AQA A-Level Biology. 3.2 - Cells.
1. Structure of Nucleus.: 1. Nuclear envelope: double membrane
surrounding nu- cleus, outer membrane continuous with the (R)ER of
the cell.
2. Nuclear pores: allow the passage of larger molecules, such as mRNA,
out of the nucleus.
3. Nucleoplasm: granular, jelly-like material making up the bulk of the
nucleus.
4. Chromosomes: protein-bound, linear DNA.
5.Nucleolus: small spherical region(s) in nucleoplasm. Manufactures
ribosomal RNA and assembles ribosomes.
2. Function of Nucleus.: 1. Controls cell's activities - produces mRNA and
tRNA
- protein synthesis. Controls entry and exit of materials, and
contains nuclear reactions.
,2. Retains genetic material in the form of DNA and chromosomes.
3. Manufactures ribosomal RNA and ribosomes.
3. Structure of Mitochondria.: 1. Double membrane surrounding organelle
- con- trols entry and exit of material.
2.Cristae - extensions of the inner membrane, providing a large surface
area for the attachment of enzymes and other proteins during
respiration.
3. Matrix - makes up the remainder - contains proteins, lipids,
ribosomes and DNA (allows mitochondria to produce own proteins) and
some respiratory enzymes.
4. Functions of Mitochondria.: 1. Sites of Krebs Cycle and oxidative
phosphoryla- tion pathway in aerobic respiration - responsible for ATP
production.
NB = found in high numbers in metabolically active cells which require
,much ATP.
5. Structure of Chloroplasts.: Found in plants and algae.
1.Chloroplast envelope - double plasma membrane, highly selective,
surrounds the organelle.
2. Grana - stacks of disc-shaped thylakoid membrane.
3.Thylakoids - contain chlorophyll used in photosynthesis, can be linked
by lamellae
, to other grana.
4. Stroma - fluid-filled matrix where Calvin Cycle takes place. Also
contains starch grains.
6. Functions of Chloroplasts.: Site of Photosynthesis:
LDR in thylakoid
membranes. LIR in
stroma.
1. Granal membranes provide a large SA for LDR - photosystems, e-
carriers and enzymes etc.
2. Chloroplasts contain DNA and ribosomes - can quickly and easily
manufacture some of the proteins needed for photosynthesis.
7. Structure of Endoplasmic Reticulum.: 1. 3D system of sheet-like
membranes
- continuous with the outer membrane of the nuclear double membrane.
2. Membrane contains a network of tubules and flattened sacs called
1. Structure of Nucleus.: 1. Nuclear envelope: double membrane
surrounding nu- cleus, outer membrane continuous with the (R)ER of
the cell.
2. Nuclear pores: allow the passage of larger molecules, such as mRNA,
out of the nucleus.
3. Nucleoplasm: granular, jelly-like material making up the bulk of the
nucleus.
4. Chromosomes: protein-bound, linear DNA.
5.Nucleolus: small spherical region(s) in nucleoplasm. Manufactures
ribosomal RNA and assembles ribosomes.
2. Function of Nucleus.: 1. Controls cell's activities - produces mRNA and
tRNA
- protein synthesis. Controls entry and exit of materials, and
contains nuclear reactions.
,2. Retains genetic material in the form of DNA and chromosomes.
3. Manufactures ribosomal RNA and ribosomes.
3. Structure of Mitochondria.: 1. Double membrane surrounding organelle
- con- trols entry and exit of material.
2.Cristae - extensions of the inner membrane, providing a large surface
area for the attachment of enzymes and other proteins during
respiration.
3. Matrix - makes up the remainder - contains proteins, lipids,
ribosomes and DNA (allows mitochondria to produce own proteins) and
some respiratory enzymes.
4. Functions of Mitochondria.: 1. Sites of Krebs Cycle and oxidative
phosphoryla- tion pathway in aerobic respiration - responsible for ATP
production.
NB = found in high numbers in metabolically active cells which require
,much ATP.
5. Structure of Chloroplasts.: Found in plants and algae.
1.Chloroplast envelope - double plasma membrane, highly selective,
surrounds the organelle.
2. Grana - stacks of disc-shaped thylakoid membrane.
3.Thylakoids - contain chlorophyll used in photosynthesis, can be linked
by lamellae
, to other grana.
4. Stroma - fluid-filled matrix where Calvin Cycle takes place. Also
contains starch grains.
6. Functions of Chloroplasts.: Site of Photosynthesis:
LDR in thylakoid
membranes. LIR in
stroma.
1. Granal membranes provide a large SA for LDR - photosystems, e-
carriers and enzymes etc.
2. Chloroplasts contain DNA and ribosomes - can quickly and easily
manufacture some of the proteins needed for photosynthesis.
7. Structure of Endoplasmic Reticulum.: 1. 3D system of sheet-like
membranes
- continuous with the outer membrane of the nuclear double membrane.
2. Membrane contains a network of tubules and flattened sacs called
