CELLS Flashcards
TOPIC 2
STRUCTURE OF NUCLEUS
- Nuclear envelope: double membrane surrounding nucleus, outer membrane continuous w/RER of cell
- Nuclear pores: allow passage of larger molecules, such as mRNA, out of nucleus
- Nucleoplasm: granular, jelly-like material making up bulk of nucleus
- Chromosomes: protein-bound, linear DNA
- Nucleolus: small spherical region in nucleoplasm-Manufactures rRNA and assembles ribosomes
FUNCTION OF NUCLEUS
- Controls cell’s activities - produces mRNA and tRNA - protein synthesis-controls entry and exit of materials, and contains nuclear reactions
- Retains genetic material in form of DNA and chromosomes
- Manufactures rRNA and ribosomes
STRUCTURE OF MITOCHONDRIA
- Double membrane surrounding organelle - controls entry and exit of material
- Cristae - extensions of inner membrane, providing large surface area for attachment of enzymes and other proteins during respiration
- Matrix - makes up remainder - contains proteins, lipids, ribosomes and DNA and some respiratory enzymes
FUNCTION OF MITOCHONDRIA
responsible for ATP production
STRUCTURE OF CHLOROPLAST
- Chloroplast envelope - double plasma membrane, highly selective, surrounds organelle
- Grana - stacks of disc-shaped thylakoid membrane
- Thylakoids - contain chlorophyll used in photosynthesis, can be linked by lamellae to other grana
- Stroma - fluid-filled matrix + contains starch grains
FUNCTION OF CHLOROPLAST
Site of Photosynthesis:
Granal membranes provide large SA for photosystems, enzymes
Chloroplasts contain DNA and ribosomes - can quickly and easily manufacture some of proteins needed for photosynthesis
STRUCTURE OF ENDOPLASMIC RETICULUM
- 3D system of sheet-like membranes - continuous w/outer membrane of nuclear double membrane
- Membrane contains a network of tubules and flattened sacs called cisternae
- RER - ribosomes on outer surface of membranes
- SER - lacks ribosomes on its surface and is often more tubular in its appearance
FUNCTION OF ENDOPLASMIC RETICULUM
RER
1. Large SA for protein/glycoprotein synthesis
2. Provides a pathway for material transport throughout cell, especially for proteins
SER
1. Synthesises, stores and transports lipids and carbohydrates
STRUCTURE OF GOGLI BODY
- Compact system of flattened sacs and stacked membranes-cisternae
- Vesicles - modified proteins and lipids transported to cell membrane where they fuse with it, and then egest contents to outside
FUNCTION OF GOLGI BODY
- Form glycoproteins by adding carbs to proteins
- Produce secretory enzymes, such as those secreted by pancreas - apparatus is developed in secretory cells, especially those in small intestine
- Secrete carbs, such as cellulose for plant cell walls
- Transports, modifies and stores lipids
- Forms lysosomes
STRUCTURE OF LYSOSOMES
spherical membrane bound sacs containing lysozymes
FUNCTION OF LYSOSOMES
- Hydrolyse foreign material ingested by phagocytes
- Exocytosis of enzymes to destroy extra-cellular material
- Apoptosis - programmed cell death.
Autolysis - breaking down cells after death - Digest worn out organelles - can recycle chemicals
STRUCTURE OF RIBOSOMES
- Small cytoplasmic granules found in all cells, free-floating or associated w/RER
- 80S - found in eukaryotic cells, slightly larger
- 70S - in prokaryotic cells, slightly smaller
- 2 Subunits - large and small - contain ribosomal RNA and proteins
FUNCTIONS OF RIBOSOMES
Carry out translation stage of protein synthesis to produce polypeptides
STRUCTURE OF CELL WALL
Found in plants, algae and fungi
- Cellulose microfibrils embedded in a matrix - contribute to overall cell wall strength are considerably strong.
and other polysaccharides - Middle lamella - marks the boundary between adjacent cell walls and cements adjacent cells together
FUNCTION OF CELL WALL
- Cellulose to provide mechanical strength to prevent cell wall bursting under pressure created by osmotic entry of water
- To provide mechanical strength to cell as a whole
- Allows water to pass along it - contributes to the movement of water through the plant
STRUCTURE OF VACUOLES
- Fluid-filled sac bounded by a single membrane
- Single membrane around it called tonoplast
- Solution of mineral salts, sugars, amino acids, wastes and sometimes pigments
FUNCTION OF VACUOLES
- Support herbaceous plants and herbaceous parts of woody plants by making cells turgid
- The sugars and amino acids can act as temporary food source
- Pigments - may attract pollinating insects due to colour
OUTLINE THE ROLE OF ORGANELLES IN PRODUCTION, TRANSPORT + PROTEINS FROM EUKARYOTIC CELLS (4)
DNA in the nucleus
ribosomes produces proteins
mitochondria produce ATP
Golgi body package
vesicles fuse with cell membrane
RER transport
ALL FEATURES PROKARYOTES HAVE
70s ribosome
murine cell wall
no membrane bound organelles-no nucleus
SOME FEATURES PROKARYOTES HAVE
capsid
flagella
EUKARYOTES VS PROKARYOTES
DNA enclosed in nucleus VS DNA floating free in cytoplasm
DNA is long + linear VS DNA is circular
contains histones VS contains no histones
has membrane organelles VS has no membrane organelles
cell wall is cellulose + chitin VS cell walls contain murien
ribosomes 80s VS ribosomes 70s
no slime capsule VS sometimes have slime capsule
VIRUSES
Viruses are acellular as they have no cell surface membrane, are not made of cells, have no organelles, cannot respire and no metabolic reactions
Viruses are extremely small and cannot be seen w/light microscope-enter living cells and multiply w/assistance of the host cells, causing diseases
FEATURES ALL VIRUSES HAVE
genetic material-codes for viral proteins
capsid-protects genetic material
attachment proteins-complementary to + bind to receptors on its specific host cell