Cell Biology Overview

A set of flashcards to help review key concepts and terms related to cell biology and its components.

What are the two main types of cells?

Prokaryotic and Eukaryotic

What term refers to the process by which cells come from existing cells?

Cell Theory

What are the three types of RNA involved in protein synthesis?

Messenger RNA (mRNA), Transfer RNA (tRNA), Ribosomal RNA (rRNA)

What is the fundamental concept of 'Cells as the building blocks of life,' and how is it related to Cell Theory?

The basic structural and functional units of all known living organisms, meaning all organisms are composed of cells, and all life processes occur within cells. This concept is a core tenet of Cell Theory, which states that all living things are made of cells, cells are the basic unit of life, and all cells arise from pre-existing cells.

What part of the nucleus is responsible for the synthesis of ribosomal RNA?

The nucleolus is a dense, non-membrane-bound structure located within the nucleus of eukaryotic cells. Its primary function is the synthesis of ribosomal RNA (rRNA) and the assembly of ribosomes, which are essential for protein synthesis.

In microscopy, what does 'magnification' refer to?

The process of enlarging the apparent size of an object, creating an image larger than the actual specimen. It is typically expressed as a factor (e.g., 100\times), indicating how many times larger the image appears compared to the real object.

What is 'resolution' in the context of microscopy?

Also known as resolving power, the ability of a microscope to distinguish between two closely spaced objects as separate entities. A higher resolution allows for clearer and more detailed images, revealing finer structures. It is often limited by the wavelength of light used.

Explain what 'contrast' means in microscopy.

Refers to the difference in intensity between an object and its background, or between different parts of the object itself. Adequate contrast is crucial for making structures visible, especially colorless or transparent biological specimens, and can often be enhanced through staining techniques or specialized microscopy methods (e.g., phase-contrast, differential interference contrast).

What is Messenger RNA (mRNA)

Carries genetic information from DNA in the nucleus to the ribosomes in the cytoplasm, serving as a template for protein sequence.

What is Transfer RNA (tRNA)

Acts as an adaptor molecule, matching specific amino acids to their corresponding codons on the mRNA during translation.

What is Ribosomal RNA (rRNA)

A major component of ribosomes, where it plays a catalytic role in peptide bond formation during protein synthesis.

What are Prokaryotic cells?

Lack a membrane-bound nucleus and other membrane-bound organelles. Their genetic material is found in the cytoplasm. Examples include bacteria and archaea.

What is the nucleoid region in prokaryotic cells?

An irregularly shaped area within the prokaryotic cell cytoplasm where the genetic material (chromosomal DNA) is concentrated. Unlike eukaryotes, it is not enclosed by a membrane.

What is a common component of the cell wall in many prokaryotes?

Many prokaryotes, particularly bacteria, have peptidoglycan as a major structural component of their cell wall, which provides rigidity and protection.

Which key organelles are absent in prokaryotic cells, besides a membrane-bound nucleus?

Prokaryotic cells lack several membrane-bound organelles found in eukaryotes, including mitochondria, endoplasmic reticulum, lysosomes, and the Golgi apparatus. Ribosomes are present, but these are not membrane-bound.

What is Gram staining, and what does it distinguish in prokaryotes?

A Differential staining technique used to classify bacteria based on the biochemical and structural properties of their cell walls, particularly the peptidoglycan content. It distinguishes between Gram-positive and Gram-negative bacteria.

What are Eukaryotic cells

Possess a membrane-bound nucleus that houses their genetic material, and various other membrane-bound organelles (e.g., mitochondria, endoplasmic reticulum). Examples include animal, plant, fungal, and protist cells.

What is the universal role of ribosomes within the cell's cytoplasm?

Ribosomes are the cellular structures that serve as the primary sites of protein synthesis in the cytoplasm of both prokaryotic and eukaryotic cells, translating genetic information into functional proteins.

What essential layer defines the boundary of a cell and surrounds the cytoplasm?

The plasma membrane is a selectively permeable barrier that envelops the cell, surrounding its cytoplasm and controlling the movement of substances into and out of the cell.

What is the primary function of the nucleus in eukaryotic cells?

Houses the cell's genetic material (DNA), organizing it into chromatin or chromosomes, and controls the cell's activities by regulating gene expression.

What is the structure and function of the nuclear envelope?

A double membrane that surrounds the nucleus, punctuated by nuclear pores that regulate the transport of molecules between the nucleus and the cytoplasm.

What is the role of nuclear pores?

Protein-lined openings in the nuclear envelope that control the entry and exit of molecules, such as proteins and RNA, into and out of the nucleus, often requiring chaperone proteins for transport.

What is the nucleolus and its main function?

A dense, non-membrane-bound region within the nucleus where ribosomal RNA (rRNA) is synthesized and the assembly of ribosomes begins.

Differentiate between chromatin and chromosomes.

Chromatin is the relaxed, decondensed form of DNA associated with proteins (histones) found in the nucleus when the cell is not dividing. Chromosomes are the highly condensed, visible forms of DNA (often X-shaped) that appear during cell replication and division.

What is the endoplasmic reticulum (ER), and where is it located?

 An extensive network of membranous tubules and sacs (cisternae) that is continuous with the outer nuclear envelope and extends throughout the cytoplasm of eukaryotic cells.

What is the function of the Rough Endoplasmic Reticulum (RER)?

Characterized by ribosomes attached to its surface. Its primary functions include the synthesis, folding, modification, and transport of proteins that are destined for secretion, insertion into membranes, or delivery to other organelles.

What are the main functions of the Smooth Endoplasmic Reticulum (SER)?

Lacks ribosomes and is involved in various metabolic processes, including lipid synthesis (e.g., steroids, oils), detoxification of drugs and poisons, and storage of calcium ions.

How are ribosomes structured and where are their subunits assembled?

Ribosomes consist of small and large subunits, which are assembled in the nucleolus. They are the primary sites of protein synthesis.

What is the distinction between free ribosomes and bound ribosomes in terms of their location and the proteins they synthesize?

Free ribosomes are located in the cytosol and synthesize proteins destined for the cytoplasm or nucleus. Bound ribosomes are attached to the Rough ER and synthesize proteins for secretion, insertion into membranes, or delivery to other organelles.

What is the primary role of mitochondria in cellular energy production?

Mitochondria are key players in cellular respiration, consuming oxygen to produce energy (ATP) from nutrients.

Where is the electron transport chain (ETC) located, and what is its main function?

The electron transport chain (ETC) is located in the mitochondrial inner membrane. It uses oxygen to drive the production of ATP from nutrients.

What is aerobic respiration, and what are its key inputs and outputs?

A metabolic process that requires oxygen to convert chemical energy from nutrients (like glucose) into usable ATP, producing CO2 and H2O as byproducts.

Why do mitochondria "consume oxygen" during cellular respiration?

Mitochondria consume oxygen because it acts as the final electron acceptor in the electron transport chain (ETC), which is central to the process of energy metabolism and ATP production.

What is the cytoplasm, and what are its main components?

The entire internal cellular environment, consisting of the cytosol (a semi-solid, largely water-based fluid) and cytoplasmic organelles. It is largely water-based yet semi-solid in consistency.

What is the cytoskeleton composed of, and what functions does it serve?

A network of protein filaments that provides structural support to the cell, helps maintain cell shape, and organizes intracellular transport.

Describe the structure and function of the plasma membrane.

The plasma membrane is a phospholipid bilayer with embedded proteins and attached carbohydrates. Its primary function is to regulate the movement of substances into and out of the cell, exhibiting selective permeability due to its heterogeneous composition.

What are membrane-associated features like glycoproteins and glycolipids, and what is their role?

Membrane-associated features include proteins embedded in the membrane, as well as glycoproteins and glycolipids (carbohydrates attached to proteins or lipids). These components contribute significantly to cell recognition and signaling.

Why do substances often require transport proteins to move across the plasma membrane?

Transport often requires proteins because both the outer aqueous environment and the inner cytoplasm interact with the hydrophobic interior of the plasma membrane. This hydrophobic barrier prevents many polar or charged molecules from passing through freely, necessitating protein channels or carriers.

How is Messenger RNA (mRNA) synthesized and where does it go afterward?

mRNA is transcribed from DNA in the nucleus by RNA polymerase. It then exits the nucleus via nuclear pores into the cytosol or to Rough ER-attached ribosomes.

What is the role of ribosomes in protein synthesis, particularly with mRNA and tRNA?

Ribosomes read mRNA codons and recruit appropriate tRNA molecules, which carry specific amino acids, to build a polypeptide chain.

What is the role of RNA polymerase in gene expression?

RNA polymerase is the enzyme responsible for transcription, facilitating the synthesis of RNA (like mRNA) from a DNA template.

What is Transcription?

the process where genetic information from DNA is copied into RNA (mRNA) by RNA polymerase, occurring primarily in the nucleus.

What is Translation?

the subsequent process where ribosomes use the mRNA template to synthesize a specific protein, taking place in the cytoplasm.