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biology > Module 1: Cell structure. > Flashcards

Module 1: Cell structure. Flashcards

1
Q

Define Organelle.

A

An organelle is a subcellular structure that has one or more specific jobs to perform in the cell.

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2
Q

Define Ultra Structure.

A

Structures of a cell that are revealed by an Electron Microscope.

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3
Q

State all the organelles in an animal cell.

A

Plasma membrane,

Rough endoplasmic reticulum

Ribosome

Lysosome

nuclear envelope

Golgi apparatus

Cytoplasm

Mitochondrion

Nucleus

Nucleolus

Smooth endoplasmic reticulum

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4
Q

What organelles are in Plant cells but not in animal cells.

A

Cell wall

Chloroplast

Plasmodesmata

Vacuole

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5
Q

Description of Plasma membrane?

A

The Plasma membrane is composed of a Phospholipid bilayer with embedded proteins.

it is found on the surface of an animal cell and just inside the cell wall of plant cells and prokaryotic cells.

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6
Q

What is the function of Plasma membrane?

A

It regulates the movement of substances into and out of the cell.

It also has receptor molecules on it, which allow it to respond to chemicals like hormones.

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7
Q

Description of a Cell wall?

A

The cell wall is a very strong structure that is made up of the carbohydrate polymer cellulose.

In fungal cells, it is made of chitin

In plant cells, it is made of cellulose

in prokaryotic cells, it is made of murein

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8
Q

What is the function of a Cell wall?

A

It provides structural support for cell.

It protects the cell from mechanical damage.

It helps maintain the shape of cell.

It allows for the exchange of substances between adjacent cells.

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9
Q

Description of Nucleus?

A

It is a large organelle that is surrounded by a nuclear envelope (double membrane)

Inside the nucleus is Chromatin (which consists of DNA collided around proteins called histones) and the nucleolus.

Inside is the nucleoplasm which contains molecules such as nucleotides and enzymes. (they are needed for DNA and RNA synthesis.

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10
Q

What is the function of Nucleus?

A

The nucleus controls cell activities by controlling the transcription of DNA.

It regulates gene expression, which determines the production of proteins and other molecules.

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11
Q

Describe the function of an Nuclear envelope.

A

It is a double membrane that surrounds the Nucleus.

It consists of an inner and outer membrane with a small space called the perinucular space in-between.

The nuclear envelope acts as a barrier, controlling the movement of substances in and out of the the nucleus through specialised protein channels called nuclear pores.

This helps to Protect the genetic material inside the Nucleus and Provides structural support to the nucleus.

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12
Q

Describe the Nucleolus.

A

It is a structure within the nucleus that is made up of proteins and RNA molecules.

It produces and assembles ribosomes.

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13
Q

Description of Lysosomes?

A

They are round organelles surrounded by a membrane, with no clear internal structure.

They are phospholipid rings which contain digestive enzymes separate from the rest of the cytoplasm.

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14
Q

What is the function of Lysosomes?

A

Lysosomes contain digestive enzymes.

These are kept separate from the cytoplasm by the surrounding membrane.

used to digest invading cells or to break down worn out components of the cell.

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15
Q

Description of a Ribosome?

A

A very small organelle that either floats free in the cytoplasm or is attached to the rough endoplasmic reticulum.

It is not surrounded by a membrane.

It is made up of proteins and RNA and is composed of 2 sub units.

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16
Q

What is the function of Ribosomes?

A

It is the site where proteins are made.

They read genetic code on messenger RNA (mRNA) and use it to assemble amino acids into polypeptide chain, which forms proteins.

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17
Q

Description of the Rough endoplasmic Reticulum?

A

The RER is an extension of the nuclear envelope and is coated with ribosomes.

The ribosomes on the RER gives the RER a ‘rough’ appearance under the microscope.

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18
Q

What is the function of The Rough endoplasmic Reticulum?

A

It folds and processes Proteins that have been made at the Ribosomes.

It facilitates protein synthesis by providing a large surface area for ribosomes.

It then transports the newly synthesised proteins to the Golgi apparatus for modification.

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19
Q

Description of Smooth Endoplasmic Reticulum?

A

It is a complex network of tubules and vesicles that lacks ribosomes on its surface.

It has a smooth appearance.

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20
Q

What is the function of Smooth Endoplasmic Reticulum?

A

It synthesises and processes lipids n including cholesterol and steroid hormones (such as estrogen).

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21
Q

Description of a vesicle?

A

it is a small fluid- filled sac in the cytoplasm, surrounded by a membrane.

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22
Q

What is the function of a vesicle?

A

Vesicles transport substances in and out of the cell - via the plasma membrane.

Vesicles are either formed by the Golgi apparatus or the Endoplasmic reticulum as well as at the cell surface.

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23
Q

Description of Golgi Apparatus?

A

A group of fluid-filled membrane-bound flattened sacs surrounded by vesicles.

24
Q

What is the function of the Golgi Apparatus?

A

It receives proteins from the RER and lipids from the SER.

It modifies the proteins and lipids and repackages them into vesicles.

The Golgi apparatus is also the site of lysosome synthesis.

25
Q

Description of Mitochondrion?

A

it is usually oval-shaped.

It contains a double membrane with folds called cristae, which provides a large surface area for respiration.

Inside these folds is the Matrix, which contains enzymes that are involved in respiration.

26
Q

What is the function of Mitochondrion?

A

It is the site of aerobic respiration, where ATP is produced.

It is self-replicating so can become numerous in cells with high energy requirements.

They are found in large numbers in cells that are very active and require a lot of energy.

27
Q

Description of Chloroplast?

A

A small, flattened structure that is found in plant cells only.

It is surrounded by a double membrane, and also has membranes inside called thylakoid membranes.

Thylakoid membranes are stacked up in some parts of the chloroplast to form Grana.

Grana are linked together by lamellae which are thin, flat pieces of Thylakoid membrane.

These structures are found only in plants and certain types of photosynthesising bacteria or protoctists.

28
Q

What is the function of Chloroplast?

A

It is the site where photosynthesis takes place.

Some parts of Photosynthesis happen in grana, and others happen in the stroma - a thick fluid found in chloroplasts.

29
Q

Describe Middle lamella.

A

The middle lamella is found outside of the cell walls in plant cells.

It is responsible for sticking plant cells together and providing stability.

It is mostly made of a substance called calcium pectate.

30
Q

Describe Amyloplasts.

A

These are plant storage granules which contain starch and are mostly found in bulbs and tubers.

Amyoplasts can convert the starch back into glucose when the plant cell needs more glucose for respiration.

31
Q

Describe Tonoplasts.

A

The tonoplast is a membrane which surrounds the vacuole which functions to separate the vacuole from the rest of the cell.

32
Q

Describe Vacuole.

A

The vacuole is an organelle which stores cell sap and may also store nutrients and proteins.

It helps to keep plant cells turgid.

Some vacuoles can perform a similar function to lysosomes and digest large molecules.

33
Q

Describe Plasmodesmata.

A

Plasmodesmata are narrow channels of cytoplasm within the cell walls of plants.

It allows two neighbouring plant cells to transport substances between them and to communicate.

34
Q

Describe Pits.

A

Pits are regions of a plant cell where the cell wall becomes very thin.

Pits are arranged in pairs so that the pit of one plant cell is aligned with the pit of another plant cell.

Like plasmodesmata, pits allow neighbouring plant cells to exchange substances.

35
Q

Describe Centriole.

A

Small, hollow cylinders, made of microtubules which are tiny protein cylinders.

These are bundles of microtubules which form spindle fibres during mitosis in order to pull sister chromatids apart.

They are also important for the formation of cilia and flagella.

36
Q

Description of Cilia?

A

Small, Hair and finger-like structures found on the surface of some cells.

Cilia are found on epithelial cells lining the trachea and move to sweep mucus up the windpipe.

In cross-section, they have an outer membrane and a ring of nine pairs of protein microtubules inside, with a single pair of microtubules in the middle.

37
Q

What is the function of Cilla?

A

The microtubules allow the cilia to move.

This movement is used by the cell to move substances along the cell surface.

38
Q

Description of Flagellum?

A

A tail-like structure which are made up of bundles of microtubules

They stick out from the cell surface and are surrounded by Plasma membrane.

Inside the tail, there is 2 microtubules in the center and nine pairs around the edge.

39
Q

What is the function of Flagellum?

A

The microtubules contract to make the flagellum move and propel the cell forward.

Cells with a flagellum include sperm cells, which use it to swim up the fallopian tubes to fertilise the egg cell.

40
Q

What are the two main types of organisms?

A

Prokaryotes and Eukaryotes.

41
Q

What are examples of Prokaryotes?

A

Bacteria such as Coli bacterium and salmonella Bacterium

42
Q

What are examples of Eukaryotes?

A

Human liver cell, yeast and amoeba

43
Q

Describe Prokaryotic cells.

A

They are extremely small cells (less than 2 micrometers small)

Their DNA floats freely in the cytoplasm (No nucleus) and consists of a single circular chromosome.

Cell wall is made of Polysaccharide and not Chitin or Cellulose. Bacterial cell walls are made of murein (a type of glycoprotein)

Has no membrane bound organelles.

Flagella (when present) made of the protein flagella, arranged in a helix.

Small Ribosomes 70S (20nm 0r less).

have extra bits of DNA in the form of small circular plasmids.

Prokaryotes have some organelles that are absent from eukaryotic cells. These include: Pili, Mesosomes, Plasmids and Slime capsule.

44
Q

Describe Eukaryotic cells.

A

They are large cells (about 10-100 micrometers diameter)

DNA is linear and wrapped around chromosomes.

There is a nucleus present which contains the DNA.

No cell wall (in animal cells). In Plant cells the cell wall is made of cellulose and in Fungi the cell wall is made of Chitin.

Has many organelles that are membrane bounded such as mitochondria.

Flagella, when present, is made of microtubules that are arranged in a ‘9+2’ formation.

Have Large Ribosomes 80S (over 20 nm)

45
Q

Describe Pili.

A

Pili are hair-like structures which stick out from the plasma membrane.

They are used to communicate with other cells (including the transfer of plasmids between bacteria).

46
Q

Describe Plasmids.

A

plasmids are small, circular rings of DNA which are separate from the main chromosome.

They house genes which are not crucial for survival but might prove useful - such as antibiotic-resistance genes, for example.

Plasmids can replicate independently from the main chromosomal DNA.

47
Q

Describe Mesosomes.

A

The mesosome is a folded portion of the inner membrane.

Some scientists believe that it plays a role in chemical reactions, such as respiration, other scientists doubt whether it even exists and think that it may just be an artefact produced during the preparation of bacterial samples for microscopy.

48
Q

Describe Slime Capsule.

A

In addition to a cell wall, some bacteria also have a capsule which is made of slime.

The main function of the capsule is to protect the bacterium against an immune system attack.

49
Q

What is The Cytoskeleton?

A

A network of protein fibres found in the cytoplasm of eukaryotic cells.

It gives the cell a shape and keeps organelles in position.

It is made up of small tubes of protein called microtubules which form a network throughout the cell.

It is dynamic (constantly changing), which allows it to respond to changes in the cell and carry out its functions.

50
Q

What are the main functions for the Cytoskeleton?

A

Provides mechanical strength to cells.

Allows the movement of organelles within the cell.

Enables movement of the cell.

51
Q

What is the Cytoskeleton made up of?

A

Microtubules and Microfilaments.

52
Q

Describe Microfilament.

A

Are thin fibres composed of actin proteins.

assists in cell membrane motility, endo- and exocytosis, secretion and vesicle transfer.

assists with cell movement.

52
Q

Describe Microtubule.

A

Hollow structures composed of tubulin proteins. (25 nm in diameter)

It provides structural support to cells.

Helps with cell division.

It extends throughout the cell providing it with proper shape and keeping the organelles in place.

53
Q

State the organelles involved in Protein production.

A

Ribosomes.

Rough Endoplasmic Reticulum.

Golgi apparatus.

Vesicles.

53
Q

What happens in Protein production?

A

Proteins are produced on the Ribosomes.

New proteins which are produced on the surface on RER are folded and processed in the
RER.

The proteins are then transported from the RER to the Golgi Apparatus in Vesicles.

At the Golgi, they are modified and processed by various enzymes.
The protein may have a carbohydrate chain stuck onto its surface, or the addition of a sulfate or phosphate group.

The dolled up protein is then placed into another vesicle which travels to the part of the cell where the protein is needed.

If the protein is a carrier protein, the vesicle will deliver the protein to the plasma membrane where it will be incorporated.

biology (12 decks)

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