Module 2.1.1 Cell Structure King Flashcards
Describe the passage of light through a light microscope
-condenser lens refracts light
-this increases the intensity of the light beam through the specimen
Define magnification
-the degree to which an image is larger than the object itself
Define resolution
-the clarity of the image giving us the ability to distinguish between 2 objects that are close together
Advantages of a light microscope
-cheap
-easy to use
-portable
-living specimens
Disadvantages of a light microscope
-low magnification and resolution
-objects can only be seen if a light wave passes through them
What type of cells can be observed during light microscopy?
-multicellular organisms
-single cells
- small and thin enough to let light through
- easily obtained cells eg cheek/ blood cells
What are single cells called?
Euglena
What are multicellular organisms called?
Daphnia
How do we perform sectioning ?
(For light microscope)
-dehydrate the specimen
-embed the specimen in the wax
-cut the wax block into very thin sections
(Good for soft tissue that can be deformed eg brain)
Why do we use staining ?
(For light microscopes)
-increases contrast between the objects in the cell.
-overcomes problems with lack of visible detail.
What is a stain?
Chemicals which bind to specific molecules/ structures
What is differential staining?
Using lots of stains on the same specimen allowing us to see different bits
What is acetic orcein used to stain?
DNA -> dark red
What is gentian violet used to stain?
Bacteria wall
What is Sudan red used to stain ?
Lipids
What is haematoxylin used to stain?
Nuclei
What is eosin used to stain ?
Protein -> pink
How do electron microscopes work ?
-generate beams of electrons to generate and image
-lenses are magnets that focus the beam of electrons on the specimen
How is a scanning electron microscope used ?
-electron doesn’t pass through specimen it’s reflected
-3D image of surface specimen is created
How is a transmission electron microscope used ?
-thin specimen
- electron beam passes through specimen
-2D image
-some electrons are transmitted, some absorbed
First step of preparing samples for TEM?
1) fix sample in glutaraldehyde
Second step of preparing samples for TEM?
2) dehydrate with ethanol to remove water
Fourth step of preparing samples for TEM?
4) stain with leaf salts -> electrons can have contrast
Fifth step of preparing samples for TEM?
5) mount on a copper grid and place grid in the vacuum specimen chamber
What is an artefact?
A specimen that is caused by human interaction- non natural
Advantages of electron microscopes
-really high resolution
-highest magnification (TEM)
-detailed images of organelles
-3D image of how tissues are arranged (SEM)
Disadvantaged of electron microscopes
-very expensive
-hard to learn to use
Description of plasma membrane
(Both)
-membrane bound
-made of lipids and proteins
Function of plasma membrane
-regulates movement of substances in and out the cell
-receptor molecules -> allow it to respond chemicals eg hormones
Description of cell wall
(Plant)
-non membrane bound
-rigid
-carbohydrate cellulose
Function of cell wall
Supports cell
Description of Nucleus
(Both)
-nuclear envelope ->membrane bound
-chromatin -> DNA and proteins
Function of nucleus
-controls cell activities (transcription in dna)
-DNA contains instructions to make proteins
Function of nuclear pores
-allow substances to move between nuclei and cytoplasm
Function of nucleolus
-make ribosomes
Description of lysosome
(Animal)
-membrane bound
-no clear internal structure
Function of lysosome
-contains digestive enzymes (digests invading cells)
-breaks down worn our components
-kept separate from cytoplasm by membrane
Description of ribosome
(Both)
-non membrane bound
-made of proteins or RNA
Function of ribosome
-site where proteins are made
Description of rough endoplasmic reticulum - RER
(Both)
-system of membranes enclosing a fluid filled space
-surface covered in ribosomes
Function of rough endoplasmic reticulum - RER
-folds and processes proteins made of ribosomes
Description of smooth endoplasmic reticulum - SER
(Both)
-same as RER but no ribosomes
Function of smooth endoplasmic reticulum - SER
-synthesises and processes lipids
Description of vesicle
(Both)
-membrane bound
-small fluid filled sac in cytoplasm
Function of vesicle
-transports substances out the cell and between organelles
How are vesicles formed ?
-by the Golgi apparatus, endoplasmic reticulum or at the cell surface
Description of Golgi apparatus
(Both)
-membrane bound
- group of fluid filled flattened sacs
Function of Golgi apparatus
-process and packages new lipids
-makes lysosomes
Description of mitochondrian
(Both)
-double membrane
-inner membrane folds to form cristae
-inside is the matrix-> contains enzymes for protein synthesis
Function of mitochondrian
-site of aerobic respiration
-where ATP is produced
-lots in cells that are very active and require lots of energy
Description of chloroplasts
(Plant)
-double membrane
-inside membrane called thylakoid ->stacked to be grana
-grana -> linked by lamellae
Function of chloroplasts
-site of photosynthesis
-some parts of photosynthesis happened in the grana some in the stomata
Description of centriole
(Animals and some plants )
-Small, hollow cylinders made of micrrotubules
Function of centriole
-seperates chromosomes during cell division
Description of cilia
(Some animals)
-membrane bound
-hair like strictures on the membrane
Function of cilia
-microtubules allow cilia to move and move substances along cells surface
Description of flagellum
(Eukaryotic cells)
-surrounded by plasma membrane
Function of flagellum
-made of microtubules
-help cell move by motor proteins
Division of labour definition
How organelles work together to provide the function of the cell
What is insulin ?
-a protein made of 2 polypeptide chains
When are the 2 polypeptide chains formed in insulin ?
When a single protein is cut in the endoplasmic reticulum.
What is a eukaryote?
-an organism consisting of one or more cell cell that contain dna in a membrane bound nucleus separate form the cytoplasm.
What are protoctists?
-Plant animals and fungi cells that are eukaryotic.
What are prokaryotes?
-any organism whose DNA is suspended freely in the cytoplasm.
What are the 2 types of prokaryotes ?
-bacteria
-Cyanobacteria
What cells ARENT in prokaryotes but are in eukaryotes?
-nucleus
-mitochondria
-chloroplast
-ER
What are bacteria capsules?
Mucus like protective layer around pathogenic bacteria
What does the capsule do?
-protects bacteria from viruses, or attack from a host organism immune system
-by hiding ANTIGENS on the cell surface
What is the bacterial capsule made of?
-polysaccharides
-water -> protect against desiccation (drying out)
What does the bacteria cell wall do?
-gives bacteria stiffness and determines its form
-offers defence against osmotic damage
What makes up the rigid portion of the cell?
Peptidoglycan called murein
What is murein made of?
-N-acetyl glucosamine
-N acetylmuramic
They alternate in chains and are cross connected by peptide units
What do bacterial membrane do ?
-regulates what enters and leaves the cell
What is bacterial membranes made from ?
Phospholipid bilayer
What is the function of the pili ?
Transfer genetic material from one bacterium to another during bacterial conjugation
What are plasmids
Used in genetic engineering to make copies of genes.
How do prokaryotics reproduce?
- Asexually
-using binary fission
What are microfilaments ?
Very thin protein strands made from actin
What are microtubules
Tiny protein cylinders made from tubulin
What are the 5 functions of the cytoskeleton?
1) give support and mechanical strength
2) help substances and organism move through the cytoplasm within the cell
3) keep cells organelles in position
4) cause the cell to move
5) stabilise tissues
