Bio I: Chapter 4 Cell Structure & Function

nuclear envelope

A double membrane perforated with protein-lined pores that control the flow of materials into and out of the nucleus. Water, ions, and small molecules can pass freely through the pores.

protists

A eukaryotic organism that cannot be classified as an animal, plant, or fungus.

microtubules

A hollow rod composed of tubulin protiens that makes up part of the cytoskeleton in all eukaryotic cells and is found in cilia and flagella--thick and largest component in cytoskeleton. Transport organelles within the cell and guides chromosome movement during cell division. [*Table 4-2*]

archaea

Domain of unicellular prokaryotes that are one of the simplest forms of life lacking organelles and an organized nucleus, distinct from bacteria.

bacteria

Domain of unicellular prokaryotes that are one of the simplest forms of life lacking organelles and an organized nucleus, including some that can cause disease.

intermediate filaments

Larger than microfilaments and smaller than microtubules, diverse class of cytoskeletal units built from various proteins and provides supportive internal scaffolding that helps maintain cell shape. [*Table 4-2*]

microfilaments

Long, thin fibers that function in the movement and helps cells change shape. A cable composed of actin proteins in the cytoplasm of almost every eukaryotic cell, making up part of the cytoskeleton and allows muscle cell contraction; separates daughter cells during cell division. [*Table 4-2*]

cytoskeleton proteins

There are 3 categories of proteins: thin microfilaments, medium sized intermediate filaments, thick microtubules. [*Table 4-2*]

nucleoid

a distinctive region in the cytoplasm consisting primarily of DNA with RNA and protein. The DNA within takes form of a single, circular chromosome consisting of a long, coiled strand that carries essential genetic information. It is not separated from the cytoplasm by a membrane (as the nucleus).

cell theory

a fundamental concept of biology--completed by German physician Rudolf Virchow in 1855--that concludes that all cells come from previously existing cells. It consists of 3 principles--every organism is made up of one or more cells--the smallest organisms are single cells, and cells are the functional units of multicellular organisms--all cells arise from preexisting cells.

nucleus

a large organelle with three major parts: the nuclear envelope, chromatin, and the nucleolus [*fig 4-3*]. It is isolated from the rest of the cell by a double membrane, the nuclear envelope--which is perforated by protein-lined nuclear pores. It has nuclear material called chromatin, which consist of chromosomes made of DNA molecules and their associated proteins.

central vacuole

a large vesicles that occupies 3/4 or more of the volume of most mature plant cells and serves several functions. Its membrane helps to regulate the ion content of the cytosol and secretes wastes and toxic substances.

cytoskeleton

a scaffolding of protein fibers within the cytoplasm. It is important in regulating the following properties of a cell: cell shape--cell movement--organelle movement--cell division. There are 3 categories of proteins: thin microfilaments, medium sized intermediate filaments, thick microtubules.

endoplasmic reticulum (ER)

a series of interconnected membranes that form a labyrinth of flattened sacs and channels within the cytoplasm. Makes up 50% of the total membrane of the cell and plays a major role in synthesizing, modifying and transporting biological molecules throughout the cell.

ribosome

a small particle composed of a type of RNA unique to ribosomes, called ribosomal RNA (rRNA) combined with proteins. It can be used to synthesize a multitude of different proteins. Think: protein factory.

Golgi apparatus (Golgi)

a specialized set of membranes resembling a stack of flattened and interconnected sacs. The compartments act like finishing rooms of a factory--where final touches are added to products to be packaged and exported. Performs the following functions: modifies some molecules and an important role is to add charbohydrates to proteins to make glycoproteins--it separates various proteins received from the ER according to their destinations--and packages the finished molecules into vesicles that are then transported to other parts of the cell or to the plasma membrane for export.

endomembrane system

all eukaryotic cells contain internal membranes that create loosely connected compartments within the cytoplasm called this collectively. This system segregates molecules from the surrounding cytosol and ensures the biochemical processes occur in an orderly fashion.

mitochondria

all eukaryotic cells contain this--organelles that are sometimes called the "powerhouse" of the cells because they extract energy from food molecules and store it in the high-energy bonds of ATP. They are found in large numbers in metabolically active cells--muscles cells--less abundant in cells that are less active--cartilage.

deoxyribonucleic acid (DNA)

an inherited blueprint that stores the instructions for making all the parts of the cell and for producing new cells.

chloroplasts

are organelles surrounded by a double membrane where photosynthesis occurs--which captures sunlight and provides energy to power life--and are found in the cells of plants and some proteins. [The inner membrane encloses a fluid called stroma--within stroma are interconnected stacks of hollow, membranous sacs--individual sac is called a thylakoid, a stack of thylakoid is a granum.]

ribonucleic acid (RNA)

chemically similar to DNA, this copies the genes on DNA and helps construct proteins based on this genetic blueprint.

plastids

chloroplasts are highly specialized organelles called this--they are only found in plants and photosynthesis protists. {*fig 4-18*}

chromosomes

chromatin consist of these threadlike, gene-carrying structures and surrounds the nucleolus. Each chromosome consists of one very long DNA molecule and associated proteins.

cytoplasm

consists of all the fluid and structures that lie inside the plasma membrane but outside the nucleus [ figs 4-3 & 4-4]

plasma membrane

each cell is surrounded by an extremely thin, rather fluid membrane called this...consist of a double layer (a bilayer) of phospholipids and cholesterol molecules, with many different proteins embedded within the bilayer. Important functions: selectively isolating the cell's contents from the external environment--regulating the flow of materials into and out of the cell--and allowing communication with other cells and with the extracellular environment. (covered in detail in Ch. 5)

rough endoplasmic reticulum

emerges from the ribosome-covered outer nuclear membrane. It is studded with ribosomes on the surface facing the cytosol and appears rough. This is the most important site of protein synthesis in the cell, and it also serves to modify and transport proteins.

proteins in plasma membrane

facilitates communication between the cell and its environment--some allow passage of specific molecules or ions, while others respond to signals from molecules outside the cell and promote chemical reactions inside the cell.

contractile vacuoles

freshwater protists possess these...each composed of collecting ducts, a central reservoir and a tube leading to a pore in the plasma membrane.

cilia and flagella structure

hair-like structures that propel cells through fluids or move fluids past cells. It is covered by extensions of the plasma membrane and supported internally by microtubules (a ring of 9 fused pairs and one unfused pair in the center of the ring) of the cytoskeleton. It undulates continuously.

phospholipid bilayer

helps isolate the cell from its surroundings, allowing the cell to maintain essential differences in concentrations of materials inside and outside.

Diffusion

is the process by which molecules dissolved in fluids disperse from regions where their concentration is higher to regions where concentration is lower--a relatively slow process. Many nutrients and wastes move into, through, and out of cells by this...

smooth endoplasmic reticulum

lacks ribosomes and is scarce in most cells. In certain cells is abundant and specialized. From manufacturering lipids (steroids)--containing enzymes--storing ions--if present it serves specific functions associated with the cell.

chromatin

meaning "colored substance" It is nuclear material which consist of chromosomes made of DNA molecules and their associated proteins.

cilia

meaning "eyelash"--it is a hair-like structures, along with flagella, that propel cells through fluids or move fluids past cells. It is covered by extensions of the plasma membrane and supported internally by microtubules (a ring of 9 fused pairs and one unfused pair in the center of the ring) of the cytoskeleton. It undulates continuously. Shorter and more numerous than flagella and produce force on the surrounding fluid that is similar to that created by oars on the side of a rowboat.

pili

meaning "hairs"--they are surface proteins that project from the cell walls of many bacteria. There are 2 types: 1. Attachment--short and abundant, and helps bacterias adhere to structures. 2. Sex--few in number and quite long and allows one bacterium to bind to a nearby bacterium, of the same type and draws them together.

nucleolus

meaning "little nuclei"--the site of ribosome synthesis. It consists of ribosomal RNA (rRNA), proteins, ribosomes in various stages of synthesis and the portions of chromosomes that carry genes that code for rRNA.

flagella

meaning "whip"--it is a hair-like structures, along with cilia, that propel cells through fluids or move fluids past cells. It is covered by extensions of the plasma membrane and supported internally by microtubules (a ring of 9 fused pairs and one unfused pair in the center of the ring) of the cytoskeleton. It undulates continuously. Longer than cilia and usually have only one or two of these structures. It propels the cell through the fluid, acting like somewhat like the propeller on a motorboat.

prokaryotic cells

means "before the nucleus" (fig 4-19)--forms the bodies of bacteria and archaea, the simplest forms of life. Genetic material is not enclosed within a membrane--in contrast to eukaryotic cells. {*Table 4-1*}

eukaryotic cells

means "true nucleus"--are far more complex and make up the bodies of animals, plants, fungi and protists. It is contained within a membrane-enclosed nucleus--in contrast to prokaryotic cells. {*Table 4-1*}

lysosomes

membrane-bound sacs that digest food ranging from individual proteins to microorganisms such as bacteria. Contains dozens of different enzymes that can break down almost any type of biological molecule.

basal body

microtubules of each cilia and flagella arise from this located just beneath the plasma membrane. Produced by centrioles which are identical. Consists of a ring of nice fused triplets of microtubules.

endosymbiont hypothesis

most biologist accept this--which holds that both mitochondria and chloroplasts evolved from prokaryotic bacteria.

plasmids

most prokaryotic cells contains small rings of DNA called this...located outside the nucleoid. Usually they carry genes that give the cell special properties.

centrioles

produces basal bodies and are identical to them in structure. A single pair is found near the nucleus of animal cells. They appear to play a role in organizing the proteins of the cytoskeleton that are active in cell division.

nuclear pore complex

protein lined nuclear pores of the nuclear envelope allow water, ions and small molecules to pass freely through, but the passage of large molecules--particularly proteins, parts of ribosomes, and RNA--is regulated by this specialized gatekeeper protein that lines each nuclear pore.

vesicles

small temporary sacs made of membrane are called this. One function is to ferry biological molecules among various regions of the endomembrane system.

cytosol

the fluid portion of the cytoplasm in both prokaryotic and eukayotic cells is called this...it contains water, salt, and an assortment of organic molecules including proteins, lipids, carbohydrates, sugars, amino acids and nucleotides

organelles

the nucleus and other membrane-enclosed structure are collectively called this and contribute to the far greater structural complexity of eukaryotic cells.

cell walls

the outer surfaces of plants, fungi, and some protists are covered with this nonliving, relatively stiff coatings that are secreted outside the plasma membrane. They protect the delicate plasma membrane and its cytoplasmic contents. Usually porous, allowing oxygen, carbon dioxide and water dissolved molecules to flow easily through them.

chlorophyll

the thylakoid membranes contain this pigment molecule--which give plants their green color--during photosynthesis it captures the energy of sunlight and transfers it to other molecules in the thylakoid membranes.

food vacuole

when the plasma membrane, with its enclosed food, pinches off inside the cytosol and forms a vesicle called this...lysosomes merge with these and the lysosomal enzymes digest the food into small molecules such as amino acids, monosaccharides and fatty acids.