cell metabolism

Chapter 4: Cell Metabolism

Overview

  • This chapter focuses on cell metabolism, detailing how cells utilize raw materials (food) to function through a series of chemical reactions.

  • Key terms include metabolism, anabolism, and catabolism.

Lesson Objectives

  1. Define metabolism, anabolism, and catabolism

    • Metabolism: Series of chemical reactions essential for cellular function.

    • Anabolism: Builds larger, complex substances from simpler ones; requires energy (ATP).

    • Catabolism: Breaks down complex substances into simpler ones; releases energy that is captured as ATP.

  2. Use of Carbohydrates in the Body

    • Differentiation between anaerobic and aerobic metabolism of carbohydrates.

  3. Use of Fats in the Body

  4. Use of Proteins in the Body

  5. Roles of DNA and RNA in Protein Synthesis

    • Structure of a nucleotide.

    • Steps involved in protein synthesis.

Metabolism

  • Cells require raw materials to function effectively, akin to a factory.

  • Raw materials:

    • Carbohydrates

    • Proteins

    • Fats

  • Inside cells, raw materials undergo thousands of chemical reactions, collectively termed metabolism.

Details of Metabolism

Components of Metabolism

  • ATP (Adenosine Triphosphate): Energy currency of the cell used to power various metabolic processes.

  • Amino Acids and Proteins:

    • Amino acids are vital for creating proteins and are their basic building blocks.

Carbohydrates

Types of Carbohydrates

  • Monosaccharides: Simple sugars (e.g., glucose, fructose).

  • Disaccharides: Double sugars (e.g., sucrose, maltose).

  • Polysaccharides: Complex carbohydrates (e.g., starches, glycogen).

Functions of Carbohydrates

  • Provide energy; glucose is a primary source.

  • Glycogen: Key role in regulating blood sugar levels; can be converted back to glucose as needed.

  • Cellulose: Offers dietary fiber, aiding in digestion despite being indigestible by humans.

Breakdown of Glucose

Catabolic Processes

  1. Anaerobic Catabolism:

    • Occurs without oxygen.

    • Glycolysis transforms glucose into pyruvic acid, leading to lactic acid formation.

    • Produces limited ATP.

  2. Aerobic Catabolism:

    • Occurs with oxygen present.

    • Converts glucose into carbon dioxide and water, generating significant ATP.

    • Enzymes in the Kreb's cycle and electron transport chain are involved.

Glucose Utilization

  • Glucose Functions:

    1. Burned immediately for energy.

    2. Stored as glycogen for later energy use.

    3. Converted into fat for long-term storage.

Regulation of Blood Sugar

  • Glycogen's Role: Maintains normal blood glucose levels by converting glycogen back to glucose when needed.

Lipids (Fats)

Structure and Types of Lipids

  • Lipids include triglycerides, phospholipids, steroids, and cholesterol.

  • Commonly consumed in the diet and synthesized by the liver.

Functions of Lipids

  • Provide energy and form cellular structures.

  • Can be harmful due to long-term energy storage leading to conditions like heart disease—cholesterol can form plaques in blood vessels.

Cholesterol Profiles

  • VLDL (Very Low-Density Lipoprotein): Carries triglycerides.

  • LDL (Low-Density Lipoprotein): Transports cholesterol to tissues.

  • HDL (High-Density Lipoprotein): Carries cholesterol back to the liver for excretion.

Proteins

Abundance and Functions

  • Proteins are critical to various body functions, including enzymes, hormones, muscle contraction, immune response, and structural roles in cells.

Building Blocks of Proteins

  • Composed of amino acids, which link via peptide bonds to form proteins.

Amino Acids

Categories:

  • Essential Amino Acids: Must be obtained from the diet.

  • Nonessential Amino Acids: Can be synthesized by the body. Both types are crucial for health.

Uses of Proteins

  • Functions include hormone and enzyme synthesis, energy production, and muscle structure maintenance.

Nitrogen Elimination

  • Breakdown of amino acids generates nitrogen, primarily as ammonia (NH3).

  • The liver converts ammonia into urea, which is then excreted by the kidneys.

Protein Synthesis & DNA

Role of DNA

  • DNA encodes the arrangement of amino acids, determining protein structure.

  • Structure consists of nucleotides made of sugar, phosphate, and nitrogen bases.

Base Pairing

  • DNA strands pair bases (A with T; C with G) and form the genetic code for protein synthesis.

Coping the Genetic Code

  • RNA assists in copying DNA and translates the code into proteins at ribosomes.

  • Transcription: mRNA copies DNA code.

  • Translation: tRNA brings amino acids to the ribosome according to mRNA sequence.

Summary of Protein Synthesis Steps

  1. Transcription of DNA to mRNA in the nucleus.

  2. mRNA moves to ribosomes in the cytoplasm.

  3. tRNA pairs with mRNA, aligning amino acids for protein assembly.

  4. Peptide bonds form between amino acids, culminating in protein completion.

Review Questions

  • Consider the differences between DNA and RNA.

  • Reflect on the roles of mRNA and tRNA in protein synthesis.

  • Distinguish between transcription and translation processes.