Introduction to Cell Biology

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Questions and Answers

What is the primary function of cells related to energy?

To assist in reproduction

To form tissues

To generate energy (correct)

To store nutrients

Which of the following is NOT one of the main jobs of a cell?

To transport oxygen (correct)

To generate energy

To synthesize proteins

To divide for growth

What characteristic distinguishes prokaryotic cells from eukaryotic cells?

Size of the cell

Presence of a nucleus (correct)

Type of energy source

Ability to reproduce

What type of cells obtain energy primarily from sunlight?

Plant cells Signup and view all the answers

What does a cell contain that is crucial for performing life functions?

A concentrated aqueous solution Signup and view all the answers

What process do cells undergo to make copies of themselves?

Mitosis Signup and view all the answers

What is the primary function of mitochondria in cells?

Generate chemical energy Signup and view all the answers

What molecules are synthesized from the DNA sequence during transcription?

mRNA Signup and view all the answers

Which component of DNA is responsible for encoding genetic information?

Nitrogenous bases Signup and view all the answers

How do daughter cells compare to parent cells after cell division?

They are genetically identical Signup and view all the answers

What process converts mRNA sequences into proteins?

Translation Signup and view all the answers

Which of the following is NOT a nitrogenous base found in DNA?

Uracil Signup and view all the answers

What role do template strands play during DNA replication?

They act as models for building new strands. Signup and view all the answers

What are the six main substances that compose all cells primarily used for?

Chemical reactions Signup and view all the answers

What is the end product of glucose and fatty acids breakdown in cells?

Adenosine triphosphate (ATP) Signup and view all the answers

What is the primary characteristic of water that allows it to form hydrogen bonds?

Water is polar, with an uneven distribution of electrons. Signup and view all the answers

What term describes molecules that can easily dissolve in water?

Hydrophilic Signup and view all the answers

What is the simplest form of sugars known as?

Monosaccharides Signup and view all the answers

Which type of molecule does not dissolve in water?

Hydrophobic molecules Signup and view all the answers

Which of the following ions is NOT an example of a cation?

Cl- Signup and view all the answers

What is the main storage form of glucose in the body?

Glycogen Signup and view all the answers

How are monosaccharides linked together to form larger carbohydrates?

By dehydration synthesis Signup and view all the answers

What kind of bonds hold water molecules together?

Hydrogen bonds Signup and view all the answers

Which of the following groups is known to form hydrogen bonds with water?

Charged groups Signup and view all the answers

Which is a characteristic of hydrophobic molecules?

They do not dissolve in water. Signup and view all the answers

Which statement accurately describes fatty acids?

They consist of a carboxyl group linked to a long hydrocarbon chain. Signup and view all the answers

What is the primary role of triglycerides in the cell?

They act as energy stores for the cell. Signup and view all the answers

Which lipids are identified as integral components of cell membranes?

Cholesterol and phospholipids Signup and view all the answers

What defines the structure of amino acids?

They consist of an amino group, carboxyl group, and a side chain attached to a central carbon. Signup and view all the answers

What is a polypeptide chain?

It is a sequence of amino acids linked by peptide bonds. Signup and view all the answers

Which of the following statements about lipids is false?

Lipids do not play any role in cell membrane formation. Signup and view all the answers

Which type of protein serves structural functions within a cell?

Structural proteins Signup and view all the answers

How are fatty acids synthesized in relation to triglycerides?

They are attached to glycerol molecules to form triglycerides. Signup and view all the answers

What role do functional proteins mainly play in the cell?

Act as enzymes to catalyze reactions Signup and view all the answers

What are nucleotides composed of?

A nitrogen-containing base, a sugar, and a phosphate group Signup and view all the answers

Which statement about prokaryotic cells is true?

They have circular DNA located in a nucleoid. Signup and view all the answers

What type of bonds link nucleotides in nucleic acids?

Phosphodiester bonds Signup and view all the answers

Which characteristic is typical of eukaryotic cells?

Contain membrane-bound organelles Signup and view all the answers

Which types of cells generally do NOT have a cell wall?

Animal cells Signup and view all the answers

What is the primary energy carrier in cellular processes?

ATP Signup and view all the answers

How do bacteria primarily reproduce?

Binary fission Signup and view all the answers

Which of the following statements about Gram-negative bacteria is true?

They have two inner membranes. Signup and view all the answers

What distinguishes the linear DNA structure of eukaryotic cells?

It has multiple strands. Signup and view all the answers

What type of organisms can the commensal bacteria in the human body become?

Pathogenic Signup and view all the answers

What is one of the main roles of the cytoskeleton in eukaryotic cells?

Providing structure and shape Signup and view all the answers

Which of the following types of cells has the smallest size range?

Prokaryotic cells Signup and view all the answers

Which of the following correctly describes the body of a human?

Contains a diversity of over 200 types of cells Signup and view all the answers

Study Notes

What is a cell?

The fundamental unit of life.
Small, membrane-enclosed units filled with a concentrated aqueous solution containing numerous chemicals.
Can generate copies of themselves by growing and dividing in two.

Main functions of a cell

Generate energy:
- Energy is required to power all the cell's activities.
- Energy is obtained from the environment.
  - Animal cells: Energy in chemical bonds in food molecules.
  - Plant cells: Energy from sunlight.
Synthesize proteins:
- Proteins carry out all the cell's functions.
  - Cell structure (skeleton), enzymes (reaction catalysts), signaling molecules, and receptors (communication).
Make more cells:
- Make copies of themselves by dividing.
- Required for growth and damage repair.

Energy Generation

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

Storing Cellular Information

DNA is a long polymer chain made up of four types of monomers called nucleotides.
These nucleotides contain four different nitrogenous bases: Adenine (A), Guanine (G), Thymine (T), Cytosine (C).
These are joined together in a linear sequence that encodes the genetic information.

Protein Synthesis

DNA sequence guides the synthesis of mRNA molecules (transcription).
mRNA sequence guides the synthesis of protein molecules (translation).

Cell Division

Cells make copies of themselves that are genetically identical.
To do this, cells duplicate their DNA and then divide in two.

DNA Replication

The two strands of the DNA helix are pulled apart and used as templates for the synthesis of complementary strands.

Chemical Constituents of Cells

Water, ions, amino acids, sugars, fatty acids, and nucleotides.

Water

70-85% of most cells.
Water molecules are held together by hydrogen bonds.
Molecules that are also polar can be dissolved in water by forming hydrogen bonds.

Hydrophilic Molecules

Easily dissolve in water - “Water-loving”.
Polar or charged (negative/positive) molecules.
Can form hydrogen bonds with water.

Hydrophobic Molecules

Do not dissolve in water – “Water-fearing”.
Do not form hydrogen bonds with water.
Non-polar/uncharged side chains.
Non-polar, composed of hydrocarbon chains and ring structures.

Ions

Atoms carrying an electrical charge, either negative (anions) or positive (cations).
Provide inorganic chemicals (e.g. potassium, calcium) for chemical reactions.
Required for key cellular control mechanisms.

Sugars

The simplest forms are monosaccharides.
Made of carbon, hydrogen, and oxygen.
Monosaccharides can be linked together by glycosidic bonds to form larger carbohydrates.

Glucose

Very important energy source for cells.
Broken down into smaller molecules through a series of metabolic reactions to release energy in the form of ATP.
Stored as glycogen in the form of a polysaccharide.

Fatty Acids

Organic molecules with two distinct regions:
- Long hydrocarbon chain (hydrophobic)
- Carboxyl group (-COOH), hydrophilic and chemically reactive.
Can be broken down in the mitochondria to produce energy.

Lipids

Organic, complex molecules that are insoluble in water, but soluble in non-polar organic solvents.
Contain long hydrocarbon chains or multiple rings.
Important types of lipids:
- Phospholipids and cholesterol: Constitute 2% of the cell’s mass, help form the cell membrane and intracellular membranes around organelles.
- Triglycerides: The body’s main store of energy-rich nutrients, stored in the cytoplasm as lipid droplets.

Phospholipids & Cholesterol

Main constituents of cell membranes.

Triglycerides

Made of glycerol and three fatty acids.
Fatty acids can be used as sources of energy in the cell.
Act as energy stores for the cell.

Amino Acids

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

Proteins

Polymers of amino acids joined together in a long chain by forming peptide bonds (polypeptide chain).
Polypeptide chain folded into a 3D structure.
Perform most of the cell's functions (workhorses of the cell).
Two types of proteins:
- Structural proteins: Long chains of proteins - filaments (actin, intermediate, microtubules)
- Functional proteins: Mainly enzymes - catalysts for specific reactions in the cell.

Structural Proteins

Form the cytoskeleton that holds the cell together and allows the cell to move.
Also found outside the cell in connective tissue, tendons, and ligaments.

Functional Proteins

Bind to specific molecules called ligands and convert them into chemically modified products.

Nucleotides

Consists of a 5-carbon sugar linked to a nitrogen-containing base and one or more phosphate groups.
Sugar is either ribose or deoxyribose.
5 different bases: Adenine, thymine, uracil, cytosine, guanine.

Nucleic Acids

Nucleic acids are linked by phosphodiester bonds forming long polymers called nucleic acids.
DNA (deoxyribose as sugar) and RNA (ribose as sugar)
Storage and retrieval of biological information.

Adenosine Triphosphate (ATP)

A molecule that carries energy needed for cellular processes.
Captures the chemical energy released from the breakdown of glucose and fatty acids.
Stored in the high-energy phosphate bonds.
Cleavage (breakage) of phosphate bonds releases large amounts of energy which can be used by the cell.

The Diversity of Cells

Three major divisions of the living world
- Bacteria, archaea, eukarya.
Genome analyses suggest that the first eukaryotic cell emerged after an archaeal cell engulfed a bacterium.

Prokaryotic and Eukaryotic Cells

Prokaryotic cells (no nucleus):
- Pro (before) – karyon (kernel/nucleus).
Eukaryotic cells (with nucleus):
- Eu (good) – karyon (kernel/nucleus).

Prokaryotic Cell Structure

Small size (0.2-2 μm).
Spherical, rod-like, or cork-screw shape.
No membrane-enclosed organelles.
Cell wall: Tough protective coat.
Plasma membrane: Enclosing cytoplasm.
No nuclear compartment to house DNA.
DNA is located in a compartment called the nucleoid.
Circular DNA.
Divide very quickly (every 20mins).

Prokaryotic Cells

Live as individual cells or as loosely organized communities.
Survive in a large variety of ecological niches.
Utilize a wide range of energy sources to survive.

Bacteria

Traditionally classified by shape (spherical, rod-shaped, spiral).
Classified as Gram-positive or negative.
Been around for 3.5 billion years.
The human body contains approximately 1014 microbes - primarily in the gut, mouth, skin, and vagina.
10X more bacterial cells than human cells in the human body.
Large numbers of harmless or beneficial bacteria - commensal bacteria.
Some bacteria can cause disease.

Archaea

Differ from bacteria in terms of their cell wall and lipid and ribosomal structures.

Eukaryiotic Cell Structure

Larger size (10-100μm).
Contain membrane-enclosed organelles.
No cell wall (only cell membrane).
DNA enclosed in the nucleus.
Linear DNA - multiple strands.

Cell Sizes

1 nm = 1x10-9 m.
1 μm = 1x10-6m
Requires either an electron or light microscope to view.

Human Cell Diversity

30 trillion cells in the human body.
200 types of cells with different morphologies and functions.
Different cell types have different life spans.

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Description

This quiz explores the fundamental concepts of cell biology, including the structure and functions of cells. It covers how cells generate energy, synthesize proteins, and replicate themselves, highlighting the importance of these processes in living organisms.