✅3 - Cell Structure Flashcards
Describe the structure of the nucleus:
A nucleolus within a nuclear envelope and surrounded by nucleoplasm
Describe the function of the nucleus:
- contains the genetic material
- controls the cell’s activities
Describe the structure of the mitochondria :
Rod shaped double membrane bound structures with a folded inner membrane and matrix
Describe the function of the mitochondria:
- sites of aerobic respiration
- production of ATP
Describe the structure of the chloroplasts:
A double membrane bound organelle with stacks of thylakoids (grana) all connected by lamellae
Describe the function of the chloroplasts:
-to harvest sunlight for photosynthesis
Describe the structure of the Golgi apparatus + vesicles:
A stack of membranes that make up flattened stacks, or cisternae
Describe the function of the Golgi apparatus + vesicles:
- add carbohydrates to proteins to form glycoprotiens
- transport, modify and store lipids
- produce secretory enzymes
- secrete carbohydrates
- make lysosomes
Describe the structure of the lysosomes:
Golgi vesicles which contain enzymes such as proteases and lipases
Describe the function of the lysosomes:
- digest worn out organelles (using lysozymes)
- break down cells completely after they’ve died
- hydrolyse material ingested by phagocytic cells
Describe the structure of the ribosomes:
Small cytoplasmic granules, with ribosomal DNA and protein
Describe the function of the ribosomes:
-the site of protein synthesis int he cell
Describe the structure of the RER and SER:
RER: Three dimensional sheet like membranes continuous with the outer nuclear membrane, studded with ribosomes
SER: Three dimensional sheet like membranes continuous with the outer nuclear membrane, no ribosmes
Describe the function of the RER and SER:
RER: -provides large surface area for synthesis of proteins and glycoprotiens
-provides pathway for transport of materials. especially proteins, throughout the cell
Describe the structure of the cell wall:
Microfibrils of cellulose embedded in a matrix
Describe the function of the cell wall:
-provides mechanical strength to prevent the cell bursting when water enters by osmosis
Describe the structure of the vacuole:
A single membrane bound sac filled with cell sap (sugars and salts)
Describe the function of the vacuole:
- temporary food store
- keeps cells turgid
How do prokaryotic cell differ from eukaryotic cells in terms of size?
The are much smaller
How do prokaryotic cell differ from eukaryotic cells in terms of organelles?
The have no membrane bound organelles
How do prokaryotic cell differ from eukaryotic cells in terms of nuclei?
The don’t have a nucleus, instead a singular circular DNA molecule, free in the cytoplasm and not associated with any proteins.
How do prokaryotic cell differ from eukaryotic cells in terms of cell membrane
It contains murein, a glycoprotien
What other features may a prokaryotic cell have?
- one or more plasmids
- a capsule surrounding the cell
- one or more flagella
Viruses are…
…acellular and non-living
Describe the structure of a virus:
They include genetic material, capsid and attachment protein
Describe the principles of an optical microscope:
Creates a magnified image of an object specimen with an objective lens and magnifies the image further with an eyepiece.
Light source —-> condenser lens —-> object —-> objective lens —-> intermediate image —-> eyepiece lens—-> eye
Describe the limitations of an optical microscope:
- the resolution is only half the wavelength of visible light
- magnification is relatively low
- the surface view is not always very clear
Describe the principles of an transmission electron microscope:
Electron gun focuses a beam of electrons onto the specimen using a condenser electromagnet. It passes through a thin section of the specimen.
Electron source —-> magnetic condenser —-> object —-> magnetic objective —-> intermediate image —-> magnetic projector —-> fluorescent screen
Describe the principles of an transmission electron microscope:
Electron gun focuses a beam of electrons onto the specimen from below using a condenser electromagnet. It passes through a thin section of the specimen.
Electron source —-> magnetic condenser —-> object —-> magnetic objective —-> intermediate image —-> magnetic projector —-> fluorescent screen
Describe the limitations of a transmission electron microscope:
- The whole system must be in a vacuum so living things can’t be observed
- Complex staining processes are involved, and the image is still in black and white
- Specimen must be thin
- The image may contain artefacts
Describe the principles of a scanning electron microscope:
Directs a bean of electrons on to the surface from above rather then below. Beam passed back and forth in a regular pattern, electrons are then scattered
Describe the limitations of a scanning electron microscope:
- The whole system must be in a vacuum so living things can’t be observed
- Complex staining processes are involved, and the image is still in black and white
- The image may contain artefacts
What is magnification?
How many times larger the image is than the real life object
What is resolution?
The smallest distance below which two discrete objects will be seen as one
What is the equation for magnification?
size of image/size of real object
How are cell components separated?
Using cell fractionation and ultracentrifugation
Do all cells retain the ability to divide?
No
Where in the cell cycle does DNA replication occur?
Interphase
What is mitosis?
The part of the cell cycle in which a eukaryotic cell divides to produce two daughter cells, each with the identical copies of DNA produced by the parent cell during DNA replication
What happens to the chromosomes in prophase?
They spiralize
What happens to the chromosomes in metaphase?
They align with their centromeres on the ‘equator’ and attach to the spindle
What happens to the chromosomes in anaphase?
Chromatids of each chromosome separate into daughter chromosomes and move to opposite poles
What happens to the chromosomes in telophase?
Two nuclei reform at the poles
What is cytokinesis?
The division of the cytoplsam, forming two new cells
Mitosis is a…
…controlled process
What can uncontrolled cell division lead to?
The formation of tumours and cancers. Many cancer treatments are directed at controlling the rate of cell division.
What doe binary fission in prokaryotic cells involve?
- replication of the circular DNA and of plasmids
- division of the cytoplasm to produce two daughter cells, each with a single copy of the circular DNA and a variable number of copies of plasmids.
Do viruses undergo cell division?
No, because they’re not living. Following injection of their nucleic acid, the infected host cell replicates the virus particles.
What is a retrovirus?
One which rewrites DNA in the host cells and puts genetic instructions in
What is adenovirus?
The common cause of colds/sore throats
What is a bacteriophage?
A virus which uses a bacteria cell as a host
What are the features of a prokaryotic cell?
- No true nucleus
- Some DNA in the form of plasmids
- No membrane bound organelles
- No chloroplasts, only bacterial chlorophyll in some bacterium
- ribosomes are smaller (70s)
- Cell wall made of murein (peptidoglycan)
- May have a capsule
What is the function of the capsule?
Protects bacterium form other cells and helps groups of bacteria to stick together for further protection
What is the function of circular DNA?
Possesses the genetic information for the replication of bacterial cells
What is the function of a plasmid?
Possesses genes that may aid the survival of bacteria in adverse conditions eg. produces enzymes that break down antibiotics
How does a cell differentiate?
Every cell contains the genes needed for it to develop into any one of the different cells, but only one is switched on (expressed) in any one cell.
What are epithelial tissues?
Sheets of cells found in animals, lining the surface of organs and often having a protective secretory function.
What is the xylem?
Found in plants, made up of a number of similar cell types. Used to transport water and mineral ions throughout the plant and provides mechanical support
What are organs in plants made up of?
- palisade mesophyll
- spongy mesophyll
- epidermis
- phloem
- xylem
What is spongy mesophyll adapted for?
Gaseous diffusion
What does the phloem do?
Transports organic materials away from the leaf
Describe the digestive system:
Digests and processes food. Made up of organs such as the salivary glands, oesophagus, stomach, ileum, liver
Describe the respiratory system:
Used for breathing and gas exchange,made of organs such as the trachea, bronchi and lungs
Describe the circulatory system:
Pumps and circulates blood, made up of organs that include the heart, arteries and veins
What are the three stages of the cell cycle?
- interphase
- nuclear division
- cytokinesis
What is a haploid cell?
A cell with half the number of chromosomes, GAMETES
What is a diploid cell?
One which has two sets of chromosomes
What is cancer caused by?
A growth disorder of cells, the result of damage to the genes that regulate mitosis and the cell cycle
Why do most cells divide by mitosis?
Either to increase the size of a tissue during developmental growth replace dead or worn out cells.
What can the rate of mitosis be affected by?
The environment of the cell and by growth factors
How do drugs used to treat cancer usually disrupt the cell cycle how?
- preventing DNA from replicating
- inhibiting the metaphase stage of mitosis by interfering with spindle formation
What are the problems with cancer drugs?
They also disrupt the cell cycle of normal cells
What does the cell look like in prophase?
The chromosomes become visible and get shorter and thicker
What does the cell look like in metaphase?
The centromeres attach to the spindles and arrange at the equator
What does the cell look like in anaphase?
The centromeres divide in two and chromatids are pulled to poles
What does the cell look like in telophase?
Chromosomes reach poles and become thinner, finally disappearing
What is the energy for anaphase provided by?
Mitochondria
