Chapter 4 - Cell Structure

Question 1

What did Robert Hooke do?

Answer 1

Coined the term cell.
In 1665, created an illustrated book of microscopic observations.

Question 2

What did Anton van Leeuwenhoek do?

Answer 2

Late 1600s, made the most high-quality lenses of the day, looked at tons of cells (human blood, sperm, pond water), and wrote about it.

Question 3

What is the first postulate of cell theory?

Answer 3

(1839) all living things are composed of cells.

Question 4

What is the biogenic law?

Answer 4

(1855) Rudolph Virchow stated that “all living cells arise from pre-existing cells”, not spontaneously generated as previously thought.

Question 5

What was Louis Pasteur’s experiment and its significance?

Answer 5

(1862) Performed experiments with open and closed sterilized flasks + broth to show that “life” needed a way into the flask to grow.
It proved the biogenetic law.

Question 6

In 1880 August Weissman added another part to cell theory – what was it?

Answer 6

“…cells living today trace their ancestry back to ancient times” i.e., there must be a common ancestral cell.

Question 7

Currently cell theory has 3 main principles…what are they?

Answer 7

All living things are made of cells.
A cell is the smallest unit in a living thing.
All cells come from other cells.

Question 8

Define magnification.

Answer 8

The increase in apparent size of an object. Reported as #x.
i.e. 200x magnification.

Question 9

Define resolution.

Answer 9

A measure of the clarity of an image. The ability of an optical instrument to show 2 nearby objects as separate.

Question 10

What are the two types of microscopes and their differences?

Answer 10

Light microscopes use light, good for live specimens.
Electron microscopes use electron beams and have much greater resolution.

Question 11

What are the two ways electron microscopes can be used to look at specimens?

Answer 11

Can focus a beam of electrons through a specimen (transmission electron microscopy, TEM = 2-D) or onto its surface (scanning electron microscopy, SEM = 3-D).

Question 12

The smaller the cell the _____ its surface area to volume ratio. The larger a cell, the _________ its surface area to volume ratio.

Answer 12

Higher; lower.

Large cells have more surface area than small cells, but they have much LESS surface area RELATIVE to their volume than smaller cells do.

Question 13

Why does size matter in cells?

Answer 13

Must be large enough to hold DNA and sub-cellular materials, but small enough to allow for adequate exchange with the environment.

Question 14

What living things have prokaryotic cells? What has eukaryotic cells?

Answer 14

Prokaryotic – Achaea and Bacteria (including cyanobacteria). (pro = before, karyon = nucleus).
Eukaryotic - Higher plants and animals. (eu = true, karyon = nucleus)

Question 15

How do prokaryotic cells differ from eukaryotic cells (5)? How are they similar (4)?

Answer 15

Both have a cell (plasma) membrane; one or more chromosomes with DNA; ribosomes to make proteins; cytoplasm.
Prokaryotes have no nuclear membrane (DNA is in the nucleoid region); smaller slightly different ribosomes; a rigid cell wall outside of the plasma membrane; a sticky outer coat (capsule) sometimes; much smaller than eukaryotic cells.

Question 16

What organelles have we talked about in eukaryotic cells and what do they do (10)?

Answer 16

Nucleus controls all functions of the cell using DNA.
Ribosomes make protein.
Endoplasmic reticulum makes and transports things.
Golgi apparatus finishes, sorts and ships things.
Lysosomes digest and recycle.
Vacuoles digestion, storage, and osmotic regulation.
Mitochondria the powerhouse of the cell.
Chloroplasts photosynthesis.
Cytoskeleton holds shit together.
Cilia + Flagella wiggle wiggle.

Question 17

What are the four major cellular functions?

Answer 17

Genetic Control.
Manufacture and Digestion.
Energy processing.
Structural Support, Movement, & Communication.

Question 18

What’s in the nucleus (5)? What does it do?

Answer 18

Double membrane/nuclear envelope holds it together, nuclear pores molecules can pass thru, nucleoplasm jelly-matrix things “float” it, chromatin composed of DNA/chromosomes, nucleolus makes special RNA used to create ribosomes.

Question 19

What’s in the nucleolus? What does it do?

Answer 19

Are rich in RNA. Makes special RNA used to create ribosomes, the ribosomal RNA (rRNA). Proteins interact with rRNA to form subunits of ribosomes. These subunits exit the nucleus and form functional ribosomes.

Question 20

What are ribosomes? Where are they found?

Answer 20

Protein making machines found in the rough endoplasmic reticulum (bound ribosomes) or floating in the cytoplasm (free ribosomes).

Question 21

What is the endomembrane system and which organelles does it include (6)?

Answer 21

Organelles that synthesize, distribute, store, and export molecules.
Includes the nuclear envelope, the Endoplasmic Reticulum (smooth and rough), Golgi Apparatus, lysosomes, vacuoles, and the plasma membrane.

Question 22

What is the endoplasmic reticulum (ER)? Where is it located?

Answer 22

An extensive membrane system within the cytoplasm of the cell.
Involved in the synthesis, modification and transport of substances produced in the cell. Connected to the nuclear envelope.

Question 23

What is smooth (SER) and rough endoplasmic reticulum (RER) and what do they produce?

Answer 23

RER: has ribosomes that make proteins, modified by the RER, makes a transport vesicle, which goes to the Golgi apparatus.
SER: involved in the synthesis of steroid hormones, lipids, oils, and other non-protein substances and in the storage of calcium.

Question 24

What is the cisternae? Where are they found?

Answer 24

Tubules and sacs that enclose an interior space that is separate from the cytoplasmic fluid. Found in the endoplasmic reticulum and Golgi apparatus.

Question 25

What and where is the Golgi Apparatus (GA). What does it do?

Answer 25

A stack of flattened membranous sacs or cisternae close to the nucleus. Continues processes begun in the ER. Sorts and modifies proteins for selective export.
Transport vesicles - cis face (receiving) - modified thru the stacks- exported from trans face (closest to plasma membrane).

Question 26

What’s a lysosome?

Answer 26

Small vacuoles that aid in cell digestion. Contain powerful digestive enzymes from the ER/GA. Food vacuoles combine with a lysosome to be digested. Can recycle old organelles.

Question 27

What’s a vacuole? How do vacuoles differ in plant and animal cells?

Answer 27

Large water containing vesicles (Digestion, Storage, and Osmotic Regulation).
Animals: contractile vacuoles help eliminate water from cytoplasm.
Plants: may have digestive functions, contain cell pigments or poisons. Are large and allow plant cells to grow bigger.

Question 28

What are contractile vacuoles and why are they important?

Answer 28

Vacuoles found in many freshwater organisms. Fill with water (from cytoplasm) and contract to expell their contents. Removes water that enters by osmosis from the environment.

Question 29

What are the parts of mitochondria (5)?

Answer 29

Outer membrane, inner membrane (highly folded) containing the mitochondrial matrix (containing mitochondrial DNA + ribosomes). In between membranes is the intermembrane space. The folds of the inner membrane are called cristae (increase surface area).

Question 30

What are mitochondria? What important cellular process are they involved in?

Answer 30

Energy producing organelles found
in all eukaryotic cells (both plant and animal). The site of cellular respiration. Converts energy from
sugars to energy of adenosine
triphosphate (ATP).

Question 31

What are the parts of a chloroplast (5)?

Answer 31

Inner and outer membrane with intermembrane space, stroma (fluid) inside the inner membrane containing chloroplast’s DNA, ribosomes, enzymes and a third membrane = thylakoids (system of flattened disks) that contain thylakoid space and chlorophyll. A stack of thylakoids is called a granum.

Question 32

What important cellular process are chloroplasts involved in?

Answer 32

Converting solar (light) energy to chemical (sugar) energy via photosynthesis.

Question 33

Do animal cells have chloroplasts?

Answer 33

No.

Question 34

What is the theory of endosymbiosis?

Answer 34

A theory that mitochondria and chloroplasts were formerly small
prokaryotes that began living within larger cells.

Question 35

What support is there for the theory of endosymbiosis?

Answer 35

Mitochondria and chloroplasts have:
A single circular DNA molecule (similar to prokaryotes); ribosomes similar to prokaryotes; a double membrane and divide independently from the cell.

Question 36

What is the cytoskeleton?

Answer 36

A network of protein fibres extending throughout the cytoplasm of a cell providing structural support and motility (movement) of internal cellular components.

Question 37

What are the three components of the cytoskeleton? What do they each do?

Answer 37

Smallest to largest:
Microfilaments (inside cell membrane, supports cells shape)
Intermediate Filaments (fibrous coil, reinforces shape, anchors organelles)
Microtubules (hollow tubes, maintains shape, makes tracks for organelles to move along).

Question 38

What does the cytoskeleton do? What does it do when combined with motor proteins?

Answer 38

Provides support to cells. Combined with motor proteins, microtubules act as tracks for organelles to move along within the cell – the transport highways of the cell.

Question 39

What are microtubules used to make?

Answer 39

Microtubules make up centrioles (important in cell division), cilia and flagella

Question 40

What are centrioles?

Answer 40

Small “clusters” of microtubules arranged in a circular bundle. They have a nine triplets of microtubules (9 x 3 arrangement).

Question 41

What do cilia and flagella do?

Answer 41

Move the cell through the environment or move fluid (of the environment) over the surface of the cell.

Question 42

What is a basal body? How are they configured?

Answer 42

An extension of each cilium or flagellum in the cytoplasm of the cell. Basal bodies have nine triplets of microtubules and no central microtubules.

Question 43

What is the configuration of centrioles in a cilia and flagella? How does this differ from that in centrioles or basal bodies?

Answer 43

Nine pairs of microtubule doublets form a circular arrangement around a central pair. “Nine-plus-two” (or, 9 x 2 +2) arrangement.
Basal bodies and centrioles have nine triplets of microtubules and no central microtubules. (9 x 3)

Question 44

What are doublets and triplets of microtubules connected by?

Answer 44

The doublets and triplets are all connected by dynein proteins.

Question 45

What are the primary differences between cilia and flagella?

Answer 45

They differ only in length, number per cell and type of motion. Flagella are much longer and fewer than cilia.
Cilia row, flagella undulate.

Question 46

What motor protein is responsible for the movement of cilia and flagella?

Answer 46

Dynein. Movement of cilia/flagella is the result of sliding movements of the protein between microtubule pairs.

Question 47

How do environmental contaminants appear to affect sperm?

Answer 47

Hormonally active chemicals in the environment (like phthalates) interfere with sex hormones and
negatively affect sperm quality.
Lower sperm counts, higher percentages of malformed sperm and reduced motility.

Question 48

What would happen to cilia and flagella if there were no dynein protein arms connecting pairs of microtubules? (as with the rare disease: primary ciliary dyskinesia)

Answer 48

Cilia of the lung and flagella of sperm cannot move, because the microtubules cannot bend. So lungs can’t be cleared and sperm can’t swim!

Question 49

What holds cells together in tissues (in animals)?

Answer 49

The extracellular matrix. Made of glycoproteins and strong collagen fibres that helps hold tissues together and support the plasma membrane.

Question 50

What are the three types of cell junctions in animal cells? Describe each.

Answer 50

Tight (very close, no leaks, tied by proteins);
Anchoring (desmosomes, cells riveted together with keratin proteins anchored in the cytoplasm);
Gap (communicating, protein-lined pores connect cells allowing ions to flow through)

Question 51

What type of junction allows for the coordination of heart muscle cells, so they all beat at once?

Answer 51

Gap junctions. The flow of ions through gap junctions of adjacent cells coordinates their contraction.

Question 52

What functions do plant cell walls have?

Answer 52

Skeletal support, preventing enlargement and rupturing of the plant cell in hypotonic solutions; important for absorption, transport and secretion of substances

Question 53

What are plasmodesmata?

Answer 53

Holes in the cell walls of plants that
allow for intercellular communication in plant tissues. Cell membrane and the cytoplasm extend through the plasmodesmata.

Question 54

What are pectins?

Answer 54

Pectins “glue” the cells together (in plants).

Question 55

What organelle controls gene expression?

Answer 55

The nucleus (and ribosomes which operate with RNA instructions).

Question 56

Which organelles are involved in the manufacture, distribution, and breakdown of cellular materials (6)?

Answer 56

The Endomembrane system:
Nuclear envelope;
Endoplasmic reticulum (ER);
Golgi apparatus;
Lysosomes;
Vacuoles; and
Plasma membrane.

Question 57

Which organelles produce energy in plants and animals?

Answer 57

Mitochondria in plants and animals.
Chloroplasts in only plants

Question 58

Which organelles provide structural support, movement and intercellular communication (4)?

Answer 58

Cytoskeleton (microfilaments, intermediate filaments and microtubules), extracellular matrix (in animals), cell junctions (between animal cells), and cell walls with plasmodesmata in plant cells.

Question 59

Which organelles are found only in plants?

Answer 59

Chloroplasts and cell walls.