unit 2 - cells Flashcards
Eukaryotic (eg human) cells compared with Prokaryotic (bacterium) (7)
- Bacterial cell is much smaller than a human cell; (or human cell is much larger than a bacterial cell)
- Bacterial cell has a cell wall but human cell does not;
- Bacterial cell lacks a nucleus but human cell has a nucleus;
- Bacterial cell lacks membrane-bound organelles but human cell has membrane-bound organelles;
- Bacterial ribosomes smaller than human ribosomes / bacteria have 70S ribosomes whereas humans have 80S
- Bacterial DNA is circular but human DNA is linear
- Bacterial DNA is ‘naked’ whereas human DNA is bound to histones/proteins
Eukaryotic - Describe the structure and
function of the nucleus.(4)
Nuclear envelope/double membrane (Nuclear) pores (in the membrane) Chromosomes/chromatin/(linear) DNA with histones Nucleolus/nucleoli Function Holds/stores genetic information for production of proteins DNA replication OR interphase
Production of mRNA/tRNA OR transcription
Production of rRNA/ribosomes;;;;
Eukaryotic - Name the main polymer that
forms the following cell walls – plants
cells & fungal cells (1)
Cellulose (plant) and chitin (fungi);
Eukaryotic - Describe the role
of one named organelle in digesting
these bacteria. (3)
- Lysosomes
- Fuse with vesicle; Accept phagosome for vesicle
- (Releases) hydrolytic enzymes;
Eukaryotic - Identify two organelles in
cells that enable the production of
glycoproteins (1)
Rough endoplasmic reticulum/ribosomes and Golgi (apparatus/vesicles);
Eukaryotic - Give two structures found in
all prokaryotic cells and in all eukaryotic
cells. (2)
- Cell(-surface) membrane;
- Ribosomes; Ignore 70S
- Cytoplasm;
- DNA;
Eukaryotic – Give one feature of the
chloroplast that allows protein to be
synthesised inside chloroplast and describe one difference between this feature in the chloroplast and a eukaryotic cell. (2)
Mark in pairs, 1 and 2 OR 3 and 4
1. DNA;
2. Is not associated with protein/histones but nuclear DNA is
(2) OR Is circular but nuclear DNA is linear OR Is shorter than nuclear DNA;
3. Ribosomes;
4. Are smaller than cytoplasmic ribosomes;
Eukaryotic - Eukaryotic cells produce
and release proteins.
Outline the role of organelles in the
production, transport and release of
proteins from eukaryotic cells.(4)
- DNA in nucleus is code (for protein);
- Ribosomes/rough endoplasmic reticulum produce (protein); Accept rER for ‘rough endoplasmic reticulum’
- Mitochondria produce ATP (for protein synthesis);
- Golgi apparatus package/modify; OR Carbohydrate added/glycoprotein produced by Golgi apparatus; Accept body for ‘apparatus’
- Vesicles transport OR Rough endoplasmic reticulum transports;
- (Vesicles) fuse with cell(-surface) membrane;
Eukaryotic – state three differences
between DNA in the nucleus of a plant
cell and DNA in a prokaryotic cell.(3)
Plant v prokaryote
1. (Associated with) histones/proteins v no histones/proteins;
2. Linear v circular;
3. No plasmids v plasmids; Do not credit if suggestion that prokaryotic DNA only exists as plasmids.
4. Introns v no introns;
5. Long(er) v short(er);
Eukaryotic – Name the main biological
molecule in the cell membrane (1)
phospholipids
Eukaryotic – Describe the role of
mitochondria in secreting a protein (1)
(Many mitochondria) release energy / ATP for movement of vesicles / synthesis of protein / active transport;
Eukaryotic – Describe the role of the
golgi apparatus in lipid absorption
- Modifies / processes triglycerides;
- Combines triglycerides with proteins;
- Packaged for release / exocytosis OR Forms vesicles;
Prokaryotic - Name the main biological molecule in a bacterial cell wall (1)
murein/glycoprotein
Prokaryotic - Give two features
of all prokaryotic cells that
are not features of eukaryotic cells.
Cytoplasm with no membrane-bound organelles
Single, Circular DNA
DNA free in the cytoplasm
DNA that is not associated with proteins/histones
A cell wall that contains murein
Viruses – Give 2 features of all viruses (2)
- attachments proteins
- capsid
- nucleic acid
Microscopes - How to measure objects
using an eyepiece graticule (3)
- Use eyepiece graticule to measure the object e.g. nucleus or capillary
- Calibrate eyepiece graticule against stage micrometer
- Take a number of measurements and calculate the mean
Microscopes - Advantages and Limitations
of Transmission Electron Microscope (TEM)
(6)
- TEM use electrons and optical use light;
- TEM allows a greater resolution;
- (So with TEM) smaller organelles/named cell structure can be observed
- TEM view only dead/dehydrated specimens and optical (can) view live specimens;
- TEM does not show colour and optical (can);
- TEM requires thinner specimens;
- TEM requires a more complex/time consuming preparation;
- TEM focuses using magnets and optical uses (glass) lenses;
Microscopes – Advantage of electron
microscope over optical microscope (2)
- High resolution;
- Can see internal structure of organelles
Microscopes - The resolution of an
image obtained using an electron
microscope is higher than the
resolution of an image obtained using
an optical microscope.
Explain why. (2)
Shorter wavelength between electrons;
OR
Longer wavelength in light rays;
Microscopes - Describe and
explain one difference between TEM
and SEM (2)
- 3D image (with SEM), not 2D image
OR Lower resolution (with SEM)
OR (Only) surface visible with SEM, but internal structures visible with TEM; - (Because) electrons deflected/bounce off (using SEM) OR Electrons transmitted/pass through (using TEM);
Homogenisation – Conditions required for
cell homogenisation (3)
- Ice-cold – Slows/stops enzyme activity to prevent digestion of organelles/mitochondria;
- Buffered – Maintains pH so that enzymes/proteins are not denatured;
- Same water potential – Prevents osmosis so no lysis/shrinkage of organelles/mitochondria;
Homogenisation & Ultracentrifugation –
How to separate mitochondria? (4)
- Break open cells/homogenise/produce homogenate;
- Remove unbroken cells/larger debris by filtration;
- Centrifuge highest density organelle nuclei obtained as pellet at slowest speed
- Mitochondria in 2nd pellet as less dense than nucleus/organelle in first pellet;
Suggest why scientists can use
detergent to break open cells instead of
homogenisation (2)
- Cell membranes made from phospholipid; 2. (Detergent) dissolves membranes / phospholipid (bilayer);
Viruses - Describe viral replication.(4)
- Attachment proteins attach to receptors;
- Virus injects nucleic acid (into host cell); For this mp accept ‘genetic material’ for ‘nucleic acid’?
- Host cell replicates viral nucleic acid; Accept ‘RNA/DNA’ for ‘nucleic acid’.
- Host cell produces (viral) protein/capsid/enzymes;
- Virus (particles) assembled and released (from cell);
Bacteria - Describe binary fission in
bacteria. (3)
- Replication of (circular) DNA;
- Replication of plasmids;
- Division of cytoplasm (to produce daughter cells);
Bacteria -Describe how bacteria divide.(2)
- Binary fission;
- Replication of (circular) DNA;
- Division of cytoplasm to produce 2 daughter cells;
- Each with single copy of (circular) DNA;
Eukaryotic division - What is a tumour? (2)
- Mass of cells;
Accept abnormal growth for ‘mass’ - Many cells in mitosis/dividing cells
OR Uncontrolled cell division;
Eukaryotic division - Describe and
explain the arrangement of the genetic
material in prophase (2)
- Chromosomes (are) becoming visible/distinct;
- Because (still) condensing; OR Accept ‘chromosomes are condensed’ for 2 marks. Accept shorten or thicken for ‘condensed’
- Chromosomes (arranged) at random/not lined up;
- Because no spindle (activity); OR Because not attached to spindle fibres;
Eukaryotic division - Chromosome behaviour in all Stages (8)
(During prophase)
1.Chromosomes coil/condense/shorten/thicken/become visible;
2. (Chromosomes) appear as (two sister) chromatids joined at the centromere; (During metaphase)
3. Chromosomes line up on the equator/centre of the cell;
4. (Chromosomes) attached to spindle fibres;
5. By their centromere;
(During anaphase)
6. The centromere splits/divides;
7. (Sister) chromatids/chromosomes are pulled to opposite poles/ends of the cell/separate;
(During telophase)
8. Chromatids/chromosomes uncoil/unwind/become longer/thinner;
Eukaryotic division - Describe the role of
the spindle fibres and the behaviour of
the chromosomes during mitosis (5)
- (In) prophase, chromosomes condense; Accept chromatin for ‘chromosomes’ and for ‘condense’, shorten and thicken
- (In) prophase OR metaphase, centromeres attach to spindle fibres;
- (In) metaphase, chromosomes/pairs of chromatids at equator/centre of spindle/cell; 4. (In) anaphase, centromeres divide;
- (In) anaphase, chromatids (from each pair) pulled to (opposite) poles/ends (of cell); Accept for ‘chromatids’, chromosomes but reject homologous chromosomes
- (In) prophase/metaphase/anaphase, spindle fibres shorten;
Eukaryotic division – state name given to
the division of cytoplasm during the cell
cycle. (1)
cytokinesis
Eukaryotic division - Give two pieces of
evidence that the cell was undergoing
mitosis (2)
- The (individual) chromosomes are visible because they have condensed;
- (Each) chromosome is made up of two chromatids because DNA has replicated;
- The chromosomes are not arranged in homologous pairs, which they would be if it was meiosis;
Eukaryotic division – Evidence for a cell in
anaphase (2)
- Chromosomes / chromatids are (in two groups) at poles of spindle / at ends of spindle;
- V-shape shows that (sister) chromatids have been pulled apart at their centromeres / that centromeres of (sister) chromatids have been pulled apart.
Eukaryotic division – During the cell cycle,
the amount of DNA in a cell changes.
Explain how the behaviour of
chromosomes causes these changes in
the amount of DNA per cell (2)
(Increase)
1. Chromosomes / DNA replicates; (First decrease)
2. Homologous chromosomes separate; (Second decrease)
3. Sister chromatids separate.
Eukaryotic division - Suggest why
preventing the formation of spindle
fibres stopped the cell cycle.
- Chromosomes/centromeres cannot attach (to spindle)
OR
Chromosomes cannot line up (on spindle); - (So, no) metaphase;
OR - Chromatids cannot separate (on spindle); Accept description of ‘cannot separate’ e.g cannot move to poles Ignore ‘split’
- (So, no) anaphase;