Stuctures inside cells

Nucleus

• largest organelle

• Found in all eukaryotic organelles apart from erythtocytes/mature phloem sieve tube elements

• Controls activities of cell - contains genetic information in the form of chromatin containing instructions for cell functioning

• Surrounded by nuclear envelope

• Contains one or more nucleoli

Nuclear envelope

• 2 membranes surrounding nucleus

• Outer membrane is continuous w rer and often has ribosomes on it carrying out protein synthesis

Nuclear pores

• perforations in the membrane

• Allow molecules to pass through from nucleus to cytoplasm

• Smaller molecules such as atp can pass freely

• Larger molecules - rna are regulated

Chromatin

• dna wrapped around histones

• Stains

• During cell division becomes chromosomes

• Euchromatin - loose

• Heterochromatin - tightly coiled

Nucleolus

• darkly staining

• Synthesis of ribosomes - move out through nuclear pores

• Contains instructions in the form of DNA and rRNA

Cytoplasm

• aq solution

• Contains biochemicals (salts, sugar, amino acids), waste products, cell organelles

• Site for chemical reactions, metabolic pathways

Endoplasmic reticulum

• flattened membrane bound sacs - cisternae

• Only seen through EM

• Runs through cytoplasm

• Made of rer and ser

Rough Endoplasmic reticulum

• ribosomes on the surface - rough, pebbly appearance

• Transport/modify proteins

• Continues w outer membrane of nuclear envelope

• Send proteins to golgi

Smooth Endoplasmic Reticulum

• synthesis of lipids (phospholipids, steroids)

• Abundant in testes (synthesize testosterone which is derived from cholesterol)

80s ribosomes

• smallest organelle

• Site of protein synthesis

• Made of a large and small subunit - only join during protein synthesis

• Made of protein and rRNA

• 70s in prokaryotes, occur in smaller numbers in prokaryotes

• Exist as free, polysomes (chain of ribosomes), or bound to er

Golgi Apparatus

• made of cisternae and Golgi vesicles

• Cis face - new cisternae are being formed, vesicles from rer fuse here, releasing contents into Golgi sacs

• Trans Face - cisternae break up into vesicles carrying away lipids, proteins etc which were further modified from rer

• Transport and modifies materials

• Adds sugar chains forming glycoproteins

• Secretion of carbs during cytokinesis (synthesis of new plant cell wall)

• Forms lysosomes

• Important in secretory cells

lysosomes

• membrane bound sacs containing digestive enzymes, which work best at low pH

• Enzymes in lysosomes are synthesized on rer, then sent to golgi, where vesicles containing enzyme become lysosome

• Digest material taken in by Endocytosis - by fusing with vesicle/food vacuole and secreting enzymes, and any undigested products are exocytosed

• Autophagy - lysosomes fuses with unwanted structures membrane forming an autophagic vacuole - products of digestion are recycled

• Secretion of Enzymes - sperm contain lysosome acrosome which releases enzymes

• Autolysis - breakdown of cell, by releasing contents of lysosome into cell (after birth, size of uterus decreases Bcs of autolysis of many cells)

Peroxisomes

• micro body

• Contain catalyse - breaks down h2o2 which is sometimes produced as a by product of chemical reactions