Metabolic Pathways and Hormonal Regulation
40 Questions
1 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary role of insulin in carbohydrate metabolism?

  • To increase the activity of glycogen synthase (correct)
  • To activate glycogen phosphorylase
  • To decrease glucose uptake by cells
  • To promote gluconeogenesis in the liver

    • How does glucagon affect glycogen metabolism?

  • Increases activity of glycogen synthase and decreases phosphorylase activity
  • Increases gluconeogenesis and suppresses glycolysis (correct)
  • Decreases glycogen synthesis and increases glycogen breakdown (correct)
  • Promotes phosphorylation of glucose-1-phosphate

    • What happens to glycogen phosphorylase when insulin is present?

  • It is phosphorylated and activated
  • It has no effect
  • It becomes activated
  • It is inhibited (correct)

    • What is the effect of glucagon on glycolysis?

    <p>Turns glycolysis off</p> Signup and view all the answers

    Which statement best describes the role of phosphorylation in metabolic control?

    <p>Phosphorylation can either activate or inhibit enzymes depending on the context</p> Signup and view all the answers

    What is the net effect of insulin on glycogen metabolism?

    <p>Promotes glycogen storage and suppresses gluconeogenesis</p> Signup and view all the answers

    What enzyme's activity is directly increased by glucagon?

    <p>Glycogen phosphorylase</p> Signup and view all the answers

    In the presence of glucagon, which metabolic process is promoted in the liver?

    <p>Gluconeogenesis</p> Signup and view all the answers

    What is the effect of glucagon on glycolytic enzyme gene expression?

    <p>Turns OFF glycolytic enzyme gene expression</p> Signup and view all the answers

    How does insulin affect blood glucose levels?

    <p>Decreases blood glucose levels</p> Signup and view all the answers

    What happens to glycogen synthase activity when insulin levels rise?

    <p>Increased activity of glycogen synthase</p> Signup and view all the answers

    What is the role of reversible covalent modification in enzyme activity?

    <p>It modifies enzyme activity temporarily</p> Signup and view all the answers

    Which pathway is inhibited when glycolysis is activated by insulin?

    <p>Gluconeogenesis is suppressed</p> Signup and view all the answers

    What determines the rate of a metabolic pathway?

    <p>The activities of key enzymes</p> Signup and view all the answers

    What best defines the 'rate determining step' in a reaction?

    <p>The slowest step that limits reaction speed</p> Signup and view all the answers

    Which statement is true about glycolysis and gluconeogenesis pathways?

    <p>They are distinct and thermodynamically favorable.</p> Signup and view all the answers

    What is the rate-limiting step in the glycolytic pathway?

    <p>Phosphorylation of fructose-1,6-bisphosphate</p> Signup and view all the answers

    How does allosteric regulation function in metabolic pathways?

    <p>It influences enzyme activity through interaction with substrate molecules.</p> Signup and view all the answers

    What is a characteristic feature of the reaction for the generation of fructose-1,6-bisphosphate?

    <p>It is coupled to the hydrolysis of ATP.</p> Signup and view all the answers

    Which hormone has an effect opposite to that of insulin?

    <p>Glucagon</p> Signup and view all the answers

    Where are the receptors for insulin and glucagon primarily expressed?

    <p>Muscle, liver, and fat cells</p> Signup and view all the answers

    What is the role of hexokinase in the glycolytic pathway?

    <p>To phosphorylate glucose.</p> Signup and view all the answers

    What occurs during gluconeogenesis regarding the glycolytic pathway?

    <p>Different enzymes are utilized to bypass irreversible steps.</p> Signup and view all the answers

    Which statement about metabolic pathways is true regarding key regulatory points?

    <p>They often represent irreversible steps.</p> Signup and view all the answers

    Which of the following best describes Type 1 diabetes?

    <p>Destruction of pancreatic β-cells due to autoimmune processes</p> Signup and view all the answers

    What is a significant risk factor for developing Type 2 diabetes?

    <p>Sedentary lifestyle</p> Signup and view all the answers

    What percentage of diabetes cases worldwide are attributed to Type 2 diabetes?

    <p>90%</p> Signup and view all the answers

    Which ethnic groups are statistically more likely to develop Type 2 diabetes by age 80?

    <p>South Asian and Black African individuals</p> Signup and view all the answers

    What underlies the mechanism of Type 2 diabetes?

    <p>Insulin resistance</p> Signup and view all the answers

    Which is a consequence of untreated diabetes?

    <p>Increased risk of kidney failure</p> Signup and view all the answers

    What role do mouse models play in diabetes research?

    <p>Study and manipulate metabolic pathways</p> Signup and view all the answers

    Which hormone is primarily responsible for signaling satiety?

    <p>Leptin</p> Signup and view all the answers

    What role do fats play during hibernation in animals?

    <p>They serve as a primary source of metabolic fuel.</p> Signup and view all the answers

    How do bears manage to maintain stable insulin and glucose levels throughout the year?

    <p>They can turn on/off insulin resistance when necessary.</p> Signup and view all the answers

    What can cause humans to be predisposed to Type 2 Diabetes (T2D), according to the text?

    <p>Cycles of high calorie intake and obesity.</p> Signup and view all the answers

    What physiological change occurs in migratory birds to support long flights?

    <p>Their flight muscles increase in size significantly.</p> Signup and view all the answers

    What is one proposed reason why studying the metabolic profiles of migratory birds may help humans?

    <p>Birds efficiently mobilize fat deposits during activity.</p> Signup and view all the answers

    What is a key factor in the regulation of metabolic pathways, based on the provided content?

    <p>Irreversible, rate-limiting steps in reactions.</p> Signup and view all the answers

    Which gene is mentioned as being key in glucose homeostasis for bears?

    <p>Akt</p> Signup and view all the answers

    What characteristic of the hummingbird diet supports its high blood sugar levels?

    <p>High sugar diet.</p> Signup and view all the answers

    Study Notes

    Lecture Aims

    • Discuss how reaction direction and speed are controlled in metabolic pathways
    • Appreciate the prevalence and severity of diabetes
    • Provide an example of altered carbohydrate metabolism in another animal species

    Metabolic Pathways

    • Glycolysis and glycogen synthesis are distinct and regulated reciprocally
    • Glycolysis: breaks down glucose
    • Glycogen synthesis: builds glycogen from glucose
    • Glycogen phosphorylase breaks down glycogen to glucose
    • Glycogen synthase builds glycogen from glucose

    Phosphorylation Control

    • Key metabolic control process
    • Enzymes are phosphorylated/dephosphorylated in response to insulin or glucagon
    • Glycogen synthase/glycogen phosphorylase are controlled in this way
    • Insulin turns on glycogen synthase and turns off glycogen phosphorylase.
    • Glucagon turns off glycogen synthase and turns on glycogen phosphorylase

    Insulin and Glucagon

    • Both are polypeptide hormones released from the pancreas
    • Both bind specific receptors in muscle, liver, and fat cells but have opposing effects
    • Insulin promotes glucose storage
    • Glucagon promotes glucose release

    Glucose Homeostasis

    • Homeostasis is the maintenance of a stable state in the blood
    • Insulin and glucagon oppose each other to regulate blood glucose
    • Blood glucose levels are maintained around 90 mg/100mL

    Diabetes

    • Diabetes is a growing health concern
    • Globally, there are almost 415 million sufferers with projected figures doubling by 2050
    • 9% of global deaths can be attributed to this
    • A risk factor for other diseases including COVID-19
    • Two main types:
      • Type 1: Caused by B-cell destruction (autoimmune or idiopathic); insulin not produced
      • Type 2: Results from insulin resistance and B-cell dysfunction; typically arises from lifestyle factors

    Genetics and Ethnicity

    • Half of South Asian, Black African, and African-Caribbean people in the UK will develop type-2 diabetes by age 80
    • South Asian men are diagnosed at a younger age
    • Significant risk of complications compared to other ethnic groups

    Mouse Models

    • Used to study diabetes pathways
    • Often involve obese mice with single gene mutations such as leptin
    • Leptin signals satiety, mutations cause hyperphagia and hyperglycaemia
    • Useful for drug testing and pathway manipulation

    Hibernation

    • Hibernating animals store large amounts of fat each autumn
    • Fats serve as metabolic fuel throughout the winter
    • Fats produce metabolic water upon breakdown
    • Hibernation is influenced by daylight hours

    Migratory Birds

    • Some birds fly huge distances during migration
    • They accumulate large amounts of fat prior to migration
    • Accumulations of this fat is efficienty mobilized during migrations
    • Hummingbirds, in particular, have a high-sugar diet and high blood sugars

    Rate Limiting Steps

    • The rate-limiting steps in glycolysis are the phosphorylation of glucose by hexokinase (or glucokinase) and the phosphorylation of fructose-6-phosphate to form fructose 1,6-bisphosphate by phosphofructokinase-1
    • These steps are crucial regulation points, as they are essentially irreversible.

    General Themes

    • Biosynthetic and degradative pathways are usually distinct. This means they are typically thermodynamically favourable
    • The rates of metabolic pathways are determined by the activities of key enzymes and not by mass action
    • Specific hormones induce specific events in cells/tissues
    • Allosteric modulation of enzyme activity is common
    • Metabolic pathways that need to be reversed often have a rate-limiting step to control the path

    Enzyme Action

    • Enzymes lower activation energy for reactions
    • Rate limiting steps are one of the slowest steps of a chemical reaction

    Revision Questions

    • Why does phosphorylation cause a change in enzyme activity?

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Systems, Cells, Molecules and Genes Lecture 2 PDF

    Description

    Explore the intricate controls of metabolic pathways focusing on glycolysis and glycogen synthesis. Understand the significant roles of insulin and glucagon in regulating these pathways and their impact on conditions like diabetes. This quiz also enables insights into altered carbohydrate metabolism across different animal species.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser