1.2 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
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 leave via trans face by exocytosis
Describe the function of the Golgi apparatus
● 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,
contains digestive enzymes that break down macromolecules
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 structure 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
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
Eukaryotic
Large, often multicellular
Contain membrane-bound organelles and true nucleus
Linear chromosomes associated with histones
80S ribosomes
Reproduce via sexual or asexual reproduction
Cell wall made of cellulose (plants) or chitin (fungi)
Extra DNA in some organelles, e.g. mitochondria
prokaryotic cells
Prokaryotic
Small, unicellular
No membrane-bound organelles, no nucleus
Circular DNA, not associated with proteins
70S ribosomes
Reproduce via binary fission
Peptidoglycan cell wall
Extrachromosomal DNA in plasmids
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.
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?
Non-living Living
Smaller and simpler in structure Larger and more complex structure
Genetic material in the form of DNA or RNA Genetic material in the form of DNA
Can only reproduce within a host cell Independent cell division, sexual or asexual
No ribosomes
How do viruses differ from prokaryotic and
eukaryotic cells?
Non-living Living
Smaller and simpler in structure Larger and more complex structure
Genetic material in the form of DNA or RNA Genetic material in the form of DNA
Can only reproduce within a host cell Independent cell division, sexual or asexual
No 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 tissues
A group of cells working together to carry
out a specific function.
define tissues
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
function of lysosomes
Fluid-filled vesicles surrounded by a single
membrane, contain enzymes
● Role in phagocytosis, digest unwanted materials
in the cytoplasm
define plasmodesmata
Microscopic channels between plant cell
walls that facilitate communication and
symplastic transport.
