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Cell Ultrastructure Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q
  1. What are the characteristics of eukaryotic cells?
A

A membrane bound nucleus, DNA organised into chromosomes and a range of complex membrane bound organelles (each with specific roles)

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2
Q
  1. Which organisms are eukaryotes?
A

Animals, plants and fungi

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3
Q
  1. What are the characteristics of prokaryotic cells?
A

Simple cells with no nucleus or other membrane bound organelles. DNA is not associated with histone proteins and they have plasmids.

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3
Q
  1. Label a typical bacterial cell
A

see notes

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4
Q
  1. What type of organisms are prokaryotes?
A

Bacteria

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5
Q
  1. In microscopy, what is resolution?
A

Resolution is the ability to distinguish between 2 adjacent points, so that they can be seen as separate entities

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6
Q
  1. How do bacterial (prokaryotic cells) differ from eukaryotic (animal, plant and fungal) cells?
A
  • Prokaryotic cells (5um) are much smaller than eukaryotic cells (10 - 200um) * Prokaryote cells have circular DNA * Prokaryote cells have no nucleus, eukaryotic cells have genetic material in a nucleus, which is enclosed in a nuclear membrane. * Prokaryote cells contain no membrane bound organelles, eukaryotes do * Prokaryotes may have a slime capsule, eukaryotes do not * Prokaryotic DNA is not associated with histones, while eukaryotic DNA is associated with proteins called histones * Prokaryotic cells have smaller ribosomes * Prokaryote cells contain plasmids, eukaryotic cells do not * Prokaryotes do not have microtubules, eukaryotes do (eg spindle)
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7
Q
  1. In microscopy, what is magnification?
A

The number of times larger an image is than the specimen.

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7
Q
  1. Which type of microscope has higher resolution and why?
A

Electron microscopes have much higher resolution than light microscopes as electrons have a shorter wavelength than light

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8
Q
  1. State the advantages of a light microscope.
A
  • Can use living specimens * No artefacts * Simpler preparation before viewing * Cheaper and more portable
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9
Q
  1. State the disadvantages of the light microscope.
A

Lower resolution

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10
Q
  1. State the advantages of the electron microscope
A

Greater resolution as well as magnification

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11
Q
  1. State the disadvantages of the electron microscope
A
  • Only dead material can be viewed as the microscope contains a vacuum. * Specimens must be cut very thin and stained (TEM). * Artefacts can occur (TEM). * Expensive, less portable, need specialised training to use.
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11
Q
  1. What is the TEM (Transmission Electron Microscope)?
A

In the TEM, electrons pass through a very thin specimen. Result is image with a high degree of resolution and magnification.

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12
Q
  1. What is an artefact?
A

Distortions in the image due to the preparation techniques involved for the electron microscope

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13
Q
  1. What is the easy way to remember the equation for magnification
A

I AM

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13
Q
  1. What is the SEM (Scanning Electron Microscope)?
A

In the SEM, electrons reflect off the surface of an object to give a 3D image. Result gives slightly less resolution and magnification.

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14
Q
  1. What is cell ultrastructure?
A

Cell ultrastructure is the detail of a cell when viewed through an electron microscope.

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14
Q
  1. Why do we say that the nucleus is the control centre of the cell?
A

It contains DNA organised into chromosomes and it is these chromosomes that code for the synthesis of proteins in the cytoplasm

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15
Q
  1. What are histones?
A

Histones are special proteins that support and protect DNA in a chromosome.

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16
Q
  1. Why are chromosomes contained within the nucleus?
A

In the nucleus, the DNA is isolated from the reactions of the cytoplasm and is protected from damage

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17
Q
  1. What is chromatin?
A

The form chromosomes take when a cell is not dividing. The chromosomes aren’t visible and the DNA is more diffusely organised.

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18
Q
  1. What is heterochromatin?
A

Heterochromatin is more densely packed chromatin which appears darker.

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18
Q
  1. What is the nucleolus?
A

A discrete structure in the nucleus which makes rRNA (ribosomal RNA) and uses it to make ribosomes

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19
Q
  1. What is euchromatin?
A

Euchromatin is less densely packed chromatin which appears lighter.

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20
Q
  1. Describe the nuclear membrane/envelope
A

The nuclear envelope is a double membrane with pores in it and which has ribosomes attached (encrusted) to its outer surface

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21
Q
  1. What is the role of SER?
A

Many varied roles including: Synthesis of lipids (e.g. phospholipids) Detoxification of drugs and poisons Carbohydrate metabolism

21
Q
  1. What is ER
A

Endoplasmic Reticulum is a 3d membrane system, enclosing flattened sacs called cisternae, whi extend throughout the cytoplasm. Specifically, Rough Endoplasmic Reticulum (RER) has ribosomes attached whilst Smooth Endoplasmic Reticulum (SER) doesn’t.

22
Q
  1. What is the role of RER?
A

RER is the scaffolding for the ribosomes to make proteins and then distribute them through the ER. (The primary protein structure is synthesised at the ribosome on the RER and the secondary and tertiary structure of the protein develops within the cisternae)

22
Q
  1. What is a ribosome?
A

A very small organelle, which is the site of protein synthesis and is found attached to ER or free in the cytoplasm (as groups called polyribosomes)

23
Q
  1. How are ribosomes different in prokaryotic cells?
A

Prokaryotic cells have smaller ribosomes than eukaryotic cells.

24
Q
  1. Why is the Golgi body described as being continually formed and broken down?
A

Vesicles from the RER fuse at the forming (cis) face and then bud off at the maturing (trans) face of the Golgi body.

25
Q
  1. What is the Golgi apparatus?
A

A series of curved flattened sacs called cisternae that modify, process and package proteins.

26
Q
  1. Specifically, what does the Golgi do?
A

It modifies, processes anur proteins by: * Adding carbohydrates to form glycoproteins * Adding lipids to form lipoproteins * Adding prosthetic groups or cofactors * Joining polypeptides together to form quaternary structure * Labelling, packaging and sorting proteins for export Forming lysosomes

27
Q
  1. Where do the vesicles go after being pinched off the maturing face of the Golgi?
A

The vesicles are transported within the cell or fuse with the cell surface membrane to release their protein outside (exocytosis).

28
Q
  1. What is a lysosome?
A

A tiny vesicle containing hydrolytic enzymes, found in animal and fungal cells

28
Q
  1. What structures are made from the hollow fibres we call microtubules?
A

Microtubules form cytoskeleton, spindle fibres and centrioles, cilia and flagella.

28
Q
  1. Label the mitochondrion
A

1-outer membrane 2-inner membrane 3-cristae 4-matrix 5-intermembrane space

29
Q
  1. What is the role of lysosomes?
A

They fuse with other vesicles containing, food, pathogens and old organelles and then they digest or destroy the contents. They may even break down the cell they are in (autolysis).

30
Q
  1. What is the role of mitochondria?
A

Mitochondria are the site of ATP synthesis during aerobic respiration.

30
Q
  1. What are centrioles?
A

Structures unique to animal cells which help assemble spindle fibres during cell division

31
Q
  1. If a cell has HIGH energy demands, how does the cell meet this need for ATP?
A
  • More mitochondria present in the cell * More deeply folded and numerous cristae for holding respiratory enzymes
32
Q
  1. What is the cytoskeleton?
A

The cytoskeleton is a network of fibres that: * maintains the cell shape * anchors organelles in place * aids movement of structures within the cell

32
Q
  1. What is the role of spindle fibres?
A

Spindle fibres pull chromosomes apart during cell division (mitosis and meiosis )

33
Q
  1. Distinguish between the terms, cytoplasm, cytosol and protoplasm?
A

Protoplasm - all the cell contents including the nucleus and all other organelles. Cytoplasm - all the cell contents excluding the nucleus. Cytosol - all the cell contents excluding the nucleus and other membrane bound organelles.

34
Q
  1. Which two structures, found in animal cells, are absent in plant cells?
A

Lysosomes and centrioles are absent in plant cells. (Lysosomes are found in animal and fungal cells. Centrioles are only found in animal cells)

34
Q
  1. What surrounds a cell and what is its role?
A

The cell surface membrane surrounds a cell, is selectively permeable and determines which substances can enter or leave a cell.

34
Q
  1. What structures are unique to plant cells?
A

Cellulose cell wall, plasmodesmata, chloroplasts and a large vacuole

35
Q
  1. Describe the general structure of the plant cell wall
A

The plant cell wall is made of cellulose microfibrils which are made of many long chains, crosslinked to each other via hydrogen bonds

36
Q
  1. Cellulose is structurally important in making plant cell walls. Why is it good for this job? (revision from Biochemistry!)
A

It has high tensile strength because: * 1, 4 glycosidic bonds hold the beta glucose molecules in long, straight chains, making it fibrous. * Adjacent long chains are held in place by cross-links formed by hydrogen bonds.

37
Q
  1. Describe the two components of the plant cell wall, the primary and secondary cell walls
A
  • The primary cell wall is a loose arrangement of microfibrils orientated in random directions, that allows expansion as the cell grows * The secondary cell wall (more mature) consists of additional layers of cellulose microfibrils, which form a lattice arrangement and give great tensile strength
37
Q
  1. What is the function of the cell wall?
A

Provides support to the cell, directly by forming a fairly rigid structure, and also by providing turgor pressure

38
Q
  1. What is the middle lamella?
A

The middle lamella cements or glues adjacent plant cells together via their cell walls and is made mainly of pectin and calcium pectate

39
Q
  1. What are plasmodesmata?
A

Strands of cytoplasm that connect neighbouring plant cells, via gaps in the cell walls

40
Q
  1. What term describes the fact the cell wall plays no role in determining what substances enter or leave a cell?
A

Fully permeable

41
Q
  1. Describe the structure of a chloroplast.
A

Chloroplasts are bound by a double membrane/envelope and contain a stroma within which is a system of membranes (thylakoids) containing chlorophyll molecules. The membranes are stacked to form grana

42
Q
  1. Label this chloroplast
A

1-outer membrane 2-stroma 3-thylakoid 4-granum 5-lamella 6-inner membrane

43
Q
  1. What structures (not shown above) store the products of photosynthesis inside the chloroplast?
A

Starch grains and lipid droplets

43
Q
  1. How are palisade mesophyll cells adapted for maximum light absorption for photosynthesis?
A
  • Numerous chloroplasts (site of photosynthesis) * Grana consisting of many layers of thylakoids Many grana are present in each chloroplast
44
Q
  1. What is the role of the large vacuole within the cytoplasm?
A
  • Storage of ions and water * Plays an important role in the development of turgor for support.
45
Q
  1. What are the features of fungal cells?
A
  • They are made from long elongated threads called hyphae * They have cell walls made from chitin * They have a vacuole * They are often multinucleate * Glycogen is their carbohydrate store * They contain lysosomes
46
Q
  1. How are fungal cells similar to plant cells?
A

The presence of a cell wall and a vacuole.

47
Q
  1. How are fungal cells similar to animal cells?
A
  • Neither has chloroplasts as neither one photosynthesises * Both do contain glycogen and lysosomes.
48
Q
  1. What features are unique to fungal cells?
A
  • Cell wall made of chitin * Often they are multinucleate (many nuclei per cell, rather than just one)
49
Q
  1. What are the different storage carbohydrates in eukaryote cells?
A

Excess glucose is stored as: Starch in plant cells Glycogen in animal and fungal cells.

Biology (11 decks)

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