Moduel 2 : Cell Structure Flashcards
What is a eukaryote?
These are mostly multicellular organisms made up of eukaryotic cells like animals, plants, fungi and protists.
What is a prokaryote?
These are single felled organisms made up of prokaryotic cells like bacteria.
What makes eukaryotic cells more complex?
They contain membrane bound organelles, and have their DNA it the form of chromosomes within a nucleus.
What organelles are typically found in an animal cell?
- nucleus
- nucleolus
- smooth endoplasmic reticulum
- rough endoplasmic reticulum
- Golgi apparatus
- ribosomes
- lysosomes
- mitochondria
What is the structure of a nucleus?
- contains genetic information in the form of chromosomes.
- contains a structure called the nucleolus.
- surrounded by a nuclear envelope (double membrane) containing pores.
How does the nucleus control the cells activities?
It contains DNA with instructions to produce proteins.
How does the nucleus control the synthesis of ribosomes?
The nucleolus makes ribosomal RNA.
How does the nucleus control the exchange between nucleus and cytoplasm?
Substances can either enter or leave the nucleus via the nuclear pores.
What molecules make up the cell surface membrane?
- a phospholipid bilayer is the main component of the cells.
- glycoproteins and glycolipids on the outside of the membrane.
- Extrinsic proteins though half the bilayer.
- Intrinsic proteins through all of the bilayer for transport.
- cholesterol for fluidity.
How does the cell membrane allow the movement of substances into and out of the cell?
The membrane is partially permeable.
How does the cell membrane control cell signalling?
Receptors can detect signals form other cells.
What is the structure of the mitochondria?
- contain an enzyme-rich liquid known as the matrix.
- surrounded by a double membrane in which the inner membrane if folded to form structures known a cristae.
- contain their own DNA (mtDNA) and ribosomes.
What is the primary function of mitochondria?
It is the site of aerobic respiration. It produces ATP.
What are the two types of ribosomes?
70S ribosomes found in eukaryotes.
80S ribosomes found in prokaryotes.
What is the structure of ribosomes?
Made up of proteins and rRNA. Consists of a larger and a smaller subunit. Not surrounded by a membrane.
What is the function of ribosomes?
Ribosomes are the site of protein synthesis, this involves the process of translation.
What does the Golgi apparatus contain?
Cisternae and vesicles.
What is the cisternae?
Fluid filled, membrane bound sacs.
What is the function of cisternae?
Processing and packaging lipids and proteins.
Whoa is the function of vesicles?
Store and transport lipids and proteins.
What synthesises lysosomes?
Specialised vesicles.
What is the structure of rough endoplasmic reticulum?
Contains a network of membranes enclosing a fluid-filled space, known as cisternae. The surface of the cisternae is covered with ribosomes.
What is the function of rough endoplasmic reticulum?
They can synthesise and transport proteins and proteins are made using ribosomes.
What is the structure of a smooth endoplasmic reticulum?
Contains a network of membranes enclosing a fluid filled space, known as cisternae.
What is the function of smooth endoplasmic reticulum?
Synthesis, storage, and transport of lipids and carbohydrates.
What is the structure of lysosomes?
Contains hydrolytic enzymes. Surrounded by a membrane to keep enzymes separate form the cytoplasm of the cells.
What are the functions of lysosomes?
Digest pathogens - this process uses enzymes.
Break down waste material - this material includes old organelles and cells.
What organelles usually make up a plant cell?
Mitochondria, rough endoplasmic reticulum, nucleus, nucleolus, Golgi apparatus, chloroplast, ribosomes, smooth endoplasmic reticulum, cell wall, cell membrane, vacuole.
What is the structure of a cell wall in a plant cell?
Made up of cellulose and contains channels known as plasmodesmata.
What are the functions of a cell wall in a plant cell?
Supports the cell - content of the cell press against the cell wall to make it rigid.
Prevent the cell from bursting - the cell wall can withstand high osmotic pressure.
Allows exchange of substances between cells - plasmodesmata connects neighbouring cells.
What is the structure of chloroplast?
Contain fluid filled sacs known as thylakoids which are stacked up to form grana.
Surrounded by a double membrane, enclosing a fluid known as stroma.
Contain their own DNA and ribosomes.
What is the function of a chloroplast?
Site of photosynthesis - these reactions take place in the grana and stroma.
What is the structure of a vacuole?
Contains cell sap and it is surrounded by a selectively permeable membrane known as a tonoplast.
What is the function of a vacuole?
Helps to maintain pressure within the cell, which keepers the cell rigid and stops the plant form wilting.
What is the structure of a algal cell?
Contain the same organ eels an plant cells. Contain chloroplast with different shapes tot Hesse found in plant cells.
What is the structure of a fungal cell?
Contain Mose of the organelles found in a plant cell but do not contain chloroplast. Contain cell walls which are made up of chitin not cellulose like in plant cells.
What is a specialised cell?
These are cells with certain features that allow them to carry out a particular function.
What is a tissue?
This is a group of similar cells working together to carry out a particular function.
What is an organ?
This is a group of tissues working together to carry out a particular function.
What is an organ system?
This is a group of organs working together to carry out a particular function.
What is different about the cell wall in prokaryotes?
In prokaryotic cells, the cell wall is made up of murein or peptidoglycan.
What is differentabout ribosomes in prokaryotic cells?
Prokaryotic cells have 70S ribosomes, which are smaller than 80S ribosomes found in eukaryotic cells.
What is different about ribosomes in prokaryotic cells?
Prokaryotic cells have 70S ribosomes, which are smaller than 80S ribosomes found in eukaryotic cells.
How is the genetic material stored in prokaryotic cells?
In prokaryotic cells, this is mostly found in a large circular strands of DNA, and some extra genes are found in smaller loops called plasmids.
What is a capsule?
Some prokaryotic cells have an extra layer around the cell wall known as a capsule.
This structure is made up of polysaccharides and protects the cells for attack by antibiotics or white blood cells.
What is a flagellum?
A long, hair-like structure known as a flagellum found in prokaryotes.
This structure is attached to the cell membrane and rotates to push the cell through its environment.
What is a pili?
A short, hair-like structure on the cell surface of a prokaryotes.
Pili are used for attaching prokaryotic cells tot other cells of surfaces.
What is the approximate size of prokaryotes and eukaryotes?
Prokaryotes - 0.1 to 5 micro meters
Eukaryotes - 10 to 100 micro meters
What cell type are prokaryotes and eukaryotes?
Prokaryotes are unicellular.
Eukaryotes can be ether unicellular of multicellular.
What is a virus?
Viruses are microscopic infectious agent that can only replicate inside the cells of living organisms.
Why are viruses considered acellular?
Although they are sometimes referred t a microorganisms they are not living so so not count as ‘organisms’.
What is in a virus?
Envelope, capsid, enzyme, glycoprotein, genetic material.
How is genetic material presented in viruses?
Viral genomes may be DNA or RNA and single or double-stranded. They are always found in viruses.
What is a capsid?
Capsids are always present in a virus. It s a layer of protein molecules that surrounds and protects the genetic material.
What is an envelope?
Sometimes present in a virus. An outer layer made up of phospholipids.
What is a glycoprotein?
Sometimes present in viruses. Also known as surface, attachment, or envelope proteins, these help viruses bind to host cells.
What are the enzymes that can sometimes be found in viruses?
Some irises carry enzymes, like reverse transcriptase, high allows them to convert RNA into DNA.
How do viruses replicate?
- The virus uses its attachment proteins to bind to specific receptor proteins on host cells.
- The virus injects its viral DNA or RNA into the host cell.
- The virus uses the host cells machinery and resources, such as enzymes and ribosomes, to replicate viral particles.
- New viral particles are released form the halt cell.
What is magnification?
How many times larger an image is than the object.
What is resolution?
The ability to distinguish between two separate points.
How do you calculate the magnification?
Magnification = image size / object size
What do light/optical microscopes do?
They create an image that is much larger than the real object.
What is the maximum resolution of an optical microscope?
0.2 micro meters
What is the maximum magnification of an optical microscope?
X 1500
What is a method of sample preparation for optical microscopes which is commonly used?
Wet (or temporary) mount
How do you prepare a wet mound sample for an optical microscope?
- Use a pipette to place a small drop of water onto the centre of the glass slide.
- Use a pair of forceps to place a thin section of the specimen onto the drop of water. The specimen should be thin enough to allow light to pass through.
- Add a few drops if stain to the specimen. This increases contrast and allows cell components to become visible.
- Slowly add the cover slip onto the specimen.
What is the method of preparing specimen for optical microscopes called dry mound?
The specimen is placed directly onto the slide and covered with a cover slip.
What is the method for preparing specimen for a optical microscope called squash slides?
A wet mount is prepared ad the cover slip is pressed to squash the cells.
What is the method of preparing a specimen for an optical microscope called smear slides?
The edge of a slide is used yo smear the sample to create a thin, even coating on a separating slide.
How do you use an optical microscope?
- Clip the prepared microscope slide onto the stage.
- Select the objective lens with the lowest power.
- Use the coarse focus to bring the stage just below the objective lens.
- Look down the eyepiece and use the coarse focus to move the stage downwards until the image is roughly in focus.
- Use the fine focus to make the image clearer.
- If a higher magnification is needed, swap to a more powerful objective lens and refocus.
What would biological drawings have?
- a title
- state the magnification or scale
- be drawn with a sharp pencil
- include smooth, continuous lines
- include labels
- include accurate sizes of observable structures
What should biological drawings not have?
- include shading or colouring
- include arrow heads for labels
- involve lines overlapping each other
What is an electron microscope?
electron microscopes use electrons rather than light to form an image. Since electrons have a shorter wavelength than light, electron microscopes have a better resolution than light microscopes.
Why are electron microscopes not widely used?
They are more expensive than light microscopes and only produce images in black an white.
What are the two types of electron microscopes?
Transmission electron microscope and scanning electron microscopes
How do transmission electron microscopes work?
They use electromagnets to transmit a beam of electrons through specimen. The denser parts absorb more electrons, so appear darker in the image formed.
Way are transmission electron microscopes good?
They produce high-resolution images, meaning they can be used to observe the internal structures of organelles.
What are the negatives of using a transmission electron microscope?
The specimen must be viewed in a vacuole, meaning only non-living or dead organisms can be observed. Also, the specimen must be thin to allow electrons to pass through.
What is the maximum resolution of a transmission electron microscope?
0.5 nano meters
What is the maximum magnification of a transmission electron microscope?
X 1500000
What is a scanning electron microscope?
They scan a beam of electrons across the surface of a specimen. Reflected electrons are then used to form an image.
What are the positives of a scanning electron microscope?
They produce 3D images of the surface of the specimen. It can also be used on thicker specimens than transmission electron microscopes.
What are the negatives of a scanning electron microscope?
Can only view non-living or dead specimens.
What is the maximum resolution of a scanning electron microscope?
5 nano meters
What is the maximum magnification of a scanning electron microscope?
X 1500000
What is cell fractionation?
A laboratory method used to isolate different components of the cell, specifically the organelles, so they can be studies in detail, such as under an electron microscope. This technique involves breaking the cell often and then separating the organelles based on their size and density.
What are the four main steps of cel fractionation?
- Sample preparation
- Homogenisation
- Filtration
- Ultracentrifugation
What does sample separation in cell fractionation involve?
Placing a sample in an ice-cold, isotonic, buffered solution to protect the organelles during the fractionation process.
In cell fractionation why must the sample be ice cold?
This slows down enzyme activity that might otherwise break down organelles.
In cell fractionation why must the sample be isotonic?
It ensures that the water potential inside and outside the organelles in the same, preventing the damage through water potential.
In cell fractionation what must the sample be in a buffer solution?
Keeping the pH constant is crucial to prevent desaturation of proteins and enzymes.
What is homogenisation in cell fractionation?
This involves physically breaking open the cells. This disrupts the plasma membrane, which allows the organelles to be released into the solution. This can e achieved using various methods, such as using a blender to grind the cells.
What is filtration in cell fractionation?
Following homogenisation, the mixture is them filtered to remove larger pieces of the cell debris and any remaining tissue fragments. The filtration is typically don through a gauze which allows smaller organelles to pass through while retaining larger debris.
What is ultracentrifugation is cell fractionation?
The process used to separate organelles based on their density. By spinning the filtered solution at various speeds organelles are separated into layers according to their mass.
What is a pellet?
The sediment at the Baotou of the tube, containing the heavier organelles.
What is a supernatant?
The liquid remaining above the pellet, which contains the lighter organelles.
What is the process of ultracentrifugation in cell fractionation?
- The cell fragments are placed in a centrifuge tube and spun at a low speed.
- This results in the heaviest organelles, such a nuclei, forming a pellet at the bottom of the tube.
- The lighter organelles remain suspended in the supernatant.
- The supernatant is then transferred to a new tube and centrifuged at a higher speed.
- This leads to the next heaviest set of organelles, typically mitochondria, settling into a pellet.
- Steps 4 and 5 are repeated, increasing the speed each time to separate the remaining organelles until all the organelles have been seperated into distinct layers.
In cell fractionation it is important to know the order of organelles from heaviest to lightest what is this list?
- Nuclei
- Chloroplast
- Mitochondria
- Lysosomes
- Endoplasmic reticulum
- Ribosomes
What is the cell cycle?
The process in which all eukaryotic cells go through before dividing and replicating.
Why must all organisms divide and replicate?
For growth and repair.
What are the three main phases of the cell cycle?
- Interphase
- Mitosis
- Cytokinesis
What is interphase?
This occupies the majority of the cycle as cells prepare for division
What is mitosis?
This is when the nucleus of the cell divides in two.
What is cytokinesis?
This is when the whole cell and cytoplasm divides in two to produce two identical cells
What three main processes happen during interphase?
Cell growth, synthesis of proteins and the replicating of DNA.
What is meant by cell growth during interphase?
This includes an increase in cytoplasm.
What is meant by the synthesis of proteins during interphase?
Proteins are replicated these are usually used to make new organelles.
What is meant by replicating DNA during interphase?
This results in double the genetic material in a cell.
How is DNA stored in a nucleus?
As chromosomes.
How many chromosomes do humans have?
46 chromosomes or 23 pairs.
What is a homologous pair?
Each chromosome consists of two homologous chromosomes. One chromosome of each pair is paternal and the other is maternal.
What is an allele?
A gene identical in terms of the genes they carry but different in what the genes carry out.
What is a chromatid?
One half of a replicated chromosome.
What is a centromere?
The centre of a chromosome.
What is a diploid cell?
Contain tow copies of each chromosome, one copy from each parent.
What is a haploid cell?
Only contain one copy of each chromosome.
Why is mitosis important for growth?
Unicellular zygotes can divide by mitosis to form multicellular organisms.
Why is mitosis important for the replacement of damaged or dead tissues?
Cells are constantly dying and being replaced using mitosis.
Why is mitosis important for asexual reproduction?
Some organisms reproduce using mitosis to from genetically identical offspring.
Why is mitosis important for the development of body plans?
Mitosis is used to form the different parts of an organism.
Why is mitosis important for the production of stem cells?
Stem cells divide by mitosis.
What are the stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
What happens during prophase of mitosis?
The chromosomes condense and are now visible under a microscope. Centrioles migrate to the opposite poles of the cell. Each centriole starts forming spindle fibres. The nucleolus disappears and the nuclear envelope starts to break down, leaving the chromosomes free in the cytoplasm.
What happens during metaphase of mitosis?
The chromosomes line u along the equator of the cell. Each chromosome attaches to the spindle by their centromere.
What happens during anaphases of mitosis?
The centromeres divide t separate each pair of sister chromatids. The spindle fibres contract and shorten to pull the chromatids to opposite poles of the cell. Each chromatid is pulled by its centromere, causing the to take on a ‘v’ shape when viewed under a microscope.
What happens during telophase of mitosis?
The chromatids reach the opposite poles of the cell where they uncool to become long and thin chromosomes again. A nuclear envelope forms around each set of chromosomes to from two nuclear and the nucleolus starts to reform.
What is cytokinesis?
After the steps of mitosis., the cytoplasm divides in a process known as cytokinesis. This produces tow daughter cells that are genetically identical to one anther.
How does a tumour form?
The cell cycle is controlled by a number of genes. Mutations to these genes can lead to uncontrolled cell division cell division and growth, resulting in a group of abnormal cells known as a tumour.
When do tumours become cancerous?
When they start to invade neighbouring tissues.
How do some cancer treatments work?
They disrupt cell division by targeting specific storages of the cell cycle. This prevents the cells from dividing and stops the growth of cancerous cells.
Why might a cancer treatment disrupt the S phase?
Some drugs can prevent DNA from replicating so mutated genes are prevented from replicating.
Why might a cancer treatment disrupt metaphase?
Some drugs can interfere with the formation of spindle fibres which can prevent the replication of mutated cells.
How do prokaryotic cells replicate?
Binary fission.
What are the steps involved in binary fission?
- Cell growth
- DNA replication
- Movement of DNA
- Cell wall growth
- Cytoplasm division
How does the cell grow in the first stage of binary fission?
The cell increases in size to prepare for division.
How does the DNA replicate in the second stage of binary fission?
The circular chromosome is replicated once, and plasmids may be replicated multiple times.
How does DNA move in the third stage of binary fission?
Each replicated circular chromosome moves t opposite poles of the cell, and plasmids and distributed randomly between the two poles.
How does the cell wall grow in the fourth stage of binary fission?
The cell-surface membrane starts to divide and new cell walls form between the two DNA molecules.
How does the cytoplasm divide in the fifth stage of binary fission?
The cytoplasm of the original cell s divided into two identical daughter cells.
What DNA is found in a daughter bacteria cell?
One copy o the circular DNA and a variable number of plasmids.
What do you need to know in order to calculate the bacteria population growth?
- the number of cells you started with
- the mean division time, which is the average time taken for one bacterial cell to divide into two
- the time period during which the division occurs
What environmental factors can effect the rate of replication of bacteria?
Temperature, moisture, nutrients.
