Section 2: Cells Flashcards
How would i get an organelle out of a sample to study
Cell fractionation : break up cells in a cold buffer isotonic solution
Homogenisation: Cells broken up in homogeniser to release organelles the resultant fluid is the homogenate and debris filtered out
Ultracentrifugation: spins the homogenate in centrifuge heaviest organelle forced to bottom to form pellet and supernatant at top spinner high speed until organelle u want
What’s the equation for magnification
Magnification = image size divided by actual size
Why do we place cells in cold buffer and isotonic solution
cold ( reduced enzyme activity )
buffer ( so ph doesnt change )
isotonic ( same water potential )
all avoid cell movement or change within the cells from sample
Compare TEM and SEM
TEM you can see into cell
SEM you can’t look into cell
Which electron microscope has a high resolution and magnification
TEM
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What is the function of the cell membrane?
To regulate the entry and exit of substances.
What is a function of the smooth endoplasmic reticulum?
Lipid synthesis.
What is the primary function of lysosomes?
To digest waste materials and cellular debris.
Fill in the blank: The ______ is a rigid layer that provides support and protection in plant cells.
cell wall.
What is the role of the Golgi apparatus?
To modify, sort, and package proteins and lipids.
Which type of cell division results in two identical daughter cells?
Mitosis.
What is the function of the cytoskeleton?
To provide structural support and shape to the cell.
True or False: All cells contain DNA.
True.
Fill in the blank: The process by which cells convert glucose into energy is called ______.
cellular respiration.
What is osmosis?
The diffusion of water across a selectively permeable membrane.
True or False: The rough endoplasmic reticulum is studded with ribosomes.
True.
Fill in the blank: ______ are specialized structures within a cell that perform distinct processes.
Organelles.
What is the difference between active and passive transport?
Active transport requires energy, while passive transport does not.
Multiple Choice: Which structure is selectively permeable? A) Cell wall B) Cell membrane C) Cytoplasm
B) Cell membrane.
What is the primary purpose of mitosis?
To ensure equal distribution of genetic material to daughter cells.
True or False: Eukaryotic cells are generally larger than prokaryotic cells.
True.
Fill in the blank: The ______ is a network of protein filaments that helps the cell maintain its shape.
cytoskeleton.
What is the function of the nucleolus?
To produce ribosomal RNA (rRNA).
What process do cells use to engulf large particles?
Phagocytosis.
Fill in the blank: The ______ is the jelly-like substance within the cell.
cytoplasm.
What structure is responsible for packaging and transporting proteins?
Golgi apparatus.
Multiple Choice: Which type of cell division results in genetic diversity? A) Mitosis B) Meiosis C) Binary fission
B) Meiosis.
What is the role of the plasma membrane?
To protect the cell and control what enters and exits.
True or False: Ribosomes can be found free-floating in the cytoplasm.
True.
Fill in the blank: ______ are membrane-bound organelles that contain enzymes for breaking down waste.
Lysosomes.
What is the main function of the rough endoplasmic reticulum?
To synthesize proteins.
What is the function of vacuoles in plant cells?
To store substances and maintain turgor pressure.
what are the tree main stages of the cell cycle
Interphase
Mitosis
Cytokinesis
What is cancer
Uncontrolled growth and division of cells
Mutation results in uncontrolled mitosis
How do cancer treatments, like chemotherapy, interfere with cell division and inhibit growth of cancer cells?
Certain cancer treatments, such as chemotherapy, prevent DNA replication or inhibit metaphase during mitosis by interfering with spindle formation. This disruption halts cell division, preventing cancer cells from multiplying and spreading
List the basic structure of the plasma membrane
Phospholipid lipids
Proteins = chanel and carrier proteins
Cholesterol
Glycolipds
Glycoproteins
List the basic structure of the plasma membrane
Phospholipid lipids
Proteins = chanel and carrier proteins
Cholesterol
Glycolipds
Glycoproteins
State the role of phospholipids in the plasma membrane
Allow lipid-soluble substances to enter and leave the cell
Prevent water-soluble substances entering and leaving the cell
make the membrane flexible and self-sealing
What is the function of proteins in the membrane
- Provide structural support
- Act as Chanels transporting water soluble substances
- Allow active transport across the membrane through carrier proteins
- form cell-surface receptors for identifying cells
- help cells adhere together
- act as receptors for example hormones
What is the role of cholesterol in the membrane
- reduce lateral movement
- make membrane less fluid at higher temperatures
- prevent leakage of water and dissolved ions from the cell
What’s the role of glycoproteins in the cell membrane
act as recognition sites
help attach to one other to from tissue
Allow cells to recognise one another ei lymphocytes
Why is the cell membrane called the fluid mosaic model
fluid: flexible structure
Mosaic = proteins embedded in the bi layer have varying shapes and sizes
What features would mean a molecule cannot freely diffuse across the membrane
- polar
- not lipid soluble
3.too large - same charge as the protein chanel’s
What is facilitated diffusion
Passive process doesnt require ATP from respiration only the kinetic energy of particles
Uses protein channels and carrier proteins
Describe and distinguish the different roles of carrier proteins and protein channels
Protein chanel’s are water-filled hydrophilic chanel’s and allow water soluble ions pass through. they are selective and only open for specific ions. The ion binds to the protein and causes it to change shape in a way that closes it on one side and opens of the other can be used for facilitated diffusion
Carrier proteins bind to ion and cause it to change shape in a way that the molecule is released to the inside of the membrane can be used for facilitated diffusion and active transport
What is water potential
Water potential is the pressure created by water molecules units kPa
the addition of a solute to pure water will lower the water potential
water potential always negative
pure water has a water potential of 0
How does Active transport differ from passive forms of transport
Metabolic energy in the form of ATP is needed
Substances moved against a concentration gradient
Carrier proteins which act as pumps are involved in
The process is very selective
Describe active transport of a single molecule or ion
- A molecule or ion binds to a specific receptor site on a carrier protein in the cell membrane.
- ATP binds to the carrier protein and is hydrolyzed into ADP and an inorganic phosphate (Pi), releasing energy.
- The protein changes shape, transporting the molecule or ion across the membrane.
- The molecule or ion is released on the other side of the membrane.
- The inorganic phosphate is released from the protein, causing it to return to its original shape.
- The phosphate may later recombine with ADP during respiration to regenerate ATP.
Describe the process of the sodium-potassium pump. (excluding any mention of glucose)
• The sodium-potassium pump is an active transport mechanism requiring ATP.
• 3 Na⁺ ions bind to the pump from inside the cell. • ATP is hydrolyzed, causing a conformational change in the pump. • 3 Na⁺ ions are transported out of the cell. • 2 K⁺ ions bind to the pump from outside the cell. • The pump changes shape, transporting 2 K⁺ ions into the cell. • The pump returns to its original shape, ready to repeat. • This process maintains higher Na⁺ outside and K⁺ inside, essential for resting potential and cell function.
What are the two types of lymphocytes (white blood cells) and what are response are they involved in?
Cell-mediated responses involve T lymphocytes
HUmoral responses involve B lymphocytes
How do lymphocytes recognise cells belonging to the body
Lymphocytes constantly colliding
Some lymphocytes have receptors that exactly fit those of the body’s own cells : these lymphocytes die or are suppressed
The remaining lymphocytes are those that might fit foreign material
What are the 2 types of white blood cells
Phagocytes non-specific
lymphocytes specific
Describe a phagocyte in action
The phagocyte is attracted to chemicals released by the pathogen
Receptors on the phagocyte attach to chemicals on the pathogen
Phagocyte engulfs pathogen to form a phagosome
Lysosomes within the phagocyte migrate towards the bacterium
Lysosomes release lysozymes to hydrolyse the bacterium
The hydrolysis products of the bacterium are absorbed by the phagocyte
What is cell mediated immunity
When T cells respond to antigens that are presented on a body cell / recognise and eliminate infected cells
Please summarise the stages in response of a T lymphocytes to infection of a pathogen
- Pathogen Invasion: The pathogen invades the body.
- Antigen Presentation: Phagocytes present the pathogen’s antigens on their surface membrane.
- Helper T Cell Activation: Receptors on specific helper T cells bind to the antigens, activating the T cell.
- Clonal Expansion: Activated helper T cells divide by mitosis to form a clone of identical cells.
- Functions of Clones:
• Some become memory cells for future immunity.
• Stimulate phagocytes to engulf pathogens.
• Stimulate B cells to divide and produce antibodies.
• Activate cytotoxic T cells.
What do the cloned T cells do
The clones T cells:
develop into memory cells
stimulate phagocytes to engulf pathogens
stimulate b cells to divide and secrete their antibodies
activate cytotocic T cells
How do cytotoxic T cells kill infected cells
produce a protein called perforin that makes holes in cell-surface membrane which means membrane becomes freely permeable and cells dies
Describe the role of B cells in immunity
- Antigen Uptake: The B cell takes up the surface antigens of an invading pathogen.
- Antigen Processing and Presentation: The B cell processes the antigens and presents them on its surface.
- Activation by Helper T Cells: Activated helper T cells (which were previously stimulated by antigen-presenting cells) attach to the processed antigens on the B cell and activate it.
- Clonal Expansion: The activated B cell divides by mitosis to form a clone of plasma cells.
- Antibody Production: The cloned plasma cells produce and secrete specific antibodies that match the pathogen’s antigens.
- Antibody Action: The antibodies bind to the antigens on the pathogen and help destroy or neutralize the pathogen.
- Memory Cells: Some B cells develop into memory cells, which provide long-term immunity by remembering the pathogen for future encounters.
Contrast the cell mediated and humoral responses to a pathogen
Cell-mediated response involves T cells ( Helper T cells and Cytotoxic cells) and Humoural response involves B cells (Plasma cells and Memory B cells)
Cell-mediated response targets pathogens inside cells humoural immunity targets outside of cells pathogens
Cell-mediated response antibodies aren’t involved Humoural they are
Cell-mediated response time is slow because it requires activation to T cell while humoural response faster as involves production of antibodies
Cell mediated response directly kills infected cells
Both produce memory cells
How does the antigen enter the B cell
endocytosis
What is an antigen
A substance that triggers an immune response, typically by stimulating the production of antibodies or activating T cells
Activated B cells divide into two things…
B memory cells and plasma cells
Why may someone have measles only once and influenza several times
Measles only have 1 antigen type memory cell therefore effective
Influenza have several
antigen variability
Explain the role of macrophages in stimulating B lymphocytes
Present pathogen antigen on cell-surface membrane
What organelles do B lymphocytes need more of and why?
• Rough Endoplasmic Reticulum (RER) – For synthesizing antibodies (proteins).
• Golgi Apparatus – For modifying and packaging antibodies before secretion. • Mitochondria – To provide ATP for active processes like protein synthesis and antibody secretion
Why do antibodies passed to fetus only provide short term immunity?
Maternal antibodies have antigens that are destroyed by fetal antibodies
What is a pathogen
A microorganism that causes disease
Describe how antibodies are produced in the body following a viral infection
Virus contains antigens
Phagocytosis
Phagocyte presents antigens on cell-surface membrane
B cells activated
Form clones by mitosis which produce plasma cells or b memory cells
Plasma cells produce antibodies
antibodies attach to antigen and destroy it
Explain an advantage of using antibodies from plants to treat a disease rather than antibodies produce in an experimental animal
Fewer ethical difficulties
or
less risk of infection
Describe one way bacteria might produce symptoms of disease
Releases toxins
damages cells carrying out metabolic functions
What is a monoclonal antibody
An antibody produced by a single clone of identical B cells which are all specific to the same antigen
How do antibody’s cause the destruction of an antigen
agglutination of bacteria cells ( clump them together to make it easier for phagocytes )
serve as markers that stimulate phagocytosis
What is vaccination
An attenuated pathogen injected to produce an immune response activating b-cells producing antibody’s (plasma cells) and b-memory cells
Why are some antibodies referred to as monoclonal
produced from single b-cell clones
Describe the four types of immunity
Passive immunity = introduction of antibodies from an outside source ( anti venom or maternal antibodies )
Active immunity = produced by stimulating the production of antibodies by someone’s own immune system 2 types of this immunity include:
Natural active = natural contact with disease
artificial active = vaxcination no symptoms of disease
Why may vacinations fail to eliminate disease
people with defective immune systems
may develop disease immediately after vaccination before immunity levels develop
Pathogen may mutate frequently causing antigenic variability
individuals may object to vaccine for religious ethical or medical reasons
Describe the replication of HIV
- HIV binds to CD4 receptors on T helper cells and fuses with the membrane.
- The virus releases its RNA and reverse transcriptase into the cell.
- Reverse transcriptase converts viral RNA into DNA, which is integrated into the host genome.
- The host cell transcribes and translates viral genes to produce new viral proteins.
- New virus particles are assembled, bud off from the cell, and mature into infectious viruses
How does HIV produce the symptoms of AIDS
Kills T helper cells
which then dont stimulate B cells
Why is HIV called a retrovirus
ability to make DNA from RNA
Why are antibiotics ineffective against viral diseases like AIDS
Viruses within an organisms cell
Why are antibiotics ineffective against viral diseases like HIV?
Antibiotics are ineffective against HIV because viruses lack cell walls, ribosomes, and independent metabolism. HIV replicates inside host cells using reverse transcriptase, which antibiotics do not target. Instead, antiviral drugs are required.
Function of golgi apparatus
add carbohydrates to proteins to from glycoproteins
produce secretory enzymes
secrete carbohydrates
transport, modify and store lipids
from lysosomes
Where are 70s ribosomes found
70s in prokaryotic cells, mitochondria and chloroplasts
80s found in eukaryotic cells
Describe the structure of a bacteria cell
Cell wall contains murein
capsule
cell-surface membrane
70s ribosomes
circular strand of DNA
plasmids
Does HIV have a murein or a cell wall
no
Why do scientists use very thin slices of alveolar tissue with the optical microscope
Alveolar tissue one cell think
Allow the light to shine through to see the individual cells
What do interleukins do?
Released by activator T helper cells interleukins:
- Tigger activated T helper cells to undergo mitosis
- Stimulate macrophages to undergo phagocytosis
Describe the absorption of glucose in the ilium
Glucose Absorption in the Ileum:
• Facilitated Diffusion: Glucose moves from the lumen into epithelial cells via carrier proteins (GLUT transporters).
• Active Transport (Co-transport):
• The sodium-potassium pump maintains a low sodium concentration inside the epithelial cell.
• Sodium-glucose co-transporter (SGLT1) uses the sodium gradient to bring glucose into the cell with sodium.
• Final Step: Glucose moves into the bloodstream by facilitated diffusion through GLUT2 transporters.
Describe viral replication 3 marks
- Attachment proteins attach to receptors;
- (Viral) nucleic acid enters cell;
- Nucleic acid replicated in cell
OR
Reverse transcriptase makes DNA from RNA; - Cell produces (viral) protein/capsid/enzymes;
- Virus assembled and released (from cell)
Describe the complete digestion of starch by a mammal. 4 marks
- Hydrolysis;
- (Of) glycosidic bonds;
- (Starch) to maltose by amylase;
- (Maltose) to glucose by disaccharidase/maltase;
- Membrane-bound (disaccharidase/maltase
Describe the structure of a mitochondrion and explain how its features are adapted for its function. (6 marks)
- Structure of the Mitochondrion (Max 3 marks)
• The mitochondrion is a double-membraned organelle.
• The inner membrane is folded into cristae, which increase the surface area.
• The matrix contains enzymes for the Krebs cycle and link reaction.
• The intermembrane space is where protons accumulate during oxidative phosphorylation.
• The inner membrane contains ATP synthase and electron transport chain proteins.
• The mitochondrial DNA and ribosomes allow the mitochondrion to produce its own enzymes and proteins. - Adaptations for Function (Max 3 marks)
• Cristae increase surface area for electron transport and ATP production.
• Matrix contains necessary enzymes for respiration reactions.
• Double membrane separates processes, maintaining conditions for ATP synthesis.
• Intermembrane space allows rapid accumulation of protons for chemiosmosis.
• Mitochondrial DNA and ribosomes allow quick production of proteins needed for respiration.
Describe the structure of the chloroplasts.
Double plasma membrane - chloroplasts envelope
The grana are stacks up to 100 disc like structures called thylakoids
Within the thylakoids is chlorophyll
The stroma
How is the structure of a chloroplast adapted for its function?
The granal membranes provide a large surface area for the process of the first stage photosynthesis
The fluid of the stroma possesses all the enzymes needed to make sugars in the second stage of photosynthesis
Chloroplasts contain both DNA and ribosomes so they can quickly and easily manufacture some of the proteins needed for photosynthesis
What are the two main functions of the rough endoplasmic reticulum (RER)?
provide a large surface area for the synthesis of proteins and glycoproteins
provide a pathway for the transport of materials, especially proteins, throughout the cell
What are the two main functions of the smooth endoplamic reticulum (SER)?
synthesise, store and transport lipids and carbohydrates
Structure of the ER? (3 marks)
• The ER is a network of flattened membrane-bound sacs called cisternae.
• It is continuous with the nuclear envelope, allowing transport of molecules between the nucleus and cytoplasm.
• Two types exist: rough ER (RER) and smooth ER (SER).
Compare the RER with the SER?
There are two types of ribosomes. Name them and where they are found.
80s - found in eukaryotic cells
70s - found in prokaryotic cells, mitochondria and chloroplasts, is slightly smaller than
What’s the function of vacuoles?
Make cells turgid
Sugars and amino acids may act as temporary food store
Pigments may colour petals to attract pollinating insects
Describe the structure of a bacterial cell.
Cell wall made of murein for structural support
Plasma membrane controls entry and exit of substances
Cytoplasm contains enzymes and ribosomes for protein synthesis
Ribosomes (70s) are smaller than those in eukaryotic cells
Circular DNA is free in the cytoplasm not enclosed ina nucleus
Some bacteria have plasmids, flagella and a capsule
Contrast the eukaryotic and prokaryotic cell
Structure of a virus (3marks)
- Structure of a Virus (Max 3 marks)
• Genetic material: Either DNA or RNA, but never both, contained within the virus.
• Capsid: A protein coat that surrounds and protects the genetic material.
• Attachment proteins: Found on the surface of the virus; help the virus bind to host cells.
• Some viruses have a lipid envelope derived from the host cell membrane (e.g., influenza, HIV).
• No cytoplasm, ribosomes, or organelles—viruses rely on host cells for replication.
Contrast viruses and prokaryotic cells (bacteria).
What are the three key stages of the cell cycle?
Interphase (G1,S,G2)
Nuclear division (mitosis or meiosis)
Cytokinesis
What are the three stages of interphase and what happens in them.
G1 - Growth and all organelles double
S - DNA replication
G2 - Growth and preparation for mitosis
Describe the events that occur during mitosis that ensure the production of two genetically identical cells. (5 marks)
• Chromosomes condense and become visible as sister chromatids joined at the centromere (prophase).
• Spindle fibers attach to the centromeres and align chromosomes at the equator (metaphase). • Spindle fibers contract, pulling sister chromatids to opposite poles (anaphase). • Chromatids reach poles and new nuclear envelopes form around each set (telophase). • Cytoplasm divides during cytokinesis, forming two genetically identical daughter cells.
Suggest why an organism reproduces asexually when conditions are favourable.
Genetically identical offspring.
Offspring will find conditions favourable.
Whenever you get a question that says asexual reproduction always write genetically identical offspring
