Cell Structure, Function, and Microscopy Techniques in Biology

Genetic material function

Its genetic information, which is used for cell division and directing protein synthesis through gene expression.

Microscopy

The technique used to view objects that are too small to be seen with the naked eye, such as cells and organelles. It involves the use of microscopes to magnify and resolve fine cellular structures.

Cell Fractionation

A lab technique used to break open cells and separate their components based on size and density using centrifugation.

Lower Centrifuge Speeds

At lower centrifuge speeds, larger and heavier organelles like the nucleus pellet first.

Higher Centrifuge Speeds

At higher speeds, smaller organelles such as mitochondria, lysosomes, ribosomes, and membrane fragments are isolated.

Light Microscope

Uses visible light and glass lenses to view live or stained cells; limited resolution (~200 nm).

Transmission Electron Microscope

Uses electrons to view internal structures of thinly sliced specimens at very high resolution (up to ~0.1 nm).

Scanning Electron Microscope

Scans a beam of electrons over the surface of a specimen to produce detailed 3D-like images.

Cryo-Electron Microscopy

A technique where biological samples are rapidly frozen and imaged with an electron microscope at cryogenic temperatures, allowing scientists to determine high-resolution 3D structures of proteins and complexes without needing to crystallize them.

Prokaryotic Cells

Cell type: Bacteria and Archaea; DNA is found in the nucleoid, without a membrane; lacks membrane-bound organelles; smaller and simpler.

Eukaryotic Cells

Cell Type: Plants, animals, fungi and protists; DNA is contained within a membrane-bound nucleus; possess membrane-bound organelles, such as the mitochondria; larger and more complex.

Nucleus

A membrane-bound organelle found in the eukaryotic cells that contains cell's DNA, organized into multiple linear chromosomes.

Nucleoid

A region within the prokaryotic cell where its DNA is located; it is not enclosed by a membrane. DNA in a nucleoid is typically single, circular chromosome.

Plant Cell

It's eukaryotic; they have a nucleus and other membrane-bound organelles, cell wall, chloroplasts, and often a large central vacuole.

Bacteria Cell

Prokaryotic; it lacks nucleus and membrane-bound organelles. It has cell wall and ribosome.

Animal Cell

It's eukaryotic; has nucleus and other membrane-bound organelles like the mitochondria and lysosome; doesn't have cell wall or chloroplasts.

Advantages of Small Cell Size

Smaller cell size provides several important advantages for cellular function, including a higher surface area-to-volume ratio, allowing for more efficient exchange of materials.

Surface Area and Volume Relationship

As cell size decreases, the surface area increases relative to the total volume, leading to more efficient internal transport and communication.

plasma membrane

Thin, flexible barrier that encloses the cell and controls what enters and what exits.

cell wall

A rigid structure that surrounds the cell and provides protection, found in prokaryotic cells.

cytoplasm and cytosol

The fluid inside of the cell where organelles are suspended; cytoplasm refers to the entire contents of the cell, while cytosol is the fluid component within the cytoplasm.

ribosomes

Small structures responsible for protein synthesis, found in both eukaryotic and prokaryotic cells.

flagella

Whiplike structure that helps cells move; typically longer and usually only one per cell, found in both eukaryotic and prokaryotic cells.

cilia

Whiplike structure that helps cells move; shorter and more numerous than flagella, found in both eukaryotic and prokaryotic cells.

SER and RER

Smooth and rough endoplasmic reticulum involved in protein synthesis, modification, and lipid production, found in eukaryotic cells.

Golgi apparatus

A stack of flattened sacs responsible for packaging and distributing proteins, found in eukaryotic cells.

central vacuoles

Large storage compartments in plant cells, found in eukaryotic cells.

mitochondria

Known as the 'powerhouse' of the cell, producing ATP, found in eukaryotic cells.

chloroplast

Responsible for photosynthesis, found only in plant cells, a type of eukaryotic cell.

centrioles

Involved in cell division, found in eukaryotic cells.

cytoskeleton

Network of fibers that provides support and helps with cell movement, found in eukaryotic cells.

Lysosome

An organelle that breaks down waste materials and worn-out cell components, found in eukaryotic cells.

cell membrane

A structure that all cells have, serving as a barrier and controlling entry and exit.

cytoplasm

The fluid inside of the cell where organelles are suspended.

DNA

The genetic material found in all cells.

Ribosome

A structure responsible for protein synthesis found in all cells.

prokaryotic cell wall

Composed of Peptidoglycan or Pseudopeptidoglycan.

eukaryotic plant cell wall

Composed of Cellulose.

eukaryotic fungi cell wall

Composed of Chitin, glucans, and mannans.

largest plant cell organelle

Central vacuole, can take up to 90% of the cell's volume and stores water, nutrients, and waste.

largest animal cell organelle

Nucleus, which commands the cell's genetic material and controls cellular activities.

endosymbionts

Mitochondria and chloroplasts are considered endosymbionts because they originated from free-living bacteria that were engulfed by early eukaryotic cells.

endosymbiotic hypothesis

Explains the prokaryotic origin of mitochondria and chloroplasts, which produce ATP and perform photosynthesis respectively.

Nuclear membrane

The nuclear membrane is a double membrane, consisting of an outer membrane and an inner membrane, surrounding the nucleus. It is made of phospholipids.

Nuclear membrane function

It acts as a protective barrier, separating the nucleus from the cytoplasm and controlling the movement of molecules between the two compartments.

Pores

These are large protein complexes that form channels or openings through the nuclear envelope.

Pores function

They regulate the passage of molecules, allowing essential components proteins and mRNA to enter or leave the nucleus, while restricting larger molecules like DNA.

Nucleolus

A prominent, non-membrane bound structure located within the nucleus.

Nucleolus function

Its primary role is to synthesize ribosomal RNA (rRNA) and assemble ribosomes, which are crucial for protein synthesis in the cytoplasm.

Ribosomes function

While assembled in the new nucleolus, they are then exported to the cytoplasm. Ribosomes are responsible for translating messenger RNA (mRNA) into your proteins.

Genetic material

Refers to the DNA and associated proteins that make up the chromosomes within the nucleus.

Chromatin

The loose, decondensed form of DNA and proteins within the cell's nucleus during the interphase stage of the cell cycle, allowing for gene expression.

Chromosomes

A highly condensed, organized structure of DNA and proteins that forms from the coiling of chromatin during cell division.

Ribosomes composition

Ribosomes are made of ribosomal RNA and proteins.

Types of vacuoles

Sap vacuoles (including the plant central vacuole) for storage and turgor pressure; Contractile vacuoles for osmoregulation in unicellular organisms; Food vacuoles for digestion in protozoa and phagocytic cells; Gas vacuoles for buoyancy in prokaryotes.

Microfilaments function

Primarily responsible for cellular movement, including muscle contraction, pseudopod extension, and cytokinesis; they also contribute to cell shape and provide structural support near the cell membrane.

Microtubules function

Involved in intracellular transport, cell division (forming the spindle apparatus), maintaining cell shape, and the movement of organelles within the cell; they are also the primary component of cilia and flagella.

Intermediate fibers function

Primarily provide structural support to the cell, anchoring organelles and maintaining cell shape; they are more stable than microfilaments and microtubules and are composed of a variety of proteins like keratin.

Intercellular junctions

Connect adjacent cells, enabling structural support and communication through specialized structures like tight junctions, adherens junctions, desmosomes, and gap junctions.

Anchoring junction (desmosomes, adhering junction)

They hold cells together and provide strength, especially in tissues like skin.

Tight junction

Seal cells tightly to prevent leakage, found in linings like the intestine.

Gap junction

Allow communication between cells by letting small molecules and ions pass through.

Plasmodesmata

Channels in cell walls that connect plant cells, allowing transport and communication, like gap junctions.

Simple diffusion

The process by which molecules move from an area of higher concentration to an area of lower concentration without the need for energy.

Osmosis

The diffusion of water across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration.

Plasmolysis

The process in which cells lose water in a hypertonic solution, causing the cell membrane to pull away from the cell wall.

Turgor pressure

The pressure exerted by the fluid in the central vacuole against the cell wall, maintaining cell shape and rigidity.

Endocytosis

The process by which cells internalize substances by engulfing them in a vesicle.

Pinocytosis

A form of endocytosis in which the cell engulfs liquid from the surrounding environment.

Phagocytosis

A form of endocytosis in which the cell engulfs solid particles.

Exocytosis

The process by which cells expel materials in vesicles that fuse with the plasma membrane.

Facilitated diffusion

The process of passive transport of molecules across a cell membrane via a specific transmembrane integral protein.

Active transport

The movement of molecules across a cell membrane from a region of lower concentration to a region of higher concentration, requiring energy.

Cotransport

A mechanism that moves two substances across a membrane in the same direction or in opposite directions.

Phospholipid head

The polar and water-soluble portion of a phospholipid, which contains a phosphate group and is hydrophilic (water-loving).

Phospholipid tail

The nonpolar and water-insoluble portion of a phospholipid, made up of fatty acid chains, which is hydrophobic (water-fearing).

Fluid Mosaic Model

The plasma membrane is described as a 'Fluid Mosaic Model' because it is made of a flexible (fluid) lipid bilayer with a 'mosaic' of proteins embedded in or attached to it.

Bilayer arrangement of phospholipids

Phospholipid molecules form a bilayer because they have hydrophilic heads and hydrophobic tails, with heads facing outward and tails facing inward in an aqueous environment.

Hypertonic solution

The solution has a higher solute concentration than the cell, causing water to move out of the cell.

Hypotonic solution

The solution has a lower solute concentration than the cell, causing water to move into the cell.

Crenation

The process where red blood cells shrivel due to water moving out in a hypertonic solution.

Lysis

The process where red blood cells swell and may burst due to water moving in a hypotonic solution.

Turgid plant cell

A plant cell that becomes swollen and firm due to turgor pressure in a hypotonic solution, which is ideal for plants.

Isotonic (isosmotic)

The solution has the same solute concentration as the cell.

Water movement in isotonic solution

Water moves in and out equally; no net movement.

RBC in isotonic solution

Stays the same size and shape — normal condition.

Plant Cell in isotonic solution

Becomes flaccid (not firm), which is not ideal but not harmful.

Integral proteins

Embedded within the lipid bilayer, often spanning the membrane, involved in transport, signaling, or acting as receptors.

Peripheral proteins

Attached to the surface of the membrane and not embedded; they support the membrane and help with cell signaling or structure.

Hybrid cell experiment purpose

To show that membrane proteins can move within the lipid bilayer.

Energy

The capacity to do work or cause change.

Metabolism

All the chemical reactions that occur within a living organism to maintain life.

Activation Energy

The minimum amount of energy required to start a chemical reaction.

Thermodynamics

The study of energy transformations and how energy flows in systems.

Exergonic Reaction

A chemical reaction that releases energy (usually spontaneous).

Endergonic Reaction

A chemical reaction that requires an input of energy to proceed.

Catalyst

A substance that speeds up a chemical reaction without being consumed.

Coupled Reactions

Reactions in which an exergonic reaction drives an endergonic reaction, allowing energy transfer.

Catabolism

The set of reactions that break down molecules into smaller units, releasing energy (e.g., digestion).

Anabolism

The set of reactions that build complex molecules from smaller ones, requiring energy input (e.g., protein synthesis).