Biology Chapter 1: Cell Functions and Structures

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Questions and Answers

What is the smallest unit capable of performing life functions?

Tissue

Organism

Cell (correct)

Organ

Which of the following is NOT a primary function of a cell?

Generating energy

Transport nutrients (correct)

Synthesize proteins

Divide into two cells

Animal cells obtain energy from which source?

Chemical bonds in food molecules (correct)

Photosynthesis

Solar energy

Cellular respiration

Which statement accurately describes a characteristic of eukaryotic cells?

They are generally larger than prokaryotic cells. Signup and view all the answers

What primarily distinguishes living matter from non-living matter?

The ability to reproduce Signup and view all the answers

What is the aqueous solution found inside cells primarily composed of?

Water Signup and view all the answers

Which component is NOT essential for the functioning of proteins in a cell?

Nutrient absorption Signup and view all the answers

Which of the following correctly describes plant cells' source of energy?

Energy from sunlight Signup and view all the answers

Cells' ability to generate copies of themselves is primarily through which process?

Mitosis Signup and view all the answers

What is the primary function of functional proteins in the cell?

To act as catalysts for specific reactions Signup and view all the answers

Which of the following is TRUE regarding prokaryotic cells?

Their DNA is located in a compartment called nucleoid. Signup and view all the answers

Which molecule is known as a carrier of energy in the cell?

Adenosine triphosphate (ATP) Signup and view all the answers

What structure is characteristic of eukaryotic cells?

Membrane-enclosed organelles Signup and view all the answers

What distinguishes Gram-positive bacteria from Gram-negative bacteria?

Gram-positive bacteria retain the Gram dye after staining. Signup and view all the answers

Which types of cells lack a cell wall?

Animal cells Signup and view all the answers

What process do cells use to make identical copies of themselves?

DNA replication Signup and view all the answers

What is the primary function of mitochondria in cells?

Energy production Signup and view all the answers

Cells generate chemical energy using which of the following?

Glucose and fatty acids Signup and view all the answers

Which type of molecule does DNA encode the instructions for synthesizing?

Proteins Signup and view all the answers

What type of sequence does mRNA guide during protein synthesis?

Amino acid sequence Signup and view all the answers

What provides the hereditary information in cells?

DNA Signup and view all the answers

What are the building blocks of DNA?

Nucleotides Signup and view all the answers

In DNA replication, what happens to the strands of the DNA double helix?

They are pulled apart and used as templates Signup and view all the answers

Which of the following nitrogenous bases is NOT part of DNA nucleotides?

Uracil Signup and view all the answers

What is the role of DNA in a cell?

Store and transmit genetic information Signup and view all the answers

What percentage of cells, apart from fat cells, typically consists of water?

70-85% Signup and view all the answers

What type of molecules are easily dissolved in water due to their ability to form hydrogen bonds?

Hydrophilic molecules Signup and view all the answers

Which of the following accurately defines a hydrophobic molecule?

It is non-polar or uncharged. Signup and view all the answers

Which type of ion is considered a cation?

Mg2+ Signup and view all the answers

What is the basic structural unit of carbohydrates?

Monosaccharides Signup and view all the answers

How are disaccharides formed from monosaccharides?

By condensation reactions Signup and view all the answers

What function does glucose primarily serve for cells?

Energy source Signup and view all the answers

What is glycogen and where is it predominantly stored?

A polysaccharide stored in the liver and skeletal muscle Signup and view all the answers

What allows water molecules to bond together?

Hydrogen bonds Signup and view all the answers

Which group of molecules cannot form hydrogen bonds with water?

Hydrophobic molecules Signup and view all the answers

What characteristic of fatty acids makes them hydrophobic?

Long hydrocarbon chains Signup and view all the answers

What role do triglycerides play in the body?

Acting as a source of energy-rich nutrients Signup and view all the answers

Which of the following correctly describes phospholipids?

Essential for the formation of the cell membrane Signup and view all the answers

How are proteins synthesized from amino acids?

Through the joining of amino acids via peptide bonds Signup and view all the answers

What is a common feature of lipids?

Insoluble in water but soluble in non-polar solvents Signup and view all the answers

Which components make up a triglyceride?

Three fatty acids and one glycerol molecule Signup and view all the answers

What distinguishes one amino acid from another?

The specific side chain attached to the α-carbon Signup and view all the answers

What percentage of the cell's mass is typically constituted by phospholipids and cholesterol combined?

2% Signup and view all the answers

Which of the following is NOT a function of lipids?

Acting as enzymes Signup and view all the answers

What type of proteins are primarily responsible for maintaining the structural integrity of cells?

Structural proteins Signup and view all the answers

Study Notes

Cellular and Molecular Biology MD105

Course taught by Dr. C. Michaeloudes, European University Cyprus, School of Medicine
Topics covered include cell structure and function, lecture objectives, what is a cell, the main functions of a cell, cells generating energy by breaking down nutrients, instructions for all cell functions stored in DNA, cells making identical copies, chemical composition of cells, chemical constituents of cells, water, hydrophilic molecules, hydrophobic molecules, ions, sugars, fatty acids, lipids, phospholipids and cholesterol, triglycerides, amino acids, proteins, structural proteins, functional proteins, nucleotides, and nucleic acids.

Lecture Objectives

Understand what a cell is and its basic functions
Know the main chemical components of cells
Recognize the diversity of cell morphology and function
Learn the key differences between prokaryotic and eukaryotic cells

What is a cell?

Smallest unit capable of performing life functions
Membrane-enclosed units filled with a concentrated aqueous solution containing numerous chemicals
Capable of generating copies by growing and dividing in two
Fundamental units of life in all living organisms

The Main Functions of a Cell

Generate energy: Essential for all cell activities; animals obtain energy from food molecules, plants from sunlight
Synthesize proteins: Proteins perform diverse roles in cells (e.g., structural components, enzymes, signaling molecules)
Make more cells: Crucial for growth and repair.

Cells Generating Energy by Breaking Down Nutrients

Cells break down nutrients (glucose/fatty acids) using oxygen to produce chemical energy in the form of ATP
This process occurs in mitochondria

The Instructions for all Cell Functions are Stored in DNA

The instructions for all cell functions are stored in the DNA
Cells need to store their hereditary information (like computers store information on a hard drive or cloud)

Cells Making Identical Copies of Themselves

Cells make copies of themselves that have exactly the same DNA.
To do this, they duplicate their DNA and then divide in two.
Daughter cells can further divide, producing more cells

Cells Can Accurately Duplicate Their DNA

Cells create accurate copies of their DNA through DNA replication.
During this process, the two strands of the DNA helix are pulled apart, used as templates to synthesize complementary strands.

The Chemical Composition of Cells

Cells consist of six main components: water, ions, amino acids, sugars, fatty acids, and nucleotides.

Chemical Constituents of Cells

Although cells vary in morphology and function, they use the same chemicals for chemical reactions.

Water

Most cells (except fat cells) are 70-85% water; crucial for reactions
Water molecules are polar due to uneven electron distribution.
Water molecules are held together by hydrogen bonds.
Polar and charged molecules dissolve in water via hydrogen bonds.
Water is the solvent for most reactions in a cell.

Hydrophilic Molecules

Hydrophilic molecules readily dissolve in water ("water-loving").
Polar or charged molecules.
Form hydrogen bonds with water. (Examples include hydroxyl groups, carbonyl groups, carboxyl groups, and amino groups)

Hydrophobic Molecules

Hydrophobic molecules do not dissolve in water ("water-fearing").
Non-polar/uncharged.
Do not form hydrogen bonds with water. (Examples include hydrocarbon chains and ring structures)

Ions

Ions are atoms with an electric charge (either negative (anion) or positive (cation)).
Key inorganic chemicals (e.g., potassium, calcium) for chemical reactions.
Essential for cellular control mechanisms and transmitting electrical signals in nerves and muscles.

Sugars

Simplest forms are monosaccharides (e.g., glucose)
Made of carbon, hydrogen, and oxygen (CH₂O)n , n = 3, 4, 5, or 6
Monosaccharides can link via glycosidic bonds to form larger carbohydrates.
Disaccharides (two monosaccharides); Polysaccharides (thousands of monosaccharides)
Glucose is a vital energy source for cells; broken down into smaller molecules via metabolic reactions to release ATP energy; stored as glycogen for later energy use.

Fatty Acids

Organic molecules containing a hydrocarbon chain (hydrophobic) and a carboxyl group (hydrophilic).
Broken down in mitochondria to produce energy.
Fatty acids link to other molecules to form complex lipid molecules, including triglycerides.

Lipids

Complex molecules insoluble in water but soluble in non-polar solvents.
Contain long hydrocarbon chains or multiple rings.
Important lipids include phospholipids and cholesterol (2% of cell mass).
Phospholipids form cell membranes and intracellular membranes around organelles; Triglycerides are the body’s main energy stores.

Phospholipids and Cholesterol

Main components of cell membranes
Phospholipids have a hydrophilic head and hydrophobic tails.
Cholesterol is also a component of cell membranes.

Triglycerides

Made of glycerol and three fatty acids.
Act as energy stores for cells.

Amino Acids

Small organic molecules with a carboxyl group (-COOH) and an amino group (-NH₂) attached to a central α-carbon.
The α-carbon also carries a side chain that distinguishes one amino acid from another.

Proteins

Polymers of amino acids linked by peptide bonds.
Folded into complex 3D structures for specific functions.
Structural proteins form the cytoskeleton and extra-cellular components.
Functional proteins act as enzymes, speeding up chemical reactions within cells.

Structural Proteins

Long chains of proteins that form filaments (e.g., actin, intermediate filaments, microtubules).
Form the cytoskeleton, providing structural support and enabling cell movement.
Present in connective tissues (e.g., tendons, ligaments).

Functional Proteins

Primarily enzymes that catalyze diverse specific reactions within cells.
Bind to specific molecules (ligands) to convert them into different products, without changing the enzyme.

Nucleotides

Consist of a five-carbon sugar (ribose or deoxyribose), a nitrogen-containing base, and one or more phosphate groups.
Five different bases: adenine, thymine, uracil, cytosine, guanine.
Building blocks of nucleic acids (DNA and RNA).

Nucleic Acids

Polymers of nucleotides linked via phosphodiester bonds.
DNA (deoxyribose) and RNA (ribose)
Store and retrieve biological information.

Adenosine Triphosphate (ATP)

A molecule that carries energy within cells.
Stored in high-energy phosphate bonds; breaking the bonds releases energy for cellular processes (e.g., muscle contraction, nerve firing).

Small Organic Molecules

Building blocks of larger macromolecules.
Examples include sugars, fatty acids, amino acids, and nucleotides, which can assemble to form larger molecules such as polysaccharides, lipids, proteins, and nucleic acids.

The Diversity of Cells

The human body comprises 30 trillion cells, with over 200 cell types, distinct morphologies, and functions.
Different cell types exhibit varying lifespan.

Prokaryotic vs. Eukaryotic Cells

Prokaryotic cells (e.g., bacteria, archaea) lack a nucleus; DNA is in the nucleoid.
Eukaryotic cells (e.g., animal cells, plant cells, fungi) possess a nucleus with linear DNA.
Major differences in size, and the presence/absence of membrane-bound organelles.

Prokaryotic Cell Structure

Small size (0.2-2 µm).
No nucleus, DNA in nucleoid region.
No membrane-bound organelles.
Cell wall (protective coat).
Plasma membrane.
Circular DNA.
Divide quickly (e.g., every 20 minutes).
Live as individual cells or communities.
Can utilize diverse energy sources

Bacteria

Traditionally classified by shape (spherical, rod-shaped, spiral).
Classified as Gram-positive or Gram-negative based on cell wall structure.
Plays a crucial part of the human microbiome.

Eukaryotic Cell Structure

Larger size (10-100 µm).
Contain membrane-bound organelles.
No cell wall (except in plants).
DNA enclosed within a nucleus.
Linear DNA - multiple strands.
Multicellular organisms (e.g., animals, plants, fungi) are composed of diverse cell types.

Cell Sizes

Different cells have varying sizes (e.g., viruses, bacteria, eukaryotic cells).
Different microscopy techniques are used to visualize cells of varying sizes.

Human Cell Diversity

30 trillion cells in the human body with diverse morphology and functions.
Different human cell types have variable life spans.

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Description

Test your knowledge on the fundamental concepts of cellular biology with this quiz covering the smallest units of life. Explore key functions, energy sources, and differences between prokaryotic and eukaryotic cells. Perfect for students studying cell biology or preparing for exams.