6th week-2nd committee(81 page) PDF

Preview

Summary

ANKARA YILDIRIM BEYAZIT UNIVERSITY CLASS OF 2023 FACULTY OF MEDICINE NOTE GROUP 2nd COMMITTEE 6th WEEK CONTENTS BIOPHYSICS ........................................................................................................................... 1 ELECTRICAL EVENTS ON CELL ............................

Description

AN ANK KAR ARA A YILD ILDIR IR IRIM IM BE BEY YAZI ZIT T UNIV NIVER ER ERSIT SIT SITY Y CLASS OF

2023

FACULTY OF MEDICINE

17’/18’ NOTE GROUP

2nd COMMITTEE 6th WEEK CON CONTEN TEN TENTS TS BIO BIOPHYS PHYS PHYSICS ICS ........................................................................................................................... 1 ELECTRICAL EVENTS ON CELL MEMBRANE-Sel Sel Selcan can Çif Çiftçi tçi ........................... 1

MED MEDICAL ICAL GENE GENETI TI TIC C.............................................................................................................. 7 ORGANISATION OF HUMAN GENOME-Ga Ga Gamze mze K Korkm orkm orkmaz az ............................... 7 POPULATION GENETICS-Gize Gize Gizem m Ta Taşş .................................................................... 13 CHROMOSOME STRUCTURE Kere AND CLASSIFICATION-Sam Sam Samii Kere erem m Kah Kahrama rama raman n ............................................... 19

BIO BIOCH CH CHEM EM EMIST IST ISTRY RY ..................................................................................................................29 DIGESTION/ABSORPTION OF LIPIDS AND LIPOPROTEIN METABOLISM-A Aslıh slıhan an Taş.............................................. 59 CHOLESTEROL METABOLISM-O Osama Al-A Al-Arsh rsh rshani ani Sena Ka Karapı rapı rapınar nar .............................................. 67 HIS HISTO TO TOLO LO LOGY GY A AND ND EM EMBRIO BRIO BRIOLOG LOG LOGY-LA Y-LA Y-LAB B .........................................................................77 CELL ORGANELLES AND INCLUSIONS-Fur Fur Furkan kan Ça Çalışk lışk lışkan an ............................. 77

Beni Türk hekimleri ekimlerine ne emanet ediniz.

Bu haftaki PDF'i hazırlayan Bahadır Yazan'a buradan da teşekkür ederiz. Emeğine sağlık. Ayrıca not yazan arkadaşlara da teşekkürler. Yavaş yavaş bu yeni not düzenine hep birlikte alışıyoruz. Teknik ekip olarak bizler de hala birtakım şeyleri oturtamadık, bazı gelen notlarda hafif sıkıntılar oluyor ama çok iyi gidiyorsunuz. Azminiz ve emeğiniz için tüm not grubu üyelerine teşekkür ederiz. Daha önce de söylediğim gibi lütfen çalıştığınız notlarla ilgili geri bildirimlerinizi whatsapp grubumuzdan iletin ki hem notu hazırlayan hem de hazırlayacak olanlar kendilerini geliştirsinler ve iyi hissetsinler. Örneğin notun arkasına çıkmışları eklemek güzel bir fikirdi. Bu ve bunun gibi notlarda beğendiğiniz veya beğenmediğiniz eksik gördüğünüz yerleri paylaşmanızı bekliyoruz. İkinci dönem çok daha emin ve sağlam adımlarla ilerlememiz için bu şart.

Hepinize iyi çalışmalar diliyorum. Sevgiyle kalın Selin Ecer

BIOPHYSICS :

4

Electrical Events on Cell Membrane 1. 2. 3. 4. 5. 6. 7. 8.

SELCAN ÇİFTÇİ

Lecture Objectives Cell physiology Electrical zones of the cell Effect of changing the electrical environment of the nerve Identify methods of ion transfer across cell membrane Identify differences between electric & biological circuit Explain causes & importance of current of injury Discuss causes & importance of strain potential Discuss the uses of bioelectricity

Biological membrane It is not possible to understand the origin of resting and action membrane voltage (potential) without knowledge of structure and properties of biological membrane. In principle, it is an electrically non-conducting thin bilayer (6-8 nm) of phospholipid molecules. There are also built-in macromolecules of proteins with various functions.

Considering electrical phenomena, two kinds of proteins are the most important: the ion channels and pumps. In both cases these are components of transport mechanisms allowing transport of ions through the non-conducting phospholipid membrane.

Membrane Function Membranes organize the chemical activities of cells. The outer plasma membrane forms a boundary between a living cell and its surroundings Exhibits selective permeability Controls traffic of molecules in and out

The Cell Membrane: Barrier and Gatekeeper Concentration of dissolved substances in the extracellular and intracellular fluid is different

1

What do Membrane Proteins Do?

The phases of the action potential are associated with changes in the permeability of the cell membrane to Na, K, and

.

Ca

Permeability is controlled by ion channels.

Bioelectric phenomena The electric signal play a key role in controlling of all vitally important organs. ✓ They ensure fast transmission of information in the organism. ✓ They propagate through nerve fibres and muscle cells where they trigger a chain of events resulting in muscle contraction. ✓ They take a part in basic function mechanisms of sensory and other body organs. On cellular level, they originate in membrane systems, and their propagation is accompanied by production of electromagnetic field in the ambient medium. Recording of electrical or magnetic signals from the body surface is fundamental in many important clinical diagnostic methods.

2

Cell physiology

 The cell is the functional unit in organisms, it is the building block of the body  The cell is very very small  Cell membrane is composed of a bilayer of phospholipids  Cell membrane is almost 5 – 5.7 nm

 Inside the cell there are electrical charges, these electrical charges move inside and outside of the cell  Some of the electrical charges are bound to be inside  Cells usually are bind together by junctions, forming tissues

Types of Tissue 1. Excitable tissue, like muscle & nerves 2. Non-excitable tissues, they have charges but the can not be stimulated like excitable tissues, e.g. skin, bone, adipose tissue, connective tissue & epithelial tissue

Electric Charges  Electric charges can be found either single or compound (multiple)  They can be found inside the cell or outside the cell  Because some ions are able to move from the inside to the outside or from the outside to the inside, they are creating what we call a the convection current.

Zones of The Cell

Each excitable cell has 4 electrical zones: 1. The innermost zone (central zone ) which is negative because it has proteins & amino acids 2. The inner zone, it is positive, it has cations such as potassium 3. The outer zone, it is positive, it has ions such as sodium, calcium and potassium 4. The outermost zone which is negative, it has glycolipids • •

the most two important layers are the two negative layers These two layer are responsible for the electrical charges of the cell, the are the ones which change the cell properties

3

Charges Across The Cell Membrane

•

Intracellular 

high potassium (K+), low sodium (Na+) • Extracellular  low potassium , high sodium, high calcium Membrane is more permeable to K+ than to Na+ or other ions

Why Electricity of The Cell Is Important ?          

It is one way in which the cells communicate with each other Signals come to the cell in a form of electric charges Failure in this communication will result in disease or malfunction In order to correct that disease we give external electricity When we treat patient with electric modalities we are trying to correct that electrical charges within the cell Normally, the signals come to the cell thought what we call a first messenger (hormone or neurotransmitter) When these signals reaches the cell it activates the second messenger (enzymes or calcium) This will result in a change in cell function In case of a disease the problem lies in the first messenger We apply electricity to work as first messenger  So, electricity will activate the second messenger & will change cell function & will correct the disease

Resting Membrane Potential

 The difference in potential across the cell membrane is what causes the resting membrane potential  Inside is more negative than the outside  Resting membrane potential for skeletal muscle is -90 mV  Resting membrane potential for nerve & smooth muscle is -70 mV

Action Potential     

First there is a stimulus (hormone, neurotransmitter, mechanical stimulus) Then we have Depolarization, channels are open , ion are rushed in inside the cell It reaches a peak then goes down (Repolarization) Then we have a refractory period, in which the cell can not be stimulated again Then back to the resting membrane potential

4

 Action potential results from a chemical, electrical stimulus  To have an action potential the difference shouldn't be less than 15 from the original value of resting membrane potential (e.g. reversal of membrane potential from -90 to +30)  All or none (1 or 0) (either there is an action potential or there isn’t )

How the Movement of Ions Creates Electrical Charges? Cations - Positively charged ions; Na+, K+ Anions - Negatively charged ions; Cl-, protein anions (A-) Ions move from areas of high charge to areas of low charge and substances move from areas of high concentration to low concentration. Cell-Membrane Structure is impermeable to salty solutions Protein molecules in the membrane allow certain ions to pass

Movement of Ions Across The Cell Membrane There are 4 methods in which ions could move across the cell membrane: 1. Diffusion 2. Facilitated diffusion 3. Active transport 4. Pinocytosis

Diffusion  It is a passive process, usually small ions use this method to move across the cell, it moves from high concentration to low concentration  The rate of concentration is governed by factors such as: 1. Ion concentration, 2. Temperature (temperature diffusion) 3. Electrical charges (repulsion & attraction between charges)

Facilitated Diffusion  A passive process  Molecules attached to protein carriers to pass through the membrane  Large molecules such as glucose & amino acid use this methods for transfer

Active Transport    

An active process, energy is needed, it comes from ATP Ions and molecules are moving against their concentration and electrical charges We have pumps that will help them move across the membrane (e.g., Na+ pumps, K+ pumps) Sodium, potassium, calcium, hydrogen & chloride, use this method of transport

Pinocytosis  It is used by large molecules  Part of the cell membrane surround the molecule, then detaches itself in a vesicle into the cell

5

Differences Between Electric & Biological Circuit Biological circuit:

Electric circuit:

•Electric charge in wet environment •Atoms & ions •Components of circuit are always changing •There is a continuous leakage (Just K+ ions) •There need to be areas charge differences •Short pathway •Energy is needed all the time •Slower, the response rate is in millisecond

•Electric charge in dry environment •Uses electrons •Need occasional replacement of components •Move electric charges without leakage (or there will be a shock) •Long pathway •Energy is needed only when the circuit is working •Faster, the response rate is in nanosecond

Current of Injury        

It occurs when there is a wound in the skin, always found in & around the traumatized & healing area The skin has charges, the positive charges in the skin move to the site where there is a cut or a wound It happens a distance of 3mm from the open wound the wound This movement is associated with closure in the wound If there is large amount of current in the wound the closure will be faster If there is a minimal current the closure will take longer one of the factors that helps in closing the wound faster is moist If the wound is most  current will be higher  closure will be faster

         

Strain potential can be found when there is mechanical deformation, either compression or distraction When there is compression there will be negative charge When there is distraction there will be positive charge Strain potential increase bone growth If we have a broken bone & they placed electrodes on either side of this bone, there will be a current When we put pressure on the bone, the area where the bone is convex (distracted) the charge will be positive The are where the bone in concave (compresses) the charge will be negative Strain potential may increase bone growth Signals instruct cells to either increase or decrease formation The current also forms in the connective tissue  remodeling of connective tissue alignment

Strain Potential

How Can We Use Bioelectricity We can use it in two ways: 1. Evaluation 2. Treatment

Evaluation 1.

Electroencephalogram (EEG) Used to record electrical activity of the brain 2. Electromyogram (EMG) Used to observe the muscle function 3. Electrocardiogram (ECG) Record the activity of the heart

Treatment 1.

  2. 

In some disease the second messenger may not be working because it is not getting impulses from the first messenger We give electricity to act as a first messenger to initiate or change cell function Frequency window: some cells are sensitive to certain frequencies of electromagnetic field In some disease their could be a first messenger but the signals the cell receiving are weak The applied energy may strengthen the weak current to result in strong signals that could modify cell function

    

To educate a nerve or a muscle To relief pain & other symptoms (spasm, swelling edema) Improve neural growth (inflammation around the nerve) Heating tissues When giving some drugs (iontopherisis)

Other Therapeutic Uses

6

MEDICAL GENETIC

Organisation of Human Genome

Gamze Korkmaz Sıla Mutlu

GENOME The human genome is the term used to describe the total genetic information (DNA content) in human cells. In other words, the total genetic material of an individual or a species is called as “genome”. In human genome, there are two types of genome; one of them is nuclear genome and it consists of 99.99% (about 3200 Mbp) of the whole genome and the other one is mitochondrial genome (0.01%, 16.6 kb).

By the human genome project, it has been came out that organisation of human genome is more complex than predicted. Only less than 5% of our DNA encodes a protein. Nearly half of our genome is consisted of repeated sequences. These repeated sequences contribute to the protection of chromosome structure. Chromosomes are the package form of the DNA.so protection of the chromosome is important for us.

7

When we are looking for the patient’s DNA , we compare our DNA’s with this references sequence acording to the differences between this sequences.We decide if there is a polymorphism or there is a mutation in the patient. Polymorphism is more normal than mutation

1.General organization of the human genome: Nuclear genome: - 3284 million bp, - The length of coding region is 1000-3500bp, nearly 30,073 genes (21598 protein coding gene, 8475 RNA genes) - 1.1% of genome encodes proteins. - 4% of it consists regulatory sequences and RNA genes - 20% of genome is composed of non-coding DNA. This part includes introns, non-translated gene regions and sequences like pseudogenes. - The most of the rest 75% non-coding DNA is extragenic and most of this part (55% of genome) consists repeating sequences. Extragenic:between the genes

• Most of the repeated sequences (45% of total DNA) are transposable elements, also known as transposons. • Transposons have the ability to move within the genome and to add copies randomly to the genome. • By recombination, these repeated sequences allow the rearrangement of genome regions and the change of gene properties. Repeated sequences is important in crossing over. - The coding sequences frequently belong to families of related sequences (DNA sequence families) which may organized into groups on one or more chromosomes or may be dispersed.

- As in other complex genomes, a very large component of the human genome is made up of non-coding DNA. - A sizeable component of this part is organized in tandem repeats, but the majority consists of interspersed repeats.

8

• Human gene number: - 30,000 – 35,000 - most are polypeptide-coding, but 3-5% encode RNA that is untranslated (they don’t encode a protein).these only encode rna genes .they transcribed but they dont translate. • Human gene distribution: - Done by hybridizing CpG islands to metaphase chromosomes. The results showed that gene density in subtelomeric regions & some chromosomes (19&22) are gene rich while others are gene poor (X&18).

• Genes vary greatly in size and intron/exon organization. • Some genes don’t have any introns. Most common example is the histone genes. Histones are the proteins DNA gets wrapped around in the lowest unit of chromosomal organization, the nucleosome. • Some genes are quite huge: dystrophin (associated with Duchenne muscular dystrophy) is 2.4 Mbp and takes 16 hours to transcribe. More than 99% of this gene is intron. • Dystrophin is most biggest gene in our body • However, highly expressed genes usually have short introns.

• Most part of dystrophin composed of introns .So it is not so active.

2. Organization, distribution & function of human RNA genes Some of the human genes encode a polypeptide,a few of them encode RNA’s with different functions. 5% of nuclear genome encode RNA genes.

• rRNA genes: 28, 18 and 5,8 s rRNA’s are encoded by a transcription unit and they are tandem repeats located on chromosomes 13, 14, 15, 21 and 22 (nearly 50 repeats). The other ribosomal RNA, 5S RNA, is transcribed from large clusters elsewhere in the genome. • tRNA genes: Transfer RNA genes are dispersed throughout the genome, usually in small clusters. There are 49 families of tRNA genes

• mRNA genes: They encode polypeptides. • How much mrna genes are there in mitochondrial dna? -13genes

Other RNA Genes • Some RNA molecules are involved in RNA splicing. The genes for these are small nuclear RNA (snRNA) (2019) and small nucleolar RNA (snoRNA) (1173) genes. • MicroRNAs (miRNA) (1048) and small interfering RNAs (siRNA) regulate translation of specific mRNAs by binding to the mRNA: they are antisense RNAs, complementary to the “sense” strand of the mRNA. • miRNA seems to have a role in development. This is a very hot area of research at the moment. • siRNA is a basis for a popular technique called RNA interference, which allows specific genes to be inactivated. • İf you want to inactive some genes you can work with siRNA.

9

• Trancription occurs in the nucleus • Translation occurs in the cytoplasm

According the this we can decide if there is a change in the dna sequence or in the aminoacid or not.We look for this table when we are looking at the sequences

3. Organization, distribution & function human polypeptide-encoding genes: • Human genes show enormous variation in size and internal organization. E.g. Dystrophin gene 2.4 Mb is transcribed in 16 hours Diversity in exon-intron organization: very small number of genes lack introns. For ex:Histone For intron-containing genes, there is an inverse correlation between gene size and fraction of coding DNA. İf the gene is huge than intron part of the gene is also increase according the normal DNA Diversity in repetitive DNA content: genes have repetitive DNA in introns, flanking sequences, and to different extents in coding sequences Functionally similar genes: closely related but not identical in sequence. Genes are clustered and have arisen by tandem gene duplication (e.g. α-globin and β-globin gene clusters). Functionally related genes: genes encode products which may not be so closely related in sequence but are functionally re...