Biochemistry Block 2 Flashcards
Types of Cell Signalling
- Endocrine
- Paracrine
- Neuronal
- Contact Dependent
Endocrine Signalling
Hormones are released into blood stream and act diffusely on targeted cells throughout the body
Paracrine Signalling
“Neighbour”- local mediators (example: Eicosanoids & Nitric Oxide)
Neuronal Signalling
Neurotransmitters carry signals between neurons to other neurons (examples: Acth, dopamine, serotonin)
Contact Dependent Signalling
Direct contact between cells/or cell matrix. No secretion of molecules (Examples: plasmodesmata, gap junctions)
Types of Growth factors (4)
- Epidermal
- Nerve
- Platelet Derived
- Eicosanoids (prostaglandins, leukotrienes, thromboxanes)
3 Types of Cell surface receptors
- Ion-channel linked
- Enzyme-linked
- G-protein
2 Types of Intracellular receptors
- Gene regulating
- Enzymatic
Enzyme-linked
Cell surface receptor
Single pass
Activates tyrosine kinase
G-protein coupled receptors
Cell surface receptor
Act with aid of GTP
7 pass protein
Gs
Activates adenylyl cyclase
Gi
Inhibits adenylyl cyclase
Gq
Activates phospholipase C
Gt (transducin)
Activates cGMP-phosphodiesterase in vertebrates rod photoreceptors
Steps of G-proteins
- Hormone binds to receptor (GDP to GTP)
- G-protein breaks into subunits
- Alpha subunit activates adenylate cyclase which catalyzes cAMP from ATP
- GTP is hydrolyzed to GDP
- Now inactivated the G protein separates from the enzyme and can be reused again
Intracellular receptors
- Reside in the cytoplasm and translocate to the nucleus
- Reside in nucleus bound to DNA
- Reside in nucleus bound to proteins
Gene regulation receptors
“Transcription factors”
1. Binding of the hormone induces conformational changes in the receptor
2. It then binds to regulatory DNA to affect transcription
Second messengers
Small molecules produced in the cytoplasm in response to activation of a cell surface receptor
Signal amplification
Signal process is amplified at each step, ensuring a swifter transmission
Scaffolding proteins
- Bind to activated receptors
- Hold several molecules of a kinase in place-increasing transduction
Characteristics of Metabolism
- Irreversible
- Each step is catalyzed by a specific enzyme
- Has a first committed step
- Regulated
- Occur in specific cellular locations (eukaryotes)
Catabolism
- Degradation
- Convergent
- Oxidative
Products include: (NADH, NADPH, ATP, FADH2)
Anabolism
- Synthesis
- Reductive
- Divergent
- Uses ATP
Products: NAD+, FAD, ADP, NADP+
What is the link between Catabolism and Anabolism?
ATP
Regulation of Metabolic Pathways
- Gene regulation
- Cellular regulation
- Biochemical regulation (allosteric/covalent modification)
Feed Cycle
2-4 hrs after a meal
1. Increase plasma glucose, TAGS, and amino acids
2. B-cells in pancreas release insulin-glucose moves into cells
3. Starts anabolism
What is the nutrient distribution center?
Liver
Fast Cycle
- Decrease in plasma glucose, amino acids, and TAGs
- Glucagon/Epi secretion
- Catabolic phase
What does the Liver do for energy in the fast cycle?
- Increase glycogen degradation
- Gluconeogenesis
- B-oxidation
- Ketogenesis
What does the Adipose Tissue do for energy in the fast cycle?
Increase in TAG degradation providing fatty acids to the liver
What does the Muscles do for energy in the fast cycle?
- Use both fatty acids and ketone bodies
- Degrades protein and provides amino acids to liver for gluconeogenesis
What does the Brain use for energy in the fast cycle?
- Glucose
- Ketone Bodies
Fate of Pyruvate Anaerobic
Lactate (Lactate dehydrogenase)–>Cori Cycle
Fate of Pyruvate Aerobic
Acetyl CoA (PDH)–>TCA Cycle
3 Irreversible Reactions in Glycolysis
- Hexokinase
- PFK-1
- Pyruvate kinase
2 Substrate Level Phosphorylation in Glycolysis
- Phosphoglycerate kinase
- Pyruvate kinase
Where does Glycolysis take place?
Cytosol
Energy of Aerobic Glycolysis
- Investment 2 ATP
- Gain 2 NADH (3 ATP per)
- 4 ATP
TOTAL = 8ATP
Energy of Anaerobic Glycolysis
- Investment 2 ATP
- Gain 4 ATP
TOTAL = 2 ATP
Inhibitors of Glycolysis
- Arsenate
- Fluoride
Where does complete oxidation of glucose take place?
- Brain
- Skeletal Muscles
What is the main source of energy in RBCs?
Anaerobic glycolysis
What is PFK-2
Fructose 2,6 bisphosphate
In the presence of insulin what does PFK-2 do?
Activates PFK-1 (glycolysis)
In the presence of glucagon what does PFK-2 do?
Activates gluconeogenesis
What is the link between glycolysis and TCA?
Pyruvate Dehydrogenase (PDH)
What does 2,3-bisphophoglycerate help with?
Helps unload oxygen at tissues
4 molecules that pyruvate can form
- Acetyl CoA
- Oxaloacetate (CO2)
- Alanine (Transamination)
- Lactate
General Functions of Lipids (6)
- Structural
- Membranes
- Energy source (lipids yield more energy)
- Energy storage (TGAs)
- Insulation
- Specialized Fx (hormones, cofactors)
What role do membranes play? (4)
- Enable separation
- Selective permeability
- Allow organisms to generate energy
- Separate incompatible metabolic processes
Where does the synthesis of cholesterol take place? (4)
- LIVER
- Adrenal Cortex
- Testes
- Ovaries
What cannot cross a phospholipid bilayer without help?
LARGE, CHARGED, POLAR
What residues make up Maltose?
2 glucose residues
Alpha 1-4
Reducing sugar
What resides make up Sucrose?
Glucose and fructose
Alpha 1,2
Non-reducing sugar
What residues make up Lactose?
Glucose and Galactose
Beta 1,4
Reducing sugar
What makes up Starch?
Amylose (10-30%)
Amylopectin (70-90%)
What is Amylose?
Glucose Homopolysaccharide
Alpha 1,4
Straight chained
What is Amylopectin?
Glucose Homopolysaccharide
Alpha 1,4 and alpha 1,6 (branches)
Branches every 25-30 residues
What is Glycogen?
Glucose Homopolysaccharide
Alpha 1,4 and Alpha 1,6 (branches)
Branches every 8-10 residues
What is Cellulose?
Linear polysaccharide of glucose
Beta 1,4
Resistant to acid hydrolysis and digestive enzymes
What is Chitin?
Homopolysaccharide of N-acetylglucosamine
Beta 1,4
What is Hyaluronic Acid?
Composed of alternating D-glucuronic acid and N-acetyleglucosamine
Beta 1,4 and beta 1,3
Lubricant in synovial fluid
What are Chondroitins?
Alternating disaccharide of Glucoronate and N-acetylgalactosamine
Beta 1,4 and beta 1,3