cells Flashcards by Holly Jessica

What is cell ultrastructure?

The study of organelles

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What is the structure of the nucleus?

. Spherical, 10-20um
. Phospholytic bilayer membrane
. Nucleolus
. Nuclear membrane has many pores
. Outer membrane folded to form RER

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What is the function of the nucleus?

. Store DNA (preventing damage in cytoplasm)
. Nucleolus manufactures rRNA and ribosomes
. Controls cell activities through production of mRNA
. nuclear pores allow mRNA to leave nucleus

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What information leads scientists to believe mitochondria had a bacterial origin?

. Loops of DNA
. Shape and size
. No membrane- bound organelles

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What tissues contain lots of mitochondria?

Muscle tissue and epithelial tissue (SI)

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What is the structure of the mitochondria?

. Rod shaped, 1-10um
. Has cristae- folds of inner membrane
. Membrane- bound organelles
. Prokaryotic style DNA and ribosomes

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What is the function of the mitochondria?

. To produce energy through cellular respiration
. Synthesise ATP
. Oxidative phosphorylation
. Own DNA for replication
. Cristae provide large SA for enzymes

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What is the function of lysosomes?

. To degrade material taken up from outside the cell and to digest obsolete components of the cell itself
. Formed by golgi apparatus
. Up to 1um in diameter
. Contains hydrolytic enzymes (proteases and lipases)
. Breaks down materials from phagocytosis
. Enzyme exocytosis
. Cell autolysis
. Isolate harmful enzymes from rest of cell

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what is the structure of RER?

. folds of membrane, encrusted with ribosomes
. large SA- proteinsynthesis
. connected to nucleus membrane
. membranes enclosed, flattened sacs called cisternae

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what is the function of RER?

. proteinsynthesis (cells destined for export are synthesised)
. provides large SA
. provides pathway for transport of proteins

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what is the structure of SER?

. similar to RER but more tubular
. continuous to RER

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what is the function of SER?

. synthesise, store and transport lipids and carbohydrates

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what is the structure of golgi apparatus?

. similar to SER but more compact
. flattened sacks called cisternae and small, hollow vesicles
. found extensively in epithelial cells

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what is the function of golgi apparatus?

. recieving, sorting and delivering proteins and lipids
. modifying by adding non-protein components
. forms lysosomes
. vesicles carry finished product to fuse with cell surface membrane

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what is the structure of ribosomes?

. located in RER or free in cytoplasm
. smallest organelle
. prokaryotes have 80s ribosomes
. eukaryotes have 70s ribosomes
. have a large and small subunit (rRNA and protein)
. can account for 25% of dry mass of a cell

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what is the function of ribosomes?

. proteinsynthesis
. ribosomes on RER produce proteins designed for export
. free ribosomes in cytoplasm
. produce proteins for cellular use

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what plant cell has no chloroplasts and why?

. root hair cell
. underground and so doesnt recieve any sunlight

what is the structure of a chloroplast?

. disc-shaped plant organelle around 2-10nm length and 1nm diameter
. double phospholipid membrane
. stroma- like cytoplasm
. thykaloid discs contain chlorophyll forming stacks of granum up to 100 discs
. intergranullar lamella
. ribosomes, loop of DNA, starch

what are the function of chloroplasts?

. production of glucose stored as starch
. ribosomes and DNA allow chloroplasts to quickly produce proteins needed
. LDR- 1st stage, takes place on glana (large SA and attached chlorophyll, enzymes)
. LDR- takes place in stoma , enzymes

what is the structure of leaf pallisade cells?

. elongated
. large numbers of chloroplasts
. migrate to areas of greatest LI
. thin cell walls for efficient diffusion of co2

what is the structure of a vacuole?

. large and central
. composed of membranes containing cell sap
. helps to maintain turgour pressure
. used for storage

what is G1?

cell increases in size (growth phase)

what is S phase?

cell replicates DNA

what is G2?

the cell increases further in size and replicates organelles

what is M phase?

mitosis

what is interphase?

cell doing its usual jobs

what are the stages of mitosis?

. prophase . metaphase . amaphase . telephase . cytokenesis

what are the steps of ultracentrifugation?

. break up cell to create hemogenate . filter to remove any whole cells . increase G force . densest parts form pellet . repeat . liquid on top called supernatant

what is the structure of bacteria?

. have cell walls- made of murein . some have outer layer called capsule for protection and to stick to other bacteria . plasmids contain genes that improve survival . plasmids can be easily exchanged between bacteria

What is the magnification equation?

I = A × M

What are the principles of a light microscope?

Visible light passes through the specimen and is bent through the lense system, allowing the user to see a magnified image

What are the advantages of a light microscope?

. Living and dead material can be viewed . Doesn't require specialist training in order to operate . Small and portable . Unaffected by magnetic fields

What are the limitations of a light microscope?

. Low resolution: limit is 200nm and so objects smaller cannot be viewed . Low magnification: maximum is 1500x so is useless for small organelles . Specimen may be disfigured while being prepared . Most cells need to be stained to be seen

What are the principles of TEM?

Used to examen thin slices of cell tissues, it projects an electronic beam through a sample and a 2D image is formed

What are the advantages of TEM?

. They provide high resolution images with more detail . They have a magnification of 1000000x . They can view the internal structures of cells

What are the limitations of TEM?

. Must be positioned in a vacuum, very detailed images of cell organelles and living specimens cannot survive so cannot visualise living material . Can only be used for thin tissues as thick specimens easily absorb the electrons . Can only use dead specimens

What are the principles of SEM?

Scan a beam of electrons across the specimen, the beam bounces off the surface and electrons are detected, forming an image

What are the advantages of SEM?

. They can be used on thick or 3D specimens . They allow the external, 3D structure of specimens can be observed . Large depth of field, examination of surface structure . Resolution as low as 15nm . Chemical analysis

What are the limitations of SEM?

. Lower resolution than TEM . They cannot be used to observe live specimens . They do not produce a colour image . Expensive to buy and run . Small risk of radiation exposure

What is binary fission?

Bacterial cell division is much more simple than mitosis because instead of chromosomes, they have a singular, circular DNA molecule Plasmids are also replicated and passed on

What are the stages of binary fission?

1. dna replication of bacterial chromosome and plasmids 2. cell divides into two, each receiving half the cytoplasm, one chromosome and some plasmids

What is replication in viruses?

. Acellular and non-living so do not carry out cell division in any form . Instead, they inject nucleic acid into a host cell . The host cells dna-replicating and protein-synthesising systems make more virus particles . Eventually, they are released when host cell bursts, or by each new virus leaving through cell membrane . The host can be prokaryotic or eukaryotic