Cell structure CAQ

🛖 Cell structure Created Tags Structure of nucleus vs chloroplast June 13 , 2025 155 AM Cell structur e 1

Notes Structure of nucleus: Surrounded by a double membrane Contains linear DNA A large and dense starch Outer membrane continuous with RER Structure of chloroplasts: Surrounded by a double membrane Contains circular DNA Contains 70s ribosomes Consists of thylakoid membranes which consists of chlorophyll, ATP synthesis and electron carriers Consists of starch grain Why are there more mtDNA than nuclear DNA Cell structur e 2

Functions and features of organelles Organelle Features Functions Mitochondrion 1.Double membrane 2.highly folded inner membranes called cristae Site of aerobic respiration where ATP synthesis occurs Rough endoplasmic reticulum 1. Flattened sacs called cristae studded with ribosomes 2. Continuous with outer membrane of nuclear envelope 1. Translation of mRNA to protein/ protein synthesis by bound ribosomes 2. Glycosylation of proteins 3. Transportation of proteins in transport vesicles to Golgi apparatus Smooth endoplasmic reticulum 1. Consist of tubular network of membranes, cisternae Golgi body/ Golgi apparatus 1. stacks of flattened sac of membranes 2. Presence of vesicles at the end of the membrane that uniform in shape 1. To sort and package proteins into different vesicles and target the proteins to different parts of the cell or for secretion 2. To form lysosomes 3. To synthesise polysaccharides which is transported in vesicles to the membrane 4.to glcosylate proteins and lipids to form glycolipids and glycoproteins 5. To modify existing glycoproteins and Cell structur e 3

Organelle Features Functions glycolipids by cleaving sugar chains Centrioles A pair of cylindrical, rod like structures which are perpendicular to each other and consists of 9 triplets of microtubules arranged in a ring 1. The two pairs of centrioles move to opposite poles during prophase 2. Becomes a part of the microtubule organising centre in which assembly of spindle fibres occur Which is needed for separation of chromosomes and chromatids in meiosis I and II Ribosomes 1.Non-membrane bound 2. Composed of rRNA and proteins 3. Consists of large 60s and small subunits 40s 3. Each ribosome has 1 mRNA and 3 tRNA binding sites A,P,E 4. Contains Peptidyl transferase in the large ribosomal unit Lysosome 1. Autophagy 2. Autolysis 3. Contain hydrolytic enzymes which hydrolyse extracellular content taken in by endocytosis Cell structur e 4

Organelle Features Functions Nucleus Contains DNA where transcription occurs to produce mRNA Cell structur e 5

Cell structur e 6

Advantages of having membrane bound organelles Allows compartmentalisation which allow unique environments to be formed for highly specialised activities such as acidic environment for lysosomes Spatial Sepration of biochemical processes and thus their sequential operation within a cell such as protein modification in RER and further protein modification sorting and packagi