2A: Cell structure & division Flashcards
Describe the Nuclear Envelope
Encases the nucleus
2 lipid bilayer membranes
Describe the Nuclear Pores
Transports molecules across the nuclear envelope
E.g RNA out, proteins in
Describe the Nucleoplasm
The substance in the nucleus
Includes chromosomes and nucleolus
Describe the Chromosomes
Made up of nucleic acid and proteins
Carries genetic information in the form of genes
Describe the Nucleolus
Largest structure in the nucleus
Makes ribosomes
What does the nucleus consist of? (5)
- Nuclear envelope
- Nuclear pores
- Nucleoplasm
- Chromosomes
- Nucleolus
Describe the Double Membrane (mitochondria)
Outer membrane: like a skin
Inner membrane: folded into layered structures which increase surface area
Describe the Cristae (mitochondria)
The folds made by the inner membrane
More space for chemical reactions
Describe the Matrix (mitochondria)
Fluid contained within mitochondria
Ribosomes + DNA floating in it
Contains granules which help with ion concentrations
What do the mitochondria consist of? (3)
- Double membrane
- Cristae
- Matrix
Describe the Rough Endoplasmic Reticulum
Contains ribosomes for protein synthesis
Describe the Smooth Endoplasmic Reticulum
Lipid and carbohydrate synthesis
Describe the Golgi Apparatus (+ Vesicles)
Where things are ‘packaged’ and transported to other parts of the cell (secreted)
Makes lysosomes
Describe the cytoplasm
Jelly like substance
Where most chemical reactions in the cell take place
The site of anaerobic respiration
Describe the Cell Membrane
Allows molecules in and out of the cell
Describe the lysosomes.
Where are they made?
They contain strong digestive enzymes to digest waste e.g broken cell organelles, pathogens
Made in the Golgi Apparatus
Describe the Ribosomes
Where protein synthesis takes place
Describe the Cell Wall
Made of cellulose
Strengthens the cell
Describe the Vacuoles
Stores cell sap
Describe the Chloroplast Envelope
Similar structure to the mitochondria double membrane (except not folded)
Describe the Grana
Made up of stacks of discs called thylakoids (resembles a stack of coins)
Site of light- dependent reactions of photosynthesis
Connected by intergranal thylakoids
Describe the Stroma
Colourless fluid surrounding grana
Contains enzymes required for LIR of photosynthesis
DNA + ribosomes are also present
What does a chloroplast consist of? (3)
- Chloroplast Envelope
- Grana
- Stroma
Describe the pros of Transmission Electron Microscopes (TEM)
- high magnification
- highest resolution (due to shorter wavelength of electrons)
- produces a 2D photomicrograph, on a screen (the electrons are transmitted through the specimen)
Describe the cons of Transmission Electron Microscopes (TEM)
- cannot look at living cells
- must be in a vacuum
- must cut section / have a thin specimen
- complicated preparation may create artefact
- does not produce a colour image
Describe the pros of Scanning Electron Microscopes (SEM)
- high magnification
- specimen does not need to be thin
- focuses using condenser electromagnet
- produces a 3D image (the electrons are directed at the specimen and bounce off)
Describe the cons of Scanning Electron Microscopes (SEM)
- cannot look at living cells
- must be in a vacuum
- complicated preparation may create artefact
- does not produce a colour image
What are the outer features of a prokaryotic cell.
- Cell membrane / plasma membrane
- Cell wall
- Capsule
- Pilus
- Flagellum
What can the cell membrane also be called? (pro)
Plasma membrane
What is the cell wall made from? (pro)
Murein
What is the function of the capsule? (pro)
Protects the cell
What is the function of the pilus? (pro)
They help the cell attach to surfaces
What is the function of the flagellum? (pro)
Allows for movement
What is the function of the plasmids? (pro)
Secondary DNA storage
What is the size of the ribosomes in prokaryotic cells compared to eukaryotic cells?
Ribosomes are smaller (20nm) in prokaryotic cells.
Ribosomes are bigger (25-30nm) in eukaryotic cells.
What are the inner features of a prokaryotic cell?
- Ribosomes
- Cytoplasm
- Large circular DNA strand
- Plasmids
What are the stages of cell fractionation?
- Cold, buffered, isotonic solution
- Homogenisation
- Tissue is sieved
- Ultracentrifugation
Describe stage 1 of cell fractionation
Place cells in a cold, buffered, isotonic solution:
- Cold- reduces enzyme activity
- Buffered- maintains constant pH and prevents protein
damage
- Isotonic- to prevent organelles bursting or shrinking
Describe stage 2 of cell fractionation
Homogenisation:
- Cells are broken up in a homogeniser (blender)
Describe stage 3 of cell fractionation
Blended tissue is filtered through a sieve to remove insoluble material:
- e.g cell walls
- Large pieces of homogenised tissue
Describe stage 4 of cell fractionation
Ultracentrifugation:
- The filtrate is placed in a centrifuge and spun at a slow speed
- The heaviest organelles are forced to the bottom
- The fluid at the top is then removed
- Repeat at a higher speed (organelles get lighter)
To convert mm –> um you x by ____
x 1000
To convert um –> mm you / by ____
/1000
What is cell differentiation?
Cell differentiation is the process by which cells become specialised for different functions.
What is the function of attachment proteins? (v)
They allow the virus to attach to host cells
What is the function of the lipid envelope? (v)
Derived from host cell membrane (easier attachment)
What is the function of the capsid? (v)
Encapsulates the DNA/ RNA (protein coat)
Describe the matrix in a virus
A protein layer on the inside of the envelope
What are the 4 phases of mitosis?
- Prophase
- Metaphase
- Anaphase
- Telophase
What happens during mitosis?
Mitosis is the part of the cell cycle in which a eukaryotic cell divides once to produce two identical daughter cells.
What happens during interphase?
what no. is it?
- Interphase:
- The cell grows + replicates itself
- The chromosomes are NOT visible
What are the 6 phases of the cell cycle?
- Interphase
- Prophase
- Metaphase
- Anaphase
- Telophase
- Cytokinesis
What happens during prophase?
what no. is it?
- Prophase:
- Chromosomes condense and become visible
- Centrioles move to poles + form spindle fibers
What happens during metaphase?
what no. is it?
- Metaphase:
- Chromosomes align along the equator
- They become attached to the spindle fibers by their centromere
What happens during anaphase?
what no. is it?
- Anaphase:
- Centromeres split, allowing chromatids to separate
- Chromatids move towards the poles pulled by the spindle fibers
What happens during telophase?
what no. is it?
- Telophase:
- Spindle fibers disperse
- Nuclear envelope reforms
- Chromosomes decondense
What happens during cytokinesis?
what no. is it?
- Cytokinesis:
- A ring of protein filaments form around the equator of the cell, which then tightens and splits the cell in two
What is cell division in prokaryotic cells called?
Binary fission
What does binary fission involve?
- Replication of the circular DNA and of plasmids
- Division of the cytoplasm to produce two daughter cells,
each with a single copy of the circular DNA and a variable number of copies of plasmids.
What are the two types of tumour?
Describe them.
Benign: slow growing, does not spread and is not classed as a cancer
Malignant: fast growing, does spread and is classed as a cancer
What are the treatments for tumours?
- Surgery to remove tumours (mainly for benign)
- Radiotherapy (mainly for malignant)
- Chemotherapy
Describe chemotherapy
Chemotherapy:
- blocking enzymes involved in DNA synthesis
- preventing DNA unwinding
- Inhibiting synthesis of new nucleotides
- preventing development of the spindle fibers
What does radiotherapy do to the cells in the tumour(s)?
Radiotherapy damages the DNA of cells in the tumour(s)
Which type of tumour is radiotherapy normally used for?
Malignant
Which type of tumour is surgery (to remove the tumour) normally used for?
Benign
