What is the basic unit of all living things called?
What are the two types of fundamental cell?
Prokaryotic and eukaryotic cell
Give a description of a prokaryote.
Prokaryotes are single-celled organisms with a simple structure of just a single internal area called the cytoplasm.
Give a description of a Eukaryotic cell.
Eukaryotic cells have a structure containing a membrane bound nucleus and cytoplasm containing membrane-bound cellular components.
Where do most of the metabolic reactions take place in a cell?
In the cytoplasm
True or false? Membranes are selectively permeable and control the movement of substances into and out of the cell and organelles.
What are the three structures that plant cells contain that animal cells do not.
Cell wall, chloroplasts and a permanent vacuole.
What is the role of the nucleus?
The nucleus contains DNA which directs the synthesis of all proteins required by the cell.
Give one structure of the nucleus that helps it to carry out its function.
The nuclear envelope is a key structure that protects the DNA from damage in the cytoplasm. It contains nuclear pores which allow molecules to move in and out of the nucleus but prevents DNA from leaving.
Describe the structure of DNA.
DNA associates with proteins called histones to form chromatin. This coils and condenses to form structures called chromosomes.
What is the function of the nucleolus?
The nucleolus is responsible for producing ribosomes necessary for protein synthesis.
What is the function of mitochondrion?
Mitochondrion are the site of aerobic respiration in a cell where ATP is produced
True or false? The number of mitochondrion in a cell has no relation to the function of that cell.
False. Cells with a high number of mitochondrion often require a lot of energy to carry out its function.
Describe the structure of a mitochondrion.
Mitochondria have a double membrane. The inner membrane is folded in to cristae which contain the enzymes used in aerobic respiration. The fluid interior is called the matrix.
What are vesicles?
Vesicles are membranous sacs that have storage and transport roles.
What is the role of a vesicle?
Vesicles are used to transport materials inside the cell
What is the difference between a lysosome and a vesicle?
A lysosome is a specialised form of vesicle that contain hydrolytic enzymes.
What is the role of a lysosome?
They are responsible for breaking down waste material in cells.
What is the cytoskeleton of a cell?
The cytoskeleton is a network of fibres necessary for the shape and stability of a cell.
What is the role of the cytoskeleton in a cell?
The cytoskeleton holds organelles in place and controls cell movement. It also control the movement of organelles within a cell.
What are the three components of the cytoskeleton?
Microfilaments, microtubules and intermediate fibres.
Describe the structure and function of microfilaments.
Fibres formed from the protein actin. These are responsible for cell movement and also cell contraction during cell division
Describe the structure of centrioles.
Centrioles are composed of microtubules.
What is the name given to two associated centrioles? What is its role?
Two associated centrioles form the centrosome which is involved in the assembly and organisation of the spindle fibres during cell division.
Fill in the blanks. A key function of a cell is to .............. .............. for internal use and for ............. .
synthesise, proteins, secretion
What is the endoplasmic reticulum (ER)?
The ER is a network of membranes enclosing flattened sacs called cisternae. It is connected to the outer membrane of the nucleus.
What are the two types of endoplasmic reticulum and what are the roles of each?
The two types of endoplasmic reticulum, smooth ER and rough ER. Smooth endoplasmic reticulum is responsible for lipid and carbohydrate synthesis, and storage. Rough endoplasmic reticulum has ribosomes bound to the surface and is responsible for the synthesis and transport of proteins.
Where can ribosomes be found within a cell?
Ribosomes can be found free-floating or attached to endoplasmic reticulum.
Give two structural details about about a ribosome.
Ribosomes are non-membrane bound and they are constructed of RNA molecules.
True or false? Ribosomes are the site of protein synthesis.
What is the role of the golgi apparatus?
It modifies and packages proteins into vesicles.
Describe the process of protein production (5 stages)
Step 1- Proteins are synthesised on the ribosomes bound to the endoplasmic reticulum
Step 2- They pass into the cisternae and are packaged into transport vesicles
Step 3- Vesicles containing the newly synthesised proteins move towards the Golgi apparatus via the transport function of the cytoskeleton
Step 4- The vesicles fuse with the cis face of the Golgi appartus and the proteins enter. The proteins are modified before leaving the Golgi apparatus in vesicles
Step 5- The vesicles move towards and fuse with the cell-surface membrane, releasing their contents by exocytosis
The cell wall is an important feature of plants. Explain why.
Cell walls are permeable so substances can pass into and out of the cell through the cell wall. The cell wall provides the cells shape helping to keep the cell rigid. The cell wall also acts as a defence mechanism, protecting the contents of the cell against invading pathogens.
What is the role of the permanent vacuole in plants?
The permanent vacuole is very important in the maintenance of turgor, so that the contents of the cell push against the cell wall and maintain a rigid framework for the cell.
True or false? The membrane of a vacuole in a plant cell is selectively permeable meaning that some small molecules can pass through but others cannot.
What is the function of chloroplasts in the cell?
Chloroplasts are the organelles responsible for photosynthesis in plant cells
Describe the structure of chloroplasts.
Chloroplasts have a double membrane structure. The fluid enclosed in the chloroplast is called the stroma. They have structures called granum that contain the chlorophyll pigments.
True or false? Chloroplasts are able to make their own proteins
True. They contain DNA and ribosomes which allows them to do this.
Prokaryotes are some of the earliest forms of life. They are a diverse group of unicellular organisms that can be classified into two domains. What are these domains?
Bacteria and archaea
Why do prokaryotes still exist today despite them being far more simple than eukaryotes?
They can survive in very extreme conditions and are very very small.
True or false. Eukaryotes have undulipodium and prokaryotes have flagellum.
What type of structure does undulipodium have?
9 + 2 formation.
Give two differences between the ribosomes in prokaryotes and those in eukaryotes.
In prokaryotes, the ribsomes are smaller (70S) than in eukaryotic cells (80S) and they are not attatched to any membranes.
What is the purpose of the cytosol in prokaryotic cells?
The cytosol is where the cell processes happen
Describe the purpose of plasmids in prokaryotic cells.
Plasmids contain only a few genes and it is these that get exchanged.
True or false? Prokaryotic cells do not contain any membrane bound organelles.
What is the purpose of the capsule or slime layer in prokaryotic cells?
The capsule or slime layer assists with movement and protection.
What is the cell wall of a prokaryotic cell made from?
Compare prokaryotic and eukaryotic cells.
How many lenses do light microscopes have? Where are they located?
Two. The objective lens is placed near to the specimen and the eyepiece lens which is what the eye looks through.
In a light microscope, where is the source of light?
Illumination is usually provided by a light underneath the sample.
What are the four types of sample?
Dry mount, wet mount, squash slides and smear slides.
What is the purpose of using staining in microscopy?
Stains increase contrast between the parts of cells which allows components to become visible so they can be identified.
Describe the use of methylene blue stain including relevant charges.
Methylene blue is a positively charged dye which is attracted to negatively charged materials in the cytoplasm leading to staining of cell components.
Describe the use of Congo red stain including relevant charges.
Congo red is a negatively charged dye and are repelled by the negatively charged cytosol. These dyes stay outside cells, leaving the cells unstained, which then stand out against the stained background.
When would differential staining be used?
Differential staining can distinguish between two types of organisms that would otherwise be hard to identify.
What is the purpose of gram stain technique?
Gram stain technique is used to separate bacteria in to two groups, Gram-positive and Gram-negative.
What is acid-fast technique used for?
It is used to differentiate species of mycobacterium from other bacteria.
What are the four stages involved in the production of microscope slides?
Fixing- chemicals are used to preserve specimens
Sectioning- specimens are dehydrated with alcohols then placed in a mould with wax
Staining- specimens are treated with different stains to show different structures
Mounting- the specimens are then secured to a microscope slide
What is the definition of magnification?
Magnification is how many times larger the image is than the actual size of the object being viewed.
What is the definition of resolution?
Resolution is the ability to see individual objects as separate entities
How can resolution be increased?
Resolution can be increased by using beams of electrons which have a wavelength thousands of times shorter than light.
What is the formua triangle for magnification calculations?
What is the maximum magnification and resolving power of a transmission electron microscope?
Maximum magnification is x500 000 and maximum resolving power is 0.5nm
What are artifacts?
Artifacts are structures that are produced due to the prearation process.
What is the maximum magnification and resolution of a scanning electron microscope?
The maximum magnification is x500 000 and the maximum resolving power is 3-10nm
True or false? Both a transmission electron microscope and scanning electron microscope can produce 3D images.
False, a transmission electron microscope can only produce 2D images.
How does a laser scanning confocal microscope differ from an optical microscope?
A laser scanning confocal microscope moves a single spot of focused light across a specimen rather than illuminates it from below.
True or false? As very thin sections of specimen are examined and light from elsewhere is removed, very high resolution images can be obtained.