  then to cell .
How cell take this cholesterol  By endocytosis
Receptor-mediated endocytosis of LDLs (and other ligands) occurs as
follows (Figure 3.12):
1- Binding. On the extracellular side of the plasma membrane, an LDL
particle that contains cholesterol binds to a specific receptor in the plasma
membrane to form a receptor–LDL complex. The receptors are integral
membrane proteins that are concentrated in regions of the plasma
membrane called clathrin-coated pits. Here, a protein called clathrin
attaches to the membrane on its cytoplasmic side. Many clathrin molecules
come together, forming a basketlike structure around the receptor–LDL
complexes that causes the membrane to invaginate (fold inward).
2-Vesicle formation. The invaginated edges of the membrane around the
clathrin-coated pit fuse, and a small piece of the membrane pinches off.
The resulting vesicle, known as a clathrin-coated vesicle, contains the
receptor–LDL complexes.
3- Uncoating. Almost immediately after it is formed, the clathrin-coated
vesicle loses its clathrin coat to become an uncoated vesicle. Clathrin
molecules either return to the inner surface of the plasma membrane or
help form coats on other vesicles inside the cell.
4-Fusion with endosome. The uncoated vesicle quickly fuses with a vesicle
known as an endosome. Within an endosome, the LDL particles separate
from their receptors.
5-Recycling of receptors to plasma membrane. Most of the receptors
accumulate in elongated protrusions of the endosome. These pinch off,
forming transport vesicles that return the receptors to the plasma
membrane. An LDL receptor is returned to the plasma membrane about 10
minutes after it enters a cell.
6-Degradation in lysosomes. Other transport vesicles, which contain the
LDL particles, bud off the endosome and soon fuse with a lysosome.
Lysosomes contain many digestive enzymes. Certain enzymes break down
the large protein and lipid molecules of the LDL particle into amino acids,
fatty acids, and cholesterol. These smaller molecules then leave the
lysosome. The cell uses cholesterol for rebuilding its membranes and for
synthesis of steroids, such as estrogen. Fatty acids and amino acids can be
used for ATP production or to build other molecules needed by the cell.
‫ بمستقبالت خاصه به على‬Cholesterol ‫ المحمل بال‬LDL ‫ يعني أي شي برتبط‬Receptor LDL Complex ‫ يكون‬ Plasma membrane
‫ هاي المنطقة بتكون‬ membrane ‫هأل هاي المستقبلة بتكون مركزة على منطقة معينة من‬
Pits ‫ ويوجد بروتين مركز بهاي المنطقة ورح يشكلو اشي مثل‬membrane ‫الجزء الداخلي من‬
Clathrin-coated pits ‫ اسمه‬plasma membrane ‫في ال‬
Receptor LDL ‫ فبتكون اشي مثل السلة حول‬ ‫ هاي البروتينات بتجمع على بعضها‬
invaginated ‫ وو بسبب للغشاء‬ Complex
‫ وهال‬Clathrin ‫ بتكون مخاطة من الخارج ب‬vesicles ‫ هاي ال‬vesicles  ‫بعدين بكون‬
un coated  other vesicles ‫ عشان تعمل‬ ‫ رح تروح كمان كمان مرة‬Clathrin
‫ مع‬fusion ‫ بصير لها‬vesicles ‫ هاي ال‬uncoated vesicles ‫هيك بصير عنا‬
Receptor ‫ هأل ال‬Receptor ‫بتنفصل عن‬LDL particles ‫ بعدين‬endosome(vesicles )
) ‫ (نتوءات‬protrusions ‫ بتجمع وبتعمل‬Receptor ‫ معظم هاي‬plasma membrane ‫لل‬
‫ ورح تروح‬vesicles ‫ وبتشكل كمان‬endosome ‫ فهاي النتوءات بتفصل‬endosome ‫في‬
. min 01 ُ ‫ ويحكيلك انو هاد االشي كثير سريع تقريبا‬ membrane ‫على‬
‫) عن‬bud off ( ‫ بتشكل زي برعم خارجي‬LDL ‫ اللي تحتوي على‬transport vesicle ‫هال ال‬
‫بكون‬Degredation ‫بعدين بصير‬lysosome  ‫ وبعدين ترتبط مع‬endosome ‫ال‬
lysosome ‫ وبعدها بتغادرال‬amino acids , fatty acids , cholesterol

phagocytosis : cell engulfs large solid particle
 only a few body cells termed phagocytosis ..especially digestive cells
 two main type of phagocytosis cell
1- macrophage 2- neutrophils
- phagocytosis begin when particles bind to plasma membrane Receptor on
the phagocyte causing it to extend Pseudo pods .
* Pseudo pods surround the particle outside the cell and membrane fuse
to form vesicle called a phagosome
 Which enter the cytoplasm
* How phagocytosis occurs?
- The phagosome fuse with one or more lysosomes , and lysosomal
enzymes break down ingestion and remain in vesicle called a residual Body
.
- The process of phagocytosis is a vital defense mechanism that helps
protect the body from disease .
- Through phagocytosis macrophages dispose of invading microbes and
billions of aged , warn out red blood cells every day , neutrophils also help
rid the body from invading microbes pus is a mixture of dead neutrophils an
infected wound
- Bulk- phase endocytosis , also called pinocytosis
ECF contain a lot of bulk
 tiny droplet of ECF will taken up , Note that No receptor involved it's not
selective , all solutes dissolved in the ECF are brought into cell .
- During bulk -phase endocytosis the plasma membrane folds inward and
form a vesicle detaches or " pinches off " from the plasma membrane and
enters the cytosol , which in the cell the vesicle fuses with a lysosomes
where enzymedegrade the engulfed solutes  The resulting smaller
molecules , such as amino acids and fatty acids , leave the lysosome to be
used elsewhere in the cell .
Bulk-phase endocytosis occurs in most cells , especially absorptive cell in
the intestine and kidneys .
Exocytosis
- Exocytosis it release material from a cell .
-All cells carry out exyctosis especially 1- secretary cells , 2-nerve cell
 release substance that called neurotransmitters (we will studied later )
- secretary cells : liberate digestive enzymes hormones , mucus ,or other
secretion .
wastes are also released by Exocytosis
- There must be balance between Exocytosis and endocytosis why ?
to keep the surface area of cell's plasma membrane relatively constant
segments of plasma membrane .
Lost through endocytosis and recycled by exocytosis
- Membrane exchange is quit extensive in certain cells that . In pencrease
for Example the cells that secrete digestive enzymes can recycle an amount
of plasma membrane equal to the cell's entire surface area in 90 minute (
Balance)
Trascytosis
TRANSCYTOSIS Transport in vesicles may also be used to
successively
move a substance into, across, and out of a cell. In this
active process, called transcytosis, vesicles undergo endocytosis
on one side of a cell, move across the cell, and then undergo
exocytosis
on the opposite side. As the vesicles fuse with the
plasma membrane, the vesicular contents are released into the
extracellular fluid. Transcytosis occurs most often across the
endothelial
cells that line blood vessels and is a means for materials
to move between blood plasma and interstitial fluid. For instance,
when a woman is pregnant, some of her antibodies cross
the placenta into the fetal circulation via transcytosis
 ‫و االختالف بهاي‬,,, ‫كل االغشية بتتشابه بكب شي تقريبا اال البروتينات اللي بتحتويها‬
‫البروتينات هوالمسؤول عن االختالف بالوظيفة‬
Good luck^^