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Biology > - Module 2.1.1 > Flashcards

- Module 2.1.1 Flashcards

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1
Q

What are the components and role of the cell membrane?

A

It is the boundary of the cell.
Made of a phospholipid bi layer.
Controls exocytosis and endocytosis.
Selectively permeable.
Fragile.

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2
Q

What are the components and roles of the nucleus?

A

Controls DNA and therefore synthesis of proteins. DNA controls metabolic activity of the cell bc many of the proteins made are enzymes necessary for metabolism.
Contained within a double membrane called the nuclear envelope, protects the DNA from damage in the cytoplasm. Envelope contains gaps called nuclear pores allowing molecules to move in and out.
Usually easiest organelle to see under a microscope.
Usually one per cell.
DNA in nucleus associates with proteins called histones to form chromatin.
Chromatin coils and condenses to form chromosomes, only become visible when a cell is preparing to divide.

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3
Q

What is the structure and function of the nucleolus?

A

Area of the nucleus responsible for producing ribosomes.
Composed of proteins and RNA.
RNA is used to produce ribosomal RNA (rRNA) which is combined with proteins to form ribosomes.

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4
Q

What is the structure of the endoplasmic reticulum?

A

Network of membranes forming flattened sacs called cisternae.
Connect to the outer nuclear membrane.

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5
Q

What is the structure and function of the smooth ER?

A

No ribosomes.
Involved in lipid (cholesterol and steroid hormones) and carbohydrate synthesis and storage.

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6
Q

What is the structure and function of the rough ER?

A

Ribosomes bound to the surface.
Synthesis and transport of proteins.

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7
Q

What is the structure and function of the golgi apparatus?

A

Similar structure to smooth ER.
Compact structure of cisternae.
Looks like a stack of plates.
Stores, modifies and packages proteins into vesicles (secretory vesicles or lysosomes).
Molecules transported to and from the golgi by vesicles.

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8
Q

What is the structure and function of the mitochondria?

A

2-5 micrometers long.
Cellular respiration occurs here to release energy for the cell to use.
Double membrane, inside of which is highly folded and forms cristae.
In the centre of the mitochondria is a fluid called the matrix.
Has it’s own strand of DNA (mtDNA) and contains ribosomes.
Can produce their own enzymes and reproduce themselves.

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9
Q

What is the structure and function of the ribosomes?

A

20nm diameter.
Site of protein synthesis.
Found attached to rough ER or floating free in cytoplasm.
Constructed of RNA molecules produced in the nucleolus.
Combined of two subunits - a small and a large one that combine once they leave the nucleus.
Not surrounded by a membrane.
Mitochondria and chloroplasts contain ribosomes.

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10
Q

What is the structure and function of a vesicle?

A

They are membranous sacs with storage and transport roles.
Single membrane with fluid inside
Used to transport materials inside the cell

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11
Q

What is the structure and function of a lysosome?

A

Specialised type of vesicle that contains hydrolytic enzymes.
Break down waste material in the cell, including old organelles and pathogens ingested by phagocytic cells.
Play an important role in apoptosis.

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12
Q

What are the structures of cilia and flagella?

A

Extensions from some cells, provide motility.
Each cilium contains 2 microtubules surrounded by 9 pairs of microtubules arranged like a wheel (9+2 arrangement)

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13
Q

What is the function of cilia?

A

Hair-like
Used to move substances outside human cells
Can be stationary (nose) or mobile (oviduct or trachea).
Mobile cilia beat in a rhythmical manner which creates a current.

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14
Q

What is the function of flagella?

A

Whip like extensions.
Found on sperm cells.
Sometimes used as a sensory organelle detecting chemical changes in the cell’s environment.

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15
Q

What is the structure and function of chloroplasts?

A

4-10 micrometers long (large)
Double membrane structure
Enclosed fluid = stroma
Internal network of membranes that form flattened sacs called thykaloids.
Several thykaloids stacked togther = grana
Grana are joined by membranes called lamellae
Grana contain chlorophyll
Starch present as starch grains.
Have their own ribosomes and are able to produce their own proteins
Internal membranes give the large SA needed for enzymes, proteins and pigment molecules needed for photosynthesis.

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16
Q

What is the structure and function of the cell wall?

A

Found in plants, bacterial and fungal cells.
Contents of cell press against cell wall
Rigid, protective barrier
Outside cell membrane
Freely permeable
Made of cellulose in plants and chitin in fungi.
Contain gaps called plasmodesmata, allow for the movement of substances between cells

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17
Q

What is the structure and function of vacuoles?

A

Large central vacuole usually in plant cells
Many smaller vacuoles in animals, but not permanent
Bound by the tonoplast membrane
Storage container for water, food, enzymes, wastes, pigments etc.

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18
Q

What is the structure and function of centrioles?

A

Made up of microtubules.
Help in cell division by migrating to opposite ends of the cell (organisation of spindle in animal cells)

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19
Q

What are the 3 key organelles in protein synthesis?

A

Ribosomes, ER, golgi apparatus
Cytoskeleton plays a key role too

20
Q

How is a molecule prepared and secreted after tranlation has taken place?

A

A trasnport vesicle moves from the rough ER to the golgi along the cytokeleton.
Here modification takes place.
The molecule is then packaged into a secretory vesicle and moves along the cytoskeleton to the cell membrane.
It fuses with the cell membrane and exocytosis occurs.

21
Q

What is the cytoskeleton?

A

A network of fibres necessary for shape and stability of the cell.

22
Q

What are the 3 components of the cytoskeleton?

A

Microfilaments, microtubules and intermediate fibers.

23
Q

What are microfilaments? Describe them.

A

Each one around 7nm diameter.
Contractile fibres formed from actin (a protein)
Actin is important for muscle contraction.
Responsible for cell movement and cell contraction during cytokinesis.
Involved in phagocytosis.

24
Q

What are microtubules? Describe them.

A

18-30nm diameter.
Globular tubulin proteins that polymerise to to form tubes that form a scaffold-like structure that determines the structure of the cell.
Acts as tracks for the movement of organelles, including vesicles around the cell.
Spindle fibres are composed of microtubules, so are cilia and flagella.
Centrioles made of 9 triplets of microtubules.
Formation and function can be inhibited, including respiratory inhibitors.

25
Q

What are intermediate fibres/filaments? Describe them.

A

Average 10nm diameter. (smaller than microtubules, bigger than microfilaments).
Give mechanical strength to cells and maintain their integrity.

26
Q

What are cytoskeleton motor proteins?

A

Molecular proteins that use the cytoskeleton to move along the cytoplasm.
Actin (microfilament) motors are myosins.
Microtubule motors are kineisns and dyenins.
Move vesicles which are attached to the cytoskeleton.

27
Q

What is the definition of magnification?

A

The number of times larger an image is compared to the real size of an object.

28
Q

What is the definition of resolution?

A

The ability to distinguish between two separate points.
The resolving power of a light microscope is about 0.2 micrometers (200nm).

29
Q

What are the 3 types of microscopes?

A

Light microscopes
Scanning electron microscopes. (SEM)
Transmission electron microscopes. (TEM)

30
Q

What are the features of light microscopes?

A

Can be used to look at organelles in the cells.
Staining cells makes the objects clearer.
BUT, only can magnify up to 1500x, resolution is restricted.

31
Q

What are the advantages of electron microscopes?

A

Can see details of organelles
Can magnify objects highly (more than 500 000x)
Have a high resolution power

32
Q

What are the disadvantages of electron microscopes?

A

Very expensive.
Very large and must be operated in a special room.
Affected by magnetic fields
Prep of material is lengthy and requires specific expertise, often requires complex equipment.
Prep of material may distort it
All images are black and white
Beams can damage material.

33
Q

How are specimens prepared for electron microscopes?

A

Fixation using chemicals or freezing.
Staining with heavy metals.
Dehydration with solvents.
TEM samples set in resin and may be stained again.
SEM samples may be fractured to expose the inside and coated with heavy metal.

34
Q

What are the features of SEM microscopes?

A

Scan a beam of electrons across the specimen.
This knocks off electrons which are collected in a cathode ray tube to form an image.
Images show the surface of the specimen and can be 3D.
Resolution 3-10nm
Magnification 100,000 - 500,000x

35
Q

What are the features of a TEM microscope?

A

Uses electromagnets to focus a beam of electrons which is transmitted through the specimen and focussed to produce an image.
Denser parts of the specimen absorbs more electrons so they appear darker.
Only used on thin specimens.
Resolving power 0.5nm
Magnification 500 000 - 2 000 000x

36
Q

What are artefacts in microscopy?

A

Bubbles.
Loss of continuity in membranes
Distortion of organelles
Empty space in cytoplasm
Mesosomes (look at slides to seee what they are)

37
Q

What is a prokaryote?

A

They are unicellular organisms that are classed into two evolutionary domains - archea and bacteria.

38
Q

How long ago may prokaryotes have been around?

A

3.5 billion years ago. When the surface of the earth was a hostile environment, they were extremophiles.

39
Q

How does the cytoskeleton in a prokaryote compare to a eukaryote?

A

The cytoskeleton in a prokaryote is much less developed with no centrioles.

40
Q

What is the cell wall made of in a prokaryote?

A

Peptidoglycan.

41
Q

How are ribosomes different in prokaryotes?

A

They are smaller, 70S ribosomes.

42
Q

Do prokaryotes have a nucleus?

A

No, naked DNA wraps around histone proteins.

43
Q

Do prokaryotes have membrane bound organelles?

A

No, no mitochondria, chloroplast etc.

44
Q

What are pili on prokaryotes?

A

Pili are short, hair like structures on the cell surface.

45
Q

How to prokaryotes generate ATP if they have no mitochondria?

A

A few ATP can be generated by glycolysis, the oxidation of a six-carbon sugar (glucose) to two, three carbon products like lactic acid and pyruvate.
However glycolysis only generates two ATP for each glucose.
The ancestors of mitochondria were bacteria and so bacteria can generate ATP in a similar way to mitochondria, by generating a proton gradient across their membranes.

46
Q

What is the endosymbiont theory?

A

A prokaryote “eats” a smaller prokaryote.
The smaller prokaryote evolves a way to avoid being digested and lives inside of the host cell.
Chloroplasts and mitochondria “pay” the host cell with ATP.

Biology (18 decks)

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