Say a couple points about the nucleus
- 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
What is the matrix in the nucleus called
Nucleoplasm
What are the 3 components of the nucleus
- Chromatin
- Nucleolus
- Nuclear envelope
What structure allows communication between the nucleus and cyptoplasm?
NUCLEAR PORES
Nuclear pores?
- 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
Chromatin?
- 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.
The nucleolus
- main function RIBSOSOME SYNTHESIS
- the amount of nucleoli depends on the species
- associated with a particular region called the nucleoli organiser
Functions of the nucleus
- chromosomes contain dna, the main molecule of inheritance
- the nucleus manufactures ribosomes
- the nucleus is the basis of cell replication and hence reproduction
Consequences of having an endomembrane system
- 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
The endoplasmic reticulum (2 kinds)
-rough endoplasmic reticulum (lined with ribosomes)
- smooth endoplasmic reticulum (not lined with ribosomes)
FUNCTIONS OF THE RER
-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 .
What are synthesized proteins used for?
- USED OUT OF THE CELL
-USED FOR THE PLASMA MEMBRANE - HYDROLYTIC ENZYMES, to form part of lysosomes.
Formation of membranes?
The RER assembles the lipids into a bilayer using precursors from the cyptoplasm, also embedding proteins into the bilayer
The lysosome
-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 .
Functions of lysosomes
- Breakdown (Lysis) of biomolecules whether foreign or not,
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