Foundations of Medicine Block 1 Week 1 Flashcards

Question

What are the three exocytosis pathways ?

Answer 1

1.Constitutive exocytosis 2. Regulated exocytosis 3. Lysosome mediated exocytosis Basic process of exocytosis: Vesicles containing molecules are transported from within the cell to the cell membrane. The vesicle membrane attaches to the cell membrane. Fusion of the vesicle membrane with the cell membrane releases the vesicle contents outside the cell. Constitutive: involves regular secretion of molecules. This action is performed by all cells. Regulated: relies on the presence of extracellular signals for the expulsion of materials within the vesicles. Does not occur in all cells. Mainly only secretory cells. Secretory cells store products such as hormones, neurotransmitters and digestive enzymes that are released when triggered by extracellular signals. Lysosomes: Carry digested material to the cell membrane where they fuse with the membrane and release their content into the extracellular matrix.

Answer 2

1.receptor-mediated endocytosis (also known as clathrin-mediated endocytosis) - takes in most things. There are 20 receptors which works this way. 2. caveolae - take in nanoparticles.Particles usually 50-100 nanometres. 3. pinocytosis - take in fluid with dissolved small molecules. 4. phagocytosis - part of the immune system. Ingest particles larger than 50 micrometres into a phagosome.

Answer 3

Endocytosis is used by cells to retrieve components of the plasma membrane and to take up macromolecules from the extracellular space.

Answer 4

Phagocytosis is a specialized form of endocytosis in which large particles (e.g. bacteria or cell debris) are ingested by phagocytes. The pri

Answer 5

Peroxisomes are small membrane enclosed organelles that contain enzymes (at least 50 different enzymes) involved in a variety of metabolic reactions, including several aspects of energy metabolism. Site of oxidative reactions with hydrogen peroxide production. Hydrogen Peroxide is then converted into water and oxygen. Another site of fatty acid metabolism.

Answer 6

1. By diffusible chemical signals - allows cells to communicate at a distance 2. By direct contact between the plasma membrane of adjacent cells - important in cell-cell recognition during development. 3. By direct cytoplasmic contact via gap junctions - permits the electrical coupling of cells and plays an important role in the spread of excitation between adjacent cardiac muscle cells.

Answer 7

1. Paracrine signaling - when the secreted signal acts on cells nearby (local). The signaling molecules are destroyed rapidly by extracellular enzymes or by uptake into the target cells. Consequently very little of the secreted material enters the blood. 2. Endocrine signaling - Hormones are secreted into the blood by endocrine glands, to act on various tissues around the body. (not localized). Because hormones are circulated their actions are often slow and long-lasting ( ranging from seconds to hours) 3. Synaptic Signaling - Nerve cells release chemicals at their endings to affect the cells they contact.

Answer 8

1. Prostaglandins secreted by a cell act on neighboring cells to stimulate them to produce more prostaglandins. 2.Mast cells in tissues have secretory granules which release histamine. Histamine dilates local arteriole and increases the permeability of local nearby capillaries.

Answer 9

1. They may respond to chemical level in the blood. E.g. Insulin secretion from the B -cells of the pancreatic islets is regulated by the blood glucose concentration. 2. They may respond to the level of other hormones in the blood. E.g. Sex hormones from the ovaries ( estrogen) and testes (testosterone) which are secreted in response to hormonal signals from the anterior pituitary gland. 3. They may respond to the activity of nerves - this is how oxytocin secretion from the posterior pituitary gland and prolactin secretion by the anterior pituitary gland are controlled during lactation.

Answer 10

The releasing hormones of the hypothalamus. These hormones are released into portal blood vessels and travel to the anterior pituitary gland where they control the secretion of the anterior pituitary hormones.

Answer 11

No the only cell types which respond to hormones are the cells which have the correct receptors. Also the receptors must have a high affinity for that particular hormone.

Answer 12

If sufficient quantities of a signaling molecule are released that it is able to affect tissues remote from the point of secretion it is being employed as a hormone. Whereas if the amounts secreted are sufficient only to affect the cells close to the point of secretion, the chemical signal is acting as a paracrine signal.

Answer 13

2) Synaptic signaling molecule, opens ligand-gated ion channels and also activates G-Protein linked receptors

Answer 14

2) Hormone , wide variety of effects, acts via G-protein linked receptors

Answer 15

2) Hormone, increase water reabsorption by collecting tubule of the kidney via G-protein linked receptor

Answer 16

1) Hormone, activates catalytic receptors in the plasma membrane, increases uptake of glucose by the liver, fat and muscle cells.

Answer 17

1) Hormone and local mediator, inhibits secretion of growth hormones by anterior pituitary gland via G-protein linked receptor.

Answer 18

Water loving / polar - molecules can not easily diffuse across the cell membrane e.g. glucose and ions Water hating/ non polar - molecules can easily diffuse across the cell membrane e.g. urea Remember the inside of the cell membrane is water hating

Answer 19

Antagonist

Answer 20

Antagonist

Answer 21

1. Open an ion channel - Nicotinic ACh receptor 2. It may directly activate a membrane bound enzyme - insulin receptor 3. It may activate a G-protein - linked receptor that may modulate an ion channel or change the intracellular concentration of a specific chemical, called a second messenger. The original signaling molecule is the first messenger. - Muscarinic ACh receptor. 4. The signal may act on an intracellular receptor to modulate the transcription of specific genes. - Eostrogen receptor

Answer 22

Receptors which are directly coupled to ion channels. Ligand gated ion channels are open for a short period of time following the binding of their specific agonist, this alters the membrane potential of the target cell.

Answer 23

Depolarizes the target cell. The depolarization activates voltage - gated ion channels which trigger the appropriate cellular response.

Answer 24

Catalytic receptors are membrane bound protein kinases that become activated when they bind to their specific ligand. A typical example of a catalytic receptor is the insulin receptor that is found in the liver, muscle and fat cells. The receptor is activated when it binds insulin and in turn activates other enzymes by adding a phosphate group to tyrosine residues. This results in an increase in the activity of the affected enzymes which culminates in an increase in the rate of glucose uptake.

Answer 25

1. Phospholipids 2. Glycolipids 3. Cholestrol

Answer 26

1. Glycerophospholipid 2. Sphingolipids Glycerophospholipid are more abundant

Answer 27

The amount of lipids. The more cis -double bonds in a fatty acid the more fluid the cell membrane and the lower its melting temperature Most phospholipids have a saturated fatty acid chain in the C1 position and a cis-unsaturated fatty acid in the C2 position of the glycerol backbone.

Answer 28

Transporters - bind only one substrate at a time, transport membrane across molecule passively - facilitated diffusion ATP powered pumps - ATPases that use energy of ATP hydrolysis to move ions or small molecules across membrane against a chemical concentration gradient - active transport Channel proteins - water filled pores, when opened ions move down their concentration gradient

Answer 29

Move one molecule at a time down their concentration gradient

Answer 30

A symporter is an integral membrane protein that is involved in the transport of two different molecules across the cell membrane in the same direction

Answer 31

Is the secondary active transport of two or more different molecules or ions across a phospholipid membrane such as the plasma membrane in opposite directions, one into the cell and one out of the cell.

Answer 32

Using a uniporter carrier, down a concentration gradient. GLUT4 transporter transports glucose into fat and muscle cells. GLUT4 is transported to the membrane in response to insulin Glucose is transported into the intestines using a different method. Glucose is actively transported into Intestinal cell using a cotransporter SGTL-1 (sodium glucose transporter) found in the apical membrane of enterocytes. This symporter uses the electrochemical gradient of two sodium ion to transport one glucose into the intestinal cell. The second step is release of the intercellular glucose into the interstitial space, this is done by facilitated diffusion via the glucose transporter GLUT 2 in the basolateral membrane.

Answer 33

- Cholesterol - Bile salts - Vitamin D - Adrenocortical hormones - Sex hormones

Answer 34

The breakdown of molecules to obtain energy

Answer 35

Anabolism is the set of metabolic pathways that construct molecules from smaller units. These reactions require energy, known also as an endergonic process. Anabolism is the building-up aspect of metabolism, whereas catabolism is the breaking-down aspect. The synthesis of all compounds needed by cells

Answer 36

Glycolysis is a set of reactions in which one glucose molecule is oxidised and two molecules of pyruvicacid are produced. The reactions also produce two molecules of ATP and NADH. IS Anaerobic Formation of acetyl CoA is a transition step that prepares pyruvic acid for entrance into theKrebs cycle. This step also produces NAD and oxygen.The Krebs cycle reactions oxidise acetyl CoA and produce CO2, ATP, NADH an FADH2 The ETC oxidisesNADH and FADH2 and transfer their electrons through a series of electron carriers.The Krebs cycle and ETC both require oxygen and as such are known as aerobic cell respiration

Answer 37

Adrenaline and noradrenaline

Answer 38

Proteins are broken down to individual amino acids using protease enzymes and HCL in the GIT. Deamination (removal of amine group): These amino acids are broken down to a-keto acids ( by removing amine group) the left over which can be recycled in the body for energy and production of glucose or fat. This happens in the liver. a-ketoglutarate enters the Krebs cycle to produce NADH and FADH2 which carry electrons to the electron transport chain to produce ATP via oxidative phosphorylation. The amine group is now ammonia which is converted into urea.

Answer 39

Glycolysis - cytoplasm In glycolysis ATP is produced by substrate level phosphorylation phosphate groups are transferred to ADP. This occurs in the cytosol Link reaction and Krebs cycle - mitochondrial matrix ETC - mitochondrial cristae

Answer 40

Ketogenesis is the biochemical process through which organisms produce ketone bodies by breaking down fatty acids and ketogenic amino acids. The process supplies energy to certain organs, particularly the brain, heart and skeletal muscle, under specific scenarios including fasting, caloric restriction, sleep, or others. (In rare metabolic diseases, insufficient gluconeogenesis can cause excessive ketogenesis and hypoglycemia, which may lead to the life-threatening condition known as non-diabetic ketoacidosis.They are acidic and as such can lead to acidosis if present in high quantities Ketone bodies are produced mainly in the mitochondria of liver cells, and synthesis can occur in response to an unavailability of blood glucose, such as during fasting. There is a limit on how many can be oxidised with the main reason being the limit of oxaloacetate which isrequired to bond acetyl CoA before it can enter the citric acid cycle.Ketone bodies are converted to acetyl CoA and enter the Krebs cycle directly.30.Absorptive state

Answer 41

Acetoacetic acid Beta-hydroxybutyric acid Acetone

Answer 42

Anabolism Catabolism Metabolism is a balancing act involving two kinds of activities that go on at the same time: building up body tissues and energy stores (called anabolism) breaking down body tissues and energy stores to get more fuel for body functions (called catabolism)

Answer 43

Carbohydrate - > 260g Sugars 90g Total fat <70g Saturates <20 Protein 50g Salt >6g Dietary fiber 30g

Answer 44

- Over 10% calories come from free sugars - Over 115 calories come from saturated fat - Everyone in the UK eats well below the recommended amounts of oily fish - Adult males exceed the recommendation for red and processed meat.

Answer 45

- Only 26% of adults and 16% of children consumed the recommended amount of 5 portion of fruit and veg a day. - 1 in 5 year 6 children are classified as obese - 26 % of adults are classified as obese.

Answer 46

Triglycerides are hydrolyzed into fatty acids and glycerol by lipase enzymes. This process is stimulated by glucagon and adrenaline. The fatty acids bind to albumin so they become soluble in the blood and can be transported to tissues. Fatty acids are oxidized by beta-oxidation in the mitochondria to generate ATP. So fatty acids CANNOT be converted to glucose.

Answer 47

Liver: 100g Muscle: 350g

Answer 48

For a 65kg person free glucose - 12g Glycogen - 450g Triacylglycerol - 15kg Protein - 12.5kg Glycogen is a short term energy store Fat is a long term energy store Protein acts a source of glucose in the absence of carbohydrate.

Answer 49

3 NADH FADH2 2 ATP

Answer 50

Anaerobic glycolysis serves as a means of energy production in cells that cannot produce adequate energy through oxidative phosphorylation. In poorly oxygenated tissue, glycolysis produces 2 ATP by shunting pyruvate away from mitochondria and through the lactate dehydrogenase reaction. In rapidly contracting skeletal muscle cells with energy demand exceeding what can be produced by oxidative phosphorylation alone, anaerobic glycolysis allows for the more rapid production of ATP.[3] (Glycolysis is approximately 100 times faster than oxidative phosphorylation.) In cells lacking mitochondria altogether, pyruvate cannot undergo oxidative phosphorylation regardless of oxygen levels. Mature erythrocytes do not contain mitochondria and thus rely exclusively on anaerobic glycolysis for ATP production. Other tissues, such as the cornea and lens of the eye and inner medulla of the kidney, are poorly vascularized and rely heavily on anaerobic glycolysis despite the presence of mitochondria. Glucose > (Glyceraldehyde dehydrogenase) > Pyruvate . Instead of pyruvate being shunted to the mitochondria it is converted to lactate (by lactate dehydrogenase) with the generation of NAD+. Glucose + 2ADP + 2Pi > 2 Lactate + 2 ATP + 2 H20 Lactate may be oxidized after conversion back to pyruvate, or converted back to glucose/glycogen in the liver (Cori cycle)

Answer 51

Is a metabolic pathway in which lactate is transported to the liver and converted to glucose (gluconeogenesis). Lactate gets to the liver via the blood. Lactate > (lactate dehydrogenase) > Pyruvate Pyruvate > ( glyceraldehyde dehydrogenase) > Glucose This is a inefficient process for the production of useful energy in the cell. The liver requires 6ATP to produce glucose from the liver whereas the return through glycolysis to lactate produces only 2 ATP.

Answer 52

Red blood cells (no mitochondria) Kidney medulla ( blood supply poorer than cortex) Eye lens (blood vessels & mitochondria would obscure light) Hypoxic conditions at sites of injury or inflammation Tumor cells use glycolysis to survive under hypoxic conditions ( a Hallmark of cancer)

Answer 53

Substrates which can: Glycerol ( from triglycerides) Amino acids ( from proteins) Lactate Fatty acids cannot be converted to glucose

Answer 54

Fatty acids are oxidized by B oxidation in the mitochondria.

Answer 55

The pentose phosphate pathway is a metabolic pathway parallel to glycolysis. There are two distinct phases in the pathway. The first is the oxidative phase, in which NADPH is generated, and the second is the non-oxidative synthesis of 5-carbon sugars. For most organisms, the pentose phosphate pathway takes place in the cytosol. Pentoses: used for DNA/RNA synthesis NADPH: used for lipid synthesis

Answer 56

Active pumping of Na+ from a cell leads to a membrane potentialNa+ ions are actively pumped out of the cellThey become more concentrated in the extracellular fluid.The inner surface is more negatively charged and the outer surface is more positively charged. The difference in electrical charges between two regions constitutes an electrical gradient and because it occursacross the plasma membrane the charge difference is called the membrane potential.56.Coupled

Answer 57

Stimulates the secretion of epinephrine, glucagon and HGH. As a consequence, anxiety, sweating, tremor,increased heart rate hunger and weakness occur.When blood glucose falls, brain cells are deprived of thesteady supply of glucose they need to function effectively. Severe hypoglycaemia leads to metal disorientation,convulsions, unconsciousness, and shock.

Answer 58

Acute Slows done reflexes. Induces sleep but not an ideal hypnotic. Analgesic but not ideal. Cardiovascular Vasodilation Tachycardia and mild rise in blood pressure. Respiration Stimulates respiration BloodIncreases HDL cholesterol level Decrease in LDL oxidation

Answer 59

Increased risk of heart disease Dehydration Central nervous system depression Accumulation of acetaldehyde in the liver Cirrhosis of the liver Increased risk of cancer

Answer 60

Increased risk of heart disease Dehydration Central nervous system depression Accumulation of acetaldehyde in the liver Cirrhosis of the liver Increased risk of cancer

Answer 61

Units = strength (ABV) x volume (ml) ÷ 1000 Pure alcohol is 100% ABV