Cell Structure and Function

Flashcards for cell biology exam review, covering cell theory, prokaryotic and eukaryotic cells, cell structures, and their functions.

What are the main points of the modern cell theory?

All organisms are made of one or more cells, cells arise from pre-existing cells, and all cells have a cell surface membrane, genetic material, and cytoplasm.

What is a eukaryotic cell?

A cell with a nucleus and membrane-bound organelles.

What is a prokaryotic cell?

A cell lacking a nucleus and membrane-bound organelles, with DNA lying free in the nucleoid region.

Which kingdom includes prokaryotic cells?

Bacteria

What is a slime capsule in bacteria?

A jelly-like coating of polysaccharides outside the cell wall that allows bacteria to stick to surfaces, form colonies, and escape attacks.

What are the functions of the bacterial cell wall?

Maintains cell shape, prevents bursting, and provides attachment sites.

What is the key difference between Gram-positive and Gram-negative bacteria?

Gram-positive bacteria have a thick peptidoglycan layer, while Gram-negative bacteria have a thinner layer with an outer lipopolysaccharide layer.

What is the lipopolysaccharide layer in Gram-negative bacteria?

A phospholipid bilayer attached to peptidoglycan by lipoproteins, containing polysaccharides and toxins.

What are respiratory and photosynthetic membranes?

Infoldings of the cell membrane where cellular respiration or photosynthesis occurs.

What is a flagellum?

A simple hollow cylinder of flagellin that propels the cell by rotating.

What are pili (fimbriae)?

Fine protein rods used for attachment to cells or surfaces and, in some cases, genetic material exchange.

What is the bacterial chromosome?

A single, large, coiled, circular DNA molecule in the nucleoid region that controls cell division and contains information for protein synthesis.

What are plasmids?

Small, self-replicating DNA pieces that provide survival advantages such as antibiotic resistance.

What are 70S ribosomes?

Small structures composed of proteins and RNA, sites of protein synthesis.

What are endospores?

Thick-walled, resistant structures containing genetic material and enzymes for survival under harsh conditions.

What are the four basic shapes of bacteria?

Cocci (spherical), bacilli (rod-shaped), vibrios (comma-shaped), and spirilli (corkscrew-shaped).

What is binary fission?

Asexual reproduction by division into two genetically identical daughter cells.

What are the four nutritional categories of bacteria?

Chemo-autotrophs, chemo-heterotrophs, photo-autotrophs, and photo-heterotrophs.

What is the endosymbiotic theory?

Mitochondria and plastids originated as separate prokaryotic organisms engulfed by primitive eukaryotes.

What is protoplasm (protoplast)?

The living contents of eukaryotic cells, divided into the nucleus and cytoplasm.

What are the functions of membranes?

Separates cell contents, controls material exchange, forms compartments, provides reaction surfaces, and acts as receptor sites.

What is the composition of phospholipids in membranes?

A polar phosphate head and two non-polar fatty acid tails, arranged in a bilayer.

What is the fluid mosaic model of the cell membrane?

The membrane is fluid because phospholipids move, and proteins are embedded within the phospholipid bilayer.

What are intrinsic (integral) proteins?

Embedded proteins with hydrophobic regions interacting with fatty acid tails and hydrophilic regions facing aqueous environments.

What are extrinsic (peripheral) proteins?

Proteins on the membrane surface attached by weak bonds.

What are the functions of membrane proteins?

Transport proteins, recognition proteins, receptor proteins, catalytic proteins, structural proteins, and cell-to-cell adhesion proteins.

What are glycolipids?

Lipids with carbohydrate chains attached, involved in cell communication and recognition.

What is the role of cholesterol in membranes?

Maintains membrane fluidity and flexibility by disturbing close packing of phospholipids, and decreases permeability at high concentrations.

What are the steps in freeze-fracturing to reveal membrane structure?

Embedding tissue that is then rapidly frozen, fractured to split the membrane, coated with platinum and carbon, and then the tissue is dissolved away for EM examination.

What is the role of the nucleus?

Controls the cell's activities by containing genetic information, surrounded by a nuclear envelope, and contains one or more nucleoli.

What are the nuclear envelope and nuclear pores?

Two membranes perforated by pores that regulate the passage of large molecules.

What is chromatin?

DNA wound around histone proteins, which condenses into chromosomes during cell division.

What the function of the nucleolus?

Makes ribosomes.

What comprises the cytoplasm?

Contains cell organelles, biochemicals, and is the site of reactions and metabolic pathways.

What is rough endoplasmic reticulum (RER)?

Transport and modify proteins made by ribosomes on its surface.

What is smooth endoplasmic reticulum (SER)?

Synthesizes lipids.

What is the role of 80S ribosomes?

The site of protein synthesis.

What the function of the Golgi apparatus?

The complex transports and chemically modifies materials contained within it. It also form lysosomes.

What is the role of lysosomes?

Digest material taken by endocytosis and recycle unwanted structures. Also involve in secretion of enzymes outside the cell.

What is the role of peroxisomes?

Contain catalase, an enzyme that breaks down hydrogen peroxide.

What is the cytoskeleton?

Network of fibers determining cell shape and facilitates the movements of cell & organelles.

What is the role of centrioles?

Serve as MTOCs(microtubule-organizing centers) for creation of spindle.

What the role of Cilia and flagella?

Locomotion of individual cells and move fluids over cell surfaces.

What is role of microvilli?

Increase the surface area for absorption.

What is the role of mitochondria?

Sites of aerobic respiration and extract energy from food molecules and store it.

What is the role of chloroplasts?

Contain chlorophyll and other photosynthetic pigments.

What is the role of Vacuoles?

Create turgor pressure and provide support for non-woody parts.

What is the plant cell wall?

Provides mechanical strength and support for individual cells and for whole plant.

What is Plasmodesmata?

Connections that run through pores in plant calls, facilitates communication and cordination of cell.