Mod 2 Chap 2: Basic components of living systems Flashcards
What is the function of cell surface (plasma) membranes?
Cell surface (plasma) membranes regulate the movement of substances into and out of the cell. it also has receptor molecules on it, which allow it to respond to chemicals like hormones
What is the function of the nucleus?
The nucleus controls the cell’s activities (by controlling the transcription of DNA - DNA controls the instructions to make proteins.) The pores allow substances eg RNA to move between the nucleus and the cytoplasm. The nucleolus makes ribosomes.
What is the function of mitochondrion?
Mitochondrion is the site of aerobic respiration, where ATP is produced. They’re found in large numbers in cells that are very active and require a lot of energy.
What is the function of chloroplast?
Chloroplast is the site where photosynthesis take place. Some parts of photosynthesis happen in the grana, and other parts happen in the stroma (a thick fluid found in chloroplast)
What is the function of the Golgi apparatus?
Golgi apparatus processes and packages new lipids and proteins. It also makes lyosomes.
What is the function of the golgi apparatus?
Golgi apparatus stores lipids and proteins transports them out of the cell via the cell surface membrane
What is the function of the lyosome?
The lyosomes contain digestive enzymes called lysozymes. These are kept separate from the cytoplasm by the surrounding membrane, and can be used to digest invading cells or to break down worn out components of the cell.
What is the function of the ribosome?
The ribosome is the site where proteins are made
What is the function of the rough endoplasmic reticulum?
The rough endoplasmic reticulum folds and prcesses proteins that have been made at the ribosomes
What is the function of the smooth endoplasmic reticulum?
The smooth endoplasmic reticulum synthesises and processes lipids
What is the function of the cell wall?
The cell wall supports cells and prevents them from changing shape
What is the function of the cell vacuole?
The cell vacuole helps to maintain pressure inside the cell and keep the cell rigid. This stops plants wilting. Also involved in the isolation of unwanted chemicals inside the cells.
What is the nuclear envelope?
A nuclear envelope the double membrane that DNA is contained in to protect it from damage in the cytoplasm. It contains nuclear pores that allow molecules to move in and out of the nucleus.
How are chromosomes formed?
Chromosomes are formed when chromatin coils and condenses
What is chromatin?
Chromatin is a complex formed when DNA associates with proteins called histones
How are christae formed in mitchondria?
Christae is formed when the inner membrane of mitochondria is highly folded
What is the fluid interior of the inner membrane of mitochondria called?
The fluid interior of the inner membrane of mitochondria is called the matrix
What are the functions of the vesicles in prokaryotic cells?
Vesicles in prokaryotic cells are membranous sacs that have storage and transport roles. They transport material inside the cell.
What is the cytoskeleton?
The cytoskeleton is present throughout all cytoplasms of eukaryotic cells. It is a network of fibres necessary for shape and stability of a cell
What are the three components of the cytoskeleton?
The three components of the cytoskeleton:
-Microfilaments
-Microtubules
-Intermediate fibres
What are thylakoid membranes called when stacked in chloroplasts?
Stacked thylakoid membranes are called grana. The links between them are called intergranel lamellae.
What is the membrane that the permanent vacuole is contained in?
Permanent vacuole is contained with the tonoplast which is filled with cell sap (a watery solution of different substances). This keeps the cell firm and turgid.
What are the pores within the cell wall called?
The pores within the cell wall are plasmodesmata. They connect cells together by their cytoplasm, enabling the exchange and transport of substances.
How are proteins produced and moved in a cell?
1) mRNA copy of hormone is made in nucleus
2) mRNA leaves through nucleus pore
3) mRNA attaches to ribosome. The ribosome reads the instructions to assemble the protein.
4) Protein is pinched off in vesicles and go to golgi apparatus
5) Vesicle fuses with golgi apparatus
6) Golgi apparatus processes and packages protein
7) Packaged protein move towards cell surface membrane
8) Vesicle fuses with plasma membrane
9) Plasma membrane opens to release protein (exocytosis)
What is a eukaryote?
A eukaryote is an organism consisting of one or more cells that contain DNA in a membrane bound nucleus
What are histones?
A histone is a protein that provides structural support for a chromosome. Each chromosome contains a long molecule of DNA, which must fit into the cell nucleus. To do that, the DNA wraps around complexes of histone proteins, giving the chromosome a more compact shape.
Roles of membranes
Roles of membranes:
-Site for attachment of enzymes
-Formation of organelles
-Selectively permeable
Resolution of light microscope
Resolution of light microscope = 200nm
Resolution of electron microscope
Resolution of electron microscope = 0.5nm
Benefits of staining for light microscopy
Benefits of staining for light microscopy:
-More organelles can be seen - specific organelles - organelles bind to stain
Evidence for endosymbiotic theory
Evidence for endosymbiotic theory - mitochondria contain ribosomes that are smaller than those found in the cell cytoplasm
Roles of cytoskeleton
Roles of cytoskeleton:
-Maintains shape of cell
-Keeps organelles in place
-Transport ie cell division, vesicles, cillia
-Movement of chromosomes and chromatids
What provides structural support in plants other than cell wall?
In leaves, air spaces give buoyancy, supported by surrounding water
Roles of lignin in xylem
Roles of lignin in xylem:
-Strengthens/Thickens cell wall
-Waterproof cell > reduces loss of water
-Allows for flexibility
-Improves adhesion of water-
What is the size of each division in the following microscopes?:
4x
10x
20x
40x
100x
4x = 25 micrometers
10x = 10 micrometers
20x = 5 micrometers
40x = 2.5 micrometers
100x = 1 micrometer
How do you calculate 1 graticule division?
1 graticule division = 0.1 divided by objective magnification
Light microscope resolution
Light microscope resolution is 200nm
TEM resolution
TEM resolution = 0.005-1nm
Features not visibile using medium power of light microscope
Features not visible using medium power of a light microscope:
-Ribosomes
-Golgi
-Mitochondria
-Vesicles
Roles of cytoskeleton
-Movement of molecules eg chromosomes
-Provides support and shape
-Holds organelles in place
Features of ultrastructure of phagocytic blood cells that enable it to perform its function
Ultrastructure features:
-Microfilaments and microtubules
-Many lysosomes (for digestive enzymes)
-Many ribosomes
-Many mitochondria
Role of mesosome in bacterial cells
Mesosome roles:
-Increases SA of plasma membrane
-Releases ATP
-Helps in secretion processes
Why does single celled organisms not need a specialised area to carry out gaseous exchanges
-Large SA:Vol ratio
-Small, so oxygen demands are low
-Short diffusion distance
Function of the squamous epithelium in the gas exchange system of cells
Squamous epithelium - provides a thin surface for a short diffusion distance
Function of the elastic tissue in the gas exchange system of cells
Elastic tissue - allows for recoiling/returning to original shape
Function of the ciliated epithelium in the gas exchange system of cells
Ciliated epithelium - wafts mucus
Function of the goblet cells in the gas exchange system of cells
Goblet cells - secretes mucus
Function of the smooth muscle in the gas exchange system of cells
Smooth muscle - constricts airway/narrows the lumen
Microtubules
Microtubules - large diameter, tubulin subunits form tubulin polymers which form the hollow microtubules, involved in movement of organelles, forms spindle fibres in mitosis and meiosis, helps determine shape of cells
Microfilaments
Microfilaments -narrow fibres, contains actin which contracts, involved in cell movement, plays role in cell division - its action helps divide cells into two in cytokenisis
Intermediate fibres
Intermediate fibres - strengthens the cell, lots of diff proteins - eg preventing stress from damagingskin cells
Centrioles
Centrioles: not found in flowering plant cells, made of microtubules, comes in pairs at right angles to eachother, pairs of centrioles are called centrosome, during mitosis and meiosis they assemble spindle fibres, they form the cillia and flagellum
Cilia
Cilia: hairlike organelles, wafts particles eg dust in trachea, ones that don’t move sense chemicals around the cells eg in nose
Flagellum
Flagella: moves the cell, 9+2 structure - nine pairs of microtubules arranged in a circle with another pair of microtubules in the centre (same in cilia), atp creates bending motion
What is the ‘9+2’ structure found in cillia and flagellum?
The 9+2 structure is nine pairs of microtubules arranged in a circle with another pair of microtubules in the centre
Microtubules
Microtubules - formed from subunits of tubulin protein (the subunits assemble to form tubulin polymers, which then form hollow microtubules), involved in the movement of organelles eg vesicle movements, forms spindle fibres, helps determine cell shape by forming networks
Cellulose cell walls in plants
Cellulose cell walls in plants:
-Strengthens the plant to resist high hydrostatic pressure caused by greater water potential outside plant than inside creating a net inflow of water molecules by osmosis
-Permeable to water molecules
-Middle lamella between cell wall - consists of polysaccharides, calcium and magneisium ions - acts as glue between plant cells
Algae and fungi cell walls
-Cell walls provide them with mechanical strength
-Algae cell walls contain cellulose and glycoproteins
-Fungi - made up of chitin as well as glycoproteins and other polysaccharides
Cell theory
Cell theory states that:
-Both plant and animal tissue is composed of cells
-Cells are the basic unit of all life
-Cells only develop from existing cells
Objective lens
Objective lens - produces a magnified image, which is magnified again by the eyepiece lens
4 types of sample preparation in microscopy
4 types of sample preparation in microscopy:
-Dry mount
-Wet mount
-Squash slides
-Smear slides
Dry mount sample preparation:
Dry mount sample preparation:
Solid specimens cut into thin slices - placed on centtre - cover slip added
-Examples: muscle or plant tissue
Wet mount sample preparation
Wet mount sample preparation:
Specimens suspended in a liquid eg water or immersion oil, coverslip placed from an angle
-Eg aquatic organisms
Squash slide sample preparation
Squash slide sample preparation:
Wet mount prepared, lens tissue used to gently press down cover slip
Smear slide sample preparation
Smear slide sample preparation:
Edge of slide used to smear sample to create a thin even coating on another slide, cover slip placed over the sample
Why are stains used in microscopy?
Stains are used in microscopy to increase contrast as different components within a cell take up the stains to different degrees - the increase in contrast allows components to become visible so they can be identified
Crystal violet or Methylene blue as stains
Crystal violet/Methylene blue are positively charged dyes, which are attracted to negatively charged materials in cytoplasm leading to staining of cell components
Differential staining
Differential staining can distinguish between two types of organisms that would otherwise be hard to identify, it also differentiates organelles of a single organism within a tissue sample
Magnification definition
Magnification: how many times large the image is than the actual size of the object being observed
Resolution definition
Resolution: the ability to see individual objects separately in detail
What can limit resolution?
Resolution is limited by the diffraction of light as it passes through the sample and lenses, which results in structures being harder to distinguish from one another
How can resolution be increased?
Resolution can be increased by using beams of electrons which have a wavelength thousands of times shorter than light - short wavelength means individual beams can be much closer before they overlap - means objects small and close together can be seen seperately without being affected by diffraction
Magnification formula
Magnification formula = size of image/actual size of object (MIA)
Problems associated with electron microscopes
Problems associated with electron microscopes:
-Expensive
-Can only be used inside carefully controlled environment
-Specimens can be damaged by the electron beam
-Complex preparation process can introduce artefacts
Artefacts
Artefacts: visible structures/distorted cell structures that are produced due to the preparation process
Transmission Electron Microscopes (TEM)
TEM:
-Beam of electrons transmitted through a specimen and focused to produce an image
-Similar to light microscopy
-Best resolution (0.5nm)
Scanning Electron Microscope (SEM)
SEM:
-Beam of electrons sent across surface of the specimen and reflected electrons are collected
-Resolution 3-10nm
-Produces 3D images
Differences between light and electron microscopes
Light microscopes: inexpensive, small, simple sample preparation, vacuum not required, natural colour of sample or seen, up to 2000x mag, resolving power 200nm, specimens living or dead
Electron microscopes: expensive, large, complex sample preparation, vacuum required,black and white images, resolving power 0.5nm for tem and 3-10nm for sem, up to 500 000 mag, specimens dead
Mesosomes
Mesosome - inward foldings of cell membranes
Laser scanning confocal microscopes
Laser scanning confocal microscopes - moves a single spot of focused light across a specimen - causes fluorescence from the components labelled with a dye - emitted light from specimen filtered through a pinhole aperture
Purpose of the pinhole in laser scanning confocal microscopes
The pinhole in laser scanning confocal microscopes does not allow unwanted radiation through, a laser is used instead of light to get higher intensities which improves illumination
Positive of using fluorescent tags
Fluorescent tags - specific features can be targetered and studied by confocal microscopy with more precision than staining and light microscopy
Histones
Histones are the proteins that DNA associates with, and they form a complex called chromatin, which coils and condenses to form chromosomes
Features of mitochondria
Mitochondria features:
-Double membrane - inner membrane folded to form structures called cristae - fluid interior is called the matrix
-Their own DNA - called mitochondria (mt) DNA
Process of protein synthesis
Proteins are synthesised on ribosomes bound to endoplasmic reticulum -> pass into its cisternae and is packaged into vesicles -> vesicles move toward golgi apparatus via transport funciton of the cytoskeleton -> vesicles fuse with golgi and proteins enter (they are structurally modified) -> vesicles move from golgi to cell surface membrane -> releases their contents by exocytosis (some vesicles form lysosomes)
Why is it more likely for artefacts to be introduced in electron microscopy?
Artefacts are likely to be introduced in electron microscopy due to the long, complex staining process involved which makes it more likely for the specimen to be damaged and therefore increases likelihood of artefacts
Advantages and disadvantages of SEM:
Advantages and disadvantages of SEM:
-Adv = specimens doesn’t need to be thin, 3D images produced
-Disadv = resolution and magnification lower than TEM
Advantages and disadvantages of TEM:
Advantages and disadvantages of TEM:
-Adv = greater magnification, resolution and detail
-Disadv = 2D, specimens need to be thin
Fluorescence definition
Fluorescence = the absorption and re-radiation of light, of which light is emitted with a longer wavelength
Why is confocal microscopy not used for deep tissue imaging?
Confocal microscopy is not used for deep tissue imaging due to the light penetration of sample being limited
Intermediate fibres
Intermediate fibres - these fibres give mechanical strength to cells and help maintain their integrity
What controls cell movement?
Cell movement is controlled by the cytoskeleton, via cillia and flagella, which are hair-like structures containing microtubules which are responsible for moving them
Purpose of the cytoskeleton
The cytoskeleton:
-Provides strength and support: supports organelles and keeps them in place
-Intracellular movement: forms ‘tracks’ of which organelles can move along eg movement of vesicles and chromosomes
-Cellular movement via flagella and cilia
Why is the membrane that surrounds the lysosome important?
The membrane that surrounds the lysosome is important because of compartmentalisation - enzymes are kept away from cell structures as they could cause damage to them by the enzyme activity
Why do cells needs to be compartmentalised with examples?
Compartmentalisation:
-Reactions of cell structures require different conditions - prevents them fro being damaged by enzymes - eg nucleus, lysosomes, endoplasmic reticulucm, golgi apparatus body
How can DNA be packed in a cell with a small diameter?
DNA coils around histones, further coiling causes formation of chromatin
DNA structure in prokaryotes
DNA structure in prokaryotes:
-One molecule of DNA (a chromosome) - supercoiled to become compact - genes on chromosome grouped into operans so only a number of genes are switched on or off at the same times
Ribosomes in prokaryotes
Ribosomes of prokaryotes:
-70S, smaller than eukaryotes, their relative size is determined by the rate at which they settle
Prokaryotic cell wall
Prokaryotic cell wall:
-Made up of peptidoglycan, known as murein - complex polymer formed from amino acids and sugars
How to add a stain to a wet mount slide?
Adding stain to a wet mount slide:
-Put a drop of stain on the edge of the coverslip and paper towel on opposite edge
-Paper towel will draw stain under the coverslip and across the specimen
Why do you need to recalibrate the graticule in microscopy?
Recalibrating the graticule:
The stage micrometer will appear larger, so each eyepiece division will be smaller measurement
