B1 - Cell Biology Flashcards
What is the function of the cell membrane?
- Holds the cell together
- Separates the inside of the cell from the outside environment
- Controls what enters/exits the cell
Examples of eukaryotes?
- Animals
- Plants
Defining feature of eukaryotic cells?
Their genetic material is enclosed within a nucelus
Usual size of eukaryotic cells?
Between 10 and 100 micrometers
Example of prokaryote?
- Bacteria
Defining feature of prokaryotes?
Their genetic material is not within the nucleus, it is a single loop of DNA in the nucleus
Size of prokaryotic cells?
Usually smaller than a micrometer
How many mm in a m?
1000
How many micrometers in mm?
1000
How many nanometers in a micrometer?
1000
Main subcellular structures in animal cells?
- Nucleus
- Cell membrane
- Mitochondria
- Ribosomes
- Cytoplasm
Which organelles of an animal cell can be seen under a light microscope?
- Nucleus
- Cell membrane
- Cytoplasm
Which organelles of an animal cell can be seen under an electron microscope?
- Nucleus
- Cell membrane
- Cytoplasm
- Ribosomes
- Mitochondria
Function of the nucleus?
- Contains genetic material that controls the activities of the cell
Function of the cytoplasm?
- Gel-like substance made of water and dissolved solutes
- Supports internal cell structures
- Site of many chemical reactions
Function of the ribosomes?
- Found in the cytoplasm
- Site of protein synthesis
Function of the mitochondia?
- Site of most of the reactions involved in aerobic respiration
- Releases energy for cellular processes
- Cells with higher rates of metabolism have more mitochondria
Additional organelles plants have?
- Cellulose cell wall
- Permanent vacuole filled with cell sap
Plant organelles seen under a light microscope?
- Cell membrane
- Cell wall
- Permanent vacuole
- Cytoplasm
- Chloroplast
Plant organelles seen under electron microscope?
- Cell membrane
- Cell wall
- Permanent vacuole
- Cytoplasm
- Chloroplast
- Mitochondria
- Ribosomes
Function of the cell wall?
- Made of cellulose
- Gives extra support, defines shape
Function of the chloroplasts?
- Contains green chlorophyll pigment and the enzymes for photosynthesis
Function of the permanent vacuole?
- Contains cell sap, a solution of sugars and salts dissolved in water
- Used for storage of certain materials
- Helps support the shape of the cell
What is a specialised cell?
A cell that has a particular structure and composition of subcellular structures in order to perform a specific function
What is the process called which cells specialise?
Differentiation
Function of the nerve cells?
Conduction of impulses
Adaptations of nerve cells?
- Cell body where most of the cellular structures are located and most protein synthesis occurs
- Extensions of the cytoplasm form dendrites to receive signals and axons which transmit signals to communicate
- The axon is covered with a fatty sheath which speeds up nerve impulses
Function of muscle cells?
Contraction for movement
Adaptations of muscle cells?
- Layers of protein filaments which can slide over each other to cause contraction
- High density of mitochondria to give sufficient energy for contraction
- Skeletal muscle cells fuse together to form multinucleated cells which contract together
Types of muscle cells?
- Cardiac
- Skeletal
- Smooth
Function of sperm cells?
Reproduction
Adaptations of sperm cells?
- Acrosome contains digestive enzymes to break down the outer layer of an egg cell
- Many mitochondria to release energy for the tail
- The tail rotates to propel the sperm cell forward
Function of root hair cells?
Absorption of water and mineral ions from soil
Adaptations of root hair cells?
- Root hair increases surface area so rate of water uptake by osmosis is greater
- Thinner walls so shorter diffusion distance for water
- Permanent vacuole holds cell sap which is more concentrated than soil water, maintains a water gradient
- Mitochondria for active transport of mineral ions
Function of xylem vessels?
Transport tissue for water and dissolved ions
Adaptations of xylem vessels?
- No top and bottom walls to form continuous hollow tubes for water to flow through
- No organelles or cytoplasm to allow free passage of water
- Outer walls strengthened with lignin to support the plant
Function of phloem vessels?
Transport of dissolved sugars and amino acids
Adaptations of phloem vessels?
- Cells are joined end to end and contain holes (sieve plates) forming tubes to allow sugars and amino acids to flow easily
- Few subcellular structures to aid the flow of material
When were the first light microscopes developed?
17th century
Who developed microscopes?
Leeuwenhoek and Hooke
How have microscopes increased?
Increasing magnification and resolution
When were the first electron microscopes developed?
The first half of the 20th century
How do electron microscopes work?
Use beams of electrons instead of light, the wavelength of the electron beam is smaller than visible light so they have higher resolution and magnification
Magnification =
Drawing size / Actual size
Types of stem cells?
- Embryonic
- Adult
- Meristem
Where are embryonic stem cells found?
On the inside layer of an embryo
Where are adult stem cells found?
- Bone marrow
- Skin
- Other organs such as liver and brain
- Umbilical cord blood
Where are meristem cells found?
Tips of roots and shoots
What can stem cells be used to treat?
- Type II Diabetes
- Paralysis
What is the diffusion?
The movement of particles from an area of higher concentration to an area of lower concentration
Substances that enter cells by diffusion?
- Oxygen must diffuse into cells for aerobic respiration
- CO2 must diffuse into photosynthesising plant cells
Substances that leave cells by diffusion?
- Urea must be diffused from cells to be excreted by the kidneys
- CO2 produced by aerobic respiration must diffuse out of cells
Factors affecting diffusion?
- Concentration gradient
- Temperature
- Diffusion pathway
As the size of an organism increases…
…surface area to volume ration decreases
Function of the small intestine?
Most absorption of digested food molecules into the bloodstream happens across the wall of the small intestine
Adaption of the small intestine?
- Epithelial cells increase SA
- Only one layer of epithelial cells across each villus which decreases diffusion distance
- Each villus has good blood supply to maintain a concentration gradient
Function of the lung in the body?
Gas exchange between air in the alveoli and the blood
Adaptations of the lung?
- Millions of alveoli increase SA
- The wall of each alveolus is one cell thick with good blood supply to maintain concentration gradient and short diffusion path
Function of the gills in a fish?
Gas exchange between water flowing through the gills and the blood
Adaptations of the gills?
- Each gill is made up of smaller plates called filaments which are covered in lamellae to increase SA
- Dense capillary network to give good blood supply to maintain a concentration gradient
Function of the root hair cell?
To absorb the water and mineral ions from the soil and anchor the plant
Adaptations of the root hair cells?
- Root network is highly branched to increase SA
- Surface of the roots are covered in root hair cells to increase SA
Role of the leaves?
- Contain most of the plant’s photosynthetic cells
- Photosynthesis needs efficient gas exchange between air and photosynthetic cells
Adaptations of the leaves?
- Stomata have tiny openings to decrease diffusion distance for CO2 and O2
- The lower layer of the leaf is made of spongy mesophyll cells which allow air to circulate inside the leaf
Two ways that increase exchange of materials?
- Large surface area
- Short diffusion path
How have animals adapted for gas exchange?
- Large network of blood vessels decrease distance and maintain concentration gradients
- Gas exchange surfaces are well ventilated to maintain concentration gradients
What is osmosis?
The diffusion of water molecules from an area of high concentration to an area of low concentration across a partially permeable membrane
What is a dilute solution?
A solution with high concentration of water molecules and low concentration of solute molecules
What is a concentrated solution?
A solution with low concentration of water molecules and high concentration of solute molecules
Percentage change =
(Final mass - Initial mass) / Initial mass x 100
What is active transport?
The movement of substances from an area of high concentration to low concentration (against the gradient) that requires energy
Active transport in plants?
- Root hair cells move minerals from lower concentration in the soil to higher concentration in the cytoplasm
Active transport in animals?
- Food molecules such as glucose may be needed to be done with active transport if there is a high concentration of sugar in the blood
Examples of substances transported by diffusion?
Oxygen, carbon dioxide, glucose, amino acids, urea
Examples of substances transported by osmosis?
Water
Examples of substances transported by active transport?
Glucose, mineral ions such as sodium, potassium
Places where diffusion occurs?
Lungs, leaves, small intestine
Places where active transport occurs?
Small intestine, roots
What is cell differentiation?
The process where a cell becomes specialised to its specific function
What is a concentration gradient?
The difference in concentration between two areas
What is a eukaryotic cell?
A type of cell found in plants and animals that contains a nucleus
What is magnification?
How much bigger an image appears compared to the original object
What are meristematic cells?
A type of stem cell that can differentiate into any type of plant cell
What is mitosis?
A type of cell division which produces two genetically identical daughter cells from one parent cell
What is a plasmid?
Loops of DNA found in the cytoplasm in prokaryotic cells
What is a stem cell?
An undifferentiated cell
What is surface area?
The total area of all parts that are in contact with it’s environment
What is the cell cycle?
A series of stages preparing the cell for division
