Lecture 4: The Cell

Question 1

Properties and Actions of cells

Answer 1

growth, reproduction, absorption, metabolism, excretion and secretion, excitability, conductivity, contractibility

Question 2

Chemical Composition of cell

Answer 2

85% water
10% protein
2% lipid
1.5% inorganic matter
1.5% other substances and carbohydrates

Question 3

Important organelles

Answer 3

golgi apparatus, endoplasmic reticulum (smooth and rough), free ribosomes, mitochondria, lysosomes, peroxisomes, microtubules and microfilaments

Question 4

Endoplasmic reticulum (ER)

Answer 4

• mesh of interconnected membranes; used for protein synthesis and transport
• connects to the nuclear envelope/membrane through which the mRNA, the blueprints for proteins, travelto the ribosomes

Question 5

mitochondria

Answer 5

• “power house” of cells
• have a variety of enzymes and co-enzymes
• oxidation of nutrients to CO2, ATP, and H2O

Question 6

lysosomes

Answer 6

• small membrane-bound bags involved in digestion and detoxification
• contain 50 different digestive enzymes
• break up the material into smaller and simpler products that the cell can use
• digest worn-out cell components and pathogens engulfed by WBC’s

Question 7

cytoskeleton

Answer 7

• organized network of three primary protein filaments: microtubles, actin filaments, and intermediate fibers
• primary importance: cell motility
• maintain cell shape and the internal movement of cell organelles
• cell locomotion and muscle fiber contraction could not take place without the cytoskeleton

Question 8

microtubules

Answer 8

assist in transport of molecules within some cells

Question 9

microfilaments

Answer 9

assist with cell motility

Question 10

actin and intermediate fibers

Answer 10

assist in muscle contractions

Question 11

Nucleus

Answer 11

• largest organelle
• surround by a double membrane: nuclear envelope
• nuc. envelope is permeated with gates called nuclear pores
• pore are routes by which genetic messages pass into the cytoplasm
• nucleus=info centre

Question 12

Nucleolus

Answer 12

area of nucleus (looks like a dark dot) that contains chromosomes

Question 13

chromosomes

Answer 13

contain heredity information, made of DNA and proteins

Question 14

Chromatin

Answer 14

fragments of chromosomes, coiled together to form one

Question 15

Ribosomes

Answer 15

• protein factories
• in the nucleus, DNA’s instructions are transcribed into a messenger molecule of ribonucleic acid called mRNA
• the code in a strand of mRNA is translated into a protein by ribosomes, in the cytoplasm

Question 16

Cell Membrane

Answer 16

• double layer of lipid molecules interspersed with protein molecules
• maintains cell integrity
• functions as a semi-permeable barrier
• controls what goes in and out of cell
• usually semi-permeable

Question 17

Types of transport across CM

Answer 17

diffusion, passive transport, and active transport

Question 18

diffusion

Answer 18

• method of movement of substances to cross the membrane directly
• water, CO2, and O2 are among the few simple molecules that an cross CM by diffusion (diffusion aka osmosis)

Question 19

Osmosis

Answer 19

• diffusion of water through a semipermeable membrane from high concentration to low
• used for filtering urine through kidneys and movement of water across intestine walls

Question 20

Facilitated diffusion

Answer 20

does not use energy, membrane or proteins pick up molecules and coarry them across the membrane from high to low concentration

Question 21

Active transport

Answer 21

allows molecules to move against their conc. gradient, requires energy

Question 22

endocytosis

Answer 22

energy requiring process where cell membrane surrounds molecules, forming a pocket which becomes a vacuole in the cytoplasm
-types include phagocytosis and pinocytosis

Question 23

phagocytosis

Answer 23

• membrane surrounds large particles, forms a pocket, then a vacuole
• this is how amoeba and WBCs feed

Question 24

pinocytosis

Answer 24

• literally means cell drinking

- membrane surrounds a liquid, forms a pocket, then a vacuole

Question 25

exocytosis

Answer 25

energy requiring process where a vacuole containing large molecules joins with the membrane, makes an opening, and squeezes the molecules out of the cell

Question 26

vesicle-mediated transport

Answer 26

vesicles and vacuoles that fuse with the cell membrane may be utilized to release or transport chemicals out of the cell or to allow them to enter

Question 27

Tight Junctions

Answer 27

- the portion of the cell exposed to the lumen is called its apical surface - the rest of the cell (sides and base) make up the basolateral surface

Question 28

Gap Junctions

Answer 28

because ions can flow through them, gap junctions permit changes in membrane potential to pass from cell to cell