Unit 3 Summary 1

Question 1

Prokaryote

Answer 1

An organism with a simple cellular structure, lacking most organelles. See Bacterium.

Question 2

Eukaryote

Answer 2

An organism composed of one or more cells that contain distinct membrane-bound nuclei and many organelles; includes protists, fungi, plants and animals.

Question 3

Centriole

Answer 3

Small cylindrical structure composed of micro-tubules; occurs in pairs and involved in separation of chromosomes in animal cells.

Question 4

Chloroplast

Answer 4

Green organelle containing chlorophyll, present in some plant cells, in which photosynthesis takes place. Composed of many folded layers of membrane.

Question 5

Cytoplasm

Answer 5

All the contents of a cell except the nucleus

Question 6

Cytosol

Answer 6

Fluid component of cytoplasm in which organelles are located.

Question 7

Endoplasmic reticulum

Answer 7

Layers of intracellular membranes; links between membrane-bound organelles and the plasma membrane; may be rough endoplasmic reticulum (associated with ribosomes) or smooth endoplasmic reticulum (lacking ribosomes)

Question 8

Flagella (Flagellum)

Answer 8

Relatively long, fine, motile organelle; often only one or two per cell. In eukaryotic cells composed of a ‘9+2’ arrangement of microtubules enclosed by an extension of the cell membrane. In prokaryotic cells, composed of three protein fibres.

Question 9

Golgi apparatus

Answer 9

An organelle composed of a stack of smooth membranous cisternae (flattened sac-like structures) in which proteins and polysaccharides are assembled and packaged in vesicles for export from the cell.

Question 10

Lysosome

Answer 10

Membrane-bound vesicle, found in most animal cells, in which powerful enzymes break down debris and foreign material.

Question 11

Mitochondrion (Mitochondria)

Answer 11

Organelle in which aerobic cellular respiration occurs; composed of many layers of folded membrane.

Question 12

Nucleus

Answer 12

In a eukaryotic cell, a large organelle containing chromosomes (which control cellular activities) surrounded by a double-layer nuclear membrane with numerous nuclear pores.

Question 13

Nucleolus

Answer 13

Dark-staining body in the nucleus; site of synthesis of ribosomal RNA.

Question 14

Plasma membrane

Answer 14

(Cell membrane) Phospholipid double layer that encloses the contents of a cell and controls the movement of substances into and out of the cell.

Question 15

Plastids

Answer 15

Large organelle with a double membrane found in plant cells. Involved in either storage or photosynthesis.

Question 16

Ribosomes

Answer 16

Tiny organelles often attached to the endoplasmic reticulum; composed of protein and RNA; the site of protein synthesis.

Question 17

Vacuole

Answer 17

Membrane-bound liquid-filled space within cells. Vacuoles in plant cells are usually large and are involved in storage and turgidity. In other cells, vacuoles may be involved in intracellular digestion and water balance.

Question 18

Vesicle

Answer 18

Membrane-bound organelle often involved in transport within the cell.

Question 19

Cell wall

Answer 19

Wall outside the cell membrane in plant cells (cellulose), some protists, prokaryotes (murein) and fungi (chitin)

Question 20

• fluid-mosaic model

Answer 20

In relation to cell membranes- fluid because of the lateral movement of lipid molecules and mosaic because of the irregular location of proteins in the membrane.

Question 21

• Phospholipid

Answer 21

Fat-like substance, usually based on glycerol; phospholipids are essential components of cell membranes; are involved in the uptake of fats and fatty acids from the products of digestion.

Question 22

Hydrophobic

Answer 22

Non-polar molecules that are relatively insoluble in water; means water fearing,

Question 23

Hydrophilic

Answer 23

Polar ions and molecules that dissolve easily in water; means water loving.

Question 24

• Partially permeable

Partially permeable membrane

Answer 24

A membrane that allows the molecules of a solvent to pass freely across, but prevents the free passage of at least some solute molecules.

Question 25

Diffusion

Answer 25

Passive movement of a solute from a region of higher concentration to a region of lower concentration.

Question 26

Factors affecting diffusion rates

Answer 26

• The larger the difference in molecular concentrations (i.e the concentration gradient) he more rapid the rate of diffusion.

Question 27

Osmosis

Answer 27

Passive diffusion of free water molecules across a differentially permeable membrane from a solution in which there are more free water molecules (a dilute solution) to a solution in which there are fewer free water molecules (a concentrated solution) s

Question 28

Tonicity

Answer 28

The osmotic pressure or tension of a solution, as in the cells would swell or shrink depending on the tonicity of the environment

Question 29

Facilitated diffusion

Answer 29

Passive diffusion through selective protein channels in membranes

Question 30

Active transport

Answer 30

Movement of substances across membranes that requires the expenditure of energy; occurs through selective protein channels.