Flashcards in Cell Structure Deck (91):
What is a eukaryotic cell?
Cells with a nucleus and other membrane bound organelles, they make up multicellular organisms.
The synthesis and breaking down of molecules.
What is the purpose of compartmentalisation?
To provide distinct environments and conditions for cellular reactions.
What is a prokaryote?
Single celled organisms with a single undivided cytoplasm.
What is cytoplasm composed of?
Cytosol (water, salts and organic molecules)
What is an organelle?
Describe the membrane surrounding an organelle?
Membranes are selectively permeable and control the movement of substances into and out of the cell.
Describe the components of the nucleus...
DNA is contained within a double membrane called the nuclear envelope, this protects it from damage in the cytoplasm.
The double membrane contains nuclear pores to allow movement in and out (RNA).
Describe how DNA forms chromosomes...
DNA associates with histones (proteins) to form chromatin which coils and condenses to form chromosomes.
What is the nucleolus?
An area within the nucleus responsible for producing ribosomes (rRNA), it is composed of RNA and proteins.
What is the function of mitochondria?
It is the site of the final stages of cellular respiration where ATP (adeninetriphosphate) is produced.
Describe the membrane structure of mitochondria...
Mitochondria has a double membrane structure, The inner membrane is highly folded to form cristae which contain the enzymes.
What is the fluid interior of mitochondria called?
What are cristae?
The highly folded inner membrane of mitochondria, it contains the enzymes for cellular respiration.
What is mt(DNA)?
Mitochondrial DNA found in mitochondria which means they can produce their own enzymes and reproduce themselves.
What are vesicles?
Membranous sacs with storage and transport roles inside the cell. They have a single membrane and an interior fluid.
What are lysosomes?
Specialised vesicles that contain hydrolytic enzymes responsible for breaking down waste material in the cells.
Give 3 examples of the uses of hydrolytic enzymes in lysosomes...
Breaking down old organelles.
Immune system (pathogens ingested by phagocytic cells).
Name the 3 components of the cytoskeleton...
Microfilaments, microtubules and intermediate fibres.
What is the general function of the cytoskeleton?
It is a network of fibres responsible for cell shape and stability. It controls cell movements and movement of organelles within cells.
What are microfilaments?
Contractile fibres made from actin, responsible for cell movement/contraction during cytokinesis.
What part of the cytoskeleton is made from actin?
What are microtubules and how are they formed?
They act as tracks for vesicles and form spindle fibres. They form when globular tubulin polymerises to form tubes.
What is the function of intermediate fibres?
To give the cell mechanical strength and maintain cell integrity.
Centrioles are a component of the cytoskeleton, they are composed of microtubules. 2 associated centrioles form thr centrosome which is involved in the assembly snd organisation of spindle fibres.
Centrioles are not present in _____ ?
Flowering plants or fungi.
In simple terms, what are flagella and cilia?
Protruding extensions from cells.
What is the function of flagella?
To enable motility, it is also a sensory organelle.
How do cilia move objects?
They beat rhythmically creating a current causing adjacent objects to move
Give two examples of where cilia is present in the human body...
Trachea and fallopian tubes.
Explain the '9+2' arrangement of mobile cilia...
Each cilium contains 2 central microtubules surround by 9 pairs of microtubules. Parallel pairs slide over each other causing the cilia to beat.
What is the function of smooth ER (endoplasmic reticulum)?
Lipid and carbohydrate synthesis and storage.
What is secretion?
Transport out of a cell.
What is the function of rough ER (endoplasmic reticulum)?
Protein synthesis and transport.
What is the difference between smooth ER and rough ER?
Rough ER has ribsomes bound to it's surface.
What is ER?
Endoplasmic reticulum, a network of membranes enclosing flattened sacs called cisternae.
What are cisternae?
Flattened sacs enclosed in ER and golgi apparatus.
Secretary cells have more/less ER?
Ribosomes have no membrane, are made of rRNA and are the site of protein synthesis.
`Where are ribsomes found?
Free floating in the cytoplasm, attached to rough ER, mitochondria, chloroplasts and prokaryotic cells.
What is the function of the golgi apparatus?
It modifies and packages proteins into vesicles, it is formed of cisternae.
Where do proteins fuse at the golgi apparatus?
Where do proteins leave the golgi apparatus?
State the order of organelles involved in protein synthesis and transport.
Ribosomes (rough ER), golgi apparatus, vesicles, cell surface membrane.
Which organelles are specific to plant cells?
Cell wall, vacuoles, chloroplasts.
What is a plant cell all composed of?
Describe the plant cell wall...
It provides shape as the cell contents press against it making it rigid, it acts as a defence mechanism from invading pathogens.
What type of permeability is the cellulose cell wall?
What are vacuoles?
Membrane lined sacs in the cytoplasm containing cell sap, they maintain turgor.
What us the vacuole membrane called, and what type of permeability is it?
Tonoplast - selectively permeable.
What is the function of chloroplasts?
Responsible for photosynthesis.
What type of membrane do chloroplasts have?
What is the fluid interior of a chloroplast called?
What are thylakoids?
An internal network of membranes which form flattened sacs in chloroplasts.
Several thylakoids stacked together are called ____?
A granum (pl. grana).
What do the grana contain in chloroplasts?
Chlorophyll pigments and starch produced during photosynthesis present as starch grains.
How are grana connected in chloroplasts?
State cell theory...
Both plant and animal tissue is composed of cells, cells are the basic unit of all life, cells only develop from existing cells.
How many lenses does a compound light microscope have?
2, the objective lens (near specimen) and ocular lens. Illumination is provided by a light under the species.
What are the 4 types of slides that can be prepared?
Dry mount, wet mount, squash slide and smear slide.
How do you prepare a dry mount?
Solid specimens are sectioned and placed on a slide with a cover slip, lowered using a mounting needle.
What is a wet mount?
Species suspended in a liquid.
How do you prepare a squash slide?
A wet mount is prepared, a lens tissue is used to press down the cover slip.
How do you prepare a smear slide?
Th edge of a slide is used to smear the sample.
Why is it important to stain slides?
To increase the contrast between different components within a cell as they take up stains to different degrees.
What is differential staining?
Distinguishes between different types of organisms.
What is the process of preparing a permanent slide?
Fixing, sectioning, staining and mounting.
What is fixing?
Preservation with chemicals.
What is sectioning?
Dehydrating and slicing.
What is mounting?
Securing a specimen to a slide.
How many times larger the image is than the actual size of the object being viewed.
The ability to see individual objects as separate entities.
How do you calculate magnification?
Magnification = Size of Image/Actual Size of Object
Describe the process of magnification calibration...
Line up the stage micrometer with the eyepiece graticule and focus the microscope. Count the number of divisions and um between 2 points of coincidence.
Why do electron microscopes have a higher resolution than compound light microscopes?
Their wavelength is smaller hence individual beams can be much closer before they overlap (diffraction).
What is the calibration calculation?
Each eyepiece division = Number of EPD's/micrometers
What is an electron microscope?
A beam of electrons with a wavelength of less that 1nm is used to illuminate a specimen.
Give 3 disadvantages of electron microscopes...
Expensive, controlled environments, artefacts.
What is a transmission electron microscope?
Electrons are transmitted through a species and focused to produce an image.
What is the resolving power of an electron transmission microscope?
What is a scanning electron microscope?
An electron beam is sent across the surface of a specimen and reflected electrons are collected. It can produce 3D images.
What is the resolving power of an electron scanning microscope?
What are artefacts?
Visible structural details caused by processing the specimen.
What is a laser scanning confocal microscope?
Moves a single spot of focused light across a specimen causing fluorescence from components labelled with a dye. Emitted light from the specimen is filtered through a pinhole. 3D images can be created if multiple images are taken.
Which microscopes can produce 3D images?
Laser scanning confocal and scanning electron microscopes.
Describe the DNA in prokaryotes...
There is no nucleus, so DNA is free floating in the cytoplasm as a nucleoid/plasmids (1 molecule). 1 supercoiled chromosome (compact). Genes grouped into operons hence a number are switched on or off at any one time. DNA is circular not linear.
What are operons?
Groups of genes in prokaryotes.
Describe ribosomes in prokaryotes...
They are smaller 70S compared to 80S.
What does 70S/80S mean?
The rate at which ribosomes settle/form sediment in solution.
What is the cell wall made from in a prokaryote?