Cells and organelles Flashcards
What surrounds the nucleus?
a double membrane called the nuclear envelope
What does the nuclear envelope do?
separates the contents of the nucleus from the cytoplasm. It also has several tiny pores where substances pass between the nucleus and the cytoplasm.
What transparent gelatinous fluid does the nucleus contain?
nucleoplasm
What are chromatin?
minute tangled threads, coiled around themselves- they make up chromosomes
Are mitochondria visible with a light microscope?
Yes, but only just
What is the nucleolus?
a dense, dark spherical structure within the nucleus that makes rRNA and ribosomes
What happens to chromatin during cell division?
chromatin gets changed into rod-like structures called chromosomes
In what phase of cell division do chromosomes appear?
the metaphase
what is chromatid made up of?
nucleic acid DNA coiled around molecules of proteins, called histone.
What does the DNA do?
DNA carries the genetic information that controls the shape and structure of the cell and organizes the vital activities of the living organism’s cells.
What is the function of the cytoplasm?
It contains microtubules that help the cell to maintain its shape and form as well as various different organelles
What is the structure of the cytoplasm?
-a fluid-like substance present between the cell membrane and nucleus.
- It is mainly composed of water as well as some organic and inorganic substances.
-It contains a network of threads and microtubules.
what are non-membranous organelles?
organelles that are not surrounded by a membrane
What are some examples of non-membranous organelles?
ribosomes and centrosome
What are membranous organelles?
organelles that are surrounded by a membrane
What are some examples of membranous organelles?
endoplasmic reticulum, Golgi apparatus, mitochondria, lysosomes, vacuoles, and plastids.
What are the structure of ribosomes?
-round-shaped organelles.
-no outer membrane
-consists of 2 sub-units
-Some are found in the cytoplasm, some are bound to the RER
-80s or 70s
What are most ribosomes attached to?
the outer surface of the rough endoplasmic reticulum
What are only some proteins present?
in the cytoplasm
What is the structure of microtubules?
-Microtubules are polymers of the protein tubulin.
- They are cylindrical tubes that are 20-25nm in diameter making them the largest of cytoskeletal fibres.
What 4 things do microtubules do?
- They’re involved in the movement of organelles
- They form centrioles
- They form spindle fibres
- They help to determine the shape of cells
What are centrioles made of?
Microtubules
What is a pair of centrioles called?
Centrosome
where are the centrosome located?
near the nucleus in a region of the cytoplasm
Which organisms are centrosomes found in?
in animal and fungi cells- they are not present in plants and some fungi cells
What is each centriole made up of?
nine groups of microtubules, ordered in triples in a spherical shape.
What does the centrosome do?
Involved in the assembly of the spindle fibres during mitosis
- The centrosome also plays an important role in forming the flagella and cilia.
What is the structure of cillia?
- Hair-like organelles that extend from the surface of certain cells
-Made of 9 pairs of microtubules, plus 2 in the centre.
What does the cillia do?
-Wafts dust particles along the trachea and pushes them out of the lungs
- Wafts egg cells towards the uterus in the fallopian tubes
-Senses the chemicals around the cell e.g. in the sensory cells lining the nose
What is the structure of the endoplasmic reticulum?
It has flattened membrane sacs called cisternae
What is the structure of the smooth endoplasmic reticulum?
-It has flattened membrane sacs called cisternae
-Has no ribosomes
What is the structure of the rough endoplasmic reticulum?
-It has flattened membrane sacs called cisternae
-Has ribosomes
What is the function of the smooth endoplasmic reticulum?
-It makes an stores lipids and carbohydrates which pass through the golgi apparatus to be modified and then transported to their final destinations
-It also modifies the nature of some toxic chemicals in the cell to reduce their harmful effects
what are the two types of endoplasmic reticulum?
the rough endoplasmic reticulum and the smooth endoplasmic reticulum
How can you tell the difference between the rough endoplasmic reticulum and the smooth endoplasmic reticulum?
The rough endoplasmic reticulum is characterized by the presence of a large number of ribosomes on its surfaces; whereas the smooth endoplasmic reticulum doesn’t contain ribosomes.
What is the structure of the Golgi apparatus?
It has a series of flattened membrane sacs.
What is the number of Golgi apparatus dependant on?
the cell’s secretion activity
What do the Golgi apparatus do?
- Receive proteins from the cell and modifies them e.g. by adding lipids or carbohydrates
- Packages modified proteins into vesicles for transportation
- Secretes some modified proteins from the surface of the cell
Who are the golgi apparatus named after?
Italian anatomist and pathologist Camillo Golgi, who described them for the first time in 1898.
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What is the structure of lysosomes?
- small spherical sacs
- Surrounded by a single membrane
- Internal fluid is acidic to match optimum ph
- Contain digestive enzymes
What do the lysosomes do?
- They contains powerful digestive enzymes such as protease, which digest larger molecules into smaller ones
- They take part in phagocytosis
- Destroy damaged/unfunctional cell organelles
- Transfer their enzymes outside of the cell by exocytosis to destroy material
What happens to the remains of dead cells that lysosomes have digested?
They’re re-used to make other organelles
Why isn’t the cell affected by the lysosome enzymes when the lysosomes are digesting and destroying pathogens?
because these enzymes are surrounded by a membrane, isolating them from the cell’s components.
What is the structure of mitochondria?
Mitochondria are sac-like membranous organelles. Their walls consist of two membranes. A group of folds, known as cristae, extends from the inner membrane into its matrix figure 18. Mitochondria also include mitochondrial DNA and mitochondrial ribosomes
What do mitochondria do?
they’re the site of aerobic respiration and ATP production
What are vacuoles ?
membranous sacs containing cell sap
What is the membrane of a vacuole called?
The tonoplast
Is the vacuole a temporary or permanent structure in animal cells?
Temporary
Is the vacuole a temporary or permanent structure in animal cells?
Permanent
What do the vacuoles do in plants ?
-They help remove waste material
-they allow the plant to be turgid and so support the plant
-they’re a temporary store of sugars and amino acids
The vacuoles are small and large in number in animal cells, how are they like in plant cells?
collected in one big vacuole (or more) in plant cells.
What are plastids?
various shaped membranous organelles present in plant cells only
How many types of plastids are there?
3
What are the different types of plastid called?
White plastids/Leucoplasts, Chromoplasts, Chloroplasts
what are White plastids/Leucoplasts?
plastids that don’t contain any type of pigments. They work as centres for storing starches.
where can White plastids/Leucoplasts be found?
-in the roots of sweet potatoes
- stems of potatoes
- the internal leaves of cabbages.
What are Chromoplasts?
plastids that contain carotenoids, which are coloured red, yellow and orange
where can Chromoplasts be found?
-In the petals of flowers
- fruits
- in the roots of some plants such as rapeseed.
what do Chloroplasts do?
They contain chlorophyll that transforms the light energy of the sun into chemical energy in the form of glucose through photosynthesis.
Where can chloroplasts be found?
in the leaves and stems of green plants
What fluid do the chloroplasts contain?
The stroma
Where does the light independent photosynthesis reaction take place?
In the stroma so the stroma contains enzymes needed for light independent reactions
Where does the light dependent photosynthesis reaction take place?
In the thylakoids. So the thylakoids contain chlorophyll and enzymes
What 2 sets of reactions does photosynthesis consist of?
The light dependent reaction, where chlorophyll is used to harvest light energy and the light independent reaction, where glucose is formed
Are the chloroplasts single-membraned or double-membranes?
Double-membrane
What does the lamellae in the chloroplasts allow to happen?
Chemicals to pass between the grana
What does the loop of DNA in the chloroplasts do?
The loop of DNA encodes some of the proteins needed for photosynthesis
What are the starch granules in the chloroplasts a store of?
Glucose
What do the ribosomes in the chloroplasts do?
They synthesise the proteins encoded by the chloroplast DNA
What happens in photosynthesis?
In photosynthesis, the energy from light is used to react carbon dioxide with water to form glucose and oxygen
What does the stroma contain?
layers of disc-shaped, compact structures known as thylakoids. Each group forms what’s known as the granum.
What is the structure of the plasma membrane?
- found in all cells
-has a phospholipid bilayer that has molecules embedded within and attached on the outside
What does the plasma membrane do?
It controls what enters and leaves the cell
What is the structure of the flagellum?
- Whip-like organism that can be found on the surface of certain cells e.g sperm cells
- Larger than cillia
- Has 9 pairs of microtubules arranged in the centre, plus 2 more
What does the flagellum do ?
It helps move the cell
What is the cell wall in plants made form?
Cellulose
What is the cell wall of fungi made up of?
Chitin
Where are cell walls found?
In plants, algae and fungi
Describe the structure of the plant cell wall
- Made of cellulose
- Selectively permeable
- The middle lamella acts as a glue between plant cells
What is the cell ultrastructure?
What’s inside the cell when viewed under a high powered microscope
What are prokaryotes?
Single celled organisms like bacteria and archaea
Are organelles in eukaryotes membrane bound?
Yes
Are organelles in prokaryotes membrane bound?
no
What is a vesicle?
A small fluid filled sac that transports substances in and out of the cell
are cytoskeletons found in eukaryotic or prokaryotic cells?
eukaryotic
what is the cytoskeleton?
a network of protein threads arranged as microfilaments,microtubules and intermediate filaments, which allows for movement and stability
what are microfilaments?
fine, thread-like protein fibres,
3-6 nm in diameter.
What protein monomer are microfilaments made out of?
actin
What do microfilaments do?
These carry out cellular movements
including gliding, contraction, and
cytokinesis via myosin
Where can the microfilaments be found?
in the cytoplasm near the plasma membrane
What are intermediate filaments?
permanent structures in your cell and are integral in maintaining cell structure and anchoring organelles in place.
What is the size of intermediate filaments?
about 10 nm diameter – In
between microtubules and
microfilaments
what is the internal structure of flagella made of
microtubules 9+2 rule
what are cillia known as
motile cilia
What does Pseudopodia mean?
false feet
What forms Pseudopodia?
microtubule and filament structures.
what is the function of Pseudopodia?
locomotion and the capturing of prey.
is the cellulose cell wall permeable?
yes
what are the cell walls in fungi made out of?
chitin
Describe the steps of protein synthesis
1 An mRNA copy of the DNA is made in the nucleus via transcription
2 Proteins are synthesised in ribosomes on the RER via translation
3 Proteins undergo modification at the Golgi apparatus, where lipids or carbohydrates may be added
4 Some proteins are secreted from the cell membrane when transport vesicles fuse with cell surface membrane, some proteins work within the cell
are nearly all prokaryotes single-celled?
yes
Do prokaryotes have cell walls?
Yes, all prokaryotes have a cell wall made up of murein (a glycoprotein) and peptidoglycan
do eukaryotes have cell walls?
Only some eukaryotes e.g. plant cells
what are the cell walls in plants made up of?
cellulose
which is larger in size-prokaryotes or eukaryotes?
prokaryotes
what ribosomes do prokaryotes have?
70s
what ribosomes do eukaryotes have?
80s
which has membrane bound organelles- prokaryotes or eukaryotes?
eukaryotes
do some prokaryotes have a waxy cuticle?
yes
what does the waxy cuticle/slime capsule do in prokaryotes?
it helps to protect bacteria from drying out and from attack by cells of the immune system of the host organism
do eukaryotes have a waxy cuticle?
no
do eukaryotes have tails or flagellum?
tails
do prokaryotes have tails or flagellum?
flagellum
which cytoskeleton is simpler in structure- the cytoskeleton in prokaryotes or in eukaryotes?
the cytoskeleton in prokaryotes
what’s the difference between the way DNA is arranges in prokaryotes and the way DNA is arranges in eukaryotes?
Inside the nucleus of eukaryotes, DNA is associated with histone proteins. Whereas in prokaryotes, the DNA is naked
prokaryotic DNA is ….. and eukaryotic DNA is……
prokaryotic DNA is circular and eukaryotic DNA is linear
what are plamsids?
small loops of DNA that are separate from the main circular DNA molecule. Plasmids contain genes that can be passed between prokaryotes e.g. genes for antibiotic resistance.
what type of cell division do prokaryotes undergo?
binary fission, where no spindle fibres are involved
what type of cell division do eukaryotes undergo?
mitosis or meiosis, where spindle fibres are present in order to separate chromosomes
what do the pilli do in eukaryotes?
they attach to other cells or surfaces and are involved in sexual reproduction
what does the infolding of the cell surface membrane of bacteria allow to happen?
allows photosynthesis to happen and nitrogen fixation
Where does the light independent photosynthesis reaction take place?
In the stroma so the stroma contains enzymes needed for light independent reactions
What is ‘s’?
A unit showing how quickly organisms can centrifuge
What are examples of nutrient stores in prokaryotes?
Lipid droplets and glycogen granules
What does the slime capsule surrounding prokaryotic cell walls protect prokaryotes from?
Phagocytosis
What do the pilli do in bacterial cells?
Allow the bacterial cells to attach to other bacterial cells and allow the transfer of DNA between bacterial cells
What are mesosomes?
Infoldings in bacterial cell membranes that are artefacts created when bacterial cells are prepared for electron microscopy
Where is mRNA produced?
In the nucleus
What are the destinations of proteins?
The cytoplasm, organelles e.g lysosomes, cell membrane, secreted from the cell e.g.hormones, antibodies
Cells that secrete large amounts of proteins will have a lot of what organelle?
Rough endoplasmic reticulum e.g beta cells in the pancreas which make the hormone insulin
In aerobic respiration, what is glucose broken down into?
Carbon dioxide and water and energy is transferred to ATP
Where does glycolysis take place?
In the cytoplasm
Where does the Krebs cycle take place?
In the mitochondria
Where does oxidative phosphorylation take place?
In the mitochondria
Where are the enzymes for the Krebs cycle found?
In the matrix (fluid)
Where are the enzymes for oxidative phosphorylation found?
On the inner mitochondrial membrane (cristae)
Does mitochondria have its own DNA?
Yes, it has mitochondrial DNA
What does mitochondrial DNA contain?
The genes required for some of the enzymes involved in aerobic respiration
Does mitochondria contain ribosomes?
Yes
What do the mitochondrial ribosomes do?
They synthesise the proteins encoded by the mitochondrial DNA
Cristae provide an increased surface area for…
The enzymes needed for oxidative phosphorylation
What happens during phagocytosis?
Pathogens are engulfed by a white blood cell. The pathogen now becomes contained in a phagocytic vacuole. Lysosomes then fuse with the phagocytic vacuole and the lysosomal enzymes destroy the pathogen
What is a plant cell vacuole surrounded by?
A membrane called the tonoplast
What does the tonoplast do?
Controls which chemicals can enter and leave the vacuole
What fluid does the vacuole in plant cells contain?
Cell sap
What can contain coloured pigments to attract pollinators?
The cell sap in the vacuole
What can contain waste chemicals produced by the plant cells?
The cell sap in the vacuole
Does cell sap have a high or low water potential
Low
How does cell sap in a plant cell having a low water potential help the plant?
The low water potential allows water to move into the plant cell by osmosis and this water enters the vacuole. This creates a hydrostatic pressure acting outwards. This causes the cytoplasm to press against the cellulose cell wall. The plant is now turgid and this turgidity helps to support the plant.
Cell walls help provide……….. support to a cell
Structural
What is the plasmodesmata?
Narrow threads of cytoplasm that connect the cytoplasm of neighbouring plant cells
Apart from in prokaryotic cells, where elsecan 70s ribosomes be found?
In the mitochondria and
Apart from in prokaryotic cells, where elsecan 70s ribosomes be found?
In the mitochondria and in the chloroplasts
Is size a structural feature?
No
What is the resolution of a light microscope?
0.2 micrometeres
what is th emagnification of a light microscope?
X 1500
Does a SEM have a lower resolution than TEM?
Yes
micrometeres to centimeteres?
/ 10,000
centimetres to millimetres?
X 10
moicrometeres to millimeteres?
/ 1000
micrometeres to nanometeres?
X 1000
how do you calculate magnification?
image size/ actual object size
What are the advantages of cell staining?
- Makes the cell easier to see
- Increases the contrast
- Allows you to recognise the different parts of a cell
Describes the roles of the cytoskeleton
- Maintaining the shape of the cell
- The movement of the cellia
- Changing the shape pf the cell (exocytosis, phagocytosis, pseudopodia)
- Movement of vesicles to plasma membrane
- The formation of the spindle fibres during mitosis
- Holding organelles in place
What are the roles of membranes within cells?
- compartmentalisation
- Isolation of the contents of the organelle i.e the hydrolytic enzymes.
- Site for the attachment of enzymes
- Controls what enters and leaves an organelle
- Creates concentration gradients
