Ch 3

Question 1

Cell Structure

Answer 1

1. Plasma membrane – selectively permeable, gives form, and separates from the external environment
   - ALL cells have this, separates individual units
2. Cytoplasm and organelles – fluid part of cell and cellular functions
   - most of water stored here
   - golgi bodies, lysosomes, mitochondria, etc
3. Nucleus – contains DNA and directs cell activities
   - “brain center”

Question 2

Plasma Membrane

Answer 2

Phospholipid barrier (double layer) between the intracellular and extracellular environments

• Hydrophobic center restricts the movement of water, water-soluble molecules, and ions
• ->hydrophobic (inside, fatty acid tails) and hydrophilic (double-layer goes to outside)
• Some substances pass through protein channels
• Proteins and phospholipids constantly move laterally – the fluid mosaic model

Question 3

Membrane Proteins

Answer 3

• Integral proteins- span the membrane (integrated into membrane)
• Peripheral proteins- embedded on just one side of the
membrane (associated with phospholipid head)
Functions:
• Structural support
• Transport
• Enzymatic control of cell processes
• Receptors for hormones and other molecules
• Self markers for the immune system

Question 4

Other Membrane Components

Answer 4

Carbohydrates– attached to lipids (glycolipids) and to proteins (glycoproteins); serve as antigens and interactions with regulatory molecules

Cholesterol–gives flexibility to the membrane

Question 5

Phagocytosis

Answer 5

IN
-Bulk transport or large extracellular substances into the
cell
-Important for body defense, inflammation, and apoptosis.

Question 6

Endocytosis

Answer 6

IN

1. The plasma membrane furrows INWARD rather than extending outward.
2. A small part of the membrane surrounding the substance pinches off and is brought in as a vesicle.
   - May be mediated by a receptor, receptor-mediated endocytosis.

Question 7

Exocytosis

Answer 7

OUT

Large cellular products (proteins) are moved out of the cell.

Question 8

Cilia and types

Answer 8

tiny, hairlike structures composed of microtubules
that project from the plasma membrane
1. Primary cilium – most cells have this nonmotile cilium; may have a sensory function in some cells
2. Motile cilia- beat in unison to move substances through hollow organs. Found in respiratory tract and uterine tubes
–> motile: 9+2, nonmotile: 9+0

Question 9

Flagella

Answer 9

a single whip-like structure that can propel a cell forward; sperm only

Question 10

Microvilli

Answer 10

Projections off/folds in the plasma membrane that increase the surface area.
-important for absorption in intestines, reabsorb water in kidneys

Question 11

Cytoplasm

Answer 11

Includes: organelles, a fluid called cytosol, the cytoskeleton, and inclusions (stored chemical aggregates such as glycogen).
–> may be interchangeable with “cytosol”

Question 12

Cytoskeleton

Answer 12

“Road-map” and structural support

• system of microtubules and microfilaments in cytoplasm
• Organize the intracellular environment and allow movement of muscle cells and phagocytic cells
• Form the spindle apparatus that pulls chromosomes apart in mitosis
• facilitate vesicle and organelle movement in the cell
• -> Actin (Microfilaments - predominant), Keratin (Intermediate), Microtubules (cilia, flagella, microvilli)

Question 13

Lysosomes

Answer 13

Organelles filled with digestive enzymes (acidic)

-Fuse with vacuoles after an immune cell engulfs a bacterium or dead cell

Question 14

Primary vs. Secondary Lysosome

Answer 14

Primary: only contains digestive enzymes (no work yet)
Secondary: contains the partially digested contents of the food vacuole or worn-out organelles (doing work)

Question 15

Autophagy

Answer 15

process of digesting damaged organelles and proteins in the cell (w/mistake or worn out)

Question 16

Apoptosis

Answer 16

programmed cell death

-cell suicide - engulf WHOLE cell away from within

Question 17

Necrosis

Answer 17

blows cell up —> releases lysosomes —> inflammatory response

-different from apoptosis

Question 18

Perioxisomes

Answer 18

Digestive, membrane-bound organelle

• Contain enzymes specific to certain oxidative reactions; degrade long-chain fatty acids and foreign molecules
• in most cells, LOTS in liver
• generate hydrogen peroxide
• must compartmentalize b/c if blown up would kill cell w/toxic H2O2

Question 19

Mitochondria

Answer 19

“Powerplant”

• site of energy production through aerobic cell respiration
• Most cells have mitochondria, and there can be thousands of mitochondria in a single cell
• Mitochondria can migrate and replicate; they have their own DNA, all maternal-derived

Question 20

Mitochondria structure

Answer 20

• inner membrane, outer membrane, inter membranous space
• ->inner membrane is folded into cristae to increase surface area for reactions
• central area = fluid called “matrix”

Question 21

Ribosomes

Answer 21

Protein factories of the cell
-Very small; made of 2 subunits of ribosomal RNA
and protein
-Found free in the cytoplasm or associated with the endoplasmic reticulum

Question 22

Endoplasmic Reticulum (ER)

Answer 22

System of membranous passageways from the nuclear membrane to the the plasma membrane
-close to nucleus

Question 23

Rough vs. Smooth ER

Answer 23

Rough ER: has ribosomes embedded on the outer surface, protein synthesis and modification.

Smooth ER: has NO ribosomes, synthesis of fatty acids, steroids, lipids.

Question 24

Golgi Complex (Apparatus)

Answer 24

• Consists of stacks of hollow, flattened sacs = increased SA
• cavities are called cistern
• one side receives proteins from the ER (close to rough ER), may modify proteins
• -> proteins are packaged in vesicles called endosomes, that bud off to fuse with the plasma membrane for exocytosis
• **sending it out to wherever it needs to be” = “Distribution Center”

Question 25

Cell Nucleus

Answer 25

- most cells have 1, muscle cells have 100s, RBCs have none - enclosed by the nuclear envelope made of two membranes Nucleoli: dark region not surrounded by a membrane, contains the DNA that codes for the production of ribosomal RNA

Question 26

Two membranes of nucleus

Answer 26

Outer membrane: continuous with rough ER Inner membrane: often fused to outer by nuclear pore complexes (which allow small molecules and RNA to move into/out of the nucleus through pores)

Question 27

DNA

Answer 27

contained in the nucleus 1. the gene on the DNA is transcribed as messenger RNA (mRNA) – GENETIC TRANSCRIPTION 2. the messenger RNA is then translated at the ribosome to assemble the proper amino acid sequence – GENETIC TRANSLATION

Question 28

Gene

Answer 28

a length of DNA that codes for a specific protein

Question 29

Chromatin

Answer 29

—>How we package DNA - cannot be stored in long strands -DNA in the nucleus is packaged with proteins called histones to form chromatin -

Question 30

Histones

Answer 30

positively charged and will interact with negatively charged DNA to cause spooling --> creates nucleosomes (DNA + protein + histone)

Question 31

Euchromatin

Answer 31

- ACTIVE in transcription - looser - chemical changes in histones (such as acetylation) allow molecules access to the DNA during gene expression

Question 32

Heterochromatin

Answer 32

- inactive regions --> much of the DNA is inactive | - highly condensed

Question 33

Transcription (RNA Synthesis)

Answer 33

- Start and stop regions at the beginning and end of the gene - Promoters - Transcription factors - RNA Polymerase - DNA is GCTA, RNA is CGAU - Forms precursor messenger RNA that detaches from the DNA template - only 1 DNA strand is transcribed

Question 34

Transcription (RNA Synthesis): Promoters

Answer 34

areas of DNA that are not part of the gene but signal | enzymes involved where to begin transcription

Question 35

Transcription (RNA Synthesis): Transcription Factors

Answer 35

bind to the promoter to begin transcription

Question 36

Transcription (RNA Synthesis): RNA polymerase

Answer 36

breaks the hydrogen bonds between the base pairs of DNA and assembles the appropriate RNA nucleotide -RNA nucleotides pair up to the DNA template

Question 37

RNA Types

Answer 37

- Precursor messenger RNA (pre-mRNA) - Messenger RNA (mRNA) - Transfer RNA (tRNA) - Ribosomal RNA (rRNA)

Question 38

Precursor messenger RNA (pre-mRNA)

Answer 38

made directly by transcription

Question 39

Messenger RNA (mRNA)

Answer 39

modified pre-mRNA; contains the code to make a specific protein

Question 40

Transfer RNA (tRNA)

Answer 40

carries amino acids to mRNA for translation --> turn nucleotide code to amino acid sequence, tRNA brings in AA •A single strand of RNA bent into a cloverleaf shape •One end has the anticodon, which is three nucleotides that will be complementary to the proper codon. •The other end has the appropriate amino acid bonded by aminoacyl-tRNA synthetase enzyme

Question 41

Ribosomal RNA (rRNA)

Answer 41

along with protein, forms ribosomes - site of translation - acts as an enzyme - -> unique: ribosomal enzyme required for protein synthesis

Question 42

Introns

Answer 42

noncoding regions within gene | -removed during mRNA synthesis/splicing

Question 43

Exons

Answer 43

coding regions within gene

Question 44

Translation (Protein Synthesis)

Answer 44

- mRNA attaches to a string of ribosomes to form a polyribosome - a group of three bases on DNA (triplet), gives the complementary three base sequence in mRNA (codon) - the codon codes for an amino acid, so the order of the codons --> the order of amino acids in a polypeptide

Question 45

Post-Translational Modification

Answer 45

* Protein folding (chaperone proteins) * Cross-linkage (disulfidebonds) * Cleavage * Addition of other molecules or groups (phosphate, methyl) * Assembly into polymeric proteins

Question 46

DNA Replication

Answer 46

1. Before cell division, each DNA molecule must replicate. 2. Involves many enzymes and proteins; two important enzymes are: a. Helicases b. DNA polymerase

Question 47

Helicases

Answer 47

break hydrogen bonds between the DNA strands - This creates a fork in the double-stranded molecule where nucleotides can be added to both strands - -> two exact replicas of DNA strand

Question 48

DNA polymerase

Answer 48

attaches complementary nucleotides to the exposed strand

Question 49

Cell Cycle

Answer 49

• Divided into interphase, mitosis, and cytokinesis • Interphase is divided into G1, S, and G2 • Mitosis is divided into Prophase, Metaphase, Anaphase, and Telophase • Cytokinesis overlaps the last parts of mitosis • Produces 2 identical cells to parent cell with 46 chromosomes (23 pairs) -gives 2 identical cells w/22 pairs of chromosomes —> need to make IDENTICAL skin/gut/etc cells

Question 50

Meiosis

Answer 50

-two cell division steps produce gametes (ova and sperm) -only occurs in the gonads (ovaries and testes) 1st Division: Homologous chromosomes line up side by side. One member of the pair is then drawn to each pole. Each daughter cell now has 23 (not 46) chromosomes, w/two chromatids (duplicated chromosomes). 2nd Divison: chromatids are separated * In the ovaries, three of the daughter cells die, only one becomes mature egg * Maternal and paternal members of homologous chromosome pairs are randomly shuffled; the daughter cells from first division have randomly derived chromosomes. * Reduction to 23 chromosomes allows for sperm and egg to combine and produce 46 chromosomes.