Chapter 3- Cell Structure, Genetic Code, Protein Synthesis

Question 1

prokaryotic cell

Answer 1

-bacteria
-typically 0.2-2 um in diameter, small
-more primitive
-lack nuclei + membrane-bound organelles

Question 2

eukaryotic cell

Answer 2

human, animal, + plant cells
-typically 10-100 um in diameter, large (differs based on specific type of cell)
-contain nucleus + many other membrane-bound organelles

Question 3

amphipathic molecules

Answer 3

contain both polar + nonpolar regions
-amphipathic molecules are able to integrate/embed themselves into cell membranes

Question 4

plasma/cell membrane

Answer 4

a selective barrier surrounding all cells

Question 5

cytosol (cytoplasm)

Answer 5

watery substance found inside of the cell that surrounds organelles
-includes dissolved ions, proteins, enzymes, glucose, protein complexes (sarcomeres in muscle)

Question 6

cellular organelles

Answer 6

membrane-bound compartments

Question 7

functions of cell membranes

Answer 7

-regulate the passage of substances into/out of cells + between cell organelles + cytosol
-detect chemical messengers arriving at the cell surface
-link adjacent cells together by membrane junctions
-anchor cells to the extracellular matrix

Question 8

the specific location of a membrane protein depends on its ____

Answer 8

structure (polar, nonpolar, or amphipathic)

Question 9

3 types of membrane proteins

Answer 9

-cholesterol
-integral membrane proteins
-peripheral membrane proteins

Question 10

membrane proteins

cholesterol

Answer 10

lipid-based steroid molecule that is embedded within the cell membrane
-amphipathic
-interacts with polar + nonpolar parts of phospholipids in cell membrane
-helps to regulate/maintain membrane fluidity + stability

Question 11

membrane proteins

integral proteins

Answer 11

proteins integrated/embedded within the cell membrane
-interacts with both polar + nonpolar regions of phospholipid bilayer
-can either interact only with 1 region of the membrane, or span the entire membrane

Question 12

transmembrane protein

Answer 12

type of integral protein that spans the entirety of the cell membrane

Question 13

examples of integral proteins

Answer 13

-transporter proteins + channels: selectively allow for movement of water + other polar molecules (ions, glucose, etc.) across the cell membrane
-cellular receptors: transmit signals outside of the cell to the inside of the cell, respond to growth factors, insulin, inflammatory cytokines

Question 14

membrane proteins

peripheral proteins

Answer 14

proteins present inside the cell that attach at the periphery of the cell membrane
-interact with phosphate heads of phospholipids + cytosol (polar molecules)
-they are NOT amphipathic + do NOT embed/integrate into the membrane

Question 15

membrane junctions

Answer 15

discrete locations along the membrane where cells are physically joined
-play a role in attachment of cells to other cells + to the extracellular matrix; critical for the tissue structure + function
-allow for cells to communicate with neighboring cells

Question 16

desmosomes

Answer 16

provide strong attachments, holding cells firmly together
-present between cells that make up tissues that are often stretched like the skin, + our blood vessels
-help to maintain integrity of cell membrane

Question 17

tight junctions

Answer 17

tightly link 2 adjacent cells together, such that NO extracellular space remains between them
-ex: connect epithelial cells lining lumen of intestine
-forces selectivity in absorption of nutrients

Question 18

gap junctions

Answer 18

constitute small protein channels that link the cytosols of 2 adjacent cells together
-allow for small molecules, such as sodium + potassium ions for example, to pass from one cell to another
-muscle cells of the heart- gap junctions allow for the transmission of electrical activity between muscle cells, + synchronization of cardiac contraction

Question 19

nucleus

Answer 19

houses the cells genetic information (DNA)
-contains the genome/DNA of an organism, human DNA provides the code for making >20,000 proteins

Question 20

free ribosomes

Answer 20

translation of mRNA into proteins
-located in cytosol
-involved in linking amino acids together to form proteins (translation)

Question 21

membrane-bound ribosomes

Answer 21

attached to ER
-similar function as free ribosomes, but insert the synthesized proteins into the ER

Question 22

rough ER

Answer 22

have ribosomes attached
-protein synthesis
-folding + modification of proteins that are destined to be secreted from the cell, or go to specific organelles

Question 23

smooth er

Answer 23

involved in fatty acid + steroid synthesis, stores + releases calcium

Question 24

golgi apparatus

Answer 24

modification, sorting, + packing of proteins; delivery to other organelles
-proteins synthesized by ribosomes within the rough ER are transported to the Golgi complex… within the Golgi complex, the following occurs:
* proteins undergo modifications
* proteins are sorted + packaged into transport vesicles
->deliver proteins to other organelles
->deliver proteins to cell membrane for secretion into extracellular fluid

Question 25

mitochondria

Answer 25

primary site of ATP production -consumes O2 -produces ATP, CO2, H2O, heat -cells that are highly active will have more mitochondria (need more ATP/energy) -ex: oxidative skeletal muscles used during aerobic exercise

Question 26

mitochondria consume

Answer 26

O2

Question 27

mitochondria produces

Answer 27

-ATP -CO2 -H2O -heat

Question 28

lysosomes

Answer 28

removal of proteins/organelles that become damaged through normal wear and tear -contain enzymes that break down macromolecules into smaller subunits (ex: glycogen, lipids, proteins, nucleic acids) -remove proteins + organelles that become damaged -responsible for degradation of pathogens that have been phagocytosed “eaten” by cells of the immune system

Question 29

chromosomes

Answer 29

organized DNA -provide the code for making specific proteins -within each chromosome pair, 1 chromosome is inherited from mother, 1 from father

Question 30

how many chromosomes does each human cell have

Answer 30

23 pairs (duplicates) -exception is sex cells

Question 31

chromosome 23

Answer 31

male = XY female = XX

Question 32

chromatin

Answer 32

DNA, in association with proteins known as histones -visualized as threads projecting all around the nucleus

Question 33

genes

Answer 33

regions of DNA that codes for proteins -codes = genes -you have 2 copies of every gene, because chromosomes are in pairs ->20,000 genes present within the human genome, on specific hormones

Question 34

human genome

Answer 34

entirety of human DNA, the total genetic/hereditary information encoded by DNA that make us human

Question 35

2 regions of DNA

Answer 35

-coding regions: DNA sequences that provide code for making proteins; each region of DNA that codes for a specific protein is known as a gene -non-coding regions: DNA sequences that do not code for proteins

Question 36

alleles

Answer 36

refer to the 2 copies of a specific gene within chromosome pair (one received from mother + father)

Question 37

protein synthesis steps

Answer 37

transcription (DNA is copied forming single-strand of RNA, making short term copy of gene as mRNA) -> spicing (introns are removed) -> translation (amino acids coded for by mRNA are linked together)

Question 38

transcription

Answer 38

making short-term copy of a gene (called mRNA)

Question 39

each gene contains what 2 regions

Answer 39

-exons -introns

Question 40

exons

Answer 40

DNA sequences that provides instructions “code” for making a specific portion of the protein encoded by the gene

Question 41

introns

Answer 41

DNA sequences that “interrupt” the exons + DO NOT include instructions for making a protein

Question 42

codon

Answer 42

sequence of 3 nucleotide bases within EXONS that provide the code for a specific amino acid

Question 43

what do codons dictate

Answer 43

dictate which amino acids (and how many) will be joined together to make the protein coded by that gene

Question 44

translation

Answer 44

linking amino acids together based on code within the mRNA

Question 45

where does translation occur

Answer 45

on ribosomes -either free in cytosol or attached to rough ER

Question 46

3 ways a cell can control how much of a specific protein is present in that cell

Answer 46

-altering the rate of protein synthesis (based on controlling the rate of trascription/translation) -altering the rate of protein degradation -altering the stability of the mRNA