Introductory Biochemistry & Cell Biology – Prelim Review

A comprehensive set of question-and-answer flashcards covering foundational topics in biochemistry and cell biology, including cell theory, membrane structure, transport processes, and organelle functions.

What is the primary focus of biochemistry?

The study of the chemical substances found in living organisms and the molecular-level interactions and reactions that sustain life.

Name the three principal areas into which biochemistry is divided.

(1) Structures of the chemical components of living matter, (2) Metabolic reactions in living matter, and (3) Molecular genetics.

List the levels in the biochemical hierarchy of organization from smallest to largest.

Atom → Molecule → Organelle → Cell → Tissue → Organ → Organ system → Organism → Population → Community → Ecosystem → Biome → Biosphere.

Which four elements form the bulk of compounds in living organisms?

Carbon, hydrogen, oxygen, and nitrogen.

Why is the cell described as the universal functional unit of life?

Because all life processes occur within cells and every organism is composed of one or more cells.

How do prokaryotic and eukaryotic cells differ in the presence of a nucleus?

Prokaryotes lack a membrane-bound nucleus, whereas eukaryotes possess a membrane-bound nucleus.

Give two examples of prokaryotic organisms.

Bacteria and archaea (including cyanobacteria).

Give two examples of eukaryotic kingdoms or groups.

Animals, plants, fungi, or protists.

Who is known as the “Father of Microbiology,” and what was his key contribution?

Anton van Leeuwenhoek; he perfected the simple microscope and first observed microorganisms, which he called “animalcules.”

Which scientist first coined the term “cell” and in what publication?

Robert Hooke, in his 1665 book "Micrographia."

What did Theodor Schwann conclude about animals?

That all animals are made up of cells.

What did Matthias Schleiden conclude about plants?

That all plants are made up of cells.

State Rudolf Virchow’s famous phrase and its meaning.

"Omnis cellula e cellula" – all cells arise only from pre-existing cells.

List the three statements of classical cell theory.

1) All living things are made of cells. 2) Cells are the basic units of structure and function. 3) New cells come from pre-existing cells.

According to modern cell theory, where is hereditary information located and how is it passed on?

Hereditary information (DNA) is contained within cells and is passed from cell to cell during division.

Why are prokaryotic cells typically smaller (0.5–10 nm) than eukaryotic cells (10–100 nm)?

Because prokaryotes lack membrane-bound organelles and complex internal structures, leading to a simpler, more compact cell design.

What is the primary structural component of the cell (plasma) membrane?

A phospholipid bilayer with hydrophilic heads and hydrophobic tails.

How do cholesterol molecules affect plasma-membrane properties?

They regulate membrane fluidity and stability, preventing it from becoming too rigid at low temperatures or too fluid at high temperatures.

Differentiate integral and peripheral membrane proteins in terms of location.

Integral proteins are embedded within the lipid bilayer; peripheral proteins sit on either membrane surface and are not embedded in the hydrophobic core.

What cellular roles are typically performed by integral membrane proteins?

Acting as channels, transporters, receptors, and enzymes.

Define endocytosis.

A form of active transport in which the plasma membrane engulfs external material, forming a vesicle that brings the material into the cell.

Define exocytosis.

The process by which intracellular vesicles fuse with the plasma membrane to release their contents outside the cell.

Provide one specific physiological example of endocytosis.

White blood cells engulfing and destroying a virus.

Provide one specific physiological example of exocytosis.

Neurons releasing neurotransmitters into a synapse for cell-to-cell communication.

What is passive transport and how does it differ from active transport?

Passive transport moves molecules down their concentration gradient without energy input; active transport moves molecules (often against the gradient) using cellular energy, usually ATP.

Define osmosis.

The diffusion of water across a semipermeable membrane from a region of higher water (lower solute) concentration to lower water (higher solute) concentration.

How is osmosis different from simple diffusion?

Osmosis involves only water movement across a membrane, whereas simple diffusion involves any solute moving from high to low concentration and may not require a membrane.

What is the sodium-potassium pump?

An ATP-driven membrane protein that actively transports three Na⁺ ions out of the cell and two K⁺ ions into the cell, vital for membrane potential and cellular homeostasis.

Name the primary polysaccharide in plant cell walls.

Cellulose.

What polymer forms most bacterial cell walls?

Peptidoglycan (murein).

Explain why targeting bacterial cell walls is effective for antibiotic development.

Human cells lack cell walls, so drugs that inhibit peptidoglycan synthesis can kill or inhibit bacteria without harming host cells.

What are the two main components of cytoplasm?

Cytosol (fluid) and organelles.

What key metabolic role does cytosol play?

It provides a medium for diffusion of ions, nutrients, and signaling molecules, enabling interactions between cellular compartments.

State two unique structural features of mitochondria.

They have a double membrane (inner membrane folded into cristae) and contain their own circular DNA chromosome.

What is the overall function of mitochondria?

To convert chemical energy from food into ATP through cellular respiration.

Which organelle carries out photosynthesis in plants and algae?

The chloroplast.

What pigment inside chloroplasts captures light energy?

Chlorophyll.

Distinguish between ribosomes attached to rough ER and free ribosomes.

Rough-ER ribosomes synthesize proteins for export or membranes; free ribosomes produce proteins used within the cytoplasm.

State two main functions of the smooth endoplasmic reticulum (SER).

Synthesis of phospholipids/lipids and storage or detoxification of special enzymes and chemicals.

How does the Golgi apparatus process proteins from the ER?

It receives proteins, chemically modifies them, tags them for destination, and packages them into vesicles for transport.

What enzymes are abundant inside lysosomes and what is their general function?

Hydrolytic enzymes (e.g., hydrolases) that degrade cellular waste, damaged organelles, or invading pathogens.

Define autophagy.

The lysosome-mediated digestion and recycling of a cell’s own damaged organelles or macromolecules.

What detoxifying enzymes are found in peroxisomes and in which cells are peroxisomes present?

Oxidases and catalase; peroxisomes are present in virtually all eukaryotic cells.

State the primary function of central vacuoles in plant cells.

Storage of water and maintenance of turgor pressure to support plant structure.

List the three main types of plastids and a key role for each.

Leukoplasts – starch storage; chromoplasts – pigment storage; chloroplasts – photosynthesis.

Name the three major cytoskeletal filament systems and one function of each.

Microtubules (tubulin) – organelle movement and mitotic spindle; Microfilaments (actin) – cell motility and shape; Intermediate filaments (keratin, etc.) – tensile strength and structural support.

What is the main role of the centrosome in animal cells?

It serves as the microtubule-organizing center (MTOC), helping to assemble the mitotic spindle during cell division.