Core Concepts (Cell Structure and Organisation) Flashcards
Define eukaryotic cell
A type of cell that contains a true nucleus along with membrane-bound organelles.
Describe the structure of the nucleus.
● Surrounded by nuclear envelope which is
semi-permeable and double membraned
● Nuclear pores allow substances to enter/exit
● Dense nucleolus (made of RNA and proteins)
assembles ribosomes
Describe the function of the nucleus.
● Contains DNA coiled around chromatin into chromosomes
● Coordinates cellular activities
Describe the function of the nucleus.
● Contains DNA coiled around chromatin into
chromosomes
● Coordinates cellular activities
What is chromatin?
A DNA-protein complex found in
eukaryotic cells.
Describe the structure of mitochondria.
● Surrounded by double membrane, mitochondrial envelope
● Folded inner membrane forms cristae (large surface area)
● Fluid matrix contains mitochondrial DNA, respiratory
enzymes, lipids and proteins
Describe the function of mitochondria.
Site of aerobic respiration to produce ATP.
Describe the structure of the
endoplasmic reticulum (ER).
● Series of flattened membrane-bound sacs
(cisternae) within the cytoplasm, continuous with
the nuclear envelope
● Two types: rough ER and smooth ER
Describe the function of the smooth
endoplasmic reticulum (SER).
Lipid synthesis
Describe the function of the rough
endoplasmic reticulum (RER).
Many ribosomes attached for protein
synthesis and transport.
Describe the structure of ribosomes.
● Made from rRNA and proteins
● Found free in the cytoplasm or
associated with the RER
Describe the function of ribosomes.
Site of protein synthesis (translation)
● Large subunit joins amino acids
● Small subunit reads RNA
Describe the structure of the Golgi body.
● Planar stack of membrane-bound, flattened sacs
● Cis face aligns with RER
● Molecules are processed in cisternae
● Vesicles bud off trans face via exocytosis
Describe the function of the Golgi body.
● Modifies and packages proteins for export
● Synthesises glycoproteins
Describe the structure and function of
lysosomes.
● Fluid-filled vesicles surrounded by a single
membrane, contain enzymes
● Role in phagocytosis, digest unwanted materials
in the cytoplasm
Describe the structure of centrioles.
● Cylindrical structure
● Organised into microtubules in a 9+0 pattern
● Found in pairs in centrosomes
Describe the function of centrioles.
● Migrate to opposite poles of the cell during
prophase
● Involved in the organisation of spindle fibres
Describe the structure of a chloroplast.
● Disk shaped surrounded by double membrane
● Thylakoids - flattened discs stacked to form grana
● Grana - contain photosystems with chlorophyll
● Intergranal lamellae - tubes attach thylakoids in adjacent
grana
● Stroma - fluid-filled matrix
What is the function of a chloroplast?
Site of photosynthesis
Describe the structure of the permanent
vacuole in plants.
● Surrounded by a single membrane, tonoplast
● Contains cell sap (mineral ions, water,
enzymes, soluble pigments)
Describe the function of the permanent
vacuole in plants.
● Controls turgor pressure
● Water storage
● Isolates harmful waste products
● Maintains pH
Define plasmodesmata
Microscopic channels between plant cell
walls that facilitate communication and
symplastic transport.
Define prokaryotic cell
A type of cell that does not contain any
membrane-bound organelles or a true
nucleus.
Describe the structure and function of
the flagella in prokaryotic cells.
● Long, whip-like protrusion made of flagellin
● Rotates to propel the organism
● Sensory organ
How is genetic information stored in
prokaryotes?
● Plasmids - small rings of DNA that carry
non-essential genes, exchanged between bacterial
cells via conjugation
● Loop of DNA - circular DNA stored in the nucleoid
region of the cell
Describe the structure and function of pili
in prokaryotic cells.
● Hair-like microfibers made of pilin that extend
through the cell wall
● Enable the attachment of bacteria to each other
and to other surfaces
Describe the structure and function of
the mesosome.
● Infolds of the cell membrane
● Increase the surface area of the cell, aiding
cellular respiration
What is the function of the capsule in
prokaryotic cells?
● Protective, slimy layer
● Helps the cell to retain moisture and adhere
to other surfaces
Which organelles are found in both
eukaryotic and prokaryotic cells?
● Cell membrane
● Cytoplasm with a form of cytoskeleton (although
cytoskeleton of eukaryotes is more significant)
● Ribosomes
Contrast eukaryotic and prokaryotic
cells.
Prokaryotic
* Small, unicellular Large
* No membrane-bound organelles, no nucleus
* Circular DNA, not associated with proteins
* 70S ribosomes 80S ribosomes
* Reproduce via binary fission
* Peptidoglycan cell wall
* Extrachromosomal DNA in plasmids
Eukaryotic
* Often multicellular
* Contain membrane-bound organelles and true nucleus
* Linear chromosomes associated with histones
* Reproduce via sexual or asexual reproduction
* Cell wall made of cellulose (plants) or chitin (fungi)
* Extra DNA in some organelles, e.g. mitochondria
Contrast eukaryotic plant and animal
cells.
Plant cells
* Cellulose cell wall
* Large permanent vacuole
* Contain chloroplasts
* No pseudopodia
Animal cells
* No cell wall
* Small temporary vacuoles (vesicles)
* No chloroplasts
* Some may have pseudopodia
What is a light microscope?
A type of microscope that uses a series
of lenses to magnify the visible light
reflecting off a specimen.
What is magnification?
The number of times bigger an image
appears compared to the size of the
specimen.
How can the magnification of an image
be calculated?
image size / actual size
Describe cell theory
● The cell is the fundamental unit of all life forms
● New cells can be formed from existing cells
● Cells contain genetic material which can be transferred
to daughter cells
What is a virus?
A non-living microorganism that consists
of genetic material surrounded by a
protein husk.
How do viruses differ from prokaryotic
and eukaryotic cells?
Virus
* Non-living
* Smaller and simpler in structure
* Genetic material in the form of DNA or RNA
* Can only reproduce within a host cell
* No ribosomes
Prokaryotic and eukaryotic cells
* Living
* Larger and more complex structure
* Genetic material in the form of DNA
* Independent cell division, sexual or asexual
* Contain ribosomes
How are multicellular organisms
organised?
● Many cells make up a tissue
● Many tissues make up an organ
● Many organs make up an organ system
Define tissue
A group of cells working together to carry
out a specific function.
Define organ
A group of tissues working together to
carry out a specific function.
Define organ system
A group of organs working together to
carry out a specific function.
