Cell Structure and Function

Question 1

Cholesterol

Answer 1

Steroid (a lipid)
Increases fluidity of a cell membrane at room temperature
Decreases fluidity of a cell membrane at high temperatures (at 37°C, for example)
Provides balance

Question 2

Functions of Integral Membrane Proteins

Answer 2

Transport (with ATP)
Enzymatic activity (enzymes)
Signal transduction (from a signaling molecule using a receptor)
Cell-cell recognition (with glycoproteins)
Intercellular joining
Attachment to the cytoskeleton and extra cellular matrix (E.C.M.)

Question 3

Glycoproteins

Answer 3

Sugar (carbohydrates) + protein in a cell membrane

Question 4

Glycolipids

Answer 4

Sugar (carbohydrates) + lipid in a cell membrane

Question 5

Lipid Rafts

Answer 5

A clustering of glycolipids, glycoproteins and cholesterol in a cell membrane

Question 6

Selective Barrier

Answer 6

Cell membrane regulates what goes in and comes out (ions, macromolecules, water, etc.)
Various means of transport to get across membrane

Question 7

ATP

Answer 7

Energy used by cells

Produced through respiration (in addition to heat)

Question 8

Endocytosis

Answer 8

Vesicle transport that enters the cell

Question 9

Exocytosis

Answer 9

Vesicle transport that exits the cell

Question 10

Cell Wall

Answer 10

Can provide protection

Provides structural stability and support

Question 11

Prokaryotic Cell Characteristics

Answer 11

Capsule
Cell wall made up of peptidoglycan (protects against osmosis and infections)
Nucleoid (which has no membrane) containing a large circular chromosome and proteins
Plasmids, which are independent, smaller circular extra chromosomal DNA (non-essential genes) transferred through an arm-like pilus
Pili and flagellum used for motility
Reproduce asexually
Might or might not be aerobic (need O_2)
Are smaller than Eukaryotic cells, which helps them with diffusion

Question 12

Eukaryotic Cell Characteristics

Answer 12

Nucleus
Ribosomes
Endomembrane system: E.R. (endoplasmic reticulum), Golgi apparatus, lysosome, vacuole
Perixosome
Mitochondria
Chloroplast
Cytoskeleton

Question 13

Organelles

Answer 13

Usually membrane-bound
Have specific functions
“Float” in the semi-fluid cytosol

Question 14

Cytoplasm

Answer 14

Cytosol + organelles

Question 15

Nucleus

Answer 15

Stores genetic information (DNA) as chromosomes (the latter which form chromatin)
Surrounded by nuclear envelope, a double bilayer connected to the endomembrane system through which there is nuclear pore (proteins) to allow for trafficking
Nucleolus is an area of RNA (rRNA) production in the nucleus

Question 16

Endomembrane System

Answer 16

Connects multiple organelles (including nucleus)
Endoplasmic reticulum (E.R.): rough E.R. and smooth E.R.
Golgi apparatus
Lysosome
Vacuole and Vesicles

Question 17

Rough Endoplasmic Reticulum (Rough E.R.)

Answer 17

Has ribosomes associated to it and specializes in producing proteins (especially membrane-bound)

Question 18

Smooth Endoplasmic Reticulum

Smooth E.R.

Answer 18

Focuses on lipid synthesis

Question 19

Ribosome

Answer 19

Only organelle that is not membrane-bound
Consists of RNA + proteins
Around 2.7 MDa (one hundred times bigger than a typical protein)
Produces proteins
Found floating in the cytosol or bound to membranes (Rough E.R.)

Question 20

Golgi Apparatus

Answer 20

Sorts proteins and lipids, modifies them (such as glycoproteins), and sends them to targets (internal or external)

Question 21

Lysosomes

Answer 21

Have a pH of around 5 and contain digestive enzymes that can degrade various biomolecules (lipases, nucleases, proteases, carbohydrases) in a cell
Proton pumps help maintain an acidic pH
Transporters allow broken-down molecules to be transported out of the lysosome

Question 22

Vacuoles

Answer 22

Involved in the entry / exit of particles, including food and water
Central vacuoles, found in many mature plant cells, hold organic compound and water
Food vacuoles are formed by endocytosis
Contractile vacuoles, found in many freshwater protists, pump excess water out of cells

Question 23

Vesicles

Answer 23

Involved in the entry / exit of particles, including food and water

Question 24

Peroxisome

Answer 24

Involved in degrading alcohol and long fatty-acids

Produces hydrogen peroxide while doing so, and is specifically designed for eliminating this toxic compound

Question 25

Mitochondria

Answer 25

Energy producing centre Responsible for respiration and producing ATP from glucose in almost all eukaryotes Abundance correlates to oxygen usage and energy-requirements of a cell Double-bilayer that contains many proteins and encloses a liquid area filled with enzymes Contains some ribosomes and circular DNA

Question 26

Chloroplast

Answer 26

Energy production centre Responsible for photosynthesis and converting CO_2 into glucose Exists in plants and protists (algae) Double-bilayer enclose a liquid area filled with enzymes and thylakoids (sacs of chlorophyll) Contains some circular DNA

Question 27

Cytoskeleton

Answer 27

Provides structural framework for cells and movement system | Microtubules, microfilaments and intermediate filaments

Question 28

Microtubules

Answer 28

``` Large, hollow tubes of tubulin Radiate out from centrosome to provide structure Form centrioles in cell division Use cilia and flagella for cell movement Serve as highways for vesicular movement ```

Question 29

Centrosome

Answer 29

Microtubules form spindles that originate from the centrosome

Question 30

Microfilaments

Answer 30

Thinnest cytoskeleton element Twisted helix of long chains of actin Present in microvilli (parts of some cells that have folds) Regulators of cell movement Also involved in vesicular transport (links microtubules together) Involved in muscle contraction

Question 31

Dynamic Instability

Answer 31

Microfilaments and microtubules can grow and shorten themselves

Question 32

Vesicular Transport

Answer 32

Myosin binds, unbinds and rebinds (walking) along actin polymers ATP is used to cause conformational changes needed for this walking Kinesin does the same along microtubules Dynein goes in the opposite direction of kinesin, always along microtubules Dynein, kinesin and myosin are motor proteins, and the latter two move from the negative to the positive direction

Question 33

Intermediate Filaments

Answer 33

Intermediate in size Less often disassemble Form sturdy, cable-like structures Help maintain structure (for example, in the nucleus) Large variety of proteins used among different cells Can link multiple cells

Question 34

Cytoplasmic Streaming

Answer 34

Occurs when a flow is created, such as by motor proteins | This flow can actually assist in moving vesicles, organelles, and other particles

Question 35

Animal Extracellular Matrix (Animal E.C.M.)

Answer 35

A gel-like area filled with proteins and carbohydrates, which come from exocytosis Provides support and motility Contains collagen (strong, helical protein present in important quantities), elastin (looser chain of protein in skin, lungs and gut), proteoglycans (mostly sugar that capture and retain water, making them hydrophilic) and integrins (integral cell proteins that anchor to E.C.M.)

Question 36

Desmosomes

Answer 36

Cadherin-cadherin interactions at a specific point between two cells

Question 37

Tight Junction

Answer 37

Seals two cells together so that the only way for substances to pass between the two cells is through them (unlike desmosomes) Tight junctions are not anchored to the cytoskeleton

Question 38

Gap Junction

Answer 38

Integral protein channels that attach between two cells, allowing material to flow from the cytosol of one cell to another

Question 39

Cell Wall

Answer 39

Primary cell wall is mostly cellulose and is thin and flexible Secondary cell wall is much thicker, also mostly cellulose, with some lignin, which makes cell wall water resistant As cell grows, cell wall must be enlarged extracellularly Middle lamella is the gap between the primary cell walls of two cells Plasmodesmata are similar to gap junctions (but in plants)