Chapter 5 - Cells: The Working Units of Life

Question 1

Cell Theory

Answer 1

Cells are the fundamental units of life; all organisms are composed of cells; all cells come from preexisting cells; modern cells evolved from a common ancestor

Question 2

Size of a cell

Answer 2

Cells are small because of a high surface area-to-volume ratio; larger organisms have more cells rather than larger cells

Question 3

Magnification

Answer 3

Increases apparent size

Question 4

Resolution

Answer 4

Clarity of magnified object; minimum distance 2 objects an be apart and still be seen as 2 objects

Question 5

Light Microscopes

Answer 5

Use glass lenses and light; resolution is 0.2 micrometers

Question 6

Electron Microscopes

Answer 6

Use electromagnets to focus an electron beam; resolution is 0.2 nanometers

Question 7

Plasma Membrane

Answer 7

Outer surface of every cell; made of a phospholipid bilayer with embedded proteins and other molecules; functions as a selective barrier; cell needs a high surface area-to-volume ratio for efficient transfer of substances

Question 8

Prokaryotic Cell

Answer 8

Enclosed by a plasma membrane; DNA contained in a region called the nucleoid; cytoplasm consists of cytosol (liquid) plus filaments and particles

Question 9

Cytosol

Answer 9

Water mixed with dissolved ions, small molecules and soluble macromolecules; the liquid component of the cytoplasm

Question 10

Eukarotic Cell

Answer 10

Membrane enclosed cell with organelles and a nucleus; DNA is located in the nucleus

Question 11

Cell Wall

Answer 11

Most prokaryotes have a rigid cell wall outside the plasma membrane; some bacteria have a slimy polysaccharide capsule that surrounds the cell wall

Question 12

Flagella

Answer 12

Prokaryotes use long stringlike structures to mobilize and are made of the protein flagellin

Question 13

Pili

Answer 13

Short hairlike structures projecting from the surface on some bacteria (prokaryotes) that help attach to other cells or exchange DNA

Question 14

Cell Fractionation

Answer 14

A process in which organelles are separated from one another after cells are broken open and their contents are suspended in an aqueous medium. The medium is placed in a tube and spun in a centrifuge where heavier particles sediment at the bottom of the tube

Question 15

What do animal cells not have?

Answer 15

Chloroplasts, tonoplast, central vacuole and plamodesmata

Question 16

What do plant cells not have?

Answer 16

Lysosomes, centrioles and flagella

Question 17

Endomembrane System

Answer 17

Composed of the plasma membrane, nuclear envelope, endoplasmic reticulum (rough and smooth), golgi apparatus, and lysosomes

Question 18

Nucleus

Answer 18

Largest organelle surrounded by a double membrane (nuclear envelope and nuclear lamina) that contains most of the genetic material including chromosomes and the nucleolus

Question 19

Nuclear Lamina

Answer 19

Network of protein fibers on “nuclear” side of membrane within the inner and outer double membrane of the nucleus; maintains the shape of the nucleus

Question 20

Nucleolus

Answer 20

Concentrated region in the nucleus where ribosome components (rRNA) are synthesized from DNA; not an organelle because it is not surrounded by a membrane

Question 21

Endoplasmic Reticulum (ER)

Answer 21

Network of interconnected membranes in the cytoplasm

Question 22

Rough ER

Answer 22

Newly made proteins enter RER lumen (interior compartment inside the folds of the RER) where they are modified, folded and transported to other areas; site of first glycosilation of proteins, (carbohydrates attached to the newly synthesized proteins); contains attached ribosomes

Question 23

Smooth ER

Answer 23

Tubular structure attached to the RER; main function: site where lipids and steroids are synthesized;
also chemically modifies small molecules that may be toxic (drugs, pesticides, etc); site of glycogen degradation in animal cells (mobilization of glucose from glycogen in liver)

Question 24

Ribosomes

Answer 24

Sites of protein synthesis; not considered an organelle because they exist in both prokaryotic and eukaryotic cells; consists of ribosomal RNA (rRNA) and more than 50 different protein molecules

Question 25

Attached Ribosomes

Answer 25

Cell structure located attached to the walls of the RER; produce proteins that are transported out of the cell

Question 26

Free Ribosomes

Answer 26

Cell structure located in the cytoplasm; synthesize proteins that are released directly into the cytoplasm for use by the cell

Question 27

Golgi Apparatus

Answer 27

Cell structure that consists of flattened sacs (cisternae) and small membrane-enclosed vesicles; receives proteins from RER and further modifies them; concentrates, packages and sorts proteins; UPS packaging center of the organelles

Question 28

Lumen

Answer 28

Internal components inside the RER; liquid space

Question 29

Cis/Trans Region of the Golgi Apparatus

Answer 29

Cis region is nearest to the nucleus (faces the rough ER) that receives vesicles; trans region lies closest to the plasma membrane (faces the outer membrane) where vesicles bud of and move to the plasma membrane or other organelles

Question 30

Primary Lysosomes

Answer 30

Originate from the golgi apparatus; contain digestive enzymes which hydrolyze macromolecules into monomers

Question 31

Secondary Lysosomes

Answer 31

Primary lysosomes fuse with phagosomes to initiate digestion/hydrolysis of macromolecules

Question 32

Autophagy

Answer 32

Lysosome engulfs another organelle or some cytosol recycling cell’s own materials

Question 33

Phagocytosis

Answer 33

Materials/food molecules are enclosed from outside the cell that are engulfed in a vesicle called a phagosome; the phagosome moves through the cell and fuses with a primary lysosome to initiate digestion

Question 34

Mitochondria

Answer 34

Double membraned organelle that are considered the powerhouse of the cell that convert fuel molecules into ATP (cellular respiration); contains enzymes, DNA and ribosomes

Question 35

Chloroplast

Answer 35

Double membraned organelle in plant cell that is the site photosynthesis, converting light energy into food

Question 36

Thylakoids

Answer 36

Circular compartments in the chloroplast that contrain chlorophyll that harvest light energy for photosynthesis

Question 37

Grana

Answer 37

Stacks of thylakoids–circular compartments of inner membrane

Question 38

Stroma

Answer 38

Fluid in which grana are suspended inside a chloroplast

Question 39

Peroxisome

Answer 39

Single membranes organelle that collects and breaks down toxic by-products of metabolism such as peroxide (H2O2)

Question 40

Cytoskeleton

Answer 40

Meshwork of filaments that supports and maintain cell shape; holds organelles in position, enable movement organelles; composed of microtubules, microfilaments and intermediate filaments

Question 41

Microtubules

Answer 41

Long hollow cylinders made up of the protein tubulin (dimer of alpha and beta tubulin); thickest of the 3 components of the cytoskeleton; forms a rigid internal skeleton in some cells; can change length rapidly by adding or losing dimers; facilitates cell motility (cilia or flagella), chromosome movements in cell division and organelle movements

Question 42

Cilia

Answer 42

Many microtubules that are short and move with a stiff power stroke and flexible recovery stroke; 9 + 2 array: 9 fused pairs of microtubules called doublets form an outer cylinder and one pair of unfused microtubules runs up the center

Question 43

Flagella

Answer 43

Microtubules that are longer that are usually singular or in pairs where movement is snakelike; 9 + 2 array: 9 fused pairs of microtubules called doublets form an outer cylinder and one pair of unfused microtubules runs up the center

Question 44

Movement of Cilia/Flagella

Answer 44

Results from the sliding of the microtubule doublets past one another; dynein binds to microtubule doublets and allows them to slide; nexin can cross-link the doublets and prevent them from sliding, causing the cilium to bend

Question 45

Kinesin

Answer 45

The motor protein that moves vesicles or organelles from one part of the cell to another; binds to a vesicle and “walks” it allong by changing shape

Question 46

Centrioles

Answer 46

Cylindrical cell structure that forms the anchoring site for microtubules attached to chromosomes during cell division/mitosis; located in the centrosome and is composed of 9 sets of triplet microtubules (9 x 3 conformation); usually found in a pair

Question 47

Basal Body

Answer 47

Organelle of barrel-like microtubule structures located at the surface of the cell that anchor cilia or flagella attached to the cell

Question 48

Nexin

Answer 48

Interdoublet linkage in cilia or flagella microtubule structure; cross-links the doublets and appears to limit how far the doublets can slide. This causes the cilium or flagellum to bend.

Question 49

Microfilaments

Answer 49

2 intertwined strands of actin protein; actin has a positive and negative end that polymerizes to form long helical chains; thinnest of the 3 kinds of filaments; maintains/alters cell shape, helps cells to move in muscle contractions and cell motility (including moving whole cell or just the cytoplasm in the cell)

Question 50

Myosin

Answer 50

Motor protein associated with actin filaments in muscle cells that result in muscle contraction