Cell Organelles and Molecular Biology

Flashcards covering key vocabulary related to cell organelles and the basics of molecular biology from the lecture notes.

Plasma membrane

The border or outer part of the cell that creates the division between the inside and outside of the cell.

Cytoplasm

Everything inside the cell, composed of cytosol and organelles.

Cytosol

The liquid part of the inside of the cell.

Organelles

Structures inside the cell, categorized as membranous or nonmembranous.

Membranous organelles

Organelles made out of membranes, similar in structure to the plasma membrane.

Nonmembranous organelles

Organelles mostly made out of proteins.

Cytoskeleton

Functions as the cell's skeleton, providing internal framework, shape, and aiding in cell movement.

Microfilaments (Actin filaments)

The smallest type of protein strand in the cytoskeleton, made of actin, involved in cell structure, movement (e.g., cytokinesis, muscle contraction, pseudopods), and can also be called thin filaments.

Intermediate filaments

Middle-sized protein strand in the cytoskeleton, provides significant strength and structural support to the cell.

Microtubules

The largest type of protein tube in the cytoskeleton, involved in anchoring and moving individual components within the cell (e.g., chromosomes during mitosis, vesicles).

Microvilli

Extensions of the plasma membrane, filled with microfilaments, designed to increase the surface area of the cell for absorption (e.g., in the digestive tract).

Centrioles

Structures made of microtubules, located in the centrosome, important for cell division by creating spindle fibers to move chromosomes.

Centrosome

The area beside the nucleus where the centrioles are located.

Spindle fibers

Microtubules created by centrioles during cell division that connect to and move chromosomes.

Motile cilia

Microtubule-based structures that cover a cell's surface and sway back and forth to move substances across the cell's surface or within tubes (e.g., respiratory tract).

Primary cilium

A single, non-motile cilium found in specialized sensory cells, which moves due to external stimuli to trigger signals.

Flagellum (plural: Flagella)

A long, whip-like microtubule-based structure that allows a cell to move; in humans, an example is the single flagellum on sperm.

Ribosomes

Nonmembranous organelles, composed of protein and ribosomal RNA, where protein synthesis (making proteins) occurs.

Free ribosomes

Ribosomes located in the cytosol, making proteins that function within the cytosol.

Fixed ribosomes (Bound ribosomes)

Ribosomes attached to the endoplasmic reticulum, making proteins destined for secretion outside the cell or embedding in membranes.

Endoplasmic Reticulum (ER)

A mesh-like or net-like membranous organelle inside the cell, involved in various functions including protein and lipid synthesis and detoxification.

Rough Endoplasmic Reticulum (RER)

Part of the ER covered with fixed ribosomes, involved in the synthesis of proteins that will be secreted or integrated into membranes.

Smooth Endoplasmic Reticulum (SER)

Part of the ER without ribosomes, involved in lipid and carbohydrate metabolism, and detoxification of toxic substances.

Golgi apparatus

A membranous organelle consisting of a stack of flattened discs, involved in processing, modifying, and packaging proteins and lipids from the ER for secretion or delivery to other organelles.

Vesicles

Small, membrane-bound sacs that transport substances within the cell, release contents (exocytosis), or bring substances into the cell.

Transport vesicle

A vesicle that moves proteins from the endoplasmic reticulum to the Golgi apparatus.

Secretory vesicle

A vesicle that buds off the Golgi apparatus, releasing its contents outside the cell via exocytosis.

Exocytosis

The process by which a cell releases large substances or a large amount of substances to the outside by fusing a secretory vesicle with the plasma membrane.

Membrane renewal

The continuous process where vesicles fuse with the plasma membrane, replacing or altering its protein and lipid components.

Lysosome

A membranous organelle formed by the Golgi apparatus, containing digestive enzymes (proteins) that break down worn-out organelles, waste materials, and foreign invaders like bacteria.

Membrane flow

The continuous movement and exchange of membrane materials among the endoplasmic reticulum, Golgi apparatus, and plasma membrane, maintaining their sizes and renewing their components.

Mitochondria (singular: Mitochondrion)

Membranous organelles responsible for producing the majority of cellular energy in the form of ATP through aerobic metabolism; they have their own circular DNA and replicate independently.

Cristae

The inner folds of the inner mitochondrial membrane, which increase the surface area for the electron transport chain and ATP production.

ATP (Adenosine Triphosphate)

The primary energy currency of all cells, produced mainly in the mitochondria.

Glycolysis

The initial breakdown of glucose into pyruvate, occurring in the cytosol outside the mitochondria, producing a small amount of ATP.

Krebs cycle (Citric acid cycle)

A metabolic pathway occurring in the mitochondrial matrix, where pyruvate derivatives are completely broken down, producing some ATP and reduced compounds (NADH, FADH2).

Electron transport chain

A series of protein complexes in the inner mitochondrial membrane that utilizes the reduced compounds from the Krebs cycle to generate a large amount of ATP through oxidative phosphorylation.

Aerobic metabolism

The process of cellular respiration that requires oxygen to efficiently produce ATP, involving glycolysis, the Krebs cycle, and the electron transport chain.

Nucleus

A prominent membranous organelle that houses the cell's genetic material (DNA) in a stable and protected environment, and controls cell activities by regulating gene expression.

Nuclear envelope

A double-layered membrane that encloses the nucleus, separating its contents from the cytoplasm.

Nuclear pores

Protein structures embedded in the nuclear envelope that regulate the passage of macromolecules, such as RNA and ribosomes, between the nucleus and cytoplasm.

Nucleolus (plural: Nucleoli)

A dense region within the nucleus where ribosomes are synthesized and assembled.

Nucleoplasm

The semi-fluid substance found inside the nuclear envelope, containing chromatin and the nucleolus.

Chromatin

A complex of DNA and proteins (histones) found within the nucleus, forming a coiled structure that protects DNA while allowing access for gene expression.

Histones

Proteins around which DNA is wound to form nucleosomes, helping to package and organize DNA into chromatin and chromosomes.

Nucleosomes

The basic structural unit of chromatin, consisting of DNA wrapped around a core of histone proteins.

Chromosomes

Highly condensed and tightly coiled forms of chromatin, visible during cell division, which make it easier to protect and move DNA.

DNA (Deoxyribonucleic Acid)

A nucleic acid that carries the genetic instructions for the development, functioning, growth, and reproduction of all known organisms, organized as a double helix.

Double helix

The twisted, ladder-like structure of DNA, formed by two complementary polynucleotide strands.

Nucleotide

The fundamental building block of nucleic acids (DNA and RNA), consisting of a nitrogenous base, a pentose sugar, and one or more phosphate groups.

Phosphate sugar backbone

The repeating structural unit of a DNA or RNA strand, composed of alternating sugar and phosphate groups.

Nitrogenous bases

Adenine (A), Guanine (G), Cytosine (C), and Thymine (T) in DNA; Adenine (A), Guanine (G), Cytosine (C), and Uracil (U) in RNA.

Complementary base pairing

The specific pairing of nitrogenous bases in nucleic acids: A with T (or U in RNA), and C with G, held together by hydrogen bonds.

Gene

A segment of DNA that contains the instructions for making a specific protein or functional RNA molecule, including regulatory regions.

Genetic code

The set of rules by which information encoded within genetic material (DNA or mRNA sequences) is translated into proteins by living cells.

Triplets (Codons)

A sequence of three nitrogenous bases in a DNA or mRNA molecule that specifies a particular amino acid.

Template strand

The strand of DNA that serves as a guide for the synthesis of mRNA during transcription.

Coding strand

The non-template strand of DNA, which has a sequence identical to the mRNA produced, with thymine replaced by uracil.

Messenger RNA (mRNA)

A single-stranded RNA molecule that carries genetic information from DNA in the nucleus to the ribosomes in the cytoplasm for protein synthesis.

Uracil (U)

A nitrogenous base found in RNA, replacing thymine (T) that is found in DNA.

RNA polymerase

An enzyme that catalyzes the synthesis of an RNA strand from a DNA template during transcription.

Protein synthesis

The overall process by which cells create proteins, involving two main steps: transcription and translation.

Transcription

The first step of protein synthesis, where genetic information from DNA is copied into messenger RNA (mRNA) in the nucleus.

Translation

The second step of protein synthesis, where the genetic code in mRNA is read by ribosomes to build a specific protein, occurring at ribosomes.

Transfer RNA (tRNA)

A type of RNA molecule that carries specific amino acids to the ribosome and matches them to the corresponding mRNA codons during protein synthesis.

Anticodon

A sequence of three nucleotides on a tRNA molecule that is complementary to an mRNA codon, enabling the correct amino acid to be delivered during translation.