Biomolecules: Carbohydrates, Proteins, Lipids

Questions and Answers

What is the hydrogen-oxygen atom ratio typically found in carbohydrates?

2:1 (correct)

1:2

2:2

1:1

Which of the following monosaccharides is characterized as a ketose?

Glucose

Galactose

Fructose (correct)

Mannose

Which carbohydrate serves as the main source of energy in humans?

Glucose (correct)

Ribose

Galactose

Fructose

What type of glycosidic bond forms between two monosaccharides in disaccharides?

Covalent bond Signup and view all the answers

What type of sugar is lactose composed of?

Glucose and galactose Signup and view all the answers

What distinguishes oligosaccharides from disaccharides?

They yield 3 to 10 monosaccharides on hydrolysis. Signup and view all the answers

Which polysaccharide is primarily an energy storage form found in plants?

Starch Signup and view all the answers

Chitin is primarily found in which structure?

Fungal cell walls Signup and view all the answers

Ribose plays a crucial role in the synthesis of which molecule?

Ribonucleic acid (RNA) Signup and view all the answers

What is one of the primary roles of cellulose in plants?

Providing structural support Signup and view all the answers

Which of the following sugars is a component of lactose?

Galactose Signup and view all the answers

Which of the following carbohydrates cannot be hydrolyzed into simpler sugars?

Monosaccharides Signup and view all the answers

What is the empirical formula represented by carbohydrates?

(CH2O)n Signup and view all the answers

Mannose plays a crucial role in which of the following?

Energy production and storage Signup and view all the answers

What is the primary function of heparin in the human body?

To prevent blood clotting Signup and view all the answers

Which component is primarily responsible for the stability of the α-helix structure in proteins?

Hydrogen bonds Signup and view all the answers

What type of amino acids cannot be synthesized by the body and must be obtained from the diet?

Essential amino acids Signup and view all the answers

What defines the quaternary structure of a protein?

The arrangement of multiple polypeptide chains Signup and view all the answers

Which of the following amino acids has a negatively charged side chain at physiological pH?

Aspartic acid Signup and view all the answers

Which structure represents the overall three-dimensional arrangement of a single polypeptide chain?

Tertiary structure Signup and view all the answers

What is the main reason for protein denaturation?

Altered ionic conditions Signup and view all the answers

Which amino acids are categorized as having non-polar side chains?

Alanine, valine, and isoleucine Signup and view all the answers

What role do chaperone proteins play in the cell?

Assisting in protein folding Signup and view all the answers

What characterizes saturated fatty acids compared to unsaturated fatty acids?

Have hydrocarbon chains with no double bonds Signup and view all the answers

Which function of proteins involves catalyzing biochemical reactions?

Enzymatic Signup and view all the answers

Which of the following statements regarding fibrous and globular proteins is true?

Fibrous proteins serve primarily structural roles. Signup and view all the answers

What role does cholesterol play in cell membranes?

It regulates membrane fluidity during temperature changes Signup and view all the answers

What is the main structural feature of secondary protein structures?

Local folding patterns such as α-helices and β-sheets Signup and view all the answers

Which statement accurately describes triglycerides?

Can be hydrolyzed to produce glycerol and fatty acids Signup and view all the answers

What distinguishes essential amino acids from non-essential amino acids?

Non-essential amino acids are synthesized by the body. Signup and view all the answers

What distinguishes glycolipids in membrane function?

They serve as recognition sites for cell-cell interaction. Signup and view all the answers

Which enzyme is responsible for catalyzing the hydrolysis of proteins?

Trypsin Signup and view all the answers

Which property is attributed to phospholipids?

They contain a hydrophilic head and hydrophobic tails Signup and view all the answers

Which type of lipid serves as an important signaling molecule?

Steroids like cholesterol Signup and view all the answers

What is the primary structural characteristic of trans-fatty acids?

Hydrogens on opposite sides of the carbon chain Signup and view all the answers

What is an effect of rancidity in fats and oils?

Development of a disagreeable odor Signup and view all the answers

How do omega-3 fatty acids contribute to cardiovascular health?

Reduce inflammation in the body Signup and view all the answers

What are derived lipids primarily characterized by?

They are obtained after hydrolysis of other lipids Signup and view all the answers

What effect does hydrogenation have on unsaturated fats?

Converts them into saturated fats Signup and view all the answers

How are glycerophospholipids classified?

By containing a glycerol backbone Signup and view all the answers

Which statement about phospholipids is accurate?

Phospholipids contribute to membrane stability and fluidity Signup and view all the answers

Study Notes

Carbohydrates

Composed of carbon, hydrogen, and oxygen, typically with a 2:1 hydrogen-oxygen ratio, also known as saccharides.
Most abundant organic compounds in living organisms.
Empirical formula expressed as (CH2O)n or CnH2nOn, referred to as "hydrates of carbon."
Originates from photosynthesis, a light-driven process that reduces carbon dioxide.
Serves as a major energy source for both plants and animals.

Monosaccharides

Simplest form of carbohydrates, cannot be further hydrolyzed.
Primary building blocks for disaccharides and polysaccharides, known as simple sugars.
Types include:
- Aldose: monosaccharides with an aldehyde group.
- Ketose: monosaccharides with a ketone group.
Common examples include glucose, mannose, galactose (all C6H12O6 isomers), and fructose (structural isomer with a ketone group).
Ribose (C5H10O5) and deoxyribose (C5H10O4) are aldopentoses vital for RNA and DNA structure, respectively.

Functions of Monosaccharides

Glucose: Primary energy source in humans.
Galactose: Important for cellular metabolism, derived from lactose.
Mannose: Required for mucoproteins and glycoproteins functionality.
Fructose: Found in fruits; metabolized by the liver into glucose.
Ribose: Component of ribonucleotides, essential for gene functions.
Deoxyribose: Forms the sugar-phosphate backbone in DNA.

Disaccharides

Composed of two monosaccharide units connected by a glycosidic bond, formed via dehydration synthesis.
Examples include:
- Maltose: two glucose molecules.
- Sucrose: glucose plus fructose.
- Lactose: glucose plus galactose.
Sources:
- Maltose: found in various fruits.
- Sucrose: prevalent in sugarcane and sugar beets.
- Lactose: naturally found in milk.

Functions of Disaccharides

Maltose: Important in starch and glycogen digestion.
Sucrose: Provides energy and carbon for plant growth.
Lactose: Energy source in animals from milk.

Oligosaccharides

Comprising 3 to 10 monosaccharide units through N- or O-glycosidic bonds, forming glycolipids or glycoproteins.
N-linked oligosaccharides: Attached to asparagine.
O-linked oligosaccharides: Attached to threonine or serine.

Functions of Oligosaccharides

Glycoproteins serve as receptors, adhesion molecules, and immunoglobulins.
Glycolipids are crucial for cell recognition and modulating receptor proteins.

Polysaccharides

Chains of over 10 monosaccharides linked through glycosidic bonds, known as glycans.
Generally non-sweet and poorly soluble in water.
Key types include starch, glycogen, and cellulose.

Functions of Polysaccharides

Starch: Energy storage in plants, digestible by humans.
Glycogen: Energy storage in animal liver.
Cellulose: Structural role in plant cell walls; acts as dietary fiber for gut health.
Additional polysaccharides like chitin (fungal cell walls) and peptidoglycan (bacterial cell walls) also play crucial roles.### Cell Wall Components
Provides strength to the bacterial cell wall and aids in binary fission during reproduction.
Agarose is a structural component in the cell wall of marine algae.
Heparin serves as a natural anticoagulant, preventing blood clotting.
Chondroitin is crucial for cartilage, offering resistance to compression.

Carbohydrates Overview

Monosaccharides: Single sugar molecules like glucose, fructose, and galactose.
Disaccharides: Two sugar molecules, examples include maltose, cellobiose, lactose, and sucrose.
Oligosaccharides: Composed of 3 to 10 sugar molecules.
Polysaccharides: More than 10 sugar molecules, with examples including starch and glycogen.

Amino Acids

Building blocks of proteins, consisting of carbon, hydrogen, and nitrogen.
Structure includes an α-carbon, carboxyl group, amino group, and unique R-group (side chain).
Two forms of amino acids exist: L and D configurations; glycine has a simple R-group as a hydrogen atom.
There are 20 amino acids essential for protein synthesis.

Essential vs. Non-Essential Amino Acids

Essential amino acids: Must be obtained from diet as the body cannot synthesize them; important for muscle repair and neurotransmitter production.
Non-essential amino acids: Can be synthesized by the body and play roles in brain function and blood cell production.

Classification of Amino Acids

Non-polar (hydrophobic): Includes alanine, valine, leucine, glycine, isoleucine, methionine, tryptophan, phenylalanine, and proline.
Polar (uncharged): Includes serine, threonine, cysteine, tyrosine, asparagine, and glutamine.
Positively charged (basic): Includes lysine, arginine, and histidine.
Negatively charged (acidic): Includes aspartic acid and glutamic acid.

Proteins Definition and Peptide Bonds

Proteins are macromolecules formed by chains of amino acids linked via peptide bonds.
Peptide bonds are formed through dehydration-condensation reactions between amino and carboxyl groups, catalyzed by ribosomes.

Protein Structure

Primary structure: Linear sequence of amino acids in a polypeptide chain determined by DNA coding.
Secondary structure: Local folding patterns like α-helices and β-strands, stabilized by hydrogen bonds.
Tertiary structure: Overall 3D folding of the polypeptide chains influenced by various forces including hydrogen bonds and disulfide linkages.
Quaternary structure: Arrangement of multiple folded protein subunits, seen in proteins like hemoglobin.

Denaturation of Proteins

Denaturation involves loss of secondary, tertiary, and quaternary structures due to factors like temperature and pH changes; can be reversible or irreversible.

Protein Folding

Proper folding is essential for protein functionality, guided by interactions like hydrophobic forces and hydrogen bonds.
Misfolding can lead to diseases such as Alzheimer's and Parkinson's.
Chaperones assist in proper protein folding; the ubiquitin-proteasome system degrades damaged proteins, and autophagy removes dysfunctional components.

Functions of Proteins

Structural proteins (e.g., collagen): Provide support and shape.
Contractile proteins (e.g., myosin, actin): Facilitate muscle contraction.
Transport proteins (e.g., hemoglobin): Carry essential substances in the body.
Storage proteins (e.g., casein, ferritin): Store nutrients and minerals.
Hormonal proteins (e.g., insulin): Regulate metabolic processes.
Enzymatic proteins (e.g., trypsin, amylase): Catalyze biochemical reactions.
Protective proteins (e.g., immunoglobulins): Defend against foreign substances.

Summary of Protein Structure

Primary Structure: Linear amino acid sequence.
Secondary Structure: Local folding patterns (α-helices, β-sheets).
Tertiary Structure: Overall 3D shape, critical for function.
Quaternary Structure: Arrangement of multiple polypeptide chains.### Introduction to Lipids
Organic compounds made of hydrogen, carbon, and oxygen that are essential for the structure and function of living cells.
Comprised mainly of glycerol (three carbon atoms, hydroxyl group) and fatty acids (acid group and hydrocarbon chain, denoted as 'R').
Fatty acids can be classified as saturated (no double bonds) or unsaturated (one or more double bonds).

Physical Properties of Lipids

Soluble in non-polar solvents (e.g., acetone, chloroform, alcohol) and insoluble in water.
Hydrophobic nature contributes to their greasy texture.
Exist as energy-rich organic molecules in liquid or solid form at room temperature.
Storage form in adipose tissues.

Chemical Properties of Lipids

Hydrolysis of triglycerides produces glycerol and three fatty acids.
Saponification reacts triglycerides with a strong base, forming fatty acid metal salts for soap-making.
Hydrogenation combines unsaturated fats with hydrogen, converting them to saturated fats.
Halogenation involves unsaturated fatty acids binding halogens, leading to de-colorization.
Rancidity occurs due to oxidation and hydrolysis, causing unpleasant odors in fats and oils.

Classification of Lipids

Simple Lipids: Fatty acids forming ester bonds with alcohol (e.g., fats and oils, waxes).
Complex Lipids: Fatty acids attached to other molecules; includes phospholipids (with a hydrophilic "head" and two hydrophobic "tails") and glycolipids (lipids with carbohydrates).
Derived Lipids: Formed from hydrolysis of simple and complex lipids (e.g., steroids, ketone bodies).

Phospholipids

Glycerophospholipids and sphingolipids are the two types that make up biological membranes.
Form bilayers that contribute to cell membrane semi-permeability, with hydrophilic heads facing outward and hydrophobic tails inward.

Glycolipids

Composed of glycerol or sphingosine, fatty acids, and carbohydrates.
Found in cell membranes, they play roles in cell recognition, communication, and signal transduction.

Functions of Phospholipids and Glycolipids

Structural role in membranes, influencing membrane fluidity and stability.
Involved in cell signaling, energy storage, and trafficking within cells.
Contribute to immune responses and interaction with growth factor receptors.

Steroids

Lipids with fused ring structures, key components of cell membranes that modulate membrane fluidity.
Cholesterol serves as a structural element in membranes and a precursor for steroid hormones (e.g., vitamin D).

Fatty Acids

Carboxylic acids with aliphatic chains, classified as saturated or unsaturated.
Saturated fatty acids are linked to higher cholesterol levels and a risk of heart disease.
Unsaturated fatty acids (monounsaturated and polyunsaturated) have health benefits including anti-inflammatory effects.

Polyunsaturated Fatty Acids (PUFAs)

Omega-3 fatty acids: Essential for metabolism and found in algae and fish (e.g., ALA, EPA, DHA).
Omega-6 fatty acids: Vital for skin, bone health, and metabolism, found in nuts and vegetable oils.

Cis- and Trans-Fatty Acids

Cis-fatty acids: Found naturally in foods, generally beneficial.
Trans-fatty acids: Present in processed foods, linked to adverse health effects, including increased heart disease risk.

Functions of Lipids

Serve as energy storage molecules, structural components of membranes, and metabolic regulators (e.g., steroid hormones).
Act as insulators, protect organs, aid in the absorption of fat-soluble vitamins, and function in cell signaling.

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Description

This quiz focuses on the key biomolecules essential for life: carbohydrates, proteins, and lipids. Students will explore their structures, functions, and significance in biological systems. Perfect for those studying basic biochemistry and molecular biology.