Cell Structure and Division Flashcards
What do animal cells lack that plant cells have?
Cell wall, vacuole and chloroplast
Eukaryotic cells have ________ organelles
membrane-bound
Do plant cells have both a cell wall and membrane? What are they made of?
Yes
Cell wall made from cellulose
Cell surface membrane of phospholipids
Algal/fungal cells lack _____, which other plant cells have. Why?
Lack chloroplasts
They don’t photosynthesise
Function of the cell surface membrane?
- Regulates the movement of substances into and out of the cell.
- It also has receptor molecules on it, which allow it to respond to chemicals like hormones.
Describe the structure of a nucleus x3
Surrounded by an nuclear envelope (double membrane), which contains pores. Contains chromosomes (which are made from protein-bound linear DNA) and one or more structures called a nucleolus.
Functions of the nucleus x2
- Controls the cell’s activities (by controlling the transcription of DNA).
- The nucleolus makes ribosomes.
Describe the structure of a mitochondria x4
- Oval Shaped;
- double membrane;
– the inner membrane is folded to form structures called cristae; - inside is the mitochondrial matrix
Function of mitochondrion? x1
Site of aerobic respiration, where ATP is produced.
Describe the structure of a chloroplast x4
- Surrounded by a double membrane;
- also has membranes inside called thylakoid membranes. - These are stacked up in some parts of the chloroplast to form grana.
- Grana are linked together by lamellae – thin, flat pieces of thylakoid membrane.
Chloroplasts are found in which types of cells?
In plant and algal cells
Function of chloroplasts? x1
- Site of photosynthesis takes place. (Some parts of photosynthesis happen in the grana and others in the stroma (a thick liquid found in chloroplasts)).
Describe the structure of the Golgi apparatus
A group of fluid-filled, membrane bound, flattened sacs. Vesicles are often seen on the edges of the sacs.
Functions of Golgi apparatus? x2
Modifies and packages new lipids and proteins.
It also makes lysosomes.
Functions of Golgi vesicles? x2
Store lipids and proteins made by apparatus and transports them out of the cell (exocytosis)
Describe the structure of a lysosome
- Round organelle
- surrounded by a membrane,
- no clear internal structure
Function of a lysosome?
- Contains digestive enzymes called lysozymes. Used to digest invading cells or to break down worn out components of the cell.
What types of molecule are ribosomes made of?
Made of proteins and ribosomal RNA.
Function of a ribosome?
- Site of protein synthesis and translation. Proteins are made here.
Two parts of ribosome?
Small sub-unit and large sub-unit
Ribosomes are membrane bound organelles. True/false?
False. Ribosomes are not membrane bound organelles.
Where are ribosomes found?
Either floating freely in the cytoplasm or attached to the rough endoplasmic reticulum
Describe the structure of the Rough Endoplasmic Reticulum x2
A system of membranes enclosing a fluid-filled space.
The surface is covered in ribosomes.
Describe the functions of the Rough Endoplasmic Reticulum x2
Makes and transports proteins
Describe the functions of the Smooth Endoplasmic Reticulum x2
Synthesises and processes lipids
Describe the structure of the Smooth Endoplasmic Reticulum x2
Similar to rough endoplasmic reticulum except there is no ribosomes
Function of cell wall?
Supports cells and prevents them from changing shape
What is the cell wall made of? x2
In plants and algae it’s made mainly made of cellulose.
In fungi its made of a chitin.
Functions of cell vacuole? x2
- Helps to maintain pressure inside the cell and keep the cell rigid. This stops the plants wilting.
- It also is involved in the isolation of unwanted chemicals inside the cell.
Describe the structure of a vacuole x3
A membrane-bound organelle found in the cytoplasm of plant cells.
Contains cell sap – a weak solution of sugar and salts.
The surrounding membrane is called the tonoplast.
Bacteria are examples of…?
Prokaryotes
The cytoplasm of prokaryotes has no…? It has smaller _______.
No membrane bound organelles. Smaller ribosomes.
Prokaryotes have both a cell membrane and cell wall. True or false?
True
What is a prokaryotic cell wall made of? E.g. bacteria
Murein
What is the function and composition of bacterial capsules?
- Made of secreted slime.
- It helps protect bacteria from cells of the immune system
Function of the flagella of some prokaryotic cells?
Locomotion
Prokaryotic DNA is found where?
Structure? Associated proteins?
- DNA floats in cytoplasm.
- It is circular and not associated with histone proteins.
Structure and function of plasmids?
- DNA in prokaryotic cells
- Plasmids are small loops of DNA that are not part of the main circular DNA molecule.
- Contain genes for things like antibiotic resistance and can be passed on to other prokaryotes.
Outline binary fission x5
- Cell replicates its DNA
- Cytoplasmic membrane elongates, separating DNA
- Cross-wall forms and membrane becomes invaginated
- Cross-wall forms completely across cytoplasm
- Forms two daughter cells
What 3 things do viruses lack?
Plasma membrane, cytoplasm and ribosomes.
Describe the structure of a virus x3
- Capsid (protein coat)
- Attachment proteins
- Core of genetic material (DNA or RNA)
Viruses are cells. True/false?
False. Viruses are acellular
Magnification = what?
Magnification = Size of Image / Size of Object
Define resolution
The resolution of an optical microscope is defined as the shortest distance between two points on a specimen that can still be distinguished by the observer or camera system as separate entities.
Maximum resolution of light microscope?
0.2 micrometres
Maximum magnification of light microscope?
x1,500
Maximum resolution of TEM microscope?
0.2 nanometers (nm).
Maximum resolution of SEM microscope?
10 nanometers (nm)
Order microscopes in order of ascending resolution
Light < SEM < TEM
How does a TEM work?
- TEMs use electromagnets to focus a beam of electrons, which is then transmitted through the specimen
- Denser parts of the specimen absorb more electrons, which makes them look darker on the image you end up with.
How does a SEM work?
- SEMs scan a beam of electrons across the specimen. – This knocks off electrons from the specimen, which are gathered in a cathode ray tube to form an image.
How do you prepare a ‘temporary mount’ slide?
1) Start by pipetting a small drop of water onto the slide (a strip of clear glass or plastic).
2) Then use tweezers to place a thin section of your specimen on top of the water drop.
3) Add a drop of stain to highlight objects in a cell.
4) Finally add the cover slip. To do so, stand the slip upright on the slide, next to the water droplet. Then carefully tilt and lower it so it covers the specimen, Try not to get air bubbles as it will obstruct your view.
Describe the process of breaking up cells in ultracentrifugation. Why?
Homogenisation:
Can be done by vibrating the cells or by grinding the cell up in a blender.
This breaks up the plasma membrane and releases the organelles into solution.
Three conditions of homogenisation? Why?
- Ice-cold – To reduce enzyme activity to prevent the breakdown of the organelles.
- Isotonic – To prevent osmosis so that organelles don’t burst or shrink.
- Buffer solution – To maintain the pH
How do you separate organelles from the solution?
Filter the solution using a gauze to separate any large cell debris or tissue debris, like connective tissue, from the organelles (organelles get through gauze).
Describe ultracentrifugation
- Organelles placed into test tube with solution
- Test tube spun very fast
- Pellet forms of densest organelle in that TT
- Supernatant transferred to new TT (contains non-densest organelles)
- Spun again faster and for longer time period
- Next densest organelle forms new pellet
- Repeat
List 4 organelles in order of decreasing density
Nuclei
Mitochondria/Chloroplasts
Ribosomes
What does mitosis produce?
Two identical daughter cells
Why does mitosis occur? x2
Growth and repair
What happens when a cell is not dividing via mitosis?
Interphase - G1, S, G2
What happens in G1 of interphase?
Cellular contents, except chromosomes, are replicated
What happens in S of interphase?
Chromosomes are duplicated
What happens in G2 of interphase?
Cell reviews duplicated chromosomes
Order of mitosis stages? x4
PMAT Prophase Metaphase Anaphase Telophase
What happens in prophase of mitosis? x3
- The chromosomes condense, getting shorter and fatter.
- Tiny bundles of proteins called centrioles start to move to opposite ends of the cell, forming a network of protein fibres across it called the spindle.
- The nuclear envelope (the membrane around the nucleus) breaks down and chromosomes lie free in the cytoplasm.
What happens in metaphase of mitosis?
• The chromosomes line up along the middle of the cell and become attached to the spindle by their centromere.
What happens in anaphase of mitosis?
- The centromere divide, separating each pair of sister chromatids.
- The spindles contract, pulling chromatids to opposite poles of the spindle.
What happens in telophase of mitosis?
- Chromatids reach the opposite poles on the spindle.
- The chromatids uncoil and become long and thin again.
- A nuclear envelope reforms around each group of chromosomes, so there are two nuclei.
- The cytoplasm divides (cytokinesis) and there are two daughter cells that are genetically identical to the original.
- Interphase starts again.
What is cancer?
Uncontrolled Cell Division
Example of cancer drug mechanism?
Chemotherapy prevents the synthesis of enzymes needed for DNA replication in G1. If they aren’t produced, the S phase won’t happen disrupting cell cycle.
What does the mitochondrial matrix contain?
Enzymes involved in respiration
