B1 - Cell Biology Flashcards
What are the two main types of cells?
Prokaryotic and Eukaryotic
Prokaryotic cells are smaller and simpler, while eukaryotic cells are complex and include all animal and plant cells.
List the main subcellular structures found in most animal cells.
- Nucleus
- Cytoplasm
- Cell membrane
- Mitochondria
- Ribosomes
These structures play crucial roles in cell function and activity.
What is the function of the nucleus in a cell?
Contains genetic material that controls the activities of the cell
The nucleus is often referred to as the control center of the cell.
What is the role of mitochondria?
Where most reactions for aerobic respiration take place
Respiration transfers energy that the cell needs to work.
What additional structures do plant cells have that animal cells do not?
- Rigid cell wall
- Permanent vacuole
- Chloroplasts
These structures contribute to the support, storage, and photosynthesis functions of plant cells.
What is the function of chloroplasts?
Where photosynthesis occurs
Chloroplasts contain chlorophyll, which absorbs light needed for photosynthesis.
What do bacterial cells lack compared to eukaryotic cells?
Chloroplasts and mitochondria
Bacterial cells have a simpler structure and do not perform aerobic respiration like eukaryotic cells.
How do bacterial cells store their genetic material?
A single circular strand of DNA floating freely in the cytoplasm
Bacterial cells do not have a ‘true’ nucleus.
What are plasmids?
Small rings of DNA that may be present in bacterial cells
Plasmids can carry genes that provide bacteria with genetic advantages.
True or False: Eukaryotic cells are simpler than prokaryotic cells.
False
Eukaryotic cells are more complex than prokaryotic cells.
What is the gel-like substance where most chemical reactions happen in a cell?
Cytoplasm
The cytoplasm contains enzymes that control these chemical reactions.
What do light microscopes use to form an image?
Light and lenses
Light microscopes allow us to see individual cells and large subcellular structures like nuclei.
How do electron microscopes differ from light microscopes?
They use electrons instead of light to form an image
Electron microscopes have much higher magnification and resolution.
What is resolution in microscopy?
The ability to distinguish between two points
A higher resolution gives a sharper image.
What can electron microscopes allow us to see in detail?
Internal structure of mitochondria and chloroplasts, ribosomes, and plasmids
Electron microscopes provide much greater detail than light microscopes.
How do you calculate magnification?
magnification = image size / real size
Image size and real size should have the same units.
What is the formula for calculating image size given magnification and real size?
image size = magnification x real size
Rearranging the formula allows you to find either image size or real size.
What unit conversion is necessary when calculating magnification?
Convert micrometres (um) to millimetres (mm)
This requires dividing by 1000.
What is the purpose of a microscope slide?
To mount the specimen for viewing under a microscope
A microscope slide is typically made of clear glass or plastic.
What is the first step in preparing a slide to view onion cells?
Add a drop of water to the middle of a clean slide
This helps to keep the specimen hydrated and visible.
What solution is added to the specimen on a microscope slide to enhance visibility?
Iodine solution
Iodine is a stain that adds color to the specimen.
What is the function of the coarse adjustment knob on a microscope?
To move the stage up and down for focusing
It is used to bring the specimen into rough focus.
What is the formula for calculating magnification?
Magnification = length of drawing of cell ÷ real length of cell
This helps to determine how much larger the drawing is compared to the actual size.
Fill in the blank: A _______ is a square of thin, transparent plastic or glass placed over a specimen on a slide.
cover slip
The cover slip protects the specimen and keeps it flat.
What should be avoided when placing the cover slip on the specimen?
Air bubbles
Air bubbles can obstruct the view of the specimen.
What is the role of the fine adjustment knob on a microscope?
To adjust the focus for a clear image
It allows for precise focusing once the specimen is roughly in focus.
What is differentiation?
The process by which a cell changes to become specialised for its job
What happens to cells as they differentiate?
They develop different subcellular structures and turn into different types of cells
When does most differentiation occur?
As an organism develops
What happens to the ability to differentiate in most animal cells?
The ability is lost at an early stage after they become specialised
Do plant cells lose the ability to differentiate?
No, many plant cells do not lose this ability
What are stem cells?
Undifferentiated cells that can differentiate into various cell types
What is the primary function of sperm cells?
To get the male DNA to the female DNA
What adaptations do sperm cells have for their function?
- Long tail
- Streamlined head
- Lots of mitochondria
- Enzymes in the head
What is the primary function of nerve cells?
To carry electrical signals from one part of the body to another
What adaptations do nerve cells have for their function?
- Long structure
- Branched connections at their ends
What is the primary function of muscle cells?
To contract quickly
What adaptations do muscle cells have for their function?
- Long structure
- Lots of mitochondria
What is the primary function of root hair cells?
To absorb water and minerals
How do root hair cells increase their surface area?
They grow into long ‘hairs’ that stick out into the soil
What are phloem and xylem cells specialised for?
Transporting substances around plants
What are the structural features of xylem cells?
Hollow in the centre
Fill in the blank: Cells that differentiate in mature animals are mainly used for _______.
Repairing and replacing cells
True or False: Most cells in animals retain the ability to differentiate throughout their life.
False
What is contained in the nucleus of most cells?
Genetic material in the form of chromosomes
Chromosomes are coiled up lengths of DNA molecules.
What do chromosomes carry?
A large number of genes
Different genes control the development of different characteristics, e.g. hair colour.
What do multicellular organisms use mitosis for?
To grow or replace cells that have been damaged.
What is the result of the cell cycle?
Two new cells identical to the original cell
They have the same number of chromosomes.
What happens to DNA in a cell that is not dividing?
It is spread out in long strings.
What does a cell do before it divides?
Grows and increases the amount of subcellular structures
Includes structures such as mitochondria and ribosomes.
What forms around each set of chromosomes after they are separated?
Membranes that become the nuclei of the two new cells.
What divides last during mitosis?
The cytoplasm and cell membrane.
Fill in the blank: The daughter cells produced by mitosis contain exactly the same _______.
DNA
True or False: The daughter cells have DNA that is identical to the parent cell.
True
How many copies of each chromosome do body cells normally have?
Two copies
One from the organism’s ‘mother’ and one from its ‘father’.
What is the purpose of the cell cycle?
To produce new cells for growth, development, and repair
Body cells in multicellular organisms divide as part of this cycle.
What is the stage of the cell cycle when the cell divides called?
Mitosis
What are the two main stages of the cell cycle?
Growth & DNA Replication
These stages occur before mitosis.
What happens to DNA in a cell that is not dividing?
It is spread out in long strings.
Can embryonic stem cells turn into any type of cell?
Yes, embryonic stem cells can differentiate into any type of cell
This ability is due to their undifferentiated state in early development.
What types of cells can adult stem cells differentiate into?
Only certain types of cells, such as blood cells
Adult stem cells are more limited in their differentiation potential compared to embryonic stem cells.
What is therapeutic cloning?
A type of cloning where an embryo is created with the same genetic information as the patient
This technique aims to produce stem cells that will not be rejected by the patient’s body.
Why are some people against stem cell research?
They believe human embryos should not be used for experiments as each one is a potential human life
Ethical concerns regarding the use of embryos are a significant debate in the field.
What do some argue is more important than the rights of embryos?
Curing existing patients who are suffering
This perspective prioritizes immediate medical needs over ethical concerns about embryos.
Where are stem cells found in plants?
In the meristems
Meristems are regions in plants where growth occurs and stem cells can differentiate into any type of plant cell.
What can plant stem cells be used for?
- To produce clones of whole plants
- To grow more plants of rare species
- To grow crops of identical plants with desired features
These capabilities help in conservation and agriculture.
Fill in the blank: Stem cells from embryos and bone marrow can be grown in a lab to produce _______ cells.
genetically identical
This process is essential for research and potential medical applications.
True or False: Stem cell research is banned in all countries.
False
Stem cell research is permitted in some countries, like the UK, under strict guidelines.
What is diffusion?
The spreading out of particles from an area of higher concentration to an area of lower concentration
Diffusion is the natural tendency for substances to spread out.
In what types of substances does diffusion occur?
Solutions and gases
Particles in these substances are free to move about randomly.
What happens when the concentration gradient is larger?
The diffusion rate is faster
A larger difference in concentration leads to quicker spreading of particles.
How does temperature affect diffusion?
Higher temperature increases the diffusion rate
Increased energy causes particles to move around faster.
What is the function of cell membranes?
They hold the cell together and allow substances to move in and out
Cell membranes are selectively permeable.
What types of molecules can diffuse through cell membranes?
Very small molecules like oxygen, glucose, amino acids, and water
Larger molecules like starch and proteins cannot fit through the membrane.
What is the net movement of particles across a cell membrane?
From an area of higher concentration to an area of lower concentration
This movement occurs randomly, but there is a net movement towards the lower concentration side.
What effect does the surface area of a membrane have on diffusion?
A larger surface area increases the diffusion rate
More particles can pass through at once.
Fill in the blank: Diffusion is the gradual movement of particles from places where there are lots of them to places where there are _______.
fewer of them
True or False: Only large molecules can diffuse through cell membranes.
False
Only very small molecules can diffuse through cell membranes.
What is osmosis?
A special case of diffusion involving the movement of water molecules through a semi-permeable membrane.
What type of membrane is involved in osmosis?
Semi-permeable membrane.
What types of molecules can pass through a semi-permeable membrane during osmosis?
Tiny molecules (like water) can pass through, while bigger molecules (like sucrose) cannot.
During osmosis, where do water molecules move?
From an area of higher water concentration to an area of lower water concentration.
What happens to the concentration of a strong sugar solution during osmosis?
It becomes more dilute as water molecules flow into it.
Fill in the blank: The net movement of water molecules during osmosis aims to _______ the concentration on either side of the membrane.
even up
What is the independent variable in the osmosis experiment?
Concentration of the sugar solution.
What is the dependent variable in the osmosis experiment?
Mass of the potato cylinders.
What must be kept constant during the osmosis experiment for it to be a fair test?
Volume of solution, temperature, time, type of sugar used, etc.
True or False: An increase in mass of the potato cylinders indicates that water has been drawn in by osmosis.
True
How can the effect of errors in the osmosis experiment be reduced?
By repeating the experiment and calculating a mean percentage change.
What is the process called when substances are absorbed against a concentration gradient?
Active Transport
Why do root hair cells have a large surface area?
To absorb water and mineral ions from the soil
What do plants need mineral ions for?
Healthy growth
In root hair cells, the concentration of minerals is usually _______ in comparison to the soil.
Higher
What process takes water into root hair cells?
Osmosis
What is the role of active transport in plants?
To absorb minerals from a very dilute solution, against a concentration gradient
What is required for active transport to function?
Energy from respiration
Where does active transport also occur in humans?
In the gut and kidney tubules
Why is active transport necessary in the gut?
To absorb nutrients when their concentration is lower in the gut than in the blood
What happens when there is a higher concentration of glucose and amino acids in the gut?
They diffuse naturally into the blood
What does active transport allow nutrients to do despite the concentration gradient being unfavorable?
Be taken into the blood
How does active transport benefit glucose absorption?
It allows glucose to enter the bloodstream when its concentration is higher in the blood than in the gut
What is the primary factor that affects how easily substances move between an organism and its environment?
The organism’s surface area to volume ratio (SA : V)
This ratio determines the efficiency of substance exchange.
What process do organisms use to take in substances they need and remove waste products?
Diffusion
Diffusion is the movement of substances from an area of higher concentration to an area of lower concentration.
In humans, what waste product diffuses from cells into blood plasma for removal?
Urea
Urea is produced from the breakdown of proteins.
How is the surface area of a block calculated?
LENGTH × WIDTH
This is used to find the area of each surface and sum them for total surface area.
What is the total surface area of a hippo represented as a 2 cm x 4 cm x 4 cm block?
64 cm²
Calculated from the top, bottom, and side surfaces.
Why do multicellular organisms need exchange surfaces?
They have a smaller surface area compared to their volume, which limits diffusion.
This necessitates specialized structures for efficient substance exchange.
What adaptations do exchange surfaces have to maximize effectiveness?
They have:
* Thin membranes
* Large surface area
* Lots of blood vessels
* Ventilation in gas exchange surfaces
These features enhance the efficiency of diffusion.
True or False: Single-celled organisms can diffuse gases and dissolved substances directly across their cell membrane.
True
Their large surface area to volume ratio allows for sufficient substance exchange.
What is the primary function of the lungs?
To transfer oxygen to the blood and to remove waste carbon dioxide from it.
What are alveoli?
Millions of little air sacs in the lungs where gas exchange takes place.
List the characteristics of alveoli that maximize gas diffusion.
- An enormous surface area (about 75 m² in humans)
- A moist lining for dissolving gases
- Very thin walls
- A good blood supply
What do the colors blue and red represent in the blood around the alveoli?
Blue = blood with carbon dioxide; Red = blood with oxygen.
What are villi?
Tiny projections that cover the inside of the small intestine.
How do villi assist in the absorption of digested food?
They increase the surface area significantly so that digested food is absorbed more quickly into the blood.
What is a key structural feature of villi?
A single layer of surface cells.
Why is a good blood supply important for villi?
It assists in quick absorption of digested food.
Fill in the blank: The inside of the small intestine is covered in millions of tiny projections called _______.
[villi]
True or False: The lungs contain alveoli which have thick walls to facilitate gas exchange.
False
What process allows digested food to move into the blood from the villi?
Diffusion.
What is the total surface area provided by the alveoli in humans?
About 75 m².
What is the role of the moist lining in the alveoli?
To dissolve gases.
What happens to gas exchange in the lungs?
Oxygen enters the blood and carbon dioxide is removed.
List the components of the blood that interact with alveoli.
- Red blood cells
- Blood capillaries
- Plasma
Fill in the blank: The villi have a very good _______ to assist in quick absorption.
[blood supply]
What gas diffuses into the air spaces within the leaf for photosynthesis?
Carbon dioxide
Carbon dioxide is essential for the process of photosynthesis in plants.
What are the small holes on the underside of leaves called that allow gas exchange?
Stomata
Stomata are critical for the diffusion of gases in and out of the leaf.
Which gas produced during photosynthesis diffuses out of the leaf?
Oxygen
Oxygen is a byproduct of photosynthesis and is released into the atmosphere.
What do guard cells control in the leaf?
The size of the stomata
Guard cells regulate the opening and closing of stomata to manage water loss.
What happens if guard cells do not function properly?
The plant would wilt
Without guard cells, excessive water loss can lead to wilting.
True or False: The concentration of oxygen in water is lower than that in the blood.
False
The concentration of oxygen in water is always higher than in the blood, facilitating diffusion.
Fill in the blank: Water vapor is lost from the leaf surface through the _______.
Stomata
Stomata are the primary sites for water vapor loss in leaves.
