Lecture 7 - The Cell II

Question 1

Define a nucleoid

Answer 1

Discrete concentration of DNA located within the cell’s interior

Place, not a thing

Question 2

define plasmids

Answer 2

small circular molecules of DNA that carry a small number of genes

Question 3

describe pili

Answer 3

threadlike hollow structures that extend from one bacterial cell to another that allow the transfer of plasmids

Question 4

describe cytosol

Answer 4

liquid found inside the cells

Question 5

describe cytoplasm

Answer 5

area within the plasma membrane, which comprises of the cytosol, the mitochondria, plastids, and other organelles (but not their internal fluids and structures) but not the nucleus.

Question 6

Are organelles within the endomembrane system distinct?

Answer 6

no, they are interconnected

Question 7

how do organelles within the endomembrane system communicate?

Answer 7

by budding vesicles (small membrane enclosed sacs)

Question 8

what does the endomembrane system include?

Answer 8

nuclear envelope, endoplasmic reticulum, Golgi apparatus and visicles

Question 9

describe the nucleus

Answer 9

stores DNA

Question 10

Describe the nuclear envelope

Answer 10

• defines the boundary of the nucleus

- consists of two membranes (inner and outer) is a lipid bilayer with associated proteins

Question 11

describe nuclear pores

Answer 11

act as gateways allowing molecules to enter and leave the nucleus

Question 12

describe the nucleolus

Answer 12

appears as a mass of densely stained granules and fibers

• site where rRNA is synthesized
• assembly site of large and small ribosomal subunits

Question 13

are ribosomes part of the endomembrane system?

Answer 13

no

Question 14

describe ribosomes

Answer 14

• complexes made of rRNA and proteins (forming large and small subunits)
• sites of protein synthesis, in which amino acids are assembled into polypetides

Question 15

free ribosomes

Answer 15

found floating in the cytosol

* synthesize proteins that do not leave the inside of the cell*

Question 16

bound ribosomes

Answer 16

attached to the endoplasmic reticulum membrane

synthesize proteins that are secreted or components of the plasma membrane

Question 17

endoplasmic reticulum

Answer 17

• continuous with the nuclear envelope
• accounts for more than half of the total membrane in many eukaryotic cells
• two distinct regions of the ER that differ in structure and function

Question 18

rough endoplasmic reticulum

Answer 18

• studded with ribosomes on the surface of the membrane
• site of synthesis of proteins that are to be secreted
• synthesis of membranes

Question 19

smooth endoplasmic reticulum

Answer 19

• outer surface lacks ribosomes
• functions in diverse metabolic processes, which vary with cell type
• synthesis of lipids, metabolism of carbohydrates, detoxification of drugs and poisons, storage of calcium ions

Question 20

testosterone, a steroid hormone is synthesized in the cells of the testes. These cells would therefore have extensive amounts of WHICH organelle?

Answer 20

SMOOTH E.R.

steroids = lipids
lipids are synthesized in the smooth E.R.

Question 21

golgi apparatus

Answer 21

• looks like a series of flattened membrane sacs, called cisternae
• stacked cisternae are surrounded by many small vesicles
• not physically continuous with the E.R.
• next stop for most vesicles budding from the ER

Question 22

primary roles of golgi apparatus

Answer 22

• further modifies the lipids and proteins produced by the ER
• acts as sorting station
• synthesis of carbohydrates

Question 23

lysosomes

Answer 23

• specialized vesicles derived from the Golgi
• responsible for the intracellular digestion: degrade damaged or unneeded biomolecules, bacteria or other smaller organisms that have been engulfed
• uses digestive enzymes and an internal environment with an acidic pH

Question 24

vacuoles

Answer 24

• large vesicles derived from the endoplasmic reticulum and Golgi apparatus
• perform a variety of functions:
• food vacuole - formed by phagocytosis
• contractile vacuole - in aquatic protists, pumps excess water
• central vacuole - in plants, holds materials

Question 25

is the mitochondria part of the endomembrane system?

Answer 25

no

Question 26

what happens in the mitochondria

Answer 26

cellular respiration: a metabolic process that uses oxygen to generate ATP by extracting energy from sugars, fats and other fuels ** cellular respiration happens in the inner membrane

Question 27

how many mitochondria are in a cell?

Answer 27

some cells have a single large mitochondrion, more often a cell has hundreds to thousands of mitochondria (dependent on cell's function) tissues and organisms that require more energy have more mitochondria

Question 28

describe the mitochondria (its build)

Answer 28

enclosed by two membranes; outer membrane is smooth, inner membrane has infoldings called cristae - inner membrane divides mitochondrion into - inner membrane space: narrow region between the inner and outer membrane - mitochondrial matrix: contains enzymes, mitochondrial DNA and ribosomes.

Question 29

do animals have chloroplasts?

Answer 29

no

Question 30

chloroplasts

Answer 30

capture the energy of sunlight to synthesize sugars; a process known as photosynthesis - surrounded by double membrane and have an internal membrane-bound compartments called thylakoid

Question 31

thylakoid membrane

Answer 31

contains a specialized light-collecting molecules (eg. chloraphyll is the most common)

Question 32

what categories of cytoskeleton are found in eukaryotes vs animal cells

Answer 32

found in all eukaryotes: - microtubules - microfilaments found only in animal cells - intermediate filaments

Question 33

shape of microtubules

Answer 33

hollow rods constructed from protein dimer called tubulin

Question 34

microtubules function

Answer 34

- shape and support the cell (compression resistant) - serve as tracks along which organelles can move - form cilia and flagella - involved in separating the chromosomes during cell division

Question 35

name examples of microtubules

Answer 35

- flagella | - cilia

Question 36

flagella

Answer 36

- long, few | - has undulating motion that generates force in the same direction as the flagellum's axis

Question 37

cilia

Answer 37

- short, many | - work like oars, with alternating power and recovery strokes

Question 38

centrosome

Answer 38

- region located near the nucleus of animal cells considered to be a "microtubule organizing center" - are composed of 2 centrioles - are responsible for moving organelles and pulling the cell apart during cell division in animal cells

Question 39

do plants have a centrosome?

Answer 39

no

Question 40

microfilament structure

Answer 40

- solid rods - also called actin filaments as they are built from molecules of actin - can form structural networks

Question 41

microfilament function

Answer 41

TENSION BEARING - 3D networks support cell shape (make up the core of microvilli) - important component of muscle cells - serve as tracks along which organelles with motor proteins can move

Question 42

intermediate filaments structure

Answer 42

- found only in animal cells - not as frequently disassembled or reassembled as microtubules or intermediate filaments - especially sturdy (remain intact after cell death)

Question 43

intermediate filaments function

Answer 43

- tension bearing | - reinforce the cell's shape and fix the position of certain organelles

Question 44

path of a membrane protein

Answer 44

- mRNA translated into polypeptide at a bound ribosome (on RER) - Polypeptide moves through RER and eventually buds off as a vesicle - vesicle moves along microtubules until it reaches Golgi apparatus where polypeptide is further altered - final polypeptide moves through Golgi cisternae and eventually buds off as a vesicle - vesicle moves along microtubules until it reaches membrane, where it will stay and perform its function

Question 45

what is common in animal cells but not plant cells?

Answer 45

intermediate filaments, centrosome, centrioles

Question 46

what is common in all plant cells but not all animal cells

Answer 46

chloroplasts cell wall central value