Topic 4

Question 1

cell surface area

Answer 1

The main reason that cells are small - Surface area advantage to exchange material across plasma membrane

Question 2

cell volume ratio

Answer 2

As a cell’s size increases, its volume increases much more rapidly than its surface area.

Question 3

prokaryotic cells

Answer 3

a cell lacking a membrane bound nucleus/organelles except ribosomes

– “Pro-” greek referring to “Before nucleus” as the DNA is concentrated in a region that is not membrane-enclosed called the nucleoid.

has a cell wall

Question 4

eukaryotic cells

Answer 4

a cell characterized by membrane bound organelles & nucleus and one that possesses chromosomes whose DNA is associated with proteins

the three main parts of the generalized Eukaryotic cell are the Plasma membrane, Nucleus, and cytoplasm

Question 5

domain

Answer 5

the highest taxonomic rank in the hierarchical biological classification system, above the kingdom level

there are three domains: archaea, bacteria, and eukarya

archaea and bacteria are prokaryotes while eukarya are eukaryotes

Question 6

archaea

Answer 6

a highly diverse group of unicellular prokaryotes

cell wall made of polysaccharides and glycoconjugates

Question 7

eukarya

Answer 7

contains the eukaryotic organisms (protists, fungi, plants, animals)

Question 8

bacteria

Answer 8

a vast group of unicellular prokaryotes

cell wall made of Peptidoglycan

Question 9

eukaryote

Answer 9

organisms that have cells with a distinct nucleus and other membrane-bound organelles

are larger and more complex than prokaryotic cells

Question 10

nucleus

Answer 10

the membranous organelle that stores the chromosomal DNA and controls most of the cell’s processes & activity by controlling gene expression

Cells may be anucleate (RBCs) Mononucleate (most cells), or multinucleate (hepatocytes, and Skeletal muscles)

Question 11

nucleoid

Answer 11

the area of a prokaryotic cell, typically near the center, that contains the genome in the form of DNA compacted with protein

Question 12

cytoplasm

Answer 12

the Intracellular fluid, containing organelles, that perform specific cellular functions

Question 13

cell junctions

Answer 13

ways cells can adhere to each other or the extracellular matrix

there are three types

Question 14

gap junctions

Answer 14

a junction between adjacent animal cells that allows the passage of materials between the cells

a communicating junction between adjacent cells, which form hollow cylinders (called Connexons) that allow small molecules to pass from cell to cell.

Used to spread ions, simple sugars, and other small molecules pass through these water-filled channels.

Allows electrical signals to be passed quickly from one cell to the next cell. Are found in electrically excitable tissue, such as the heart and smooth muscle, where ion passage from cell to cell helps synchronize their electrical activity and contraction.

Question 15

tight junctions

Answer 15

region of actual fusion of plasma membranes between two adjacent animal cells that prevents materials from leaking through the tissue

Integral proteins on adjacent cells fuse to form an impermeable junction that encircles the whole cell, similar to the seal on a “Ziploc bag.” Prevents fluids and most molecules from moving in between cells

Found in the Epidermis, and digestive tract, to keep digestive enzymes and microbes from seeping into the bloodstream

Question 16

desmosomes

Answer 16

a type of anchoring junction that links adjacent cells by connecting they cytoskeletons with cadherin proteins

mechanical couplings scattered like rivets along the sides of adjacent cells to prevent their separation.

Linker proteins, Cadherins, are anchored to the cell through thickened “button-like” areas on inside of the plasma membrane called Plaques.

Plaques are connected intercellularly by keratin filaments for added anchoring strength.

reduce the possibility of tearing under tension by allowing “give” between cells

Neighboring cells are bound together into sheets and also contribute to a continuous internal network of strong fibers that act as “guy-wires,” that distribute tension throughout a cellular sheet.

Are found in abundance in tissues subjected to great mechanical stress, like skin and heart muscle.

Question 17

plasmodesmata

Answer 17

in plants, and they are the cytoplasmic connection between adjacent cells, function is similar to gap junctions in animal cells

cell walls separate every cell from all others, and cell to cell junctions occur only at holes or gaps in the walls, to allow plasma membrane of adjacent cells to communicate with one another.

Question 18

ribosomes

Answer 18

The molecular machine that carries out protein synthesis, made up of protein and ribosomal RNA (rRNA)

There are two types…
Free ribosomes – sites of synthesis of soluble proteins that function in cytosol or other organelles
Membrane-bound ribosomes – attached to membrane of endoplasmic, site of synthesis of proteins to be incorporated into membranes or lysosomes or exported from cell.

Question 19

plasma membrane

Answer 19

Consists of membrane lipids that form a flexible lipid bilayer

membrane surrounding the cytoplasm of a cell; consists of a single phospholipid bilayer with embedded proteins

acts as a selectively permeable barrier & allows cell recognition and communication

Physical barrier separating intracellular from extracellular environment

Specialized membrane proteins float through this fluid membrane, resulting in constantly changing patterns referred to as fluid mosaic (made up of many pieces) pattern

Surface sugars form glycocalyx

Membrane structures help to hold cells together through cell junctions

Lipid bilayer is made up of:
75% phospholipids, which consists of two parts:
Phosphate head: which is polar (Charged),
and are hydrophilic (water-loving)
Fatty acid tail: are nonpolar (no charge),
and are hydrophobic (water-hating)
5% glycolipids
Lipids with sugar groups on outer membrane surface
20% Cholesterol
Increases membrane stability

Question 20

flagella

Answer 20

long, threadlike structures protruding from the surface of a cell and assists in movement

Present in some prokaryotic cells, also in some Eukaryotic cells, but structure is different

Question 21

nuclear envelope

Answer 21

it is the bounding structure of the eukaryotic nucleus

composed of two phospholipid bilayers (double-membraned) that encloses the jelly-like fluid, the nucleoplasm

Outer layer Is continuous with rough endoplasmic reticulum, containing ribosomes

Inner layer (nuclear lamina) - Network mesh of proteins, which help to maintain nuclear shape, and acts as scaffolding for DNA

Nuclear pores allow substances to pass into and out of the nucleus.

Question 22

endoplasmic reticulum

Answer 22

internal membrane system that forms a netlike array of channels and interconnections within the cytoplasm of eukaryotic cells

Consists of series of parallel, interconnected cisterns – flattened membranous tubes that enclose fluid-filled interiors

IT IS CONTINUOUS WITH THE OUTER NUCLEAR MEMBRANE

divided into the rough and smooth ER

helps in protein maturation and transport

Question 23

rough endoplasmic reticulum

Answer 23

Looks rough because of the attached Ribosomes,

Synthesis of proteins to be secreted from cell,
Synthesis of many plasma membrane proteins and phospholipids.

Protein processing – proteins made by ribosomes go into the cisterns, modified as they move through, and put into a vesicle, and sent to the Golgi apparatus.

Question 24

smooth endoplasmic reticulum

Answer 24

looped tubules
continuous with rough ER

WIDE variety of jobs using enzymes in its plasma membrane…
- Lipid metabolism; cholesterol and steroid-based hormone synthesis; making lipids for lipoproteins
- Absorption, synthesis, and transport of fats
- Detoxification of certain chemicals (drugs, pesticides, etc.)
- Converting of glycogen to free glucose
- Storage and release of calcium
-Sarcoplasmic reticulum is specialized
smooth ER found in skeletal and cardiac
muscle cells
* The function will depend on which cell you are in

Question 25

centrioles

Answer 25

a cytoplasmic organelle located outside the nuclear membrane, identical in structure to a basal body

found in animal cells and in the flagellated cells of other groups

divides and organizes spindle fibers during mitosis & meiosis

Question 26

golgi apparatus

Answer 26

a collection of flattened stacks of membranous cistern sacs in the cytoplasm of eukaryotic cells

modifies, concentrates, and packages proteins and lipids received from rough Endoplasmic reticulum.

Three steps:
1. Transport vesicles from ER fuse with cis (inner) face of Golgi
2. Proteins or lipids taken inside are further modified, tagged, sorted, and packaged.
3. Golgi is “traffic director,” controlling which of three pathways final products will take as new transport vesicles pinch off trans (outer) face.

Final Transport vesicles can take one of three pathways:
- Secretory vesicles – containing proteins to be used outside of cell fuse with plasma membrane and exocytosis
- Vesicles containing lipids or transmembrane proteins, which fuse with plasma membrane or organelle membrane
- Lysosomes – containing digestive enzymes.

Question 27

mitochondria

Answer 27

consists of an outer membrane & an elaborate inner membrane

responsible for producing ATP, the cell’s main energy-carrying molecule

lozenge-shaped

Have their own circular DNA, RNA and Ribosome, Reproduce on their own, and inherited from individual’s mother

Question 28

chloroplasts

Answer 28

carry out photosynthesis, converting light energy into chemical energy

Contain Thylakoids (Thylakoid disk) which are membranous sacs that contain chlorophyll, a photosynthetic pigment for photosynthesis.

Also has a double layered membrane
and contain their own DNA and Ribosomes.

Question 29

chromosomes

Answer 29

the vehicle by which hereditary information is physically transmitted from one generation to the next

in a bacterium the chromosome consists of a single naked circle of DNA

in eukaryotes each chromosome consists of a single linear DNA molecule & associated proteins

Question 30

lysosomes

Answer 30

Spherical Membranous bags containing digestive enzymes (acid hydrolases) produced in the golgi body that isolate potentially harmful intracellular digestion from rest of cell

Digest ingested bacteria, viruses, toxins, as well as nonfunctional organelles

Also has a metabolic function in the cell, by breaking down and releasing glycogen, and Calcium from bone.

Question 31

vacuoles

Answer 31

a membrane-bounded sac in the cytoplasm of some cells, used for storage or digestion purposes in different kinds of cells

plant cells often contain a large central vacuole that stores water, proteins, & waste materials

storage compartments that sequester waste and help maintain water balance

Question 32

autolysis

Answer 32

occurs when lysosomes digestive enzymes are release intracellular due to the cell becoming injured.

Question 33

What differences distinguish prokaryotic and eukaryotic cells from each other?

Answer 33

Prokaryotes - nucleoid, 70s ribosome, no organelles except ribosomes, single circular DNA genome

Eukaryotes - nucleus, 80s ribosomes, organelles, histone proteins - DNA complex compacting DNA

Cell Size: Prokaryotic cells are generally smaller, while Eukaryotic cells are larger

• Cell Structure: Prokaryotic cells are usually unicellular, while most Eukaryotic cells are multicellular.
  .

Question 34

What structural differences between plant and animal cells exists?

Answer 34

• Cell Wall: Plant cells have a cell wall in addition to a cell membrane, while animal cells only have a cell membrane
• Shape: Animal cells are mostly round and irregular in shape, while plant cells have fixed, rectangular shapes
• Chloroplasts: These are present in plant cells for photosynthesis but absent in animal cells
• Vacuoles: Animal cells have one or more small vacuoles, while plant cells have one large central vacuole
• Energy Storage: Animal cells store energy in the form of complex carbohydrates and glycogen, while plant cells store energy as starch

Question 35

theory of the origin of eukaryotic cells (endosymbiosis)

Answer 35

It proposes the idea that the organelles found in eukaryotic cells arose from symbiotic relationship with multiple primitive prokaryotic cells. A larger cell engulfed the smaller cell(s) and kept them in its cytoplasm.

Question 36

Which of the following are differences between bacteria and archaea?

Answer 36

The molecular architecture of their cell walls

The type of ribosomes found in each

Question 37

Plasmodesmata in plants and gap junctions in animals are functionally similar in that?

Answer 37

They form channels between cells that allow diffusion of small molecules

Question 38

Eukaryotic Cell Walls

Answer 38

Found in plants, fungi, and many Protists, which protect and support the cells.

The cell walls of Eukaryotes are chemically and structurally different from Prokaryotic cells walls.

Plants have a Primary and Secondary wall, with a middle lamella (glues the walls together).

Plants and Protists, are made from Cellulose
Fungi is composed of Chitin

Question 39

Peroxisomes

Answer 39

Membranous sacs

Detoxify substances: like free radicals, toxic, highly reactive molecules that are natural by-products of cellular metabolism

Two main detoxifier enzymes: Oxidase, and Catalase
Oxidase – uses oxygen to convert toxins to hydrogen peroxide (H2O2), which is also toxic, but Peroxisomes use then catalase.
Catalase – which converts H2O2 to harmless Water H2O