Topic 1.4: Structure and Function of the Cell

Question 1

Explain why humans are made up of trillions of cells instead of just one.

Answer 1

If humans were made up of one cell, they wouldn’t be able to efficiently expel as many wastes or absorb as many nutrients. For instance, we wouldn’t be able to expel carbon dioxide.

Question 2

Explain why the cell is the basic unit of life

Answer 2

As the cell theory states, all organisms are made up of basic living units called cells, and all cells come only from previously existing cells.

Question 3

Describe the metabolic challenges of a large cell compared to a smaller size

Answer 3

When a cell is larger, the surface-area-to-volume ratio is smaller than that of a smaller cell, making it difficult to excrete and absorb as much waste or nutrients.

Question 4

What is a prokaryotic cell?

Answer 4

A cell that lacks a membrane-bound nucleus.

The domains Archaea and Eubacteria consist of prokaryotic cells. Prokaryotes generally exist as single celled organisms or as simple strings and clusters.

Question 5

What is a plasma membrane?

Answer 5

A plasma membrane is the boundary that separates the living contents in the cell from its surrounding environment. It regulates the entrance and exit of molecules into and out of the cytoplasm.

Question 6

What is a cytoplasm?

Answer 6

The cytoplasm is a semifluid composed of water, salts, and dissolved organic molecules. It is the medium for chemical reaction. It provides a platform upon which other organelles can operate within the cell. All of the functions for cell expansion, growth and replication are carried out in the cytoplasm of a cell.

Question 7

What is a cell wall?

Answer 7

A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mechanism

Question 8

What is a ribosome?

Answer 8

A site of protein synthesis in a prokaryotic cell.

Question 9

What is a flagellum/flagella?

Answer 9

Rotating filament present in some bacteria that pushes the cell forward.

Question 10

What is a fimbriae?

Answer 10

Hairlike bristles that allow adhesion to surfaces.

Question 11

What is a nucleoid?

Answer 11

Location of the bacterial chromosome

Question 12

What is a plasma membrane?

Answer 12

Sheath around cytoplasm that regulates entrance and exit of molecules.

Question 13

What is a cell wall?

Answer 13

Covering that supports, shapes and protects cell.

Question 14

What is a capsule?

Answer 14

Gel-like coating outside cell wall.

Question 15

What is peptidoglycan?

Answer 15

Peptidoglycan or murein is a unique large macromolecule, a polysaccharide, consisting of sugars and amino acids that forms a mesh-like peptidoglycan layer outside the plasma membrane, the rigid cell wall characteristic of most bacteria

Question 16

Explain the function of the plasma membrane

Answer 16

To form a barrier between the inside and outside of the cell and regulate what crosses the barrier.

Question 17

Identify the key bacterial structures and their function

Answer 17

Ribosome: site of protein synthesis

Flagellum: rotating filament present in some bacteria that pushes the cell forward

Fimbriae: hairlike bristles that allow adhesion to surfaces

Nucleoid: location of the bacterial chromosome

Plasma-membrane: sheath around cytoplasm that regulates entrance and exit of molecules

Cell-wall: covering that supports, shapes, and protects cell

Capsule: gel-like coating outside cell wall

Question 18

Explain the general differences among archaea, bacteria, and eukaryotic cells.

Answer 18

Archaea
*Has a cell wall, but with no peptidoglycan
*Does not have a nucleus
*Does not have membrane-bound organelles

Bacteria
*Has a cell wall, WITH peptidoglycan
*No nucleus
*No membrane-bound organelles, but some possess internal membranes where chemical reactions may occur

Eukaryotic cells
*Sometimes has a cell wall, never with peptidoglycan
*HAS nucleus and membrane-bound organelles

Question 19

What is the principle distinguishing feature of eukaryotic cells?

Answer 19

The presence of a nucleus, which separates the genetic material from the cytoplasm of the cell.

Question 20

What is a nucleus?

Answer 20

Command center of cell

Question 21

What is inside the nucleus?

Answer 21

Nuclear envelope

Nucleolus

Chromatin

Nuclear pore

Question 22

What is chromatin?

Answer 22

Network of DNA strands and associated proteins observed within a nucleus of a cell.

Question 23

What is a chromosome?

Answer 23

The structure that transmits the genetic material from one generation to the next; composed of condensed chromatin; each species has a particular number of chromosomes that is passed on to the next generation.

Human cells contain 46 chromosomes

Question 24

What is a nucleoplasm?

Answer 24

Semifluid medium of the nucleus, containing chromatin

Question 25

What is a nucleolus?

Answer 25

Dark-staining, spherical body in the nucleus that produces ribosomal subunits.

Question 26

What is a nuclear envelope?

Answer 26

Double membrane that surrounds the nucleus in eukaryotic cells and is connected to the endoplasmic reticulum; has pores that allow substances to pass between the nucleus and the cytoplasm.

Question 27

Define nuclear pore.

Answer 27

Opening in the nuclear envelope that permits the passage of proteins into the nucleus and ribosomal subunits out of the nucleus.

Question 28

Define ribosome

Answer 28

Site of protein synthesis in a cell; composed of proteins and ribosomal RNA (rRNA).

Question 29

Define polyribosome

Answer 29

String of ribosomes simultaneously translating regions of the same mRNA strand during protein synthesis.

Question 30

Define endoplasmic reticulum (ER)

Answer 30

System of membranous saccules and channels in the cytoplasm, often with attached ribosomes.

Question 31

Define rough ER (endoplasmic reticulum)

Answer 31

Membranous system of tubules, vesicles, and sacs in cells; has attached ribosomes.

Question 32

Define smooth ER (endoplasmic reticulum)

Answer 32

Membranous system of tubules, vesicles, and sacs in eukaryotic cells; site of lipid synthesis; lacks attached ribosomes.

Question 33

Define Golgi apparatus

Answer 33

Organelle consisting of sacs and vesicles that processes, packages, and distributes molecules about or from the cell.

Question 34

Define lysosome

Answer 34

Membrane-bound vesicle that contains hydrolytic enzymes for digesting macromolecules and bacteria; used to recycle worn-out cellular organelles.

Question 35

Define vacuole

Answer 35

Membrane-bound sac, larger than a vesicle; usually functions in storage and can contain a variety of substances. In plants, the central vacuole fills much of the interior of the cell.

Question 36

Define peroxisome

Answer 36

Enzyme-filled vesicle in which fatty acids and amino acids are metabolized to hydrogen peroxide that is broken down into harmless products.

Question 37

Define chloroplast

Answer 37

Membrane-bound organelle in algae and plants with chlorophyll-containing membranous thylakoids; where photosynthesis takes place.

Question 38

Define mitochondria

Answer 38

(sing., mitochondrion) Membrane-bound organelle in which ATP molecules are produced during the process of cellular respiration.

Question 39

Define photosynthesis

Answer 39

Process, usually occurring within chloroplasts, that uses solar energy to reduce carbon dioxide to carbohydrate.

Question 40

Define cellular respiration

Answer 40

Metabolic reactions that use the energy from carbohydrate, fatty acid, or amino acid breakdown to produce ATP molecules.

Question 41

Define stroma

Answer 41

Region within a chloroplast that surrounds the grana; contains enzymes involved in the synthesis of carbohydrates during the Calvin cycle of photosynthesis.

Question 42

Define thylakoid

Answer 42

Flattened sac within a granum of a chloroplast; membrane contains chlorophyll; location where the light reactions of photosynthesis occur.

Question 43

Define grana

Answer 43

(sing., granum) Stack of chlorophyll-containing thylakoids in a chloroplast.

Question 44

Define matrix

Answer 44

Unstructured semifluid substance that fills the space between cells in connective tissues or inside organelles.

Question 45

Define cristae

Answer 45

(sing., crista) Short, fingerlike projections formed by the folding of the inner membrane of mitochondria.

Question 46

Explain the function of a cell wall in eukaryotes

Answer 46

Protecting the cell while remaining permeable (allowing liquids/gasses to pass through)

Question 47

Describe how the endomembrane systems acts as a transport system

Answer 47

The endomembrane system transports molecules throughout the cell because the organelles that compose it are connected directly or by transport vesicles

Question 48

Explain why plant cells need both chloroplast and mitochondria

Answer 48

Plant cells make their food. Chloroplasts allow them to capture solar energy to produce organic molecules. Plant cells need mitochondria to break down the organic molecules to produce ATP which is used for energy in their metabolism

Question 49

Define cytoskeleton

Answer 49

Internal framework of the cell, consisting of microtubules, actin filaments, and intermediate filaments.

Question 50

Define actin filament

Answer 50

Component of the cytoskeleton; plays a role in the movement of the cell and its organelles; a protein filament in a sarcomere of a muscle, its movement shortens the sarcomere, yielding muscle contraction.

Question 51

Define motor molecule

Answer 51

Protein that moves along either actin filaments or microtubules and translocates organelles.

Question 52

Define intermediate filament

Answer 52

Ropelike assemblies of fibrous polypeptides in the cytoskeleton that provide support and strength to cells; so called because they are intermediate in size between actin filaments and microtubules.

Question 53

Define microtubule

Answer 53

Small, cylindrical organelle composed of tubulin protein around an empty central core; present in the cytoplasm, centrioles, cilia, and flagella.

Question 54

Define centrosome

Answer 54

Central microtubule organizing center of cells. In animal cells, it contains two centrioles.

Question 55

Define centriole

Answer 55

Cell structure, existing in pairs, that occurs in the centrosome and may help organize a mitotic spindle for chromosome movement during animal cell division.

Question 56

Define cilia

Answer 56

(sing., cilium) Short, hairlike projections from the plasma membrane, occurring usually in larger numbers.

Question 57

Identify the structural makeup of actin filaments, intermediate filaments, and microtubules.

Answer 57

All 3 are part of the cytoskeleton and are dynamic. Intermediate filaments play a structural role, while both actin filaments and microtubules have a structural and a movement role. Actin filaments are composed of actin monomers, microtubules are composed of tubulin monomers, and intermediate filaments are composed of various types of polypeptides.

Question 58

Contrast the function of cilia, flagella, and centrioles

Answer 58

Centrioles function in the process of cell division.
Flagella and centrioles function in the process of locomotion

Question 59

Explain how cilia and flagella are involved in movement

Answer 59

The dynein side arms of the microtubule doublets slide passed each other using the energy of ATP

Question 60

What is the endosymbiotic theory?

Answer 60

Explanation of the evolution of eukaryotic organelles by phagocytosis of prokaryotes.

Question 61

Recognize the evidence that suggest that chloroplasts and mitochondria were once independently living eukaryotes

Answer 61

*similar to bacteria in size and structure
*are bound by a double membrane
*divide by splitting
*have their own ribosomes (similar to prokaryotic ribosomes) and produce some protiens
*have similar ribosomal RNA sequences similar to prokaryotic rRNA sequences