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Biology > The Microstructure of Cells > Flashcards

The Microstructure of Cells Flashcards

1
Q

Nucleus main function

A

Information central of the cell (control and reproduction)

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2
Q

How many nuclei are found in cells?

A

Most have 1, fungi have several, erythrocytes (red blood cells) have none

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3
Q

Why do red bloood cells not have nuclei?

A

Mammalian erythrocytes have nuclei during early
phases of erythropoiesis, but extrude them during development as they mature in order to provide more space for haemoglobin

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4
Q

If red blood cells lose their nucleus and other organelles as they mature, why can no virus attack them?

A

The inability to carry out protein synthesis means that no virus can evolve to target mammalian red blood cells

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5
Q

Nuclear envelope

A

It is a membrane that encloses the nucleus, separating it from the cytoplasm
* This is a double membrane
* Each membrane consists of a lipid bilayer which is continuous with the endoplasmic reticulum
* Pores regulate the entry and exit of molecules from the nucleus

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6
Q

How is the shape of the nucleus maintained?

A

by the nuclear lamina, which is composed of protein – net of protein filaments

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7
Q

Where is the nucleolus located? What is its main function?

A

Within the nucleus and is the site of ribosomal RNA (rRNA) synthesis

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8
Q

What are ribosomes?

A

particles assembled from ribosomal RNA and many different proteins

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9
Q

Is it an organelle and what is it amde up of (units)?

A

No, they are not membrae-bound. Ribosomes are made up of 2 subunits, a large subunit and a small subunit

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10
Q

Where are ribosomes found?

A

-cytosol: free ribosomes (internal proteins)
-rough er/nuclear envelope : bound ribosomes (exported proteins)

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11
Q

What is the endomembrane system and what is its function?

A

Cells that works together to modify, package, and transport lipids and proteins.
Regulates protein traffic and performs metabolic functions in the cell

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12
Q

Components of the endomembrane system

A
  • Nuclear envelope
  • Endoplasmic reticulum
  • Golgi apparatus
  • Lysosomes
  • Vacuoles
  • Plasma membrane
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13
Q

Endoplasmic reticulum cell occupation?

A

accounts for
more than half of the total membrane in many
eukaryotic cells

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14
Q

What are the 2 distinct regions of the ER?

A
  • Smooth ER, which lacks ribosomes
  • Rough ER, with ribosomes studding its surface
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15
Q

Functions of the smooth ER

A
  • Synthesizes lipids
  • Metabolizes carbohydrates
  • Detoxifies poison
  • Stores calcium ions
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16
Q

Functions of rough ER

A
  • Has bound ribosomes, which make proteins that are secreted out of the cells
  • Many secretory proteins are glycoproteins
    (proteins covalently bonded to carbohydrates)
  • The carbohydrate portion is attached to the secretory proteins by enzymes embedded in rough ER
  • After synthesis secretory proteins are isolated from the cytoplasm by being wrapped in membranes
  • These bud off from the rough ER and move to other parts of the cell
  • The membrane buds containing secretory proteins are called transport vesicles
  • Is also a membrane factory for the cell
17
Q

Golgi apparatus main function

A

Shipping and receiving Center

18
Q

What does Golgi apparatus?

A

Consists of flattened membranous sacs called cisternae

19
Q

Golgi apparatus main function

A

Shipping and receiving center

20
Q

Golgi apparatus faces

A
  1. The cis face is close to the rough ER and
    is the receiving site for transport vesicles
    * The transport vesicles from the ER fuse with this face and release their content
  2. The trans face is the dispatching site where modified and sorted proteins are packaged into new vesicles and released
21
Q

Golgi apparatus functions

A
  • Modifies products of the ER (glycoproteins and phospholipids)
  • Manufactures certain macromolecules
  • Targets specific products for specific parts of receiving cells by adding molecular identification tags
  • Packages secretory products into transport vesicles
22
Q

What is a lysosome?

A

Membranous sac of hydrolytic enzymes that
can digest macromolecules

23
Q

What do lysosome’s do?

A

Lysosomal enzymes can hydrolyze proteins, fats,
polysaccharides, and nucleic acids

24
Q

Where are lysosomes made ?

A

Hydrolytic enzymes and lysosome membrane are made in the rough ER -Golgi

25
Q

What process/es requires lysosomes? Describe the process/es?

A

Phagocytosis
* A lysosome fuses with the food vacuole and digests the molecules
* The products of digestion can be used as nutrients by the engulfing cell

Autophagy
Lysosomes also use enzymes to recycle the
cell’s own organelles and macromolecules, a
process

26
Q

What are vacuoles ?

A

Essentially a large vesicle
* Contents vary according to cell – or organisms

27
Q

What is the membrane that surrounds vacuoles ?

A

Tonoplast

28
Q

Types of vacuoles

A
  • Food vacuoles: formed by phagocytosis
  • Contractile vacuoles: ound in many freshwater
    protists, pump excess water out of cells
  • Central vacuoles: found in many mature plant
    cells, hold ions and organic compounds and water
29
Q

Functions of vacuoles

A
  • In plants = structural roles
  • Toxic substances may be recycled in the vacuole
  • Storage for inorganic compounds in plants
  • Noxious compounds – defense against herbivores stored in vacuoles
  • Role in plant growth and development (Immature plant cells – small and numerous; mature plants – coalesce to form central
    vacuole)
  • Protozoa – specialized = food vacuoles or phagosomes; also contractile vacuoles – pump out water
30
Q

How do mitochondria and chloroplasts change energy from one form to another?

A
  • Mitochondria are the sites of cellular respiration - a metabolic process that generates ATP
  • Chloroplasts, found in plants and algae, are the
    sites of photosynthesis
31
Q

Defining characteristics of mitochondria and chloroplasts

A
  • Are not part of the endomembrane system
  • Have a double membrane
  • Have proteins made by free ribosomes
  • Contain their own DNA which codes for some of
    their proteins and ribosomes
32
Q

Where is mitochondria found and how do we identify it?

A
  • Mitochondria are found in nearly all eukaryotic cells
  • They have a smooth outer membrane and an inner membrane folded into cristae
33
Q

How do mitochondria convert energy?

A
  • The inner membrane creates two compartments:
    intermembrane space and mitochondrial matrix
  • Some metabolic steps of cellular respiration are
    catalyzed in the mitochondrial matrix
  • Cristae present a large surface area for enzymes that synthesize ATP
34
Q

What is a chloroplast, what does it contain and where can you find it?

A
  • The chloroplast is a member of a family of
    organelles called plastids
  • Chloroplasts contain the green pigment
    chlorophyll, as well as enzymes and other
    molecules that function in photosynthesis
  • Chloroplasts are found in leaves and other green organs of plants and in algae
35
Q

Describe the structure of chloroplast

A

Thylakoids, membranous sacs,
stacked to form a granum
The internal fluid is the stroma

36
Q

What are peroxisomes and where are they found?

A
  • Peroxisomes are like specialized lysosomes -
    metabolic compartments bounded by a single
    membrane
  • Peroxisomes are found in organisms including plants , animals (liver & kidney) and protozoa originate from SER)
37
Q

What do peroxisomes do?

A
  • Oxygen is used to break down different types of molecules
  • Peroxisomes oxidize other molecules and produce hydrogen peroxide which is then broken down - convert it to water
38
Q

What are Glyoxysomes?

A
  • These are specialised peroxisomes
  • Occur in lipid–storing regions of
    seeds
  • When seeds sprout, enzymes of
    glyoxysomes convert stored lipids
    to sugars

Biology (8 decks)

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