Chapter 2 - Cell structure and organisation Flashcards
What components does the nucleus have?
- Nuclear Envelope - this has pores which allow the passage of larger molecules (mRNA and ribosomes).
- Nucleoplasm -granular material in the nucleus.
- Nucleolus - Site of formation of rRNA.
What do mitochondria look like and what parts up make up a mitochondria?
Two membranes - separated by the inter-membrane space.
Matrix
Cristae- increase S.A of matrix for the attachment of enzymes involved in respiration.
Smaller ribosomes (70s) and a small circle of DNA.
What is the function of mitochondria?
To produce ATP in aerobic respiration. A large number of mitochondria in cells reflects the high metabolic activity taking place.
What are the flattened sacs in a chloroplast called and what is a stack of these called?
Thylakoids and a stack of these is called a granum. -Photosynthetic pigments (chlorophyll) are found here.
What is the endosymbiotic theory?
It is thought that both chloroplasts and mitochondria have their origins in free-living cells. They both have 70s ribosomes and circular DNA so it was suggested that some ancient bacteria engulfed others and maintained a symbiotic relationship.
What are the fluid-filled spaces between the flattened sacs in ER and the Golgi apparatus called?
Cisternae.
What is the function of the Rough Endoplasmic Reticulum?
It has ribosomes on the outer surface and transports the proteins made there.
What is the function of the Smooth Endoplasmic Reticulum?
It comprises of membranes that lack ribosomes. Is’s associated with the synthesis and transport of Lipids.
Where are ribosomes assembled and what are they important for?
They are assembled in the nucleolus from rRNA and protein. They are the site of protein synthesis, as they are the site of translation, where mRNA is used to assemble the polypeptide chain.
What are the functions of the Golgi body / apparatus / complex?
- Producing secretory enzymes, packaged into secretory vesicles.
- Secreting carbohydrates
- Producing glycoprotein
- Transporting and storing lipids
- Forming lysosomes, containing digestive enzymes
What are Lysosomes?
They’re small temporary vacuoles surrounded by a single membrane, formed by being pinched off from the Golgi body. They contain and isolate potentially harmful digestive enzymes from the remainder of the cell (E.g. when the cell needs to recycle worn out organelles or when they fuse with the vesicle made when WBC’s engulf bacteria by phagocytosis).
What are centrioles and what function do they have?
They’re two rigs of microtubules making hollow cylinders positioned at right angles to one another. They organise the microtubules that make the spindle during mitosis.
What is a vacuole?
Consists of a fluid-filled sac bounded by a single membrane (tonoplast). The contain cell sap which stores chemicals such as glucose, amino acids and minerals, and may store vitamins and pigments.
What is the cell wall made of and what functions does it have?
Cellulose
- Transport - the gaps make it permeable to water and dissolved minerals/ions.
- Mechanical strength - structure makes it very strong.
- Communication between cells - plasmodesmata.
What is the definition of a prokaryote?
A single celled organism lacking membrane-bound organelles, such as a nucleus, with its DNA free in the cytoplasm.
