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Summary All cases BBS1002
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All the cases (very expanded) of BBS1002. I scored an 8.8 on the course exam, by studying these cases and the lectures (this summary is also on stuvia). Good luck!!
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Case 1 – River of life1. What is the composition of blood?
Blood has both cellular and liquid components. It’s a
specialized connective tissue in which living blood cells
are suspended in a non-living fluid matrix called plasma.
When you centrifuge blood, the heavier formed elements
are packed down and the less dense elements remain at
the top. The red blood cells are at the bottom (45%). A
thin, whitish layer called the buffy coat is present on the
red blood cells, which consists the white blood cells and
the platelets (1%). The upper layer is the blood plasma
(55%).
Blood plasma is a sticky fluid, consisting of mostly water (90%), but also over 100
different dissolved solutes, including nutrients, gases, hormones, wastes an products of
cell activity, proteins and inorganic ions. Most plasma proteins are produced by the liver,
except for hormones and gamma globulins. Plasma proteins serve a variety of functions,
but are not taken up by cells. Albumin (60%) of the plasma proteins, acts as a carrier to
shuttle certain molecules through the circulation, is an important blood buffer and the
major blood protein contributing to the plasma osmotic pressure. The composition of
plasma varies continuously as cells remove or add substances to the blood, but it is kept
relatively constant by various homeostatic mechanisms.
The formed elements of blood are the erythrocytes, leukocytes and platelets. White
blood cells are the only fully functional cells in the circulation. Red blood cells have lost
their nuclei by the time they enter the blood stream (because they shouldn’t waste
energy except for oxygen transport) and platelets (thrombocytes) are cell fragments
that have split off a relatively large parent cell known as the megakaryocyte. Red blood
cells have glycoproteins and glycolipids on their plasma membrane to determine what
the blood type is. There are two main types of white blood cells: granulocytes and
agranulocytes (have no granules). Blood contains five types of mature white blood cells:
(1)lymphocytes, (2)monocytes, (3) neutrophils, (4)eosinophils and (5)basophils.
Monocytes that leave the circulation and enter the issues become macrophages.
The basic composition of interstitial fluid is water, along with solutes like sugars, fatty
acids, amino acids, salts etc. It contains nutrients as well as waste products. The
composition of this fluid is very similar to the composition of lymph fluid.
2. How can you relate the interstitial fluid to the blood plasma?
The interstitial fluid is fluid outside the cells and outside blood vessels. It contains
water and dissolved solutes and proteins. The main difference between plasma and
interstitial fluid is that plasma contains more proteins than interstitial fluid. Most of the
other dissolved products occur in similar concentrations in both plasma and interstitial
fluid. Plasma has more oxygen and less carbon dioxide than the interstitial fluid.
,3. What is the function of blood?
Erythrocytes are completely dedicated to their job of transporting oxygen and carbon
dioxide. Hemoglobin binds easily and reversibly with oxygen. Hemoglobin is made up of
the red heme pigment bound to the protein globin. This consists of four polypeptide
chains binding a ring like heme group. Each heme groups bears an atom of iron set like a
jewel in its centre. A hemoglobin molecule can transport four molecules of oxygen
because each iron atom can combine with one molecule of oxygen. Oxygen loading
occurs in the lungs, then it’s given to other cells in the body. Carbon dioxide binds to the
globin’s amino acids rather than to the heme group.
Leukocytes are complete cells. They are crucial to our defence against diseases. They
form a mobile army that helps protect the body from damage by bacteria, viruses,
parasites, toxins and tumor cells. White blood cells are able to slip out of the capillary
blood vessels and the circulatory system is actually just their means of transport to
areas of the body.
- Neutrophils: our body’s bacteria slayers. They are active phagocytes. Contain
hydrolytic enzymes.
- Eosinophils: lead the counter attack against parasitic worms, such as flatworms
and roundworms that are too large to be phagocytized. These worms are
ingested in food or invade the body via the skin.
- Basophils: their cytoplasm contains large, histamine-containing granules that
have an affinity for the basic dyes and stain purplish black. Histamine makes
blood vessels dilate(verwijden) and attracts other white blood cells to the
inflamed(ontstoken) site. Bind to an antibody
- Lymphocytes: T lymphocytes function in immune response by acting directly
against virus-infected cells and tumor cells. B lymphocytes give rise the plasma
cells, which produce antibodies that are released to the blood.
- Monocytes: when circulating monocytes leave the bloodstream and enter the
tissues, they differentiate into macrophages. They are actively phagocytic and
crucial in the body’s defence against viruses, parasites and chronic infections.
Platelets are essential for the clotting process when blood vessels are injured. By
sticking to the damaged site, platelets form a temporary seal. Then clothing factors will
become activated and add themselves to the platelets. A special kind of a clotting factor
can weave itself together with others of the same kind and form a web of fibres tissue
called fibrin. This acts like glue and holds the platelets and other clotting factors
together, creating a blood clot. After the clot has formed it stays in the whole until the
tissue is repaired. When it’s no longer needed, it will be dissolved by the body.
Blood also maintains an appropriate body temperature by absorbing and distributing
heat throughout the body and to the skin surface to encourage heat loss. It maintains a
normal pH in body tissues.
,Plasma has several functions:
- Transport nutrients throughout the body: Amino acids, lipids, sugars and fatty
acids that are formed during digestion are distributed to cells throughout the
body.
- Transport waste: such as uric acid, creatinine and ammonium salts, from cells of
the body to the kidneys. The kidneys filter these waste out of the plasma and
excrete them from the body as urine.
- Maintain blood volume: the blood plasma has a high concentration of albumin, a
protein. This concentration maintains the osmotic pressure of the blood. The
concentration of albumin in the interstitial fluid is smaller than in plasma, which
causes that water is not able to move from the interstitial fluid to the blood.
Otherwise, the blood volume would increase and cause a higher blood pressure.
- Balance electrolytes: plasma carries salts, called electrolytes, throughout the
body. These salts, like sodium, calcium, potassium, magnesium, chloride and
bicarbonate are important for many functions. Without these salts, muscles
would not contract and nerves would not be able to send signals to and from the
brain.
- Defend the body: plasma carries other proteins like immunoglobins, which fight
foreign substances such as bacteria. Fibrinogen is necessary to help the platelets.
4. How does the transport mechanism work?
1. Diffusion: molecules or ions move from an area where they are in higher
concentration to an area where they are in lower concentration. This is along
their concentration gradient. The speed of diffusion is influenced by the
molecular size and the temperature. It is a form of passive transport. A molecule
will diffuse through the membrane if the molecule is lipid-soluble, small enough
to pass through or assisted by a carrier molecule.
o Simple diffusion: nonpolar and lipid-soluble substances diffuse directly
through the lipid bilayer.
o Facilitated diffusion: certain molecules, like glucose and other sugars,
amino acids and ions are transported passively even though they are
unable to pass through the lipid bilayer. They move through the
membrane by a passive process in which the transported substance either
binds to protein carriers in the membrane and is ferried across or moves
through water filled protein channels.
▪ Carrier-mediated: when a substrate binds, it results in a change of
shape by which the molecule can pass through. (mostly sugars and
amino acids)
▪ Channel-mediated: channels are selective due to pore size and the
charges of the amino acids lining the channel. It provides a way for,
mostly ions, to get through the membrane.
2. Osmosis: the diffusion of a solvent, such as water, through a selectively
permeable membrane. Water moves freely and reversibly through water specific
channels called aquaporins, which allow single-file diffusion of water molecules.
Osmosis occurs whenever the water concentration differs on two sides of a
membrane. The total concentration of all solute particles in a solution is referred
to as the solution’s osmolarity. Water moves from a low osmolarity to a high
osmolarity. Osmosis is also passive.
, 3. Primary active transport: hydrolysis of ATP results in the phosphorylation of the
transport protein. This step causes the protein to change its shape in such a
manner that it ‘pumps’ the bound solute across the membrane. Primary active
transport include calcium and hydrogen pumps, e.g. the sodium-potassium pump.
4. Secondary active transport: a single ATP-powered pump can indirectly drive the
secondary active transport of several other solutes. By moving sodium across the
plasma membrane against its concentration gradient, the pump stores energy.
Then, just as water pumped uphill can do work as it flows back down, a substance
pumped across a membrane can do work as it leaks back. In this way, as sodium
moves back into the cell with the help of a carrier protein, other substances are
dragged along. This is also a transport system.
5. Vesicular transport: fluids containing large particles are transported across
cellular membranes inside membranous sacs called vesicles. It moves substances
into the cell (endocytosis) and out of the cell (exocytosis). Vesicular transport
processes are energized by ATP or sometimes GTP.
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