Cell Biology Big Study Guide

What are the fundamental units of life?

Cells

What did all present-day cells evolve from?

A common ancestral cell that existed over 3 billion years ago.

What structure encloses all cells and separates them from their environment?

The plasma membrane.

In what form do all cells store their genetic informations?

DNA

What guides the synthesis of RNA and proteins in cells?

DNA.

Why can cells in the same organism look and behave differently?

They express different sets of genes depedning on developmental history and environmental signals

What is the typical diameter range of animals and plant cells?

5-20 micrometers (µm)

Which microscope allows you to see the internal structures of cells?

Light microscope.

Which microscope shows the smallest organelles but requires fixed, dead samples?

Electron microscope.

What type of microscopy helps locate proteins in fixed or living cells?

Fluorescence microscopy.

What is the ‘tree of life’ based on?

Comparison of DNA sequences across species.

What are the three domains of life?

Bacteria, Archaea, and Eukaryotes.

What makes bacteria and archaea chemically diverse?

They inhabit a wide range of environments with different metabolic capabilities.

What distinguishes eukaryotic cells from bacteria and archaea?

Presence of a nucleus and membrane-bound organelles.

How did eukaryotic cells likely evolve mitochondria and chloroplasts?

By engulfing aerobic bacteria (mitochondria) and photosynthetic bacteria (chloroplasts).

Where is genetic material stored in a eukaryotic cell?

In the nucleus.

What is the cytoplasm?

Everything in the cell outside the nucleus, including organelles and cytosol.

What does the mitochondrion do?

Produces ATP by oxidizing food molecules.

What does the ER and Golgi apparatus do?

Synthesize and process complex molecules for export or membrane insertion.

What is the function of lysosomes?

Digest large molecules.

What is the function of chloroplasts?

Perform photosynthesis in plants and some eukaryotes.

What is the cytosol?

The fluid part of the cytoplasm where many biochemical reactions occur.

What is the cytoskeleton and what does it do?

A network of protein filaments that provides shape, movement, and transport within the cell.

What are protozoa?

Single-celled eukaryotic organisms that can move, hunt, and eat other cells.

How do multicellular organisms originate?

From a single fertilized egg cell.

What are model organisms?

Well-studied species like E. coli, yeast, flies, worms, and mice used in biological research.

How many protein-coding genes does the human genome have?

Around 20,000.

Archaeon

A type of prokaryote; often lives in extreme environments.

Bacterium

A single-celled prokaryotic organism.

Cell

The basic unit of life.

Chloroplast

Organelle in plants that performs photosynthesis.

Chromosome

DNA molecule with part or all of the genetic material of an organism.

Cytoplasm

All contents of the cell outside the nucleus.

Cytoskeleton

Protein filaments that provide structure and transport.

Cytosol

The liquid component of the cytoplasm.

DNA

Molecule storing genetic information.

Electron Microscope

High-resolution microscope that reveals tiny structures.

Endoplasmic Reticulum (ER)

Organelle for protein and lipid synthesis.

Eukaryote

Cell with nucleus and organelles.

Evolution

Process by which organisms change over generations.

Fluorescence Microscope

Uses fluorescence to visualize structures in cells.

Genome

The complete set of genes or genetic material.

Golgi Apparatus

Organelle that modifies, sorts, and packages proteins.

Homologous

Similar in position, structure, and origin.

Micrometer

One-millionth of a meter (µm); unit for cell size.

Microscope

Tool used to view small objects like cells.

Mitochondrion

Organelle that produces energy (ATP).

Model Organism

A species used to study biology extensively.

Nucleus

Organelle that contains DNA.

Organelle

Specialized structure within a cell.

Photosynthesis

Process of converting light energy into chemical energy.

Plasma Membrane

Boundary of the cell.

Prokaryote

Cell without a nucleus (e.g., bacteria, archaea).

Protein

Molecule made from amino acids; performs various functions.

Protozoan

Single-celled eukaryote that can move and ingest food.

Ribosome

Organelle that synthesizes proteins.

RNA (Ribonucleic Acid)

Molecule involved in protein synthesis.

Do living cells obey different physical laws from nonliving things?

No, they follow the same chemical and physical laws.

Which four elements make up 96% of a cell’s mass?

Carbon (C), Hydrogen (H), Nitrogen (N), and Oxygen (O)

What is the structure of an atom?

A nucleus with protons and neutrons, surrounded by a cloud of electrons.

What determines an element’s chemical properties?

The number and arrangement of electrons in its atoms.

When is an atom most stable?

When its outer electron shell is full.

What forms a covalent bond?

Sharing of one or more electron pairs between atoms.

What forms a molecule?

Two or more atoms held together by covalent bonds.

What forms an ionic bond?

Transfer of electrons creates oppositely charged ions held by attraction.

What percentage of a cell's mass is water?

About 70%.

What shapes the chemistry of life in cells?

The properties of water.

What types of small organic molecules are common in all life forms?

Sugars, fatty acids, amino acids, and nucleotides.

What is the main energy source for cells?

Sugars.

What do sugars form when linked?

Oligosaccharides and polysaccharides.

What is the role of fatty acids in the cell?

Energy storage and forming lipids for membranes.

What makes up the majority of the dry mass of a cell?

Macromolecules: polysaccharides, proteins, and nucleic acids.

What are proteins made from?

20 amino acids linked by peptide bonds.

What do nucleotides do in the cell?

Transfer energy and form DNA/RNA.

How are protein, RNA, and DNA synthesized?

By condensation reactions linking subunits in specific sequences.

What determines a macromolecule’s function?

Its specific sequence of subunits.

What are the four types of weak, noncovalent interactions in cells?

Hydrogen bonds, electrostatic attractions, van der Waals attractions, and hydrophobic forces.

What do noncovalent interactions allow macromolecules to do?

Fold into unique shapes and bind specifically to other molecules.

Acid

A substance that releases protons (H⁺) in solution.

Amino acid

Building block of proteins, containing an amino group and a carboxyl group.

Atom

Smallest unit of an element, composed of protons, neutrons, and electrons.

ATP (Adenosine Triphosphate)

A nucleotide used in energy transfer in cells.

Avogadro’s number

6.022 × 10²³ — the number of molecules in a mole.

Base

A substance that accepts protons or releases hydroxide ions in solution.

Buffer

A substance that minimizes changes in pH.

Chemical bond

The force that holds atoms together in molecules.

Chemical group

A specific arrangement of atoms that imparts characteristic properties.

Condensation reaction

A reaction where two molecules join with the loss of water.

Conformation

The three-dimensional shape of a macromolecule.

Covalent bond

A chemical bond formed by sharing electron pairs.

DNA

Deoxyribonucleic acid; stores genetic information.

Electron

Negatively charged particle orbiting the nucleus of an atom.

Electronegativity

An atom’s ability to attract electrons in a bond.

Electrostatic attraction

A noncovalent force between oppositely charged ions or molecules.

Fatty acid

Long hydrocarbon chain with a carboxyl group; used in energy storage and membranes.

Hydrogen bond

Weak bond between a hydrogen atom and an electronegative atom.

Hydrolysis

A reaction where water breaks bonds in molecules.

Hydronium ion (H₃O⁺)

Formed when water accepts a proton.

Hydrophilic

Water-loving; interacts well with water.

Hydrophobic force

Tendency of nonpolar substances to be excluded from water.