Cells Flashcards
What are centrioles? What type of cells have them? What are they involved in? Make sure you know what they look like?
- every animal cell has one pair of centrioles (they are not found in plants and fungi)
- they are hollow cylinders made up of a ring of nine protein microtubules (polymers of globular proteins arranged in a helix to form a hollow tube)
- They are involved in the formation of the spindle during nuclear division and in transport within the cell cytoplasm
What are centrioles formed from? What are they involved in and what do they produce?
- centrioles are formed from microtubules and are involved in cell division - producing spindle fibres
What are eukaryotic cells? Give examples
- eukaryotic cells are cells that contain a nucleus and other membrane-bound organelles
- eukaryotic cells are animal cells, plants, fungi
What is the Golgi apparatus? What does it do?
- stacks of flattened, membrane-bound sacs formed by fusion of vesicles from the ER
- it modifies proteins and lipids before packaging them into Golgi vesicles (the vesicles then transport the proteins and lipids to their required destination)
What are vesicles? What does the smooth ER form? Where do the vesicles (from the ER) enter the Golgi apparatus and where do they leave the Golgi apparatus?
- vesicles are compartments formed by a lipid bilayer separating its contents from the cytoplasm
- the vesicles (from ER) enters the Golgi apparatus by fusing with the cis face and move towards the trans face (where they leave)
What are lysosomes? What are they involved in? What are the used by? What is an example of a lysosome?
- they are specialist forms of vesicles (spherical sacs) which contain hydrolytic (hydrolysis) enzymes and they are bound by a single membrane
- involved in the breakdown of unwanted structures within the cell e.g. worn-out organelles
- they are used by cells of the immune system and in apoptosis (programmed cell death)
- the acrosome is a specialised lysosome
What is mitochondria (singular mitochondrion) the site of? What is it surrounded by? What does it contain? What else is found in the matrix and why are they needed?
- it is the site of aerobic respiration (within eukaryotic cells)
- it is surrounded by a double membrane with the inner membranes folded to form finger-like projections called cristae
- the matrix of mitochondria contains enzymes needed for aerobic respiration, producing ATP
-small circular pieces of DNA (aka mitochondrial DNA) and ribosomes are also found in the matrix, they’re needed for replication of mitochondria before cell division
Define the process of respiration?
The chemical process by which energy is released from glucose to produce ATP inside living cells
- aerobic respiration requires oxygen, anaerobic does not
What is the nucleolus?
- a dense body within the nucleus where ribosomes are made
What are prokaryotic cells? Give examples
- prokaryotic cells are cells that do not have a true nucleus or membrane-bound organelles
- prokaryotic cells are much smaller than eukaryotic cells
- examples = bacteria, archaea, mycoplasma (bacteria without cell walls)
Where are ribosomes formed? What are they composed of? Where can they be found? What are they not surrounded by? What are they the site of?
- ribosomes are formed in the nucleolus and are composed of equal amounts of RNA and protein
- these small organelles are found free in the cytoplasm or attached to the rough endoplasmic reticulum
- they are not surrounded by a membrane
- they are the site of translation, the latter part of protein synthesis
What are 80s ribosomes composed of and where are they found? What are 70s ribosomes composed of and where are they found?
- 80s ribosomes are found in eukaryotic cells
- 80S ribosomes are composed of a small 40S subunit and large 60S subunit
- 70S ribosomes are composed of a small 30S subunit and large 50S subunit
- 70s ribosomes are found in prokaryotes, mitochondria and chloroplasts
- the S stands for svedbergs, the unit used to measure how fast molecules move in a centrifuge
Where is the nucleus present? What is it surrounded by? What does it contain? What are chromosomes made of?
- nucleus is present in all eukaryotic cells
- it is surrounded by a double membrane called the nuclear envelope which has many pores
- the nucleus contains a nucleolus and contains chromatin, the material from which chromosomes are made
- chromosomes are made of sections of linear DNA tightly wound around proteins called histones
What is the smooth endoplasmic reticulum (SER)? Where is it formed? What is it involved in?
- SER is formed from folds of membrane but its function is distinct from the RER, being involved in the production, processing and storage of lipids, carbohydrates and steroids
- SER does not have ribosomes on its surface
What is the rough endoplasmic reticulum (RER) formed from? What is it covered in? What is the role of it?
- RER is formed from folds of membrane continuous with the nuclear envelope
- the surface of RER is covered in ribosomes
- the role of RER is to process proteins made on the ribosomes
What are the organelles that are involved in protein synthesis?
- the organelles that are involved in protein synthesis:
- nucleus (transcription of the DNA code occurs here)
- ribosomes (produce proteins in the process of translation)
- rough endoplasmic reticulum (RER)
- Golgi apparatus
- cell surface membrane (proteins formed within the cell are secreted here)
Function of the RER. What do ribosomes on the RER produce? What happens to the proteins that have been passed into the lumen of the RER?
- ribosomes on the RER produce proteins that can be secreted out of the cell or become attached to the cell surface membrane
- proteins that have been passed into the lumen of the RER are folded and processed here
Function of the Golgi apparatus. Where are the processed proteins from the RER transported to? What does the Golgi apparatus do to the proteins? How do the proteins leave?
- processed proteins from the RER are transported to the Golgi apparatus in vesicles which fuse with the Golgi apparatus, releasing the proteins into the Golgi
- the Golgi apparatus modifies the proteins, preparing them for secretion
- the modified proteins then leave the Golgi apparatus in vesicles
What usually happens to the proteins that go through the Golgi apparatus?
- the proteins that go through the Golgi apparatus are usually:
- exported e.g. hormones such as insulin
- put into lysosomes e.g. hydrolytic enzymes
- delivered to other membrane bound organelles
How are the Golgi apparatus and RER involved in producing, packaging and transporting proteins in a cell?
- the nucleolus manufactures ribosomes needed for protein synthesis in the RER (where protein synthesis takes place, so ribosomes are sent to RER)
- the nucleus manufactures mRNA which is needed by ribosomes to make proteins
- the ribosomes in the RER make proteins
- the RER processes the proteins which are then sent in vesicles to the Golgi body
- the Golgi body further processes the proteins and sends them in vesicles to the plasma membrane
- the vesicles fuse with the plasma membrane to secrete the finished protein product
Why do muscle cells require more mitochondria?
- muscle cells require more energy
- mitochondria is the site of respiration
- they produce ATP/ release energy
How do prokaryotic cells differ from eukaryotic cells?
- they are smaller
- they have a cytoplasm that lacks membrane-bound organelles
- they have 70S ribosomes (smaller ribosomes)
- no nucleus
- a cell wall that contains the glycoprotein murein (murein is sometimes known as peptidoglycan)
What do eukaryotes have instead of a nucleus?
- instead of having a nucleus they have a single circular bacterial chromosome that is free in the cytoplasm and is not associated with proteins
What are additions to prokaryotic cells (that eukaryotic cells do not have)?
- loops of DNA known as plasmids
- capsules
- flagella (singular flagellum)
- pili (singular pilus)
- a cell membrane that contains folds known as mesosomes
What are plasmids? What do they contain?
- they’re small loops of DNA (that are separate from the main circular DNA molecule)
- they contain genes that can be passed between prokaryotes e.g. antibiotic resistance gene
(not present in all prokaryotes)
What is the capsule?
- capsule is a polysaccharide layer that completely envelops the cell
- its a slimy layer on the surface for protection from cells of the immune system of the host organism and to prevent dehydration
What is a flagellum? Where can it be found?
- a long, cylindrical thread-like structure that rotates to move the cell/ prokaryote
- some prokaryotes have more than one
What are pili?
- hair-like structures/ thin, protein tubes on the surface of some bacteria, allowing it do adhere (attach) to other cells or surfaces
What is a mesosome? What are their functions?
- mesosomes are infolding of cell surface membrane
- its functions include:
- aerobic respiration
- cell wall formation
- DNA replication
What are the diameters of prokaryotes and eukaryotes?
- prokaryotes = 0.5-5um (diameter)
- eukaryotes = up to 100um (diameter)
How is cell division different in prokaryotes and eukaryotes?
- prokaryotes occurs by binary fission, no spindle required
- eukaryotes occurs by mitosis or meiosis and involves a spindle to separate chromosomes
What are the mark points for drawing cells in exams?
- MP1 = draw 5 cells adjacent to each other and clear continuous lines - do not award if gaps between
- MP2 = correct proportions
- MP3 = uses greater than 50% of area provided
- MP4 = label lines drawn with a ruler to correct feature - do not award if there are arrow heads
- MP5 = cell membranes and nucleus and cytoplasm labelled
- MP6 = comparative colour of any of above mentioned (not shaded in)
When and who came up with the cell theory?
- Matthias Schleidon and Theodor Schwann came up with ‘cell theory’ in 1837
What are the three main ideas that cell theory includes?
- all living organisms are made up of one or more cells
- cells are the basic functional unit in living organisms
- new cells are produced from pre-existing cells
What are some common features that all living organisms share?
- cell surface membrane
- cytoplasm
- DNA
- ribosomes
What does ultrastructure refer to?
- cell ultrastructure refers to the internal structures of the cell
Give an example of some specialised cells.
- specialised cells can perform specific functions
- epithelial cells in small intestine are specialised to absorb food efficiently
- red blood cells are specialised to transport oxygen
What is a tissue? Give an example.
- a tissue is a group of cells of similar structures that work together to perform a particular function
- muscle cells group together to form muscle tissue. Their function is to contract in order to move parts of the body
What is an organ? Give an example.
- an organ is a group of (different) tissues working together to perform a particular function
- many different tissues including cardiac muscle tissue, blood vessel tissues and connective tissue, group together to form the heart, enabling it to function
What is an organ system? Give an example?
- an organ system is made from a group of organs with related functions, working together to perform a particular function
- the stomach, pancreas, small and large intestine work together to form the digestive system, function to digest and absorb food
