cell structure Flashcards by Katie Unknown

Define Magnification

How many times bigger the image is than the specimen (object)

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Define Resolution

Minimum distance apart that two objects can be in order for them to appear as separate items

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what is the equation for magnification?

m = I/A

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what is cell fractionation?

the process where cells are broken up and the different organelles they contain are separated out

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why is the tissue placed in a cold, buffered, isotonic solution?

cold- reduce enzyme action that might break down organelles

buffered- so that pH does not denature proteins

isotonic-to prevent bursting or shrinking via osmosis

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what is homogenation?

cells are broken up by homogeniser which releases organelles from the cell. The homogenate is then filtered to remove large debris

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what is ultracentrifugation?

where organelles are separated by a centrifuge.
Filtrate is spun at low speed at first to allow heaviest organelles to form sediment.
liquid at top is removed to leave just sediment.
liquid is spun at higher speed and process is repeated so that each time, the next heaviest organelle is separated out

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State the maximum magnification for an optical microscope

x 1500

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State the maximum resolution for an optical microscope

0.2 µm

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Name 3 pros of optical microscopes

Easy and cheap to operate
Can have living specimens
can see in colour

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Name 2 cons of optical microscopes

Low resolution & magnification so can’t see organelles smaller than 0.2 µm (e.g. ribosomes, endoplasmic reticulum and lysosomes)

Specimens often need staining to show specific organelles

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Why does optical microscopes have a maximum resolution of 0.2 µm?

because of the long wavelength of light rays

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what is a TEM?

Transmission electron microscope
consists of an electron beam focused on to specimen. Some parts absorb so appear darker. This creates a 2d image

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State the maximum resolution for a transmission electron microscope

0.1 nm

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State the maximum magnification for a transmission electron microscope

x 10 000 000

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Name a pro of transmission electron microscopes

Has highest resolutions & magnification
so can see internal structure of organelles e.g. chloroplasts

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Name 4 cons of transmission electron microscopes

can not observe living organisms as system must be in a vacuum

complex staining process

not in colour

may contain artefacts which are things that appear in the image as a result of the preparation process.

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what is a SEM?

Scanning electron microscope that directs a beam of electrons on to surface of specimen, forming a 3D image.

what 2 instruments are used to measure the size of objects?

eyepiece graticule and stage micrometer

what is the structure and function of the nucleus?(5)

nucleus contains cell’s hereditary material in the chromosomes

nuclear envelope is a double membrane that surrounds nucleus controlling entry and exit of materials

nuclear pores allow passage of large molecules e.g. mRNA out of the nucleus

nucleoplasm is jelly like substance that makes up bulk of nucleus

nucleolus manufactures ribosomal RNA and ribosomes.

What are chromosomes made of?

DNA bound to histone proteins

what is the structure and function of the mitochondria?(4)

Have double membrane, the inner membrane is highly folded & called cristae

cristae provide large surface area for attachment of enzymes involved in respiration

Inner section is called matrix containing protein lipids ribosomes and DNA that allow for production of proteins

mitochondria are the site of aerobic respiration so are plentiful in cells that need ATP

what is the structure and function of chloroplasts?(4)

contain double membrane that is highly selective

grana are stacks of thylakoids that contain chlorophyll for LDR of photosynthesis. membrane provides large surface area for attachment.

stroma is fluid filled matrix where LIR of photosynthesis occurs

contains DNA and ribosomes so can easily produce proteins.

what is the structure and function of the rough endoplasmic reticulum?(3)

network of flattened membrane bound sacs called cisternae

covered in ribosomes

provides large surface area for synthesis of proteins and glycoproteins and transports these.

what is the structure and function of the smooth endoplasmic reticulum?(2)

no ribosomes, continuous with RER synthesises, stores and transports lipids and carbohydrates

what is the structure and function of the Golgi apparatus?(3)

Stacks of membrane-bound flattened sacs called cisternae transports, modifies and stores lipids and proteins form lysosomes by pinching off cisternae

What is a lysosome and what is its function?(4)

vesicles containing enzymes e.g. lysozymes hydrolyse material ingested by phagocytic cells release enzymes outside cell so material outside cell can be destroyed digest worn out organelles so that useful chemicals can be reused

what is the structure and function of ribosomes?(2)

two subunits each containing ribosomal RNA and protein. sight of protein synthesis

what are the 2 types of ribosomes and where are they found?

80S- in eukaryotic 70S- in prokaryotic

what is the function of a cell wall?

provide mechanical strength to prevent cell bursting under osmotic pressure

what is the difference between plant and fungal cell walls?

plant- made of cellulose fungi- made of chitin

what is the structure and function of the vacuole?(3)

fluid filled sac bound by membrane called tonoplast support herbaceous plants by making cells turgid contains sugars, amino acids that may be used as temporary food store

name and explain 5 structures of prokaryotic cells

cell wall-protects against mechanical damage capsule-protects and helps groups of bacteria stick together cell-surface membrane-controls entry and exit circular DNA-holds genetic information plasmid-contains survival genes

Name 4 structural differences between eukaryotes and prokaryotes

prokaryotes: Smaller ribosomes (70s type) No true nucleus (free, floating circular DNA) DNA not associated with proteins No membrane-bound organelles Cell wall made from the glycoprotein murein

what are viruses?

acellular (no organelles) non living particles(They cannot reproduce independently)

Name 5 features of viruses

Contain core of genetic material - either DNA or RNA Have protein coat around core called capsid Have attachment proteins which stick out from edge of the caspid lipid envelope may have flagella

What happens in interphase?

G1- growth of cell S1-synthesis of organelles G2-further growth the two copies of DNA are joined by a centromere

What happens in prophase?

chromosomes condense and become visible nucleolus disappears and nuclear envelope breaks down

What happens in metaphase?

chromatids joined by a centromere line up along the equator of the cell

What happens in anaphase?

spindle fibres from centrioles attach to centromeres centromeres divide and each chromatid is pulled to opposite poles of the cell

What happens in telophase?

chromosomes elongate and become thinner, leaving chromatin nucleolus and nuclear envelope reform

what is cytokinesis?

when the cytoplasm and membrane divide

what is cancer?

abnormal and uncontrolled cell division