Cellular Structure and Organization

Flashcards covering cellular structure, classification of prokaryotes and eukaryotes, types of human body cells, and the functions of various subcellular organelles based on the lecture notes.

Cell

The basic unit of life; microscopic and self-sufficient, possessing the machinery to carry out metabolic reactions and generate energy.

Genetic material

Information carried by nucleic acid (DNA); the unit of genetic information is the gene, which holds all the information a cell needs to keep itself alive.

Cytoplasm

A gel-like substance that makes up much of a cell inside the cell membrane, filling the cell and giving it its shape.

Cell membrane (Plasma membrane)

The limiting boundary of a cell composed of a phospholipid bilayer and protein matrix; it separates the cell from the outside world and selectively permits the entrance of substances.

Ribosomes

Minute organelles composed of RNA and proteins involved in protein synthesis; nicknamed the 'protein factory of the cell.'

Gametes

Reproductive sex cells (sperm in males, ova in females) produced in gonads; they reproduce by meiosis rather than mitosis.

Sperm

Motile male sex cells that contain $23$ chromosomes and have a long tail-like projection called a flagellum.

Ova (Egg)

Non-motile female sex cells that contain $23$ chromosomes and are relatively large compared to the male gamete.

Stem cells

Unspecialized cells that have the ability to develop into specialized cells for specific organs or tissues and can replicate many times to replenish and repair tissue.

Adipocytes (Fat cells)

Major components of adipose tissue that contain stored fat (triglyceride) for energy and produce hormones influencing metabolism and blood pressure regulation.

Neurons (Nerve cells)

The basic unit of the nervous system consisting of a cell body and nerve processes (axons and dendrites) used to send signals via nerve impulses.

Epidermis

The outermost layer of skin composed of flat, squamous, epithelial cells that are closely packed together to protect internal structures.

Red blood cells (RBC)

Cells responsible for transporting oxygen and determining blood type.

White blood cells (WBC)

Immune system cells that destroy pathogens and provide immunity.

Platelets

Blood components that help clot blood and prevent excessive blood loss due to damaged or broken vessels.

Prokaryotes

Small and simple unicellular organisms (e.g., bacteria and archaea) that lack a nucleus and membrane-bound organelles; their DNA is organized into a nucleoid.

Archaea

The oldest living organisms on earth, often found in extreme environments; types include thermophiles (heat-tolerant), halophiles (salt-dwelling), and methanogens (methane-producing).

Eukaryotes

Multicellular organisms (e.g., protists, fungi, plants, animals) that are $1000$ to $10000$ times larger than prokaryotes and contain a nucleus and multiple intracellular organelles.

Somatic cells

Body cells that are diploid ($2n$), meaning they contain two sets of chromosomes arranged in homologous pairs.

Haploid (n)

Cells containing one set of chromosomes (half), such as gametes (egg and sperm).

Nucleolus

The region within the nucleus responsible for ribosomal assembly and the processing of ribosomal RNA (rRNA).

Chromatin

The DNA-protein complex located in the nucleus that organizes into chromosomes immediately before cell division.

Rough Endoplasmic Reticulum (Rough ER)

ER with ribosomes present; it synthesizes proteins destined for secretion or membrane incorporation.

Smooth Endoplasmic Reticulum (Smooth ER)

ER without ribosomes; it is the site of lipid synthesis and contains cytochromes P450 for detoxification and steroid hormone biosynthesis.

Golgi apparatus

A network of flattened membrane sacs (cisternae) involved in protein modification (forming glycoproteins and lipoproteins) and secretion.

Mitochondria

The 'powerhouse of the cell' and site of cellular respiration; they use oxygen to produce energy in the form of adenosine triphosphate (ATP).

Apoptosis

Programmed cell death; initiated by the production of cytochrome c from the mitochondria.

Luft’s disease

A condition involving a defect in the mechanism controlling mitochondrial oxygen utilization, characterized by hypermetabolism and a basal metabolic rate of $200$ percent.

Lysosomes

Membranous bags containing acid hydrolases used for intracellular digestion of macromolecules and recycling of cellular components.

Autophagy

A natural process where lysosomes hydrolyze and remove unnecessary or dysfunctional cell components.

Gout

A condition caused by excess uric acid forming urate crystals in joints; cell damage occurs when lysosomal enzymes are released after attempting to digest these crystals.

Centrioles

Two short cylindrical structures used for cell reproduction; they release microtubules to split the cell and distribute chromosomes equally.

Microfilaments

Cytoskeletal fibers composed of the protein actin; they are involved in cell movement and transport of vesicles.

Intermediate filaments

Cytoskeletal fibers, such as keratin, that maintain cell shape and help cells withstand mechanical stress.

Microtubules

Hollow cylinders composed of the protein tubulin that form a supportive framework and guide organelle movement during cell division.

Cytosol

The organelle-free cell sap where metabolic pathways like glycolysis, glycogenesis, and fatty acid synthesis occur.