Biology: Cell Structure and Functions

Comprehensive vocabulary flashcards covering cell biology, history of cell theory, organelle functions, and protein structure based on the provided lecture transcript.

Reductionist Biology

A physico-chemical approach to study and understand living organisms by applying the concepts and techniques of physics and chemistry to describe biological processes in molecular terms.

G.N. Ramachandran

An outstanding figure in protein structure and founder of the ‘Madras school’ of conformational analysis of biopolymers, known for discovering the triple helical structure of collagen ($1954$) and the ‘Ramachandran plot’.

Mathias Schleiden

A German botanist who in $1838$ observed that all plants are composed of different kinds of cells which form the tissues of the plant.

Theodore Schwann

A British Zoologist who in $1839$ reported that animal cells have a thin outer layer (plasma membrane) and concluded that the presence of a cell wall is a unique character of plant cells.

Rudolf Virchow ($1855$)

The scientist who first explained that cells divided and new cells are formed from pre-existing cells ($\text{Omnis cellula-e cellula}$), giving the cell theory its final shape.

Eukaryotic Cells

Cells that possess membrane-bound nuclei and other membrane-bound organelles like the endoplasmic reticulum, mitochondria, and Golgi complex.

Prokaryotic Cells

Cells that lack a membrane-bound nucleus and membrane-bound organelles; examples include bacteria, blue-green algae, mycoplasma, and $\text{PPLO}$.

Mycoplasmas

The smallest known cells, which are only $0.3 \text{ μm}$ in length.

Plasmids

Small circular $\text{DNA}$ molecules found in many bacteria outside the genomic $\text{DNA}$ that confer unique phenotypic characters, such as resistance to antibiotics.

Mesosome

A specialized differentiated form of cell membrane in prokaryotes formed by the extensions of plasma membrane into the cell in the form of vesicles, tubules, and lamellae.

Gram Positive Bacteria

Bacteria that take up the specific stain developed by Gram.

Glycocalyx

The outermost layer of the bacterial cell envelope, which can be a loose sheath called the slime layer or a thick and tough layer called the capsule.

Polysome (Polyribosomes)

A chain formed by several ribosomes attached to a single $\text{mRNA}$ to translate it into proteins.

Inclusion Bodies

Non-membrane bound structures where reserve material is stored in the cytoplasm of prokaryotic cells, such as phosphate granules and glycogen granules.

Fluid Mosaic Model

A model of cell membrane structure proposed by Singer and Nicolson ($1972$) describing the quasi-fluid nature of lipids that enables the lateral movement of proteins within the bilayer.

Passive Transport

The movement of molecules across a membrane along the concentration gradient without the requirement of energy.

Active Transport

An energy-dependent process in which molecules are transported across a membrane against their concentration gradient using $\text{ATP}$, such as the $\text{Na}^+/\text{K}^+$ Pump.

Middle Lamella

A layer mainly composed of calcium pectate that holds or glues neighboring plant cells together.

Plasmodesmata

Structures that traverse the cell wall and middle lamella to connect the cytoplasm of neighboring plant cells.

Endomembrane System

A coordinated group of organelles including the endoplasmic reticulum ($\text{ER}$), Golgi complex, lysosomes, and vacuoles.

Smooth Endoplasmic Reticulum ($\text{SER}$)

The major site for the synthesis of lipids and steroidal hormones in animal cells, characterized by the absence of ribosomes.

Golgi Apparatus

A system of flat, disc-shaped sacs (cisternae) involved in packaging materials and the formation of glycoproteins and glycolipids.

Lysosomes

Membrane-bound vesicular structures rich in hydrolytic enzymes ($\text{hydrolases}$) such as lipases and proteases, which are active at an acidic $\text{pH}$.

Tonoplast

The single membrane that binds the vacuole in plant cells and facilitates the transport of ions against concentration gradients.

Mitochondria

Double membrane-bound organelles known as the 'power houses' of the cell, functioning as the sites of aerobic respiration and $\text{ATP}$ production.

Cristae

Infoldings of the inner mitochondrial membrane that increase the surface area for enzymatic activity.

Plastids

Organelles found in plant cells and euglenoides that contain pigments; they include chloroplasts, chromoplasts, and leucoplasts.

Amyloplasts

A type of leucoplast that stores carbohydrates such as starch in plants like potato.

Centrosome

An organelle containing two cylindrical centrioles that help in cell division by forming the spindle apparatus in animal cells.

$9+2$ Array

The arrangement of axonemal microtubules in eukaryotic cilia and flagella consisting of nine doublets of peripheral microtubules and a pair of centrally located microtubules.

Nucleolus

A non-membrane bound spherical structure in the nucleoplasm that is the site for active ribosomal $\text{RNA}$ synthesis.

Chromatin

A network of nucleoprotein fibers in the interphase nucleus containing $\text{DNA}$, basic proteins called histones, non-histone proteins, and $\text{RNA}$.

Metacentric Chromosome

A chromosome with a centromere positioned in the middle, forming two equal arms.

Kinetochores

Disc-shaped structures present on the sides of the centromere to which spindle fibers attach.