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Flashcards in Cell Structure And Organisation Deck (12)
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1

The ribosome:

Very small organelles - 25 nm diameter

Present in large numbers

Found free in the cytoplasm of on the outer surface of the rough ER

made up of 2 subunits, one large, one small

Made up of ribosomal RNA and protein

Involved in protein synthesis

70s found in prokaryotes
80s found in eukaryotes

Manufactured in the nucleolus

2

Nucleolus:

2 micrometers

1/2 per nucleus

Synthesises ribosomal RNA and assemble the ribosomes from it

Spherical, darkly stained

3

Mitochondria:

0.5-10 micrometers

Site of aerobic respiration

Synthesises ATP

numbers may vary from 50-100

The highly folded inner membrane provides a large surface area for the respiration reactions. Some reactions also take place in the matrix.

There will be more in cells with high ATP requirements:
- cells that move a lot (sperm, muscles)
- cells which carry out active transport (small intestine)
-cells with high metabolic rate (lots of chemical reactions - liver)
- mitochondrial size and folding inner membrane may also be greater in these cells

4

Lysosomes:

Membrane bound vesicles which contain digestive enzymes

0.1-1.2 micrometers

Contribute a dismantling and recycling facility

They assist degrading material taken in from outside the cell and life expired components from within the cell e.g. Destruction of invading bacteria

5

Nucleus:

Largest organelle

20 micrometers diameter

Controls cells activities and retains the chromosomes

Contains chromatin, the material that condenses to form the chromosomes during cell division

Surrounded by a double membrane (nuclear envelope) which has pores to allow exchange with the cytoplasm (e.g. MRNA out, nucleotides in)

6

Chromatin:

Material chromosomes are made from

Condensed into chromosomes during cell division

Made of DNA and histone proteins, that it is wrapped around to be packaged

7

Endoplasmic reticulum:

An elaborate system of membrane bound sacs (cisternae), often continuous with the nuclear envelope and Golgi body

ROUGH
-has ribosomes lining it
-involved with protein synthesis as a transport system

SMOOTH
-lacks ribosomes
-involved with the synthesis and transport of lipids

8

Golgi body:

Similar to ER but has a more compact form

A collection of flattered membrane sacs that are constantly forming on one side and budding off as vesicles on the other

Forms lysosomes

Produces glycoproteins

Secretes carbohydrates

Packages proteins for secretion

Transports and store lipids

9

Plasmodesmata:

Small channels that directly connect the cytoplasm of neighbouring plant cells to each other, establishing living bridges between cells

10

Vacuole:

Animal cells contain small, temporary vacuoles and occur in large numbers

Plant cells have large permanent vacuoles which consist of fluid filled sac bounded by a single membrane, the tonoplast.

Contains cell sap, which provides osmotic system which functions in support of young tissues. It is also a storage site for chemicals such as glucose

11

Chloroplast:

Site of photosynthesis

Approx 3 micrometers wide, 6 in length

12

Centrioles:

Hollow cylinders 0.5 micrometers in diameter

At cell division they migrate to opposite poles of the cell where they synthesis the micro tubules of the spindles.