The Nucleus

Question 1

Say a couple points about the nucleus

Answer 1

• the LARGEST organelle
• usually at the CENTRE of a cell
• Found in almost ALL cells except the sieve tube phloem cell and red blood cells
• spherical or ovoid in shape

Question 2

What is the matrix in the nucleus called

Answer 2

Nucleoplasm

Question 3

What are the 3 components of the nucleus

Answer 3

• Chromatin
• Nucleolus
• Nuclear envelope

Question 4

What structure allows communication between the nucleus and cyptoplasm?

Answer 4

NUCLEAR PORES

Question 5

Nuclear pores?

Answer 5

• nuclear pores are CHANNELS lined with proteins which control what can exit the nucleus or enter the nucleus
• Ribosomes EXIT the nucleus into the cytoplasm
  -precursors (building blocks for dna/RNA ) enter the nucleus from the cytoplasm
  -MRNA enters the nucleus from the cytoplasm

Question 6

Chromatin?

Answer 6

• consists of dna bundles around basic proteins called HISTONES
  -heterochromatin, is tightly bundled and is considered to be inactive dna
  -Euchromating, is loosely bundled and is thought to be active dna.
  During cell division, chromatins fuse together to create Chromosomes
  -chromatin is attached to NUCLEAR LAMINA, which are a network of proteins around the nucleus. Nuclear lamina, helps give the nucleus is spherical shape and supports it in maintaining the shape.

Question 7

The nucleolus

Answer 7

• main function RIBSOSOME SYNTHESIS
• the amount of nucleoli depends on the species
• associated with a particular region called the nucleoli organiser

Question 8

Functions of the nucleus

Answer 8

• chromosomes contain dna, the main molecule of inheritance
• the nucleus manufactures ribosomes
• the nucleus is the basis of cell replication and hence reproduction

Question 9

Consequences of having an endomembrane system

Answer 9

• creates MICROENVIRONMENTS which are optimal for the enzymes which habit that certain area
  -Seperated reactions which will be harmful for each other, hence no damage is done to the rest of the cell
  -creates a HIGH CONCENTRATION OF MOLECULES
  -Groups of enzymes cluster together instead of floating in the cyptoplasm

Question 10

The endoplasmic reticulum (2 kinds)

Answer 10

-rough endoplasmic reticulum (lined with ribosomes)
- smooth endoplasmic reticulum (not lined with ribosomes)

Question 11

FUNCTIONS OF THE RER

Answer 11

-CREATES PROTEINS
-ISOLATES proteins from the cyptoplasm
- TRANSPORTS PROTEINS, proteins get threaded into the cisternae which then move through the sacs to become generally packaged into vesicles
- MODIFIES PROTEINS, RER can chemically modify proteins .

Question 12

What are synthesized proteins used for?

Answer 12

• USED OUT OF THE CELL
  -USED FOR THE PLASMA MEMBRANE
• HYDROLYTIC ENZYMES, to form part of lysosomes.

Question 13

Formation of membranes?

Answer 13

The RER assembles the lipids into a bilayer using precursors from the cyptoplasm, also embedding proteins into the bilayer

Question 14

The lysosome

Answer 14

-optimal ph 5.5
- found in animal cells, its presence in plant cells is still unknown
- It’s a vesicle crated by the RER or GOLGI APPARATUS
- contains DIGESTIVE ENZYMES which perform the intracellular breakdown of foreign substances, biomolecules .

Question 15

Functions of lysosomes

Answer 15

1. Breakdown (Lysis) of biomolecules whether foreign or not,
   -