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BIOLOGY > cell structures > Flashcards

cell structures Flashcards

1
Q

define the terms eukaryotic and prokaryotic cell.

A
  • eukaryotic : DNA is contained in a nucleus, contains membrane-bound specialised organelles.
  • prokaryotic : DNA is “free” in cytoplasm, no organelles (bacteria /archaea.)
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2
Q

State the relationship between a system and specialised cells .

A
  • Specialised cells —> tissues that perform —> specific function —> organs made of several tissue types —> organ systems .
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3
Q

Describe the structure + function of the cell-surface membrane .

A

STRUCTURE:
- “fluid mosaic” phospholipid bilayer with extrinsic + intrinsic proteins embedded

  • enclosed semi solid substance - cytosol (pale orange) jelly-like where proteins dissolved in water

FUNCTION:
-isolates cytoplasm form extracellular environment .
- selectively permeable to regulate transport of substances.
- involved in cell signalling / cell recognition

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4
Q

Describe the structure of the nucleus.

A
  • surrounded by nuclear envelope - semi-permeable double membrane , contains pores allowing small molecules (single stranded RNA) pass into cytoplasm
  • dense nucleolus made of RNA + proteins assembles ribosomes.
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5
Q

Describe the function of the nucleus.

A
  • controls activities of the cell by containing base sequences the “instructions” needed to make proteins
  • contains DNA coiled around chromatin into chromosomes .
  • gene expression determines specialisation + site of mRNA transcription, mitosis, semiconservative replication.
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6
Q

explain the role of cholesterol, glycoproteins and glycolipids in cell surface membrane .

A
  • cholesterol : steroid molecule connects phospholipids + reduces fluidity.
  • glycoproteins : cell signalling, cell recognition (antigens) + binding cells together
  • glycolipids : cell signalling + cell recognition
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7
Q

Describe the structure of a mitochondrion.

A
  • surrounded by double membrane folded inner membrane forms cristae : site of electron transport chain/ large SA for respiration.
  • fluid matrix - (contains free enzymes catalyse reactions) - contains mitochondrial DNA, respiratory enzymes, lipids, proteins.
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8
Q

State the function of mitochondria.

A
  • site of ATP production during aerobic respiration
  • self-replicating so can become numerous in cells with high energy requirements
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9
Q

Describe the structure of a chloroplast.

A
  • (vesicular plastid) enclosed by double membrane + mixture of h2o + other substance- stroma (fluid-filled matrix)
  • thylakoids - flattened discs stack to form grana —> chlorophyll embedded / photo systems with chlorophyll
  • linked by intergranal LAMELLAE - tubes attach thylakoids in adjacent grana .
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10
Q

state the function of chloroplasts .

A
  • site of photosynthesis to convert solar energy to chemical energy .
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11
Q

Describe the structure of+ function of Golgi apparatus .

A
  • group of fluid filled membrane-bound flattened sacs surrounded by vesicles —> aligns with rER
  • molecules are processed in cisternae vesicles bud off trans face via exocytosis :

—> function = receives proteins from the RER and lipids from the SER.
—> modified the proteins + lipids and repackages them (into vesicles) for export
—> synthesised glycoproteins
—> site of lysosome synthesis .

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12
Q

Describe the structure of a lysosome.

A
  • vesicles produced by the Golgi apparatus that contain digestive enzymes called lysozymes
  • phospholipids rings contain digestive enzyme separate from rest of cytoplasm.
  • sacs surrounded single membrane embedded H+ pump maintains acidic conditions
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13
Q

Describe the function of a lysosome.

A
  • digests contents of phagosomes
  • exocytosis of digestive enzymes
  • (lysozymes) engulfs and destroy old organelles or foreign material —> used to hydrolyse material that’s taken into endocytosis
  • break down excess muscle in uterus after birth / destroy milk producing tissue in breasts
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14
Q

Describe the structure and function of a ribosome.

A
  • formed of protein + rRNA free in cytoplasm or attached to ER (endoplasmic reticulum.)
  • site of protein synthesis via translation:
    —> large subunit = joins amino acids
    —> small subunit = contains mRNA binding site.
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15
Q

Describe the structure and function of the endoplasmic reticulum (ER.)

A
  • membrane bound channels : lumina run throughout cytosol of cells.
  • cisternae = network of tubules + flattened sacs extends from cell membrane through cytoplasm + connects to nuclear envelope:—> rough ER + smooth ER.
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16
Q

Describe the functions of Rough ER and Smooth ER.

A
  • Rough ER - many ribosomes attached + extension of nuclear envelope
  • facilitates protein synthesis - provides large SA for ribosomes + transport newly synthesised proteins to GAV = modification
  • Smooth ER - synthesises lipids including cholesterol + steroid hormones (oestrogen)
17
Q

Describe the structure + function of the cell wall.

A
  • rigid structure made of cellulose (in plants), chitin (fungi) + murein (prokaryotes).
    = mechanical strength + support

BACTERIA- made of polysaccharide murein.

PLANTS- made of cellulose microfibrils plasmodesmata
—> molecules pass between cells : middle lamellae acts boundary between adjacent cell walls.

  • physical barrier against pathogens
  • part of apoplast pathway (plants) to enable easy diffusion of water .
18
Q

Describe the structure and function of the cell vacuole in plants.

A
  • surrounded by single membrane: tonoplast contains cell sap: store nutrients/mineral ions, water, proteins, soluble pigments.
  • help plant cells turgid/ controls turgor pressure
  • absorbs + hydrolyses potentially harmful substances to detoxify cytoplasm.
19
Q

Explain some common cel adaptions.

A
  • folded membrane or microvilli increases surface area (e.g- diffusion.)
  • many mitochondria = large amounts of ATP for active transport.
  • walls one thick - reduce distance of diffusion pathway.
20
Q

What is meant by “Plasmodesmata.”

A
  • channels (threads of cytoplasm) found between plant cells that enable them to communicate.
21
Q

State the role of plasmids in prokaryotes.

A
  • small, circular rings of DNA that carries non-essential genes
  • can be exchanged between bacterial cells via conjugation.
  • replicate independently from main chromosomal DNA
22
Q

State the role of flagella in prokaryotes.

A
  • tail-like structure - made of bundles of microtubules.
    —> contract to make flagellum move/ propel cell forward.
  • use to swim up fallopian tubes to fertilise egg cell.
23
Q

State the role of the capsule in prokaryotes.

A

polysaccharide layer:

  • prevents desiccation.
  • acts as food reserve
  • provides mechanical protection against phagocytosis + external chemicals.
  • sticks cells together / protect bacterium against immune system attack
24
Q

State the role of Pili in prokaryotic cells.

A
  • hair-like structures - stick out from plasma membrane
  • communicate with other cells (transfer of plasmids between bacteria.)
25
Q

Compare eukaryotes and prokaryotic cells.

A

both have:

  • cell membrane
  • cytoplasm
  • ribosomes (don’t count as organelle since not membrane-bound.)
  • flagella = pro: made of protein: flagellin + euk: formed from microtubules.
26
Q

contrast eukaryotic and prokaryotic cells.

A

PROKARYOTIC -
- smaller cells + always unicellular
- no membrane-bound organelles + no nucleus.
- circular DNA not associated with proteins.
- smaller ribosomes.
- binary fission - always asexual reproduction
- cellulose cell wall (plants) / chitin (fungi)
- capsules, sometimes plasmids
- single circular chromosomes

EUKARYOTIC-
- larger cells + often multicellular
- always have organelles + nucleus.
- linear chromosomes associated with histones
- larger ribosomes.
- mitosis + meiosis - sexual or asexual
- murein cell walls
- no capsule, no plasmids
- DNA is linear and wrapped around chromosomes.

27
Q

Why are viruses referred to as “particles” instead of cells?

A
  • acellular + non-living = no cytoplasm, cannot self-reproduce, no metabolism.
28
Q

Describe the structure of a viral particle.

A
  • tiny particles of nucleic acid (DNA/RNA)
  • surrounded by a protein coat made of capsomeres: capsid
  • enclosed in a viral envelope with attachment proteins sticking out .
  • don’t contain cytoplasm, cell membrane or ribosomes
  • linear generic material + viral enzymes (reverse transcriptase.)
29
Q

Describe the structure of an enveloped virus.

A
  • simple virus surrounded by matrix protein.
  • matrix protein surrounded by envelope drives from cell membrane of host cell .
  • attachment proteins on surface .
30
Q

Explain what is meant by the Cell Theory.

A
  • all life exists as cells - so a virus is not a living organism - cannot reproduce on their own —> unable carry out respiration/ growth / excretion.
31
Q

State the role of the capsid on viral particles.

A
  • protect nucleic acid from refraction by restriction endonucleases.
  • surface sores enable viral particle to bind to + enter host cells or inject their genetic material .
32
Q

State the role of attachment proteins on viral particles.

A
  • enable viral particle to bind to complementary sites on host cell - entry via endosymbiosis.
33
Q

Explain the process of Viral Replication.

A
  • viruses get inside host cells by binding to receptors on membranes of host cells using their attachment proteins.
    —> virus only infect one cell type
  • virus releases its capsid (contain nucleic acid/enzymes) into the cell
  • single strand nucleic acid converted into double-stranded DNA + integrated into host cells genome
  • host cells ribosomes used to translate viral DNA into viral proteins - assembled into new viral particles .
34
Q

Explain the process of Bacterial replication.

A
  • bacteria replication by binary fission - cell replicates DNA + splits to form 2 genetically daughter cells

1) large loop of chromosomal DNA replicates once. Plasmids also replicate. DNA moves to opposite ends of cell

2) cell grows bigger + cytoplasm divides - new cell wall synthesised

3) cytoplasm completely splits in 2 + 2 new cells formed that are clones of each other .

35
Q

give two types of molecule from which a ribosome is made .

A

BIOLOGY (14 decks)

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