cellular organisation

Question 1

what are cells and its functions

Answer 1

• smallest unit of life
• all organisms are made up of one or more cells
• the activities of cells are dictate by their shapes, and by the types of relative numbers of the sub-cellular structures they contain
• cells arise from mitosis
• sperm and ovum cells arise by meiosis

Question 2

what are extracellular materials

Answer 2

substances contributing to body mass that are found outside the cells.

Question 3

what are extracellular fluid

Answer 3

• include interstitial fluids, blood plasma and cerebrospinal fluid
• dissolves and transport substances in the body

Question 4

what are interstitial fluid

Answer 4

• fluid in tissue that bathes all of our cell
• contains thousands of ingredients including amino acids, sugar, fatty aids, regulatory substances and wastes

Question 5

what is cellular secretions

Answer 5

• includes substances that aid in digestion (intestinal and gastric fluids) and some acts as lubricants (saliva, mucus and serous fluids)

Question 6

What is extracellular matrix

Answer 6

• most abundant extracellular material
• most body cells are in contact with a jellylike substance composed of proteins and polysaccharides
• secreted by the cell, the molecules self-assemble into an organised mesh int he extracellular space, where they serve as a universal “cell glue” that helps bind body cells together.
• extracellular matrix is connective tissues range from soft to rock hard

Question 7

What is the plasma membrane

Answer 7

made up mainly of phospholipids and proteins

Question 8

What is the functions of the plasma membrane

Answer 8

• separates two of the body’s major fluid compartments: intracellular fluid (within the cell) and extracellular (outside cells)
• defines the external boundary of the cell
• unique structure that plays many roles in cellular activities

Question 9

What is the fluid mosaic model

Answer 9

• structure of the plasma membrane
• consists of phospholipid membrane layer with protein inserted into it.

Question 10

what are membrane lipids

Answer 10

• the lipid bilayers form the basic “fabric” of the membrane.
• constructed largely of phospholipids, with smaller amounts of cholesterol

Question 11

what are phospholipids

Answer 11

• modified fatty acids which have a polar head, a phosphate group and a non polar tail
• polar hydrophilic heads of phospholipids are attracted to water- the main constituent of both the intracellular and extracellular fluids.
• lies on both the inner and outer surfaces of the membrane.
• the non-polar tails of phospholipids, being hydrophobic, avoid water and line up in the centre of the membrane

Question 12

describe the structure of plasma membrane

Answer 12

• two parallel sheets of phospholipid molecules lying tail to tail, with their polar heads bathed in water on either side of the membrane.

Question 13

what is the function of membrane proteins

Answer 13

• provide structural support and anchor the cell together
• allow selected molecules to cross the membrane
• allows transfer of signals across the membrane
• catalyse chemical reactions
• transport, receptors for signal transduction, enzymatic activity, cell-cell recognition, attachment to the cytoskeleton and extracellular matrix and cell-cell joining.

Question 14

what are other membranes in the cell

Answer 14

• plasma membrane surrounds the outside of the cell
• organelles divides it into different compartments
• organelles are surrounded by their own membrane, which is smaller in composition to the plasma membrane, but will have different proteins associated with it.

Question 15

what are the major components of the cells

Answer 15

• plasma membrane (outer cell boundary)
• cytosol
• cytoplasmic organelles enclosed by plasma membrane
• the nucleus

Question 16

what is the nucleus ad its functions

Answer 16

• control centre of the cell
• contains the blueprint materials for all of the proteins in the body
• activity in the nucleus decides which proteins a cell will express
• the code for the proteins is contained in a chemical sequence called DNA

Question 17

what is the cytosol (or cytoplasm) and its functions

Answer 17

• the fluid within the cell
• site of most cellular activity
• a suspensory fluid for the organelles
  contains enzymes for chemical reactions
• the initial metabolism of glucose occurs here
• cellular region between the nuclear and plasma membranes
• consists of fluid cytosol containing dissolved solutes, organelles (the metabolic machinery of the cytoplasm), and inclusion (stored nutrients, secretory products, pigment granules

Question 18

name the main organelles found in a cell

Answer 18

mitochondria, endoplasmic reticulum (rough and smooth), ribosomes and Golgi apparatus

some cells: lysosomes and peroxisomes

Question 19

what is the function of the mitochondria

Answer 19

• power plant of the cell
• conduct the aerobic metabolism of glucose and lipids to produce most of the cells ATP
• can divide to reproduce and increase their number
• when cellular requirements for ATP increases, the mitochondria synthesis more cristae or pinch in half to increase their numbers

Question 20

what is the endoplasmic reticulum (ER)

Answer 20

• comes in two forms: rough endoplasmic reticulum and smooth endoplasmic reticulum

Question 21

what is the function of the rough ER

Answer 21

• has ribosomes in its surface
• principally important for protein and plasma membrane synthesis
• sugar groups are attached to proteins within the cristerns
• proteins are bound in vesicles for transport to the golgi apparatus and other sites
• external face synthesises phospholipids

Question 22

what is the function of the smooth ER

Answer 22

• doesn’t have ribosomes on it
• important for metabolising lipids, detoxifying drugs and in muscle for storing calcium
• site of lipids and steroid synthesis

Question 23

what is the function of the ribosome

Answer 23

• important for the translation of DNA into a sequence of amino acids
• present on rough ER and thus also close to the nucleus
• site of protein synthesis

Question 24

what is the function of the golgi apparatus

Answer 24

• responsible for processing of proteins and the packaging of proteins into vesicles to send to other organelles and the plasma membrane
• packages, modifies and segregates proteins for secretion from the cell, inclusion in lysosomes, and incorporation into the plasma membrane
• modifies carbohydrates on proteins

Question 25

key points of chapter summary

Answer 25

• cells are defined by the presence of plasma membrane allowing the formation of an intracellular environment separate from the rest of the body
• cells are partitioned into organelles, each of which has a functional role in helping the cell to function
• each organelles have processes associated with it, many of which relate to macromolecule processing.
• examine, the nucleus, endoplasmic reticulum and golgi apparatus are all involved in protein synthesis, the ER is involved in lipid synthesis and breakdown, which the mitochondria break down lipids and carbohydrates to form ATP