PHASE 1 Revision Akanksha Sinha Regina Sarbaratnam The Peer Teaching Society is not liable for false...

PHASE 1 Revision

Akanksha SinhaRegina Sarbaratnam

The Peer Teaching Society is not liable for false or misleading information…

• METABOLISM(Carbohydrates, Protein, Lipid, Alcohol, Glycogen)

• ATP(ATP-ADP cycle, Glycolysis, Kreb’s cycle, Oxidative Phosphorylation)

• FATTY ACID OXIDATION/KETONES(Beta oxidation, Ketogenesis)

• ACID/BASE/BUFFER (Henderson-Hasselbach equation)

• OXYGEN TOXICITY (ROS, Haber-Weiss and Fenton reactions)

• HISTOLOGY (Stains, Epithelia)

Aims - Overview

Metabolism The chemical processes that occur within a living organism in order to maintain life

Metabolism 4 main energy sources:

Carbohydrates: Starch, fructose, sucrose, glucose, lactose Mainly come from starchy foods and fruit.

Proteins: Largely come from meat ,dairy ,pulses , fish

Alcohol: typically ethanol

Lipids: triacylglycerols

4kcal/g

7kcal/g

9kcal/g

What happens to the excess energy intake? 1. Stored as triglycerides (approximately 15kg)

2. Stored as glycogen (approximately 200g in liver, 150g in muscle)

3. Stored as protein (approximately 6kg)

Energy needed to stay alive at rest

Increase BMR:•Increased body weight •Hyperthyroidism•Low ambient temperature•Fever/infection•Caffeine/stimulant intake•Pregnancy

Decrease BMR:•Increased age•Being female •Dieting/Starvation•Hypothyroidism

ATP ‘Adenosine Triphosphate’ Structure components: Adenine, Ribose, 3 Phosphate

How does it provide Energy?

-The ATP molecule has two phosphoanhydride bonds.

-These are RELATIVELY WEAK bonds, hence require relatively less energy to break

-Overall more energy is released in forming the products that used to break bonds in the reactants

Hydrolysis

ATP-ADP Cycle ATP

ADP + Pi

Respiration:Energy productionCarbohydrateLipidProtein

Energy utilization:Biosynthesis of macromoleculesMuscle contractionActive ion transportThermogenesis

ATP- ways to generate ATP? - Glycolysis- Kreb’s cycle- Oxidative phosphorylation- Substrate level phosphorylation- Via electron transport chain- Beta oxidation (Discussed in fatty acid oxidation)

Glycolysis• GlycolysisPathway of 10 stepsTakes place in cytoplasmIn short – Glucose 2Pyruvate + 2ATP + 2NADH (AEROBIC)2Lactate + 2ATP (ANAEROBIC)

Glycolysis Energy Investment Phase

- 2 ATP

Energy Generation Phase

+ 4 ATP

Glycolysis generates a NET 2 ATP plus 2 NADH

• Facilitated diffusion of Glucose into cell mediated by Insulin

• Phosphorylation of Glucose by Hexokinase• -ATP

Step 1

• Isomerism• G6PF6P

Step 2

• F6P F1,6BP• Via phosphofructokinase (PFK is primary

regulated step of glycolysis; responds to both cellular energy and hormonal regulation)

• -ATP

Step 3**

• 6: NADH (x2) produced• 7: ATP (x2) produced• 8:• 9:• 10: 2Pyruvate + ATP (x2) produced• Remember all the enzymes• “Good Gracious, Father Franklin Did Go By Picking

Pumpkins (to) Prepare Pies

Step 6-10

Pyruvate enters the TCA cycle

• PFK1 is pH dependent– Inhibited in acidosis

Control of glycolysis via:

• Step 1• Step 3* -key regulatory step in glycolysis

Acidosis affecting glycolysis

Positive regulators: AMP Negative regulators: H+, ATP, Citrate, hormonal

Kreb’s/ TCA cycle

In Mitochondrial matrixAcetyl CoA can come from glycolysis/ fatty acid breakdown/ amino acids’ carbon skeletons

Kreb’s/TCA cycle • Inhibited

by ATP, NADH, succinyl CoA

• Activated by ADP

Electron Transport Chain• The electron transport chain (ETC) is a

process in which the NADH and [FADH2] produced during glycolysis, β-oxidation, and other catabolic processes are oxidized

thus releasing energy in the form of ATP. The mechanism by which ATP is formed in the ETC is called chemiosmotic phosphorylation

The chemiosmotic theory Based on the following:-inner mitochondrial membrane is impermeable to protons, hence the mitochondrial matrix is a closed environment-the proton pumping of the ETC leads to the proton motive force which in turn provides the energy for ATP synthesis (Proton flow through the ATP synthase protein drives ATP synthesis)

The chemiosmotic theory

Substrate level phosphorylation • some ATP can be made in the cytoplasm

through a process called substrate-level phosphorylation

• With this type of phosphorylation you have an adenosine diphosphate (ADP), which is a unit of adenosine attached to two (di) phosphate groups

oxidative phosphorylation • Oxidative phosphorylation is the metabolic

pathway in which the mitochondria in cells use their structure, enzymes, and energy released by the oxidation of nutrients to reform ATP

(involves ETC!!!)

TOTAL ATP • Total ATP made from one molecule of glucose:34 ATP

But this is very debatable- Some sources will say 30 or 32 ATP

Fatty acid oxidation/ Beta oxidation Examples of fatty acids: •Palmitoleic acid•Linoleic acid•Palmitic acid

Fatty acid oxidation/ Beta oxidation

Fatty Acid Acetyl CoA (used in TCA/Krebs cycle)

Fatty Acid Acyl adenylate

ATP PPi

Acyl adenylate

Acyl CoA

CoA AMP

Acyl CoA synthetase

The carnitine shuttle !!!

The Carnitine Shuttle

Acyl CoA Acyl Carnitine

Carnitine CoA

Carnitine Acyl Transferase I

Inner mitochondrial membrane

Acyl Carnitine

Acyl CoA

CoA Carnitine

Carnitine Acyl Transferase II

Acyl CoA Acyl CoA – 2C

Acetyl CoA

• Sequential removal of 2- carbon units • Each round of β-oxidation produces: 1 mole of NADH 1 mole of FADH2 1 mole of acetyl-CoA

Ketogenesis The process by which ketone bodies are produced as a result of fatty acid breakdown.

Ketones are used for energy at low fat states.

Ketogenesis 2 Acetyl-CoAthiolase CoA-SH

Acetoacetyl-CoAHMG-CoA synthase

Acetyl-CoA + H20

CoA-SH

HMG-CoA HMG-CoA lyase Acetyl-CoA

Acetoacetate

Acetone β- hydroxybutyrate

I know, no pathology … Diabetic ketoacidosis

• Reduced supply of glucose due to a significant decline in circulating insulin and an associated increased in circulating glucagon.

• The increased production of Acetyl-CoA leads to ketone body production

• This lowers the pH of the blood

Acid/Base/Buffer • Acid = proton (H+) donor

HA H⇔ + + A-

• Base = proton (H+) acceptor

B + H+ BH⇔ +

• Buffer = weak acids or bases that act to maintain H+ concentration

Acid/base/buffer • Acidosis can either be respiratory or metabolic• Alkalosis can either be respiratory or

metabolic

• pH range is 7.35-7.45. But ideal pH is 7.4

• Compensation: metabolic is slow, respiratory is fast.

Henderson-Hasselbalch equation • Henderson’s formula:- [H+ ] x [HCO3 - ] = K x pCO2

• Hasselbalch converted it to pH pH = pK + log ([HCO3 - ] / [CO2])

• Respiratory• Insufficient ventilation retains CO2

so there is more carbonic acid in the blood leading to acidosis

• Causes include COPD (chronic bronchitis + emphysema), asthma

Acidosis

• Metabolic• Low bicarbonate levels leading to

acidosis• Causes include bicarbonate losses

from the GI tract e.g. diarrhoea, DKA, lactic acidosis (anaerobic respiration), renal failure

Carbonic anhydrase

Alkalosis

• Respiratory• Blowing off too much CO2 leading

to alkalosis• Causes hyperventilation, pink

puffers COPD (i.e. type 1 respiratory failure), anxiety, fever

• Metabolic• Loss of H+ or too much

bicarbonate leading to alkalosis• gastric secretions contain large

quantities of hydrogen ions.• Causes include excess vomiting

(because you’re losing H+), pyloric stenosis, anorexia nervosa, ingestion of bicarbonate

Anion Gap The anion gap is calculated by subtracting the serum concentrations of ANIONS (Cl- and HCO3-) from the concentrations of CATIONS (Na+ and K+)

potassium concentrations, being very low, usually have little effect on the calculated gap. This leaves the following equation:

Anion gap = [Na+] − ([Cl−] + [HCO3−]) =16 meq/lit

The magnitude of this difference (i.e., "gap") in the serum is often calculated when attempting to identify the cause of metabolic acidosis.

If the gap is greater than normal, then high anion gap metabolic acidosis is diagnosed (due to increased cation: H+)

• Proteins (51%)– Weak acid/base groups

• Bicarbonate (43%)– CO2 removed via lungs, Bicarbonate regenerated

by kidneys

• Haemoglobin (6%)– Deoxy Hb binds H+ HHb + Bicarbonate– Amine group on Deoxy Hb bind CO2

carbaminohaemoglobinThe Peer Teaching Society is not liable for false or misleading information…

Types of Buffer systems

Most important

Haemoglobin binds both CO2 and H+ and so is a powerful buffer

Oxygen Toxicity Toxic reactive oxygen derivatives with:•Free radicals•Unpaired electrons in outer shell•High reactivity

ORDEF: Chemically reactive molecules with unpaired electrons in outer shell & free radicals (unpaired electron) derived from oxygen

Formation of ROS

Oxygen

Superoxide

Hydrogen peroxide

OH• + H2O

Hydroxyl radical

e- e-, 2H+

e-, H+

Produced by ETC

Generates radicals with transition metals (Fenton or Haber Weiss rx)

OH• (hydroxyl radical)•Most potent radical•Lipid soluble•Chain reaction forms lipid peroxides & organic radicals

H202 (hydrogen peroxide)•Not actually a radical•Oxidising agent in presence of Fe2+ or other transition metals•Generates hydroxyl radical•Lipid soluble

Formation of hydroxyl radical

H2O2Fe2+

Haber-Weiss reaction

Fenton reaction

• Endogenous – natural by-product of O2 metabolism– Produced mainly inside cell organelles ie.

(mitochondria)

• Exogenous– UV radiation, smoking, inflammation

Production of ROS

• Respiratory bursts– ROS released during phagocytosis of bacteria– Damages bacterial cell membrane– Fenton’s reaction

• O2 O2-H2O2+Fe2+Fe3+ + OH- + OH•

+ve ROS

• Cellular damage• Damage to membranes of nucleus,

mitochondria, endoplasmic reticulum & cell• Increased permeability leads to influx of

calcium, water & sodium

-ve ROS

• Enzymes– Catalase H2O2 2 H20 + 02– Superoxide dismutase O2- H2O2– Glutathione peroxidase

• Antioxidant vitamins/Free radical scavengers (vitC, vitE, carotenoids)

• Cellular Compartmentation• Repair

Anti-oxidants

Histology of Epithelia • Roles of epithelia - Protection(skin) - Absorption(gut)- Secretion(pancreas)

Simple Epithelium Stratified Epithelium-Almost always squamous

Pseudo-stratified Epithelium

Simple squamous epithelia

Found in: -Alveoli -Serosa

Simple cuboidal epithelia

Found in: -Kidney tubules -Ducts of glandsSweat Salivary Pancreatic

Simple columnar epithelia

Found in: -Small intestine -Gall bladder -Bronchus

Protection •Continually being worn down•Cells replaced from below•Found in areas where there is continuous abrasion

Squamous:Keratinised – skinNon keratinised – mouth, oesophagus, vagina

Cuboidalfound in some large ducts

Stratified epithelium

Stratified squamous non-keratinising

Found in:-Mouth-Oropharynx-Oesophagus -Vagina

Found in: -Skin (hairy or non-hairy skin)

Stratified squamous keratinising

Found in:•Trachea and large airways (respiratory epithelium) •Urinary tract

Pseudostratified columnar epithelia

1) Adherent (tight) junctions

Cell Junctions

2) Desmosome

Cell Junctions

3) Gap junction

Cell Junctions

Staining

Alcian Blue

GAG-rich structuresMucous goblet cellsMast cell granulesCartilage matrix

Staining

Eosin Colloidal proteins (e.g. plasma)Keratin

Staining

Haematoxylin

NucleiRNA

Staining

PAS Hexose sugars

Questions?

asinha1@sheffield.ac.uk

rcsabaratnam1@sheffield.ac.uk

PHASE 1 Revision Akanksha Sinha Regina Sarbaratnam The Peer Teaching Society is not liable for false...

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