Unit 1 – Cell Structure
Lesson B12.09 – Nucleus and Cytoplasm
Image diameter 10mm
Unit 1 – Cell Structure
Lesson B12.09 – Nucleus and Cytoplasm
Image diameter 10mm
Learning Intentions
I can describe and explain the structure of the cell membrane.
I can describe and explain the structure of the nucleus.
I can describe and explain the structure of the mitochondria.
Cell surface mebrane
Extremely thin (7nm)
At high magnification – three layers
Controls exchange between cell and
environment.
More in chapter 4
Microvilli
Singular microvillus
Finger like extensions
Typical on animal epithelial cells
Increase surface area
Knowledge check
What is the purpose of microvilli and where are they commonly found?
What are the three layers of the cell surface membrane?
Nucleus
Largest cell organelle
Nuclear Envelope
Two membranes – together the
nuclear envelope
Outer is continuous with the
endoplasmic reticulum
Many nuclear pores – allow and
control exchange of substances
between nucleus and cytoplasm e.g
mRNA, tRNA and ribosomes leave;
proteins, nucleotides, ATP and
hormones enter.
Chromosomes and Chromatin
Nucleus contains chromosomes.
DNA in sections, genes, control activities
of cell.
DNA 2m long, folded round histones.
DNA + proteins = chromatin.
Chromatin also contains some RNA.
Chromosomes are made of chromatin.
Nucleolus
Darkly stained rounded structure.
May be more than one.
Makes ribosomes using information in own DNA.
Contains core of DNA from one or more chromosomes with the genes that code for rRNA.
Also genes for tRNA.
Around core ribosomal subunits are manufactured combining rRNA with ribosomal proteins from cytoplasm.
Different parts of nucleolus only come together during ribosome synthesis. During nuclear division this ceases
and the nucleolus disappears.
Keywords
Nuclear envelope
Nuclear pores
Nuclear envelope
Chromatin
Chromosome
Knowledge check
Highlight some differences between chromosome and chromatin.
What is the purpose of the nuclear pore and what are some substances
than commonly pass?
What occurs in the nucleolus?
Why does the nucleolus disappear during cell division?
Mitochondria
Singular mitochondrion
1micrometer length – various shapes
Two membranes: inner folded into cristae
(sing crista) projecting into internal space –
matrix.
Space between – intermembrane space
Mitochondria function
Carry out aerobic respiration
Additionally some lipid synthesis
Energy released from carbohydrates and fats and transferred to ATP (adenosine
triphosphate). Energy is released elsewhere by breaking down ATP to ADP
(adenosine diphosphate)
Cells high demand for energy – more mitochondria (muscle, liver)
Respiration reactions take place in matrix and inner membrane; matrix contains
enzymes for this
Endosymbiont theory
Mitochondria and chloroplast contain ribosomes slightly smaller than
those in cytoplasm, as well as small circular DNA (like bacteria).
Mitochondria and chloroplasts are ancient bacteria now living inside
larger plant and animal cells.
They can no longer live independently but their DNA is still active for
vital proteins.
Keywords
Endosymbiosis
Mitochondria
Matrix
Cristae
ATP
Knowledge check
Why when you exercise would your muscle cells make more
mitochondria?
Why is ATP referred to as the universal energy carrier?
What evidence made scientists begin looking into endosymbiont
theory?
Learning Intentions
I can describe and explain the structure of the cell membrane.
I can describe and explain the structure of the nucleus.
I can describe and explain the structure of the mitochondria.
Plenary
Make a first attempt at this quiz.