Bio Cell structure A-level

Structure of nucleus

Nuclear envelope- Double membrane

Nuclear Pores

Nucleoplasm- Jelly-like

Chromosomes- Protein bound, linear DNA

Nucleolus- Site of rRNA production, Makes ribosomes

Function of Nucleus

Site of DNA replication and Transcriptions (Making mRNA)

Contain Genetic code for each cell

Site of ribosome synthesis

Flagella

Tail like structure, used for mobility

Cilia

Hair-like projections, Help sweep substances. Can be Mobile or Stationary.

Centrioles

Made of microtubules. Involved in production of spindle fibres and organisation of chromosomes in cell division.

Structure of cytoskeleton

Network of fibres found within the cytoplasm.

Consists of microfilaments, microtubules and intermediate fibres

Function of cytoskeleton

Provides mechanical strength to cells, maintain stability and shape where many organelles are bound to it

Microfilaments needed in cell movement

Microtubules used to create a scaffold like structure

Intermediate Fibres to provide strength

Endoplasmic reticulum Structure

SER and RER- both have folded membranes called cisternae, RER has ribosomes on cisternae

Smooth ER Function

Synthesises and stores proteins and lipids

Rough ER Function

Protein synthesis for proteins that leave the cell. Transported into secretory vesicles

Golgi Apparatus and secretory vesicles

Made of folded membranes, Secretory vesicles pinch of.

Adds carbs to proteins to make glycoproteins

Produce secretory enzymes

Transport and modify lipids

Finished products undergo exocytosis

Forms lysosomes

Lysosomes

Bags of digestive enzymes

Hydrolyse Phagocytic cells

Exocytosis to release enzymes outside cell

Digest worn out organelles for material reuse

Mitochondria structure

Double membrane

Inner membrane called cisternae

Fluid centre called mitochondrial matrix

Loop of mitochondria DNA

Mitochondria Function

Aerobic respiration

ATP production

DNA to code for enzymes needed in respiration

Ribosomes structure and function

Small, made up of sub-units of protein and rRNA

80s Large ribosome found in eukaryotic cells (25nm)

70s Smaller ribosome found in prokaryotic cells, mitochondria and chloroplasts

Function is where protein synthesis occurs

Chloroplasts Structure and function

Surrounded by double membrane

Contains thylakoids which stack to form grana

Fluid with enzymes

Function is photosynthesis

Cell wall in plants is made of

Microfibrils of the polymer cellulose

Cell wall of fungi made of

Chitin

Function of Cell wall

Provide structure and support to the cell

Plasma membrane

Has a phospholipid bilayer

Controls what enters and exits a cell

Process of producing and secreting Proteins

1- Polypeptide chains synthesised on the RER

2- These chains move to cisternae of RER where they get packaged into vesicles to be sent to Golgi Apparatus via the cytoskeleton

3- In Golgi proteins are modified and packaged into secretory vesicles

4- Secretory vesicles carry protein to the cell surface membrane where they are released by exocytosis

Why are prokaryotes different to eukaryotes

Smaller cells

No membrane bound organelles

Smaller ribosomes 70s

DNA not in nucleus and is circular

Cell wall made of peptidoglycan ( Glycoprotein)

Plasmids?

Small loops of DNA carry a few genes

Slime Capsule

Capsule is a slimy layer made of protein

Prevents them from drying out