Definitions For As Level Biology - Chapter 2

Front 1

Active Transport

Back 1

The pumping of substances across cell membranes. From a low concentration to a high concentration. This uses energy from respiration and ATP.

Front 2

Osmosis

Back 2

The net movement of water molecules frokm a solution with a lower concentration of solute (high conc. of water) to a solution with a higher concentration of solute (low conc. of water) across a partially permeable membrane.

Front 3

Exocytosis

Back 3

The release of substances (usually proteins or polysaccharides) from the cell as vesicles (small membrane-bound sacs) which fuse with the cell surface membrane, releasing their contents.

Front 4

Endocytosis

Back 4

The absorption of substances (usually proteins or polysaccharides) into a cell by the creation of a vesicle. Part of the cell membrane engulfs the substance to be transported.

Front 5

Diffusion across membranes

Back 5

The net movement of molecules or ions from a region where they are at a higher concentration to a region of their lower concentration, until equilibrium is reached.

Front 6

Facilitated Diffusion across membranes

Back 6

Channel proteins are used to aid large hydrophilic molecules and ions that cannot diffuse ordinarily. Each channel protein has a specific shape to allow only one type of molecule or ion.

Front 7

Hydrophilic

Back 7

Water-attracting

Front 8

Hydrophobic

Back 8

Water-repelling

Front 9

Peripheral Proteins

Back 9

Proteins that are loosely attached on the outside of a membrane

Front 10

Integral Proteins

Back 10

Proteins that are fully embedded inside a membrane phospholipid bilayer.

Front 11

Glycoproteins

Back 11

A molecule consisting of a protein and a carbohydrate chain. It is used for cell recognition, to make cells form together to form tissues.

Front 12

Receptor Proteins

Back 12

Allow the cell to react to other cells and hormones

Front 13

Primary structure of a protein

Back 13

A chain of amino acids joined by peptide bonds - Polypeptides

Front 14

Secondary structure of a protein

Back 14

The polypeptide chain starts to curl up due to interactions between the different side groups of the amino acids. Contains alpha-helix (coil) and beta-pleated sheets (zig-zags). Both are held together with hydrogen bonds.

Front 15

Tertiary structure of a protein

Back 15

The three-dimensional shape caused after all sections of the polypeptide chain have curled or twisted.

Front 16

Peptide bond

Back 16

The bond between two amino acids

Front 17

Ester bond

Back 17

The bond between the glycerol and the fatty acid tail in a phospholipid. (Phosphoester bond between phosphate group and glycerol)

Front 18

Glycosidic bond

Back 18

The bond between the monosaccharides to form carbohydrates

Front 19

How to calculate the actual width of a magnified object

Back 19

actual measurement= measured size / magnification

Front 20

Validity

Back 20

When something supports the idea, it is said to be valid

Front 21

Reliability

Back 21

When results from a repeated experiment are similar they are said to be reliable

Front 22

Precision

Back 22

When a repeated experiment gives a similar result every time

Front 23

Accuracy

Back 23

How close to the true value a reading/measurement is.

Front 24

Dependent Variable

Back 24

The variable that relies on the result of the experiment

Front 25

Independent Variable

Back 25

The fixed variable that the experimenter may have cintrol over

Front 26

Gene

Back 26

A section of DNA that codes for a polypeptide

Front 27

Allele

Back 27

A different form of the same gene

Front 28

Homologous

Back 28

The chromosomes in each of pair of the 23 pairs in each cell.

Front 29

Homozygous

Back 29

Identical alleles (HH)

Front 30

Heterozygous

Back 30

Two different alleles (Hh)

Front 31

Carrier

Back 31

Someone with both a mutated gene and a normal gene, but the mutated gene is recessive.

Front 32

Genotype

Back 32

The two alleles that a person has (HH, Hh or hh)

Front 33

Phenotype

Back 33

The appearance of a characteristic in an organism (cystic fibrosis/ not cystic fibrosis)

Front 34

Recessive

Back 34

The allele that only affects the phenotype of the other homozygote. Written as a lower case letter.

Front 35

Dominant

Back 35

The allele that affects the phenotypes of one of the homozygotes and the heterozygote. Written as a capital letter