Chapter 4: Cell Structure Flashcards
Robert Hooke
dude who first observed cells
What did Robert Hooke first observe?
Cells in a cork
Antony van Leeuwenhoek
dude who first observed single-celled organisms
What did Leeuwenhoek call the single-celled organisms he observed?
Animalcules
Micrographia
publication where Hooke published his findings
Who contributed to the cell theory?
Matthias Schleiden, Theodor Schwaan and Rudolf Virchow
What does the unified cell theory state?
- All organisms are composed of cells
- The cell is the basic unit of life
- All cells come from existing cells
nucleoid
central part of prokaryotic cell where its DNA is stored
What type of cell wall do many prokaryotes have?
A peptidoglycan cell wall
What do some prokaryotes have that surrounds their cell wall?
A polysaccharide capsule
What types of structures do some prokaryotic cells have on their outside?
Flagella, pili and fimbriae
flagellum
tail-like structure used by cells for movement
pilus
exchanges genetic material between cells
fimbria
used to attach to host cells
Why do cells need to be small?
Due to the decreasing area-to-volume ratio as size increases, the cell would function less efficiently
Are prokaryotic or eukaryotic cells smaller?
Prokaryotic cells are smaller
microvillus
finger-like structures in a cell membrane that specialises in absorption
celiac disease
where gluten consumption damages microvilli and individuals cannot absorb nutrients
plasma membrane
phospholipid bilayer that separates inside and outside of cell
cytoplasm
entire region of cell from plasma membrane to nuclear envelope
cytosol
gel-like liquid in which cell organelles are suspended in
nucleus
houses the cell’s DNA and controls protein synthesis
nuclear envelope
double-membrane structure that is the outermost part of the nucleus
What is the nuclear envelope made of?
It is a phospholipid bilayer
nuclear pore
holes that control what goes in and out of the nucleus
nucleoplasm
semi-solid fluid that fills the nucleus
How is DNA stored in prokaryotes?
There is one single chromosome that is a closed loop
chromosome
structure that contains DNA
How is DNA stored in eukaryotes?
There are multiple linear chromosomes
chromatin
substance made of DNA attached to proteins
What are chromosomes made of?
Chromatin
nucleolus
dark-staining area of nucleus that assembles ribosome subunits
polyribosome
cluster of ribososmes
What are the two subunits of ribosomes?
Large and small subunits
mitrochondrion
powerhouse of the cell
cristae
inner folds of mitochondria
mitochondrial matrix
area that is surrounded by cristae
How many membranes do mitochondria have?
Two membranes
What are mitochondrial membranes made of?
Phospholipid bilayer
peroxisome
carries out oxidation reactions that break down fatty acids and amino acids
What do peroxisomes usually release in oxidation reactions?
Hydrogen peroxide
hydrogen peroxide
H2O2
Is hydrogen peroxide harmful to cells?
Yes
How do peroxisomes prevent hydrogen peroxide from damaging the cell?
Peroxisomes confine the H2O2 and with enzymes, break it down into oxygen and water
glyoxysome
specialised peroxisomes in plants that convert stored fats into sugars
vesicle
membrane-bound sacs in the cell
vacuole
membrane-bound sacs in the cell
What are the differences between vesicles and vacuoles?
Vesicles can fuse with other membranes and are smaller whereas vacuoles cannot fuse and are larger
What are the functions of vacuoles and vesicles?
They are used for storage and transport
centrosome
microtubule-organising area near the nucleus
centriole
cylinder-shaped structures that are involved in cell division
What cells are centrosomes found in?
Animal cells only
What is the centrosome made of?
Two centrioles
How are centrioles orientated?
They lie perpendicular to each other
What is a centriole made of?
Nine triplets of microtubules held together by nontubulin proteins
lysosome
organelle that breaks down waste in cells
What cells are lysosomes found in?
Animal cells
How do lysosomes break down waste?
Enzymes in lysosomes break down waste
How does the pH in lysosomes and the cytoplasm differ?
The pH in lysosomes is more acidic than the cytoplasm
How is waste and other molecules broken down in plant cells?
Instead of lysosomes, molecules are broken down in vacuoles
What is the plant cell wall mainly made of?
Cellulose
How many membranes do chloroplasts have?
Two
chloroplast intermembrane space
space between a chloroplast’s inner and outer membrane
thylakoid
fluid-filled membrane sacs in chloroplasts
granum
a stack of thylakoids
stroma
fluid inside of the inner membrane of a chloroplast
central vacuole
large, central vacuole in a plant cell
What is stored in the central vacuole?
Mainly water
Why do plants will when they are not watered enough?
When water concentration in the soil is lower than inside plant cells, water from the vacuole and cytoplasm moves out and the cell shrinks
endomembrane system
a group of organelles that work together to modify, pack and transport lipids and proteins
What organelles made up the endomembrane system?
Nuclear envelope, lysosomes, vesicles, endoplasmic reticulum, Golgi apparatuses and the plasma membrane
endoplasmic reticulum
membranous sacs and tubules that modifies proteins and synthesises lipids
lumen
space inside the ER’s tubules
cisternal space
space inside the ER’s tubules space
What is another name for the lumen in the ER?
Cisternal space
Where do proteins synthesised by ribosomes go?
To the lumen in the RER
Where are phospholipids produced?
In the RER
How are modified proteins transported from the RER?
In a transport vesicle
What are the roles of the SER?
Synthesising carbohydrates, lipids and steroid hormones, detoxifying poisons and storing calcium ions
sacroplasmic reticulum
specialised SER in muscle cells that store calcium ions required for muscle cells
Where do transport vesicles come from?
They bud from the ER
What is the role of the Golgi apparatus?
They sort, tag, package and distribute lipids and proteins
cisterna
flattened membrane disk in the ER and Golgi apparatus
Golgi apparatus
organelle made of
a series of cisternae
cis face
side of Golgi apparatus that modified proteins from the ER first enter
trans face
side of Golgi apparatus where proteins leave
What is the most frequent modification that Golgi apparatuses make?
They add short sugar molecule chains
How do proteins and other molecules leave the Golgi apparatus?
Vesicles bud off from the trans face and they carry proteins to their final destination
What additional role do Golgi apparatuses have in plant cells?
They synthesise polysaccharides
What immune role do lysosomes have?
They use their digestive enzymes to destroy pathogens
phagocytosis
when a cell folds part of its membrane in to engulf something
How do lysosomes destroy engulfed pathogens?
Lysosome membrane fuses with the engulfed area in which the pathogen is in, and the lysosome’s enzymes destroy pathogen
cytoskeleton
network of protein fibres in a cell
What is the function of the cytoskeleton?
To support the cell, secure organelles in place and help the cell move
What are the three types of fibres in the cytoskeleton?
Microfilaments, intermediate filaments and microtubules
Which cytoskeleton fibre is the narrowest?
Microfilaments
What is the role of microfilaments?
They help in cellular movement
What is the diameter of a microfilament?
About 7 nanometers
What are microfilaments made up of?
Two intertwined strands of actin proteins
What is another name for microfilaments?
Actin filaments
What powers actin to assemble into filaments?
ATP
Why are microfilaments good for cellular movement?
They can depolymerise and reform quickly so the cell can change shape quickly
What is the structure of intermediate filaments?
They consist of several fibrous proteins wound together
What is the diameter of intermediate filaments?
8 to 10 nanometers
What is the role of intermediate filaments?
To provide structure to the cell
dimer
two molecules bound together
What is the structure of microtubules?
A tube composed of 13 polymerised dimers of alpha-tubulin and beta-tubulin
What is the diameter of a microtubule?
About 25 nanometers
What is the widest fibre in the cytoskeleton?
Microtubules
What are the roles of microtubules?
They provide structure and help in vesicle movement and cell division
What are microtubules the structural elements to?
Flagella, cilia and centrioles
cillium
short, hair-like structure used to move a cell or substances along the outer surface of a cell
9+2 array
the common structure that both flagella and cilia share
What is the structure of flagella and cilia
They are both in the 9+2 array where a ring of nine microtubule doublets surrounds a single microtubule doublet in the centre
extracellular matrix
network of extracellular macromolecules
What are the main components of the extracellular matrix?
Collagen fibres interwoven with glycoproteins
glycoprotein
carbohydrate-containing protein molecules
What is the role of the extracellular matrix?
It holds cells together and allows them to communicate with each other
Where are microfilaments located?
They surround the cell’s inner edge
plasmodesma
channel between two adjacent cells that allows cells to pass materials to each other
What type of cells do plasmodesata occur in?
Plant cells
tight junction
watertight seal between two adjacent cells
How are tight junctions held together?
By two proteins called claudin and occludin
In what type of tissue are tight junctions typically found?
Epithelial tissue
desmosome
linkage between two cells when cadherins connect to intermediate filaments of adjacent cells
cadherin
glycoprotein that connects intermediate filaments of adjacent cells in desmosomes
connexin
protein that is involved in creating gap junctions
connexon
tube-like structure made of six connexin proteins
What type of cell are tight junctions found in?
Animal cells
What type of cell are desmosomes found in?
Animal cells
gap junction
channel between adjacent cells that allow for transportation of materials
What type of cell are gap junctions found in?
Animal cells
What are the ways plant cells can communicate with direct contact or intercellular junctions?
Plasmodesmata
What are the ways animal cells can communicate with direct contact or intercellular junctions?
Tight junctions, desmosomes and gap junctions
How are gap junctions formed?
When connexons from adjacent cells align, they form a channel between the two cells
