Basic components of living systems: Eukaryotic cell structure

Question 1

What is a eukaryotic cell?

Answer 1

multicellular and make up animal, plant and fungi

Question 2

What do chemical reactions require?

Answer 2

enzymes and specific reaction conditions

Question 3

what is metabolism?

Answer 3

involves the synthesis and breaking down of molecules

Question 4

membrane bound organelles provide…

Answer 4

distinct environments and therefore conditions for different cellular reactions are not the same

Question 5

What is DNA’s function?

Answer 5

directs the synthesis of all proteins. In this way DNA controls the metabolic activities of the cell as many of these proteins are necessary enzymes for metabolism to take place.

Question 6

The nuclear envelope

Answer 6

double membrane to protect it from damage in the cytoplasm. Contains nuclear pores. DNA is too large to leave the nucleus, therefore it it is transcribed into smaller mRNA molecules.

Question 7

Histones and chromatin

Answer 7

DNA associates with proteins called histones to form a complex called chromatin. Chromatin coils and condenses to form chromosomes which are only visible when the cells are prepared to divide.

Question 8

Nucleolus

Answer 8

-responsible for producing ribosomes
-composed of proteins and RNA.
-RNA is used to produce ribosomal RNA (rRNA) which is then combined with proteins to form ribosomes

Question 9

Mitochondria function

Answer 9

-site of cellular respiration
-produces ATP which is the carrier of energy

Question 10

Mitochondria structure

Answer 10

-double membrane
-inner membrane is highly folded to form structures called cristae
-the fluid is called the matrix
-the membrane forming cristae contains enzymes for aerobic respiration.
-contains its own DNA called mitochondrial (mt) DNA. Therefore it can produce their own enzymes and reproduce itself. Mitochondria was engulfed.

Question 11

Vesicles

Answer 11

membranous sacs that have storage and transport roles. They contain fluid and its function is to transport materials inside the cell.

Question 12

Lysosomes

Answer 12

-specialised form of vesicle
-contains hydrolytic enzymes which are responsible for breaking down waste in cells, including old organelles. They breakdown pathogens ingested by phagocytic cells.

Question 13

Cytoskeleton

Answer 13

network of fibres necessary for the shape, stability and movement. The three components are microfilaments, microtubules and intermediate fibres

Question 14

microfilaments

Answer 14

-formed from actin protein
responsible for cell movement and contraction during cytokinesis ( the process when the cytoplasm is divided)

Question 15

microtubules

Answer 15

-formed from tubular protein
- tubes that act as tracks for the movement of organelles
-determines shape of cell
-spindle fibres which have a role in the physical segregation of chromosomes in cell division are composed of microtubules

Question 16

intermediate fibres

Answer 16

provides mechanical strength to cell

Question 17

centrioles

Answer 17

-composed of microtubules
-two associated centriols form a centrosome which is involved in the organisation of spindle fibres during cell division

Question 18

flagella function?

Answer 18

-enable cell motility
-longer than cilia
-sometimes used as a sensory organelle detecting chemical changes

Question 19

cilia function?

Answer 19

-present in great numbers
-stationary cilia are present in sensory organs
-mobile cilia beat in a rhythmic manner creating current and causes fluid or objects to move, e.g they remove mucus from the lungs in the trachea.

Question 20

structure of flagella and cilia

Answer 20

A circle of 9 groups of microtubules, every group has two microtubules. The centre has two microtubules. This is called the 9+2 arrangement. Pairs of microtubules slide over each other causing movement.

Question 21

The endoplasmic reticulum

Answer 21

network of membranes enclosing flattened sacs called cristernae. There is the smooth ER and the rough ER

Question 22

smooth endoplasmic reticulum

Answer 22

responsible for lipid and carbohydrate synthesis and storage

Question 23

rough endoplasmic reticulum

Answer 23

-ribosomes are bound to the surface
-responsible for the synthesis and transport of proteins

Question 24

why do secretory cells have more endoplasmic reticulum?

Answer 24

Because they release hormones and enzymes which are proteins

Question 25

ribosomes

Answer 25

-free floating or attached to endoplasmic reticulum
-not surrounded by membrane
-made from rRNA and protein molecules
-site of protein synthesis
-mitochondria, chloroplasts and prokaryotic cells also contain ribosomes
-translates genetic material into proteins
-contains two subunits which come together during protein synthesis, a smaller subunit 40S and larger 60S

Question 26

Golgi apparatus

Answer 26

-compact structure formed of cisternae and doesn’t contain ribosomes
-modifies proteins and packages them into vesicles

Question 27

what occurs after proteins are synthesised in ribosomes on rough ER

Answer 27

1) synthesised on ribosomes bound to endoplasmic reticulum
2) passed into cisternae and packaged into transport vesicles
3)vesicles containing new proteins move towards the Golgi apparatus via the transport function of the cytoskeleton
4) vesicles fuse with cis face of Golgi apparatus and proteins enter. The proteins are structurally modified.
5)secretory vesicles carry proteins that are to be releases from the cell. vesicles move and fuse with cell surface membrane, releasing their contents by exocytosis.

Question 28

what is the surface outer cell membrane made of?

Answer 28

2 layers of phospholipids (phospholipid bilayer)

Question 29

Describe the structure of a phospholipid?

Answer 29

-hydrophilic phosphate head (water attracting)
-two hydrophobic fatty acid tails
-therefore in aqueous conditions, the hydrophilic heads form two outer rows while the hydrophobic tails are protected in a non-aqueous core.
- this creates a partially permeable membrane.
-fluid but stable

Question 30

how do vesicles move along the cytoskeleton?

Answer 30

by motor proteins

Question 31

what is the role of the nucleus?

Answer 31

DNA synthesis, directs protein synthesis

Question 32

Describe the structure of the rough endoplasmic reticulum? (3 marks)

Answer 32

-ribosomes found on the surface
-phospholipid bilayer
-contains cristernae
-continuous nuclear envelope

Question 33

explain the role of the membrane in the rough endoplasmic reticulum? (2 marks)

Answer 33

-proteins are packaged into vesicles
-compartmentalisation
-hold ribosomes in place

Question 34

Describe the structure of the rough endoplasmic reticulum?(3 marks)

Answer 34

-ribosomes attached to the surface
-cisternae structure
-phospholipid bilayer

Question 35

explain the role of the membrane in the rough endoplasmic recticulum?(2 marks)

Answer 35

-holds ribosomes at surface where translation occurs
-membrane allows compartmentalisation
-separates synthesised proteins from cytoplasm