Cellular Organisation

Ciliates have two nuclei, a macronucleus, and a micronucleus. 

• These are used for regulation of genetic activity and help with sexual reproduction. (smarter, 2024) 

(C. OpenStax, 2016d) 

• The germ-line micronucleus is the smaller nucleus and is transcriptionally inert. It passes on the genome during sexual reproduction onto next generations. (Meyer & Garnier, 2002) 

• It’s diploid, so it has two full sets of chromosomes, one coming from each parent. ( Aufderheide, 2019) 

• The micronucleus contains the germ cells (the sex cells) (Landweber & Gott, 2013) 

• This is the bigger nucleus and its polyploid meaning it has 3 or more sets of chromosomes. 

• the macronucleus contains somatic cells, which are any other cell except the sex cells. (Landweber & Gott, 2013) 

• The macronucleus is transcriptionally active, so it makes a copy of the DNA producing RNA. The macronucleus determines the phenotype (the observable characteristics) of the cell.  

• ( Aufderheide, 2019) 

(Maurice, 1960) 

• The ciliate protist also consists of many vacuoles and round membranous structures, which are used to help encase food, waste, and other substances. 

• digestive vacuole – it forms at the end of the gullet (mouth like area) as food is being ingested. 

• Cytoproct – if there is waste in the vacuoles, they get excreted via this cytoproct 

• Contractile vacuole – its shaped like a star and it gathers excess water using the microtubule-lined channels called canals and then removes it. The process that occurs is known as osmoregulation and the contractile vacuole expands to collect the water and then contracts to release it.(Vandivort, 2023) 
• The contractile vacuole is very important in preventing the cell from being ruptured or destroyed because it controls the amount of water that is allowed to be there. If there was too much water, the cell would swell up which would eventually cause severe damage. (Unacademy, 2022) 

• This provides the cell’s shape and gives it the ability to be flexible. 

• Because of this, it prevents the cell from being torn or pierced and it also makes sure the mobility of the cell hasn’t been interrupted. (Libretexts, 2022) 

• The pellicle is also seen to be able to maintain the cells shape and size after cell death. If we undergo detergent extraction, the pellicle will remain and would be seen as the ‘ghost’ of the cell. (Gould et al., 2010) 

• ciliate protists have a coating of cilia on the cell surface (Landweber & Gott, 2013) 

• Cilia are short hairlike projections, which help the cell move and collect food. 
• The cilia are situated on the pellicle of the cell and they can form small limb-like tufts called cirri which assists in cell movement. (encyclopaedia , 2018) 

(Robinson, 2006) 

(Maurice, 1960) 

Trichocytes (defense organelle) 

• Ciliate protists have this organelle, which is a hair-like structure, on the inside of the cell and is used to help protect the cell from any harm/danger from invading predators or help catch any prey. 

• To protect them from predators, they inject toxins into invading organisms which will then eventually cause that organism to die. 

•  To capture prey, they can release a sticky protein, which will adhere to the prey, making it easier for the cell to capture and ingest it.

(Chaitanya, 2022) 

(Mediran, 2012) 

• This is semipermeable and it controls the entry and exit of substances. 

• Its main function is to protect the cell 

• It is a layer of proteins and lipids. (Admin, 2024) 

• As this is a eukaryotic cell, it contains a nucleus which also contains the cell’s DNA.  

• It coordinates the cell activity, so it helps with reproduction, growth, protein synthesis and metabolism. 

• The nucleus contains chromatin which is the unstructured form of DNA. This then later lines up to form chromosomes through mitosis and cell division. 

Nucleolus: 

• This is the site of protein synthesis, and it forms the macromolecule – ribosome. 

Nuclear envelope; 

• This has a double membrane, and it segregates the contents of the nucleus with the contents of the cytoplasm. 

Nuclear pores: 

• These are holes within the nuclear envelope, and it allows specific types and sizes of molecules to pass through the nucleus into the cytoplasm and vice versa. (Davidson, 2015) 

(C. OpenStax, 2016) 

(OpenStax, 2016) 

• This is a series of membrane bound  sacs, which also helps in the process of protein synthesis, metabolism of lipids and storing calcium. 

(Schwarz & Blower, 2016) 

• There can either be a smooth or rough endoplasmic reticulum  

• Rough endoplasmic reticulum is studded with ribosomes, which is where the proteins are made. 

• The smooth endoplasmic reticulum synthesizes lipid and carbohydrates. (Carlson, 2019) 

• Smooth ER are a type of vesicle which are disk-like in shape 

• Muscle cells and the synthesis of steroids involve the SER . (Cole & Kramer, 2016) 

• It’s a gel-like substance which helps support the cells shape and structure and it also stores all the organelles that are within the cell membrane. 

• It’s a place for metabolic reactions to take place providing those organisms with energy. (Fletcher, 2023) 

(Preproom, 2008) 

(C. OpenStax, 2016) 

• They are barrel shaped organelles made up of microtubules 

• They are found within the centrosome  
• They are involved in the process of cell division. The centrioles take the role of going to opposite ends of the nucleus and it creates the area where the spindle fibres come about, these spindle fibres are used to pull the chromosomes to the opposite sides of the nucleus and it leads to cytokinesis. (institute, 2024) 

• It’s where microtubules are formed. 

• It is an area next to the nucleus where the centriole is found within. (Bornens, 2012)  

• They organise the way that microtubules are arranged, and the centrosome is duplicated in order to aid in the process of cell division (National Human Genome Research Institute, 2024) 

(Kelvinsong, 2012) 

(Physiology, 2016) 

• They are a membrane bound organelle 

• Contains digestive enzymes which engulf invading pathogens or dead/worn out cells. 

•  These digestive enzymes are also known as hydrolytic enzymes, and they’re used for breaking down larger molecules into smaller molecules. For instance, larger protein gets broken down into smaller amino acids or larger carbohydrates get broken down into smaller, simple sugars 

• If a cell has a point of no return, then lysosomes can initiate apoptosis. (Gahl, 2019) 

• It’s made up of a series of membrane bound flattened sacs called cisternae 

• It receives and modifies proteins from the endoplasmic reticulum and packages them into vesicles to be transported around the cell e.g. to the plasma membrane for exocytosis. 

• Golgi apparatus also has the ability to process enzymes and undergo post transcriptional modifications which can be done by phosphorylation (Byjus, 2019) 

(kelvinsong, 2012) 

(Song, 2012) 

• This is a membrane bound organelle found within all eukaryotic cells. 

• They are rod shaped 

• Its main function is to produce energy in the form of ATP. This can be done through respiration where phosphorylation, the Kreb cycle and oxidative phosphorylation come in 

• They have a double membrane

• The outer membrane allows small molecules to pass through by simple diffusion or large molecules with the help of transport channels. (Rogers, 2020) 

• The inner membrane, known as the matrix, folds into Cristae which increases the surface area making chemical processes such as respiration occur more efficiently. (Leveille et al., 2017) 

• Within the matrix of mitochondria, it contains its own DNA genome  

• The number of mitochondria around the body will vary depending on how much that place will need energy, for example muscle cells: they are constantly working and therefore need a large supply of energy therefore there will be more mitochondria located in these areas. (Rogers, 2020) 

• Ribosomes are involved in the translation process of protein synthesis. 

• They contain rRNA and when mRNA leaves the nucleus it comes into the cytoplasm where it binds to the ribosome 

• Here the mRNA has open bases and free floating tRNA molecules which carry amino acids and are used to help build the protein.

• To choose the correct amino acids, the tRNA lines up with its complementary base with the mRNA  

• mRNA has triplet bases called codons and the tRNA has anticodons which match up with it. The tRNA will then leave the amino acid that it carries in order to build the chain. 

• The amino acids will join via peptide bonds and this chain will continue until the ribosome reaches a stop codon, meaning that no more amino acids will be able to join on. Therefore, we are left with a specific protein which carries out specific functions around the body (British Society for Cell Biology, 2019) 

•  The ribosomes which are found in eukaryotes are the 80s 

• We have free floating ribosomes but also ribosomes which are bound to rough endoplasmic reticulum. (Byju’s, 2017) 

(Thomas, 2006) 

(Woland and Szczepan , 2009) 

• They are a membrane bound fluid filled sac which unlike vesicles can’t fuse with the membrane of other organelles. (Texts, 2021) 

• vacuoles are made by the fusing of many vesicles together which therefore makes them larger in size compared to vesicles. Their main function is to store substances such as water and many nutrients for example proteins, carbohydrates and lipids.  

• They help store and potentially break down substances before endo or exocytosis occurs. (Sarikas, 2019) 

• There are many vesicles within animal cells with different functions: some are secretory, some are transport vesicles, and we have lysosomes which are a type of vesicle 

• we have looked into lysosomes a bit earlier on in this page but to reiterate, they can be used to help defend against pathogens as they can engulf them and the enzymes within lysosomes can kill that pathogen. They have the ability to break down larger molecules into smaller molecules by releasing specific enzymes. 

• Transport vesicles move molecules throughout the cell to where it needs to be in order to help that area carry out its function.  

• Secretory vesicles are used to transport molecules outside the cell to the rest of the body via exocytosis. 

• We also have secretory vesicles at the end of nerve cells which help transfer chemical signals around the body to assist in the nervous response. (Lewsley, 2020) 

(Blaus, 2013) 

( OpenStax, 2016)

(OpenStax, 2016)