Chapter 6: A Tour of the Cell

How does bound ribosome protein synthesis work?

As a protein destined for the endomembrane system is being synthesized by a ribosome, the first amino acids in the growing polypeptide chain act as a signal sequence. That signal sequence ensures that the ribosome binds to the outer membrane of the ER and that the protein enters the ER lumen.

_____ is/are identical in structure to centrioles. Basal bodies Microfilaments Mitochondria Chromatin Nuclear envelopes

Basal bodies and centrioles have identical structures.

Which of these manufactures cellular membranes by adding membrane proteins and phospholipids to its own membrane? rough endoplasmic reticulum ribosomes nucleolus lysosomes Golgi apparatus

Rough ER: As membrane proteins grow from ribosomes on rough ER, the proteins are embedded into the rough ER membrane.

What does the smooth ER do?

Synthesis of lipids, metabolism of carbs, s tores calcium, detoxifies drugs & poisons

Under which of the following conditions would you expect to find a cell with a predominance of free ribosomes? a cell that is enlarging its vacuole a cell that is secreting proteins a cell that is digesting food particles a cell that is producing cytoplasmic enzymes a cell that is constructing its cell wall or extracellular matrix

a cell that is producing cytoplasmic enzymes

pseudopodia

a cellular extension of amoeboid cells used in moving and feeding

secondary cell wall

added between the plasma membrane and the primary cell wall, a strong and durable matrix often deposited in several laminated layers for plant cell protection and support

The movement of potassium into an animal cell requires

an energy source such as ATP or a proton gradient.

endoplasmic reticulum

an internal membrane system in which components of cell membrane and some proteins are constructed

plasmodesmata

an open channel in the cell wall of plants through which strands of cytosol connect from adjacent cells

Which of the following contain the 9 + 2 arrangement of microtubules? cilia, centrioles, and flagella flagella cilia cilia and flagella only centrioles

cilia and flagella only

peroxisomes

contain oxidase enzymes that detoxify alcohol, hydrogen peroxide, and other harmful chemicals

integrins

in animal cells, a transmembrane receptor protein that interconnects the extracellular matrix and the cytoskeleton.

transmission electron microscopy

electrons penetrate an ultrathin section of tissue to strike a photographic plate

keratin

hard protein material found in the epidermis, hair, and nails

microtubules

hollow tubes of protein about 25 nanometers in diameter, support the cell and moves organelles within the cell, composed of tubulin polymers

nucleolus

the organelle where ribosomes are made, synthesized and partially assembled, located in the nucleus

basal body

a structure resembling a centriole that produces a cilium or flagellum and anchors this structure within the plasma membrane

middle lamina

a thin layer of adhesive extracellular material, primarily pectins, found between the primary walls of adjacent young plant cells.

endosymbiont theory

mitochondria and plastids, including chloroplasts, originated as prokaryotic cells engulfed by an ancestral eukaryotic cell. The engulfed cell and its host cell then evolved into a single organism.

mitochondria

powerhouse of the cell, organelle that is the site of ATP (energy) production

phagocytosis

process in which extensions of cytoplasm surround and engulf large particles and take them into the cell

desmosomes

specialized junctions that hold adjacent cell together, consist of dense plate at point of adhesion plus extracellular cementing material

golgi apparatus

stack of membranes in the cell that modifies, sorts, and packages proteins from the endoplasmic reticulum

grana

stacked portion of the thylakoid membrane in the chloroplast. Grana function in the light reactions of photosynthesis

cell wall

strong supporting layer of cellulose or chitin around the cell membrane in plants, algae, and some bacteria

centrosome

structure present in the cytoplasm of animal cells, important during cell division; functions as a microtubule-organizing center. A centrosome has two centrioles.

smooth ER

synthesis of lipids, phospholipids and steroid sex hormones-help detoxify drugs and poisons (liver cells) involves adding hydroxyl groups to drugs to make soluble and easier to flush from body

Which of the following proteins are synthesized by bound ribosomes? Insulin DNA polymerase Ribosomal protein ER protein Actin Lysosomal enzyme

Insulin, ER protein, lysosomal enzyme

The sodium-potassium pump in animal cells requires cytoplasmic ATP to pump ions across the plasma membrane. When the proteins of the pump are first synthesized in the rough ER, what side of the ER membrane will the ATP binding site be on?

It will be on the cytoplasmic side of the ER.

Which proteins are synthesized by free ribosomes?

Proteins that function in the cytosol (such as actin) or in the nucleus (such as DNA polymerase) are synthesized by free ribosomes.

Which proteins are synthesized by bound ribosomes?

Proteins that function within the endomembrane system (such as lysosomal enzymes) or those that are destined for secretion from the cell (such as insulin) are synthesized by bound ribosomes.

cytoplasmic streaming

a circular flow of cytoplasm, involving myosin and actin filaments, that speeds the distribution of materials within cells.

dynein

a contractile protein connecting microtubules in the '9+2- arrangement of cilia and eukaryotic flagella. The contraction of dynein produces the characteristic movement of these structures.

nucleoid

a dense region of DNA in a prokaryotic cell.

thylakoids

a flattened membrane sac inside the chloroplast, used to convert light energy to chemical energy.

actin

a globular protein that links into chains, two of which twist helically about each other, forming microfilaments in muscle and other contractile elements in cells.

proteoglycans

a glycoprotein consisting of a small core protein with many carbohydrate chains attached, found in the extracellular matrix of animal cells.

fibronectin

a glycoprotein that helps animal cells attach to the extracellular matrix.

food vacuole

a membranous sac formed by phagocytosis of microorganisms or particles to be used as food by the cell.

central vacuole

a membranous sac in a mature plant cell with diverse roles in reproduction, growth, and development.

cytoskeleton

a microscopic network of actin filaments and microtubules in the cytoplasm of many living cells that gives the cell shape and coherence

nuclear lamina

a netlike array of protein filaments that maintains the shape of the nucleus.

scanning electron microscopy

a process that utilizes an electron beam to produce an image of the three-dimensional surface of biological samples; the sample is coated with a thin layer of a heavy metal such as gold or palladium and then exposed to an electron beam

myosin

a protein present in muscle fibers that aids in contraction and makes up the majority of muscle fiber, thick filaments

motor proteins

a protein that interacts with cytoskeletal elements and other cell components, producing movement of the whole cell or parts of the cell.

primary cell wall

a relatively thin and flexable cell wall furthest outside that is first secreted by a plant cell

chloroplast

a structure in the cells of plants and some other organisms that captures energy from sunlight and uses it to produce food

nuclear envelope

double membrane perforated with pores that control the flow of materials in and out of the nucleus

tubulin

globular protein subunit forming the hollow cylinder of microtubules

Peroxisomes produce _____ as a by-product of their metabolic processes.

hydrogen peroxide

Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a salt solution become limp and soft. From this we can deduce that the cells of the celery stalks are...

hypertonic to fresh water but hypotonic to the salt solution.

cristae

infoldings of the inner membrane of a mitochondrion that houses the electon transport chain and the enzyme catalyzing the synthesis of ATP.

chromatin

long strands of DNA found in the eukaryotic cell nucleus; condense to form chromosomes

tight junctions

membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid

centrioles

one of two tiny structures located in the cytoplasm of animal cells near the nuclear envelope; play a role in cell division.

lysosome

organelle filled with enzymes needed to break down certain materials in the cell

ribosomes

organelles made of protein and RNA that direct protein synthesis in the cytoplasm

plastids

organelles that are surrounded by a double membrane and contain their own DNA

glycoproteins

proteins that have carbohydrates covalently bonded to them

gap junctions

provide cytoplasmic channels between adjacent animal cells

intermediate filaments

range from 7-11nm in diameter, and strengthen the cell and help maintain its shape, stabilize the positions of organelles, and stabilize the position of the cell with respect to surrounding cells through specialized attachment to the cell membrane, composed of keratin subunits

contractile vacuole

saclike organelles that expand to collect excess water and contract to squeeze the water out of the cell

cilia

short, hair-like structures made of microtubules that enable movement of cells or movement of materials outside a cell

vesicles

small membrane sacs that specialize in moving products into, out of, and within a cell

cell fractionation

technique in which cells are broken into pieces and the different cell parts are separated

rough ER

that portion of the endoplasmic reticulum studded with ribosomes, attached to nuclear membrane and synthesizes phospholipids for cell membrane

cytosol

the aqueous part of the cytoplasm within which various particles and organelles are suspended

mitochondrial matrix

the compartment of the mitochondrion enclosed by the inner membrane and containing enzymes and substrates for the Krebs cycle.

stroma

the fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.

nucleus

the organelle that contains the DNA and controls the processes of the cell

extracellular matrix

the substance in which animal tissue cells are embedded, consisting of protein and polysaccharides.

microfilaments

thinner, solid rods of protein that enable the cell to move or change shape when protein subunits slide past one another, composed of actin subunits

light microscopy

uses light to permit magnification and viewing of cellular structures up to 1000 times their natural size

hemolysis

when the cell bursts when placed in a hypotonic solution

crenation

when the cell shrinks when placed in a hypertonic solution

flagella

whiplike tails found in one-celled organisms to aid in movement

what does a central vacuole do?

Stores compounds produced by the cell, creates internal pressure (keeps the cell turgid), regulates the composition of the cytoplasm