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A Level Biology > Cell Organelle Structure And Function > Flashcards

Cell Organelle Structure And Function Flashcards

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1
Q

What is the structure of a nucleus?

A

Structure

  • A large structure containing chromatin which forms chromosomes.
  • This genetic information (DNA) is enclosed within a double membrane called a nuclear envelope.
  • The DNA codes for proteins which are produced outside the nucleus in the ribosomes.
  • The genetic information is copied and transported out of the nucleus via mRNA molecules.
  • The nucleolus is situated in the centre of the nucleus.
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2
Q

What is the function of a nucleus (3 parts)?

A

Function

Nucleus - control metabolic activities and contain genetic material.

Nucleolus - responsible for the production of ribosomes. It is made up of proteins and RNA. RNA is used to produce rRNA (ribosomal RNA) which combines with the ribosome necessary for protein synthesis.

Nuclear envelope - Porous double membrane where genetic information is enclosed. Contains nuclear pores in which mRNA can travel and transport copies of genetic information

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3
Q

What is the structure of a smooth endoplasmic reticulum?

A
  • A network of membrane enclosing flattened sacs called cisternae.
  • Is connected to outer membrane of nucleus.
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4
Q

What is the structure of a rough endoplasmic reticulum?

A
  • A network of membrane enclosing flattened sacs called cisternae.
  • Is connected to outer membrane of nucleus. -Contains many ribosomes.
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5
Q

What is the function of the smooth endoplasmic reticulum?

A

Responsible for the synthesis and storage of carbohydrates and lipids.

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6
Q

What is the function of the rough endoplasmic reticulum?

A

To synthesis and and transport proteins

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7
Q

What is the structure of the Golgi apparatus?

A

-Similar to smooth endoplasmic reticulum - compact structure of cisternae which are highly folded. -Doesn’t contain ribosomes.

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8
Q

What is the function of the Golgi apparatus?

A

Modifies proteins and packages them into vesicles. This could be secretory vesicles, if the protein is leaving the cell, or lysosomes, which stay on the cell.

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9
Q

What is the structure of the ribosomes?

A
  • Free floating in cytoplasm or attached to endoplasmic reticulum, forming rough endoplasmic reticulum.
  • No membrane.
  • Constructed of RNA molecules, constructed in the nucleolus.
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10
Q

What is the function of a ribosome?

A

Site of protein synthesis. This takes place by reading coded genetic material copied and secreted out of the nucleus.

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11
Q

What is the structure of mitochondrion?

A

Made up of two membranes:
- Outer membrane
- Inner membrane folded to form cristae
This contains a fluid interior called the matrix.
- Also contains small amount of DNA, called mitochondrial DNA. They can produce their own enzymes and reproduce themselves.

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12
Q

What is the function of mitochondria?

A

Site of the final stage of cellular respiration.
- This takes place as the production of the molecule ATP. This releases the energy stored in bonds which can now be used by the cell.

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13
Q

What is the structure of lysosomes/vesicles?

A
  • Membranous sacs that consists of a single membrane with fluid inside.
  • Lysosomes contain hydrolytic enzymes
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14
Q

What is the function of lysosomes/vesicles?

A

Specifically responsible for breaking down waste material in cells - this include old organelles. They are also key in the immune system, as they are responsible for the decomposition of pathogens ingested by phagocytic cells.

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15
Q

What is the structure of centrioles?

A

Component of the cytoskeleton present in eukaryotic cells, except flowering plants and most fungi.
- Composed of microtubules

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16
Q

What is the function of centrioles?

A

Part of the cytoskeleton, which gives cells shape and stability. This means it is also responsible for the movement of the cell and of organelles within cells.

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17
Q

What is the structure of cilia?

A

Two central microtubules surrounded by nine pairs of microtubules, arranged like a wheel - the “9+2” arrangement.

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18
Q

What is the function of cilia?

A

There are mobile and stationary cilia.

Stationary cilia may be present on the surface of cells and have an important role in sensory organs e.g. nose.

Mobile cilia beat in a rhythmic manor, which is used to move fluid/objects. This includes cilia present in the trachea to waft mucus away from the lungs, or cilia in Fallopian tubes to move egg cells from the ovary to the uterus.

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19
Q

What is the structure of plasma membrane?

A

The plasma membrane is composed of a phospholipid bilayer. These are embedded with proteins.

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20
Q

What is the function of the plasma membrane?

A

The primary function is to protect the cell fro, the surroundings. This takes place through the regulation of the movement of substances in and out of the cells.

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21
Q

What is the structure of cytoskeleton?

A

Microfilaments - contractile fibres formed from actin, which is a protein.

Microtubules - globular tubular proteins polymerise to form tubes that are used to form scaffold-like structures that determines the shape of a cell.

Intermediate - composed fibres

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22
Q

What are 3 functions of the cytoskeleton?

A

Cell movement, mechanical strength and transport

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23
Q

What is the structure of flagella?

A

Hair-like extensions that extends past some cell types. Much longer than cilia, but in much fewer number.

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24
Q

What is function of flagella?

A

Primary used to enable cell mobility. Sometimes used as a sensory organelle that detects changes chemically in the cell’s environment.

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25
Q

What is the structure of chloroplast?

A

Found in leaves in stems, but not in roots. They have a double membrane. The internal networks of membranes, to make flattened sacs called thylakoids. Contains chlorophyll pigments.

26
Q

What is the function of chloroplast?

A

Responsible for photosynthesis. Chloroplasts contains DNA and ribosomes, meaning they are therefore able to make their own proteins.

27
Q

What is the structure of the cell wall?

A

A cellulose structure, which is a complex carbohydrate. Completely permeable, meaning substances easily move in and out of cell wall.

28
Q

What is the function of the cell wall?

A

Keeps the cell rigid, giving the cell and the whole plant support. Acts as a defence mechanism to protect the contents of the cell from invading pathogens. All plants cells have cellulose cell walls.

29
Q

Define a eukaryote?

A

A eukaryote is any organism consisting of one or more cells that contain DNA in a membrane-bound nucleus, that separate from the cytoplasm.

30
Q

Describe the process of protein synthesis

A
  1. mRNA copies gene in the nucleus
  2. mRNA travels through nucleus pores in the nucleus envelope to the ribosome.
  3. Ribosomes may be attached to the rough ER (Endoplasmic reticulum). The ribosome then translates the mRNA molecule to create the protein until the stop codon is reached.
  4. The protein then travel towards Golgi apparatus in vesicles.
  5. These vesicles then fuse with Golgi Apparatus.
  6. Golgi apparatus then processes and packages molecules ready for release.
  7. The packaged protein then travels in vesicles from Golgi apparatus towards cell membrane.
  8. Vesicles fuses with cell membrane.
  9. Cell membrane opens to release protein molecule outside.
31
Q

Describe the features of eukaryotic cells?

A
  • Fungi, animals, plants and protists
  • Contains DNA enclosed in a nucleus
  • Usually multicellular
  • Usually more complex organisms
  • Sexual and Asexual reproduction
32
Q

Describe features of Prokaryotic cells?

A
  • Archaea and bacteria
  • Free-flowing DNA not enclosed in nucleus, sometimes circular loops called plasmids.
  • Usually much smaller than eukaryotic cells
  • Unicellular organism
  • Reproduce through binary fission.
33
Q

What is the difference between a scanning electron microscope (SEM) and a Transmission electron microscope (TEM)?

A

Both - expensive
Both - beams of electron
Both - require vacuum (therefore requires dead specimen)

SEM magnification - x 100,000
TEM magnification - x 500,000

SEM max resolution - 0.1nm
TEM max resolution - 0.2nm

SEM - 3D Images
TEM - 2D Images

specimen doesn’t have to be as thin in SEM as in TEM.

34
Q

What is the calculation for magnification?

A

Magnification = Image size/actual size

35
Q

What is the function of phospholipid in cell membrane?

A

Contains hydrophilic head and hydrophobic tail. This creates the bilayer, as well as acting as a barrier preventing water-soluble substances from entering through the membrane. Fat-soluble substances can pass through the hydrophobic bilayer.

36
Q

What is the function of glycoprotein in cell membrane?

A

Glycoproteins are branching carbohydrate portion of protein which acts as a recognition site for chemicals (e.g. hormones) and plays a role of cell signalling and cell adhesion.

37
Q

What is the function of glycolipids in cell membranes?

A

Lipids attached to carbohydrate chains, which are called antigens and can be recognised by cells of the immune system.

38
Q

What is the function of channel proteins in cell membranes?

A

Allows passive movement of polar molecules and ions down a concentration gradient, through providing a hydrophilic channel. It is held in position by interaction between hydrophobic core of membrane and hydrophobic R-groups on the outside of the proteins.

39
Q

What is the function of carrier proteins?

A

Plays an important role in passive and active transport, which may involve changing the shape of the protein.

39
Q

What is the function of cholesterol?

A

Lipids with hydrophilic and hydrophobic end which regulates the fluidity of membranes. Adds stability without making it too rigid.

40
Q

What is the function of receptor sites?

A

Sites which act as a boundary between internal and external environments. Ligands (e.g. drugs, hormones and neurotransmitters) bind to receptor cells.

41
Q

What is the function of intrinsic proteins?

A

Amino acids that interact the hydrophobic core of membrane, keeping them in place.

42
Q

What is the function of extrinsic proteins (peripheral proteins)?

A

Present on one side of the bilayer, and interacts with polar heads of the phospholipids. Involves in cell recognition and cell signalling.

43
Q

What is the function of cell surface membrane?

A
  • Control which substances enter and leave the cell.

- Site of cell communication

44
Q

What are examples of intrinsic proteins?

A

Channel proteins, carrier proteins and glycoproteins

45
Q

What are the 6 methods of movement across the plasma membrane?

A
  • Diffusion
  • Facilitated diffusion
  • Active transport
  • Bulk transport (Endocytosis and Exocytosis)
  • Osmosis
46
Q

What is diffusion?

A

The net random movement of particles down a gradient from an area of higher concentration to an area of lower concentration, until equilibrium is achieved.

47
Q

What is facilitated diffusion?

A
  • Transport of substances across a membrane, from an area of high concentration to an area of low concentration, with the help of a transport molecule (e.g. channel protein)
48
Q

What is active transport?

A

The movement of molecules into and out of a cell from an area of lower concentration to an area of higher concentration, against the concentration gradient, using external energy (ATP)

49
Q

What is Endocytosis?

A

Bulk transport of materials INTO cells.

  • cell membrane bends inwards
  • membrane enfolds material forming vesicles
50
Q

What is Exocytosis?

A

Bulk transport of material out of the cell.

  • Vesicles move towards cell surface membrane.
  • Contents inside the vesicle is released out of the cell
51
Q

What is osmosis?

A

Movement of water molecules from an area of higher water potential, to an area of lower potential across a partially permeable membrane.

52
Q

What is the water potential of pure water?

A

0kPa

53
Q

Describe the water potential of a dilute solution

A

High water potential (many water molecules)

54
Q

Describe the water potential of a concentrated solution

A

Low water potential (few water molecules)

55
Q

What is a hypertonic solution?

A

Concentrated solution

56
Q

What can happen to an animal cell if it becomes a hypertonic solution?

A

Crenation

57
Q

What is a hypotonic solution?

A

A dilute solution

58
Q

What can happen to an animal cell if it becomes a hypotonic solution?

A

Lysis

59
Q

What is an isotonic solution?

A

Osmosis concentration is equal

60
Q

What happens when water leaves a plant cell?

A

It can become plasmolysed

61
Q

What happens when water enters a plant cell?

A

It can become turgid.

A Level Biology (13 decks)

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