2A: Cell Structure and Division Flashcards
What are the two main types of organism?
Prokaryotic and Eukaryotic
Definition of Prokaryotic
single-celled organisms that lack a nucleus and other membrane-bound organelles
Definition of Eukaryotic
any cell or organism that possesses a clearly defined nucleus
What are Organelles?
Parts of Cells
Name all of the Organelles in an Animal Cell
Cell-Surface Membrane
Rough Endoplasmic Reticulum
Smooth Endoplasmic Reticulum
Nucleolus
Nucleus
Mitochondrion
Cytoplasm
Golgi Apparatus
Nuclear Envelope
Ribosome
Lysosome
Name all of the Organelles in a Plant Cell
Cell-Surface Membrane
Rough Endoplasmic Reticulum
Smooth Endoplasmic Reticulum
Nucleolus
Nucleus
Mitochondrion
Cytoplasm
Golgi Apparatus
Nuclear Envelope
Ribosome
Lysosome
Chloroplast
Cell Wall
Vacuole
Plasmodesmata
Name all of the Organelles in an Algal Cell
Cell-Surface Membrane
Rough Endoplasmic Reticulum
Smooth Endoplasmic Reticulum
Nucleolus
Nucleus
Mitochondrion
Cytoplasm
Golgi Apparatus
Nuclear Envelope
Ribosome
Lysosome
Chloroplast
Cell Wall
Vacuole
Name all of the Organelles in a Fungal Cell
Cell-Surface Membrane
Rough Endoplasmic Reticulum
Smooth Endoplasmic Reticulum
Nucleolus
Nucleus
Mitochondrion
Cytoplasm
Golgi Apparatus
Nuclear Envelope
Ribosome
Lysosome
Chloroplast?
Chitin Cell Wall
Vacuole
Description and function of the Cell-surface Membrane
Description:
found on the surface of animal cells and just inside the cell wall of other cells. made mainly of lipids and proteins
Function:
regulates movement of substances into and out of the cell. also contains receptor molecules which allow the cell to respond to chemicals like hormones
Description and function of the Nucleus
Description:
a large organelle surrounded by nuclear envelope which contains pores. nucleus contains chromosomes and one or more structures called the nucleolus
Function:
controls cell’s activities. DNA contains the instructions to make proteins. the pores allow substances to move between nucleus and cytoplasm. the nucleolus makes ribosomes
Description and function of a mitochondrion
Description:
oval-shaped and have a double membrane, the inner folds to form cristae. inside is the matrix which contains enzymes involved in respiration
Function:
site of aerobic respiration which produces ATP. found in cells that are very active so require lots of energy
Description and function of a chloroplast
Description:
small, flat structure found in plant and algal cells. filled ith stroma, surrounded by a double membrane and also has a membrane inside called thylakoid membranes. these membranes are stacked up in some parts of the chloroplast to form grana. grana are linked by lamellae which are thin, flat pieces of thylakoid membrane
Function:
site of photosynthesis, some parts of photosynthesis take place in the grana and other parts happen in the stroma
Description and function of a Golgi Apparatus
Description:
fluid-filled membrane-bound flattened sacs. vesicles are often seen at the edges of the sacs
Function:
processes and packages new lipids and proteins. makes lysosomes
Description and function of a Golgi Vesicle
Description:
small fluid-filled sac in the cytoplasm surrounded by a membrane and produced by Golgi Apparatus
Function:
stores lipids and proteins made in Golgi Apparatus and transports them out of the cell
Description and function of a Lysosome
Description:
round organelle surrounded by a membrane, with no clear internal structure
Function:
contains hydrolytic enzymes. kept separate from cytoplasm by surrounding double membrane and can be used to digest invading cells or break down worn out components of the cell
Description and function of a Ribosome
Description:
very small organelle that floats free in the cytoplasm or is attached to the rough endoplasmic reticulum. made of proteins and RNA, not surrounded by a membrane
Function:
site of protein synthesis
Description and function of the Rough Endoplasmic Reticulum
Description:
system of membranes enclosing a fluid-filled space, surface covered by ribosomes
Function:
folds and processes proteins that have been made at the ribosomes
Description and function of the Smooth Endoplasmic Reticulum
Description:
similar to rough ER but with no ribosomes
Function:
synthesises and processes lipids
Description and function of the Vacuole
Description:
a membrane-bound organelle found in the cytoplasm. contains cell sap- a weak solution of sugar and salts. the surrounding membrane is called the tonoplast
Function:
maintains cell pressure and keeps cell rigid. stops wilting. involved in the isolation of unwanted chemicals inside the cell
How are Epithelial Cells specialised
villi and microvilli increase surface area, lots of mitochondria
How are Red Blood Cells specialised
no nucleus to make more space for haemoglobin
How are Sperm Cells specialised
contain lots of mitochondria to provide energy to propel themselves toward egg
Order smallest to largest cells-organism
Cell, Tissue, Organ, Organ System, Organism
Structure and function of a Flagellum
Structure:
a long, hair-like structure
Function:
rotates to allow the cell to move
Where does a Prokaryotic Cell Store its Genetic Information?
in Circular DNA that is free floating in the cytoplasm, one long coiled up strand not associated to any proteins
they also have plasmids which are small loops of DNA that contain genes for things like antibiotic resistance and can be passed between cells
Structure and function of a Capsule
Structure:
made up of secreted slime
Function:
helps protect bacteria from attack by cells of the immune system
Describe the process of Binary Fission
- circular DNA and plasmids replicate- plasmids may be replicated multiple times
- cell gets bigger and DNA loops move to opposite ‘poles’ of the cell
- cytoplasm begins to divide and new cell walls begin to form
- cytoplasm divides and two daughter cells are produced.
Definition of Acellular
being without cells
Structure of a Virus
a core of genetic material- either DNA or RNA- surrounded by a capsid (protein coat) with attachment proteins
Describe the process of Viral Replication
- attach to host cell surface using their attachment proteins to bind to complementary receptors on the cell-surface membrane of the host cell
- the virus then injects its DNA or RNA into the host cell
- genetic material and proteins are replicated by host cell
- viral components assemble
- replicated viruses released from host cell
The equation for magnification
magnification = size of image/size of real image
Definition of Resolution
how well a microscope distinguishes between 2 points that are close together
Name the 3 types of microscope
Light, electron (transmission and scanning)
Characteristics of the optical microscope
uses light to form an image
maximum resolution of about 0.2 micrometers
maximum magnification of about x 1500
produces coloured images
can view living specimens
Characteristics of the transmission electron microscope
focuses beams of electrons through the specimen to create an image
denser parts absorb the electrons and appear darker
produce high resolution images
Characteristics of electron microscopes
higher resolving power (about 0.0002 micrometers)
max magnification of about x 1500000
produced black and white images
can’t view living specimens as must ne in vacuum
Characteristics of scanning electron microscopes
scan beam of electrons across specimen which knocks electrons from the specimen which are gathered in a cathode ray tube to form an image
produces a 3d image
good for thick specimens but have lower resolution than TEMs
How to prepare a microscope slide
- pipette a small drop of water onto the centre of the slide
- use tweezer to place a thin section of your specimen on top of the water
- add a drop of stain
- add a cover slip, lower it tilted- one side at a time
What is a microscope artifact?
things that you can see down a microscope that aren’t part of the cell or specimen that you’re looking at
How to do cell fractionation
- homogenisation: bland the specimen with cold, buffered, isotonic solution
- filtration: filter through gauze to remove unbroken cells and debris
- ultracentrifugation: pour cell fragments into a tube and place in centrifuge. spin at different speed and repeat with supernatent at higher speed each time.
- each sequential pellet will be the organelles in order of mass
What is the order of organelles separated in cell ultracentrifugation?
nuclei
chloroplasts
mitochondria
lysosomes
endoplasmic reticulum
ribosomes
name the sections of the cell cycle
Interphase:
Gap Phase 1 (G1)- cell grows and new organelles and proteins are made
Synthesis (S)- cell replicates DNA
Gap Phase 2 (G2)- cell keeps growing and proteins are made
Mitosis:
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
What happens in prophase?
- chromosomes shorten and condense
- centrioles begin to move to poles and start to form spindle fibres
- nuclear envelope breaks down and chromosomes lie free in cytoplasm
What happens in metaphase?
- chromosomes line up along equator and become attached to spindle fibres by their centromere
What happens in anaphase?
- centromeres divide, separating each pair of sister chromatids
- spindle fibres contract, pulling chromatids to opposite poles of the cell
- v-shaped chromatids appear
What happens in telophase?
- chromatids reach opposite poles on the spindle
- they uncoil and become long and thin again
- nuclear envelope reforms
what happens in cytokinesis?
cell divides to form 2 identical daughter cells
What is cancer?
a tumor that invades surrounding tissues
How is knowledge of mitosis used tp treat cancer?
treatments are designed to control cell cycle in the cancer which kills the tumor
these treatments don’t differentiate between cancer cells and body cells, so they die too
How to prepare a root tip squash
Preparing the root tip
- Add some 1mol hydrochloric acid into a boiling tube, enough to cover the root tip (only a few mm deep). Put the tube in a water bath that has been allowed to reach 60c.
- Use a scalpel to cut 1 cm from the tip from a growing root, must be the tip because this is were mitosis takes place.
- Carefully transfer the root tip into the boiling tube containing the acid. Incubate for about 5 minutes.
- Use tweezers to remove the root tip from the tube and use a pipette to rinse it well with cold water. Leave the tip to dry on a paper towel.
- Place the tip on a microscope slide and cut 2mm from the very tip, get rid of the rest.
- Use a mounted needle to break the tip open and spread the cells out thinly.
- Add a few drops of stain and lave it for a few minutes. The stain will make the chromosomes easier to see under the microscope.
- Place a cover slip over the cells and put a piece of folded filter paper on top. Push down firmly to squash the tissue. Don’t smear or you will damage the chromosomes
- Now look at the stages of mitosis under an optical microscope
Using an optical microscope
- Clip the slide on the stage
- Select lowest-powered objective lens
- Use the course adjustment knob to bring the stage up to just below the objective lens
- Look down the eyepiece. Use the course adjustment to move stage lower until the image is roughly in focus
- Adjust focus with the fine adjustment knob to make image clearer
- If you need greater magnification, swap to a higher-powered objective lens and refocus
Calculating mitotic index
- Count cells in view
- Count cells in view in mitosis
- Divide cells in mitosis by number of cells and multiply by 100
How to use an optical micoscope
Using an optical microscope
- Clip the slide on the stage
- Select lowest-powered objective lens
- Use the course adjustment knob to bring the stage up to just below the objective lens
- Look down the eyepiece. Use the course adjustment to move stage lower until the image is roughly in focus
- Adjust focus with the fine adjustment knob to make image clearer
- If you need greater magnification, swap to a higher-powered objective lens and refocus
The equation for calculating mitotic index
mitotic index = number of cells with visible chromosomes/total number of cells observed
