As Biology Chapter 3 Keywords

Front 1

Microscopy

Back 1

The process of using microscopes to magnify the image of an object.

Front 2

Object

Back 2

The material put under the microscope.

Front 3

Image

Back 3

The appearance of the material when viewed under the microscope.

Front 4

Resolution

Back 4

The minimum distance apart that two objects can be in order for them to appear as separate items.

Front 5

Cell fractionation

Back 5

The process where cells are broken up and the different organelles they contain are separated out.

Front 6

Isotonic

Back 6

Solutions that possess the same concentration of solutes and therefore have the same water potential.

Front 7

Homogenation

Back 7

When cells are broken up by a homogeniser (blender) which results in a fluid called homogenate.

Front 8

Ultracentrifugation

Back 8

The process by which the fragments in the filtered homogenate are separated in a machine called an ultracentrifuge.

Front 9

Light microscope

Back 9

A microscope which has poor resolution due to the relatively long wavelength of light.

Front 10

Transmission Electron Microscope (TEM)

Back 10

A microscope that focuses a beam of electrons onto the specimen. It must be in a vacuum, stained and extremely thin.

Front 11

Scanning Electron Microscope (SEM)

Back 11

A microscope that focuses a beam of electrons onto the specimen, which does not have to be thin (as it does in TEM).

Front 12

Photomicrograph

Back 12

A photograph of an image produced by a microscope.

Front 13

Epithelial cell

Back 13

They are eukaryotic cells, which have a distinct nucleus and possess membrane-bounded organelles.

Front 14

Ultrastructure

Back 14

The further, internal structure of a cell.

Front 15

Nuclear envelope

Back 15

A double membrane that surrounds the nucleus. The outer membrane is continuous with the ER of the cell and often has ribosomes of its surface. It controls the entry and exit of materials.

Front 16

Nuclear pores

Back 16

They allow the passage of large molecules, such as messenger RNA, out of the nucleus.

Front 17

Nucleoplasm

Back 17

The granular, jelly-like material that makes up the bulk of the nucleus.

Front 18

Chromatin

Back 18

The DNA found within the nucleoplasm. This is the diffuse form that chromosomes take up when the cell is not dividing.

Front 19

Nucleolus

Back 19

The small, spherical body within the nucleoplasm. It manufactures ribosomal RNA and assembles the ribosomes.

Front 20

Mitochondrion

Back 20

Rod-shaped in length and made up of a double membrane, cristae and matrix.

Front 21

Double membrane

Back 21

Surrounds the organelle. The outer one controlling the entry and exit of material. The inner one is folded to form extensions known as cristae.

Front 22

Cristae

Back 22

Shelf-like extensions of the inner membrane. These provide a large surface area for the attachment of enzymes involved in respiration.

Front 23

Matrix

Back 23

Makes up the remainder of the mitochondrion. It is a semi-rigid material containing proteins, lipids and traces of DNA for the production of its own proteins.

Front 24

Rough Endoplasmic Reticulum (RER)

Back 24

3D system of sheet-like membranes which has ribosomes present on the outer surfaces of the membranes.

Front 25

Smooth Endoplasmic Reticulum (SER)

Back 25

3D system of sheet-like membranes which lacks ribosomes on its surface and is often more tubular in appearance.

Front 26

Golgi apparatus

Back 26

A stack of membranes that make up flattened sacs, or cisternae, with small, rounded hollow structures called vesicles.

Front 27

Lysosomes

Back 27

When vesicles produced by the golgi apparatus contains enzymes, such as proteases and lipases.

Front 28

Ribosomes

Back 28

Small, cytoplasmic granules found in all cells. They may be found in the cytoplasm or be associated with the RER.

Front 29

Microvilli

Back 29

Tiny finger-like projections from cell-surface membrane of some animal cells to increase surface area for more efficient absorption.

Front 30

Lipids

Back 30

A varied group of substances that contain C, H and O. They are insoluble in water, but are soluble in organic solvents, such as alcohols and acetones.

Front 31

Saturated

Back 31

A fatty acid in which there are no double bonds between the carbon atoms.

Front 32

Mono-unsaturated

Back 32

Fatty acid that possesses a carbon chain with a single double bond.

Front 33

Polyunsaturated

Back 33

Fatty acid that possesses carbon chains with many double bonds.

Front 34

Phospholipids

Back 34

Triglycerides in which one of the three fatty acid molecules is replaced by a phosphate molecule. Phospholipids are important in the structure and functioning of the membranes.

Front 35

Hydrophilic head

Back 35

Interacts with water but not with fat.

Front 36

Hydrophobic tail

Back 36

Orients itself away from water, but mixes readily with fat.

Front 37

Polar

Back 37

Molecules that have two ends which behave differently (lipids).

Front 38

Plasma membranes

Back 38

Surrounds the cell and forms a boundary between the cell cytoplasm and the environment.

Front 39

Extrinsic proteins

Back 39

Occur either on the bilayer or partly embedded on it. They give mechanical support to the membrane or as cell receptors for molecules, such as hormones.

Front 40

Intrinsic protiens

Back 40

Completely span the phospholipid bilayer from one side to the other. Some act as carriers to transport water-soluble material across the membrane while others are enzymes.

Front 41

Fluid-Mosaic model

Back 41

Where individual phospholipid molecules can move relative to one another (fluid) and when proteins in the bilayer vary in shape, size and pattern (mosaic).

Front 42

Diffusion

Back 42

The movement of molecules or ions from a region where they are in high concentration to one where their concentration is lower.

Front 43

Facilitated diffusion

Back 43

Diffusion involving the presence of protein carrier molecules to allow the passive movement of substances across plasma mebranes.

Front 44

Osmosis

Back 44

The passage of water from a region of high water potential to a region where its water potential is lower, through a partially permeable membrane.

Front 45

Water potential

Back 45

The pressure created by water molecules. It is the measure of the extent to which a solution gives out water. The greater number of water molecules present, the higher (less negative) the water potential. Pure water has a water potential of zero.

Front 46

Active transport

Back 46

Movement of a substance from a region where it is in low concentration, to a region where its concentration is high. The process requires the expenditure of metabolic energy.

Front 47

Villi

Back 47

Finger-like projections of the intestinal wall, which increases the surface area for more efficient absorption.

Front 48

Absorption

Back 48

Uptake of substances.

Front 49

Lumen

Back 49

The hollow cavity inside a tubular structure, such as the gut or a xylem vessel.

Front 50

Sodium-potassium pump

Back 50

The mechanism by which glucose is absorbed from the small intestine.

Front 51

Carrier protein

Back 51

A protein on the surface of a cell that helps transport molecules and ions across plasma membranes.

Front 52

Cholera

Back 52

An infectious disease characterised by dehydration, watery faeces (diarrhoea), vomiting, etc.

Front 53

Cell wall

Back 53

Physical barrier that protects against mechanical damage and excludes certain substances.

Front 54

Capsule

Back 54

Protects bacterium from other cells and helps groups of bacteria to stick together for further protection.

Front 55

Flagella

Back 55

Aids movement of bacterium because of its rigid, corkscrew shape and rotating base that helps the cell spin through fluids.

Front 56

Plasmids

Back 56

A small, circular piece of DNA found in bacterial cells.

Front 57

Diarrhoea

Back 57

An intestinal disorder in which watery faeces are produced frequently.