eukaryotic cells - notes Flashcards
kms
what does the cell theory state? (5 points)
- the cell is the basic unit of life
- ALL organisms are made up of cells
- ALL cells arise from pre-existing cells by DIVISION
- the cell contains information (DNA/hereditary materials) which is used as instructions for growth, development and functioning
- the cell is the functional unit of life in which chemical reactions that maintain life take place within it
a) what are eukaryotes?
b) what living organisms are eukaryotes?
a) the cell of eukaryotes POSSESSES a true nucleus containing genetic materials known as DNA, enclosed within the nuclear envelope
b) animals, plants
a) what are prokaryotes?
b) what living organisms are prokaryotes?
a) the cell of prokaryotes LACKS a true nucleus. the genetic material is not enclosed within membranes but lies freely in the cytoplasm
b) bacteria, archaea
what is the value of 1 Angstrom in terms of m? what is it used for?
1Å = 10**^(-10) **m
it is used to measure the thickness of membranes and sizes of macromolecules
rank the following things in terms of relative sizes:
(from largest to smallest)
- ribosome
- average bacteria
- average mitochondria
- DNA molecule
- average animal cell
- hydrogen atom
- average plant cell
- nucleolus
- grana
- chloroplast
- vesicles
- plant cell
- animal cell
- chloroplast
- bacteria = mitochondria
- nucleolus
- grana
- vesicles
- ribosome
- DNA molecule
- hydrogen atom
a) what is a protoplasm?
b) what are the 3 major structures of the protoplasm in eukaryotic cells.
a) living matter of the cell
b)
- cell surface membrane
- nucleus
- cytoplasm
what makes up the cytoplasm?
- cytosol
- organelles
- cytoskeleton
what is the cytosol?
a fluid component, and an aqueous solution of various essential ions, soluble organic compounds and soluble proteins
what are organelles?
subcellular components which carry out specific functions to maintain the cell or the multicellular organism.
(they may or may not be membrane bound)
what is a cytoskeleton?
a network of fine strands of globular proteins that support the cell and maintain its overall shape
name the parts that can be found in/around nucleus
- nucleoplasm
- nucleolus
- nuclear envelope
- RER
- nuclear pores
- chromosomes
- DNA
describe the structure of nucleus
- largest organelle, spherical / ovoid in shape
- surrounded by double-membrane known as nuclear envelope
- outer membrane of nuclear envelope is continuous with the ER
- inner membrane of nuclear envelope is in contact with contents in nucleus
- nuclear envelope is perforated with nuclear pores
- nearly all cell’s DNA is found here
- has one or more nucleolus/nucleoli within nucleoplasm
what are the 3 main functions of the nucleus?
- controls cellular activities by regulating protein and enzyme synthesis
- responsible for nuclear division, which is the basis of cell replication
- nucleolus is responsible for synthesis and PARTIAL assembly of ribosomes
describe the basic structure of the cell surface membranes
a phospholipid bilayer with the hydrophobic tails on the interior of the membrane and hydrophilic heads on the exterior.
also contains:
- cholesterol
- glycoproteins / glycolipids
- transport proteins
(elaborated further in fluid mosaic model)
describe a phospholipid
made up of a glycerol molecule attached to a phosphate group and 2 fatty acid chains
more on this in fluid mosaic model
what are the 3 main functions of the cell surface membrane?
- partially permeable membrane
- acts as a barrier between cytoplasm and environment
- prevents most water-soluble substances from entering and leaving the cell
describe the structure of centrioles and centrosomes, and where they are found
centrioles: cylindrical structures composed of microtubules (a single centriole consists of 9 microtubule triplets arranged in a cylinder)
centrosome: made up of 2 centrioles
location:
(i) in pairs only in animal cells in cytoplasm outside nucleus
(ii) as single structures at the base of cilia and flagella
what are the 2 functions of centrosomes?
- produce spindle fibres which attach to chromosomes and separate them during cell division
- involved in formation of cilia and flagella
describe the structure of ribosome, and where they are found
- has no membranes
- made up of protein and ribonucleic acid (ribosomal RNA)
- comprises 2 subunits
(a large subunit = 60s ribosome, and
a small subunit = 40s ribosome)
location:
(i) attached to the RER
(ii) free ribosomes in cytosol
what is the function of ribosome?
site of protein synthesis
describe the structure of endoplasmic reticulum
- originates from outer membrane of nuclear envelope
- consists of a network of membranous tubes / sacs called cisternae (singular is cisterna)
RER:
- ribosomes bound to its surface
SER:
- lacks ribosomes
- more tubular
the membranous sacs in both ER and GA are called cisternae
what is the function of SER and RER
SER: synthesis of lipids, especially membrane phospholipids and steroid hormones
RER: site where proteins are synthesised and transported
describe the structure of Golgi apparatus
- consists of stacks of flattened membrane-bound sacs known as cisternae
- it is continually being formed at cis face by fusion of vesicle from ER, and continually budded off at the trans face where vesicles are pinched off
the membranous sacs in both ER and GA are called cisternae
what are the 2 functions of the Golgi apparatus?
- chemically modifies, sorts, and transports molecules within it (for secretion across the cell membrane or deliver to other parts of cell)
- lysosome formation
describe the struction of lysosome
- bound by a single membrane
- contains concentrated mixture of hydrolytic digestive enzymes
lysosomes can carry out 3 processes
what are the 3 functions of lysosomes?
- Digestion of materials taken in by cells
- Autophagy: digestion of worn-out/improperly functioning organelles
- Autolysis: self-digestion of cell by releasing the lysosome contents in cell
describe the structure of mitochondrion
- rod-shaped / cylindrical
- bound by double membrane, with an outer and inner membrane separated by inter-membrane space
- outer membrane is a smooth and continual boundary
- inner membrane is extensively folded to form cristae, which project into the interior (aka matrix)
- within the matrix, hereditary materials like circular DNA and RNA, as well as ribosomes can be found
*additional point: these materials found within matrix are traits of prokaryotic bacteria, leading to the theory behind the origin of mitochondrion and chloroplast
what is the function of mitochondrion?
involved in cellular respiration to release energy
describe the structure of chloroplast
- large organelle, only smaller than nucleus and large central vacuole
- contains chlorophyll (photosynthetic pigments) which make the chloroplast look green
- bound by double membrane
- outer membrane: smooth and continuous
- inner membrane: gives rise to membranes called lamallae and thylakoids that extend throughout interior
- interior of chloroplast: gel-like matrix called stroma
- within stroma: thylakoids are stacked into grana, which are joined together by intergranal lamallae
- has 70s ribosomes and circular DNA
lamalla (singular), lamallae (plural)
granum (singular), grana (plural)
*additional point: these materials found within matrix are traits of prokaryotic bacteria, leading to the theory behind the origin of mitochondrion and chloroplast
chloroplast extension
what is the function of choloroplast?
site of photosynthesis
describe the structure of vacuoles (and their respective names in animal and plant cells)
- fluid-filled structures bound by a single membrane
animal cells:
- relatively smaller and less permanent (vesicles)
plant cells:
- large central, permanent vacuole surrounded by a membrane called tonoplast, containing cell sap
cell sap contains aqueous solution of dissolved materials like sugars, ions, organic acids, waste products and pigments
what are the functions of vacuoles? (5 points)
- entry of water is important during cell expansion during cell growth, as well as in normal water relations of plants
- contains pigments in solutions
- hydrolytic enzymes may sometimes be present, making the vacuole act as a lysosome
- waste products may accumulate within vacuole
- some of the dissolved substances act as food reserves
describe the structure of (cellulose) cell wall
- consists predominantly of cellulose
- cell wall materials are strong and permeable therefore allowing the free passage of substances into and out of the cell
what are the 2 functions of cell wall?
- mechanical support
- protective layer
group the following organelles as organelles with single membranes, double membranes, no membranes or is a membrane itself.
- nucleus
- cell surface membrane
- centrioles
- ribosomes
- ER
- Golgi apparatus
- lysosome
- mitochondrion
- chloroplast
- vacuole
- cell wall
1. single membrane
- ER
- Golgi apparatus
- lysosome
- vacuole
2. double membrane
- nucleus
- mitochondrion
- chloroplast
3. no membranes
- centrioles
- ribosome
4. is a membrane / layer
- cell surface membrane
- cell wall
similarities between plant and animal cells
- protoplasm has cell surface membrane, nucleus, and cytoplasm has ER, Golgi apparatus mitochondria and ribosomes
- chromosomes are composed of linear DNA wound around proteins
differences between plant and animal cells (name at least 3)
- cell wall present in plant cell but absent in animal cell
- lysosomes usually absent in plant cell but often present in animal cell
- chloroplasts usually present in plant cell but absent in animal cell
- vacuoles are present, large and central in plant cell, but absent, or small and scattered in animal cell
- centrioles usually absent in plant cell but present in animal cell
what is protein synthesis?
how are the following proteins synthesised (name/process)?
a) proteins that need to be secreted out of cell
b) proteins needed for use within cell
genetic information from nucleus directs synthesis of particular proteins using ribosomes
a) protein secretory pathway
b) synthesised by free ribosomes
ESSAY QUESTION: describe the protein secretory pathway
for an essay question, might also have to define protein synthesis and state the name “protein secretory parthway.
- ribosomes bound to RER synthesise the polypeptide chain into RER
- protein becomes enclosed in an ER/transport vesicle, and the ER vesicle containing the protein buds off from ER
- the ER vesicle travels and fuses with the cis-face of Golgi apparatus
- the GA chemically modifies, sorts and transports the proteins. the proteins move through the GA by Golgi vesicles budding off from one cisterna and fusing with another cisterna
- a secretory vesicle containing the protein buds off from trans-face of GA, travels and fuses with cell surface membrane, thus releasing protein out of cell
specificity might be necessary if the question named a specific protein
