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Biology 🧬 > 2.1 Structure of eukaryotic cells > Flashcards

2.1 Structure of eukaryotic cells Flashcards

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1
Q

Define the term eukaryotic cell

A

DNA is contained in a nucleus, contains membrane-bound specialised organelles

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2
Q

Define the term prokaryotic cell

A

DNA is ‘free’ in cytoplasm, no organelles e.g. bacteria

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3
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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4
Q

Describe the structure of the cell-surface membrane

A

‘Fluid mosaic’ phospholipid bilayer with extrinsic and intrinsic proteins embedded

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5
Q

Describe the function of the cell-surface membrane

A
  • Controlling the movement of substances in and out of the cell
  • Isolates cytoplasm from extracellular environment
  • Selectively permeable to regulate transport of substances
  • Involved in cell signalling / cell recognition
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6
Q

Explain the role of cholesterol in the cell-surface membrane

A

Cholesterol is present to make the membrane more rigid and reduce the lateral movement of the phospholipids. It also prevents the leakage of water and dissolved ions from the cell as it is very hydrophobic

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7
Q

Explain the role of glycoproteins in the cell-surface membrane

A

These are carbohydrates that attach to extrinsic proteins and acts as cell surface receptors and neurotransmitters. These allow cells to recognise one another as well as attach to form tissues

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8
Q

Explain the role of glycolipids in the cell-surface membrane

A

These are made up of a carbohydrate that is bound to lipids. These extend from the surface of the cell and acts as cell surface receptors for certain molecules. They also allow cells to adhere to one another to form tissues

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9
Q

Describe the structure of proteins in the cell-surface membrane

A

These may be integrated throughout the membrane (intrinsic proteins) or may be on the surface (extrinsic proteins). Intrinsic proteins include carrier proteins which allow substances to cross the membrane

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10
Q

Describe the function on proteins in the cell-surface membrane

A
  • Aid movement across the membrane
  • Provide mechanical support
  • Act in conjunction with glycolipids as receptors
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11
Q

Describe intrinsic proteins

A

Proteins which are integrated throughout the membrane

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12
Q

Describe extrinsic proteins

A

Proteins which are on the surface of the membrane

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13
Q

Describe the structure of the nucleus

A
  • Surrounded by nuclear envelope, a semi-permeable double membrane
  • Nuclear pores allow substances to enter / exit
  • Dense nucleolus made of RNA and proteins assembles ribosomes
  • Nucleoplasm makes up the bulk of the nucleus
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14
Q

Describe the function of the nucleus

A
  • Contains DNA coiled around chromatin into chromosomes
  • Controls cellular processes: gene expression determines specialisation and site of mRNA transcription, mitosis, semi-conservative replication
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15
Q

Describe the structure of a mitochondrion

A
  • Surrounded by double membrane, inner membrane folded forms cristae: site of electron transfer chain
  • Fluid matrix: contains all the enzymes needed for respiration, mitochondrial DNA, lipids, proteins
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16
Q

State the function of mitochondria

A

Site of aerobic respiration to produce ATP

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17
Q

Describe the structure of a chloroplast

A
  • Double membrane
  • Thylakoids: flattened discs stack to form grana; contain photosystems with chlorophyll
  • Intergranal lamellae: tubes attach thylakoids in adjacent grana
  • Stroma: fluid-filled matrix
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18
Q

State the function of chloroplasts

A

Site of photosynthesis to convert solar energy to chemical energy

19
Q

Describe the structure of the golgi apparatus

A

A series of fluid filled, flattened and curved sacs with vesicles surrounding the edges

20
Q

State the function of the golgi apparatus

A
  • Modifies and packages proteins for export
  • Synthesises glycoproteins
  • Produces lysosomes
21
Q

Describe the structure of a lysosome

A

Sac surrounded by single membrane embedded H+ pump maintains acidic conditions, contains digestive hydrolase enzymes glycoprotein coat protects cell interior

22
Q

State the function of a lysosome

A
  • Containing digestive enzymes
  • Digests content of phagosome
  • Exocytosis of digestive enzymes
23
Q

Describe the structure of a ribosome

A

Composed of two sub-units, formed of protein and rRNA, free in the cytoplasm or attached to the endoplasmic reticulum

24
Q

State the function of a ribosome

A

Site of protein synthesis via translation:
- large subunit: joins amino acids
- small subunit: contains mRNA binding site

25
Q

Describe the structure of the rough endoplasmic reticulum

A

A series of flattened sacs enclosed by a membrane with ribosomes on the surface

26
Q

State the function of the rough endoplasmic reticulum

A

RER folds and processes proteins made on the ribosomes

27
Q

Describe the structure of the smooth endoplasmic reticulum

A

SER produces and processes lipids

28
Q

What features do only prokaryotic cells have?

A
  • Cell wall
  • Capsule
  • Plasmid
  • Flagellum
  • Pili
  • Ribosomes
  • Mesosomes
29
Q

Describe the structure of the cell wall

A

Bacteria: made of the polysaccharide murein
Plants: made of cellulose microfibrils plasmodesmata allow molecules to pass between cells, middle lamella acts as boundary between adjacent cell walls

30
Q

State the functions of the cell wall

A
  • Mechanical strength and support
  • Physical barrier against pathogens
  • Part of apoplast pathway to enable easy diffusion of water
31
Q

Describe the structure of the cell vacuole in plants

A

Surrounded by a single membrane: tonoplast, contains cell sap: mineral ions, water, enzymes, soluble pigments

32
Q

State the function of the cell vacuole in plants

A
  • Controls turgor pressure
  • Absorbs and hydrolyses potentially harmful substances to detoxify cytoplasm
33
Q

Explain some common cell adaptations

A
  • Folded membrane or microvilli increase surface area, e.g. for diffusion
  • Many mitochondria = large amounts of ATP for active transport
  • Walls one cell thick to reduce distance of diffusion pathway
34
Q

State the role of plasmids in prokaryotes

A
  • Small ring of DNA that carries non-essential genes
  • Can be exchanged between bacterial cells via conjugation
35
Q

State the role of flagella in prokaryotes

A

Rotating tail propels (usually unicellular) organism

36
Q

State the role of the capsule in prokaryotes

A

Polysaccharide layer:
- Prevents desiccation
- Acts as food reserve
- Provides mechanical protection against phagocytosis and external chemicals
- Sticks cells together

37
Q

Compare eukaryotic and prokaryotic cells

A

Both have:
- Cell membrane
- Cytoplasm
- Ribosomes

38
Q

Contrast eukaryotic and prokaryotic cells

A

Prokaryotic:
- small cells and always unicellular
- no membrane-bound organelles and no nucleus
- circular DNA not associated with proteins
- small ribosomes (70S)
- binary fission
- cellulose cell wall (plants) / chitin (fungi)
- capsule, sometimes plasmids

Eukaryotic:
- larger cells and often multicellular
- always have organelles and nucleus
- linear chromosomes associated with histones
- larger ribosomes (80S)
- mitosis and meiosis
- murein cell walls
- no capsule, plasmids

39
Q

Why are viruses referred to as ‘particles’ instead of cells?

A

Acellular and non-living: no cytoplasm, cannot self-reproduce, no metabolism

40
Q

Describe the structure of a viral particle

A
  • Linear genetic material (DNA or RNA) and viral enzymes, e.g. reverse transcriptase
  • Surrounded by capsid
  • No cytoplasm
41
Q

Describe the structure of an enveloped virus

A
  • Simple virus surrounded by matrix protein
  • Matrix protein surrounded by envelope derived from cell membrane of host cell
  • Attachment proteins on surface
42
Q

State the role of the capsid on viral particles

A
  • Protect nucleic acid from degradation by restriction endonucleases
  • Surface sites enable viral particle to bind to and enter host cells or inject their genetic material
43
Q
A

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