Cell structure Flashcards
What is a eukaryotic cell?
has a nucleus.
usually have mitochondria.
In plants cells only they have chloroplasts.
What is a nucleus?
conrol center of the cell.
What is cytoplasm?
A jelly like liquid where most chemical reactions take place.
What is cell membrane?
Controls what passes in and out of the cell.
What are mitochondria?
Organelles that contain the enzymes for respiration, and where most energy is released in respiration
What are ribosomes?
Tiny structures where protein synthesis occurs
What is a cell wall?
Made of cellulose it strengthens the cells and gives it support.
What are chloroplasts?
They absorb energy from the sun to make food by photosynthesis. in plants
What is a permanent vacuole?
A space in the cytoplasm filled with cell sap that keeps the cells rigid to support the plant.
What are specialised cells?
Cells specialised to carry out a particular function.
What are adaptations of root hair cells?
Root hairs provide a large surface area.
A large permanent vacuole affects movement of water from soil.
Root hair positioned close to xylem
What is the function of a root hair cell?
Enables plants to take in water and mineral salts.
What are the adaptations of a sperm cell?
It has a middle section full of mitochondria to release energy.
What is the function of a sperm cell?
To fertilise egg cells.
What is the flagellum on a sperm cell for?
To swim to the egg cell for fertilization.
What is the function of red blood cells and how is adapted to this?
The function is to carry oxygen and the adaptations for this are
cytoplasm contains haemoglobin to transport oxygen
no nucleus - can contain more haemoglobin
biconcave shape to maximise surface area
What is the function of a nerve cell?
To send nerve impulses around the body.
What is the equation for magnification?
Magnification = size of image (I) / actual size (A)
What are fat cells?
Storage cells. They help animals to survive when food is in short supply.
What are the adaptations of fat cells?
They have little amounts of cytoplasm - to leave room for large amounts of fat.
They have very few mitochondria as they use little energy.
They can expand when it fills up with fat.
What are specialised cells grouped together to form?
A tissue
What joins parts of the body together?
Connective tissue
What does nervous tissue do?
Carries information around the body.
What do photosynthetic cells do?
Make food by photosynthesis
What do storage tissues do?
Store extra food made as starch
What are stem cells?
Unspecialised cells that can change to different types of cells
Where are stem cells found? - animals
Human embryos and adult bone marrow
What can stem cells be used to treat?
Paralysis and diabetes
Where are stem cells found? - plants
Meristems
Advantages of stem cells?
Some stem cells can be collected without harming the donor (adult, umbilical cord)
Will provide vital clues about how tissues develop
Could treat Parkinson’s, Alzheimer’s, heart disease, strokes, arthritis, burns by replacing damaged cells
Disadvantages of stem cells?
use of embryonic stem cells is controversial cuz it involves the destruction of embryos, which some people believe is unethical.
immune system might recognize transplanted stem cells as foreign and attack them, leading to rejection and failure of treatment.
Stem cell therapies are still experimental, and there is a risk of uncontrolled cell growth, which could lead to tumours
What does the nucleus contain?
Chromosomes
How many pairs of chromosomes are in a human nucleus?
23 (pairs) (46 total)
What does a chromosome contain?
(DNA - ) Genes
What is a gene?
parts of DNA that code for specific proteins e.g. eye colour
What is mitosis?
It’s for growth repair and replacement of cells
Intense Pleasure Makes All Things Cum
Interphase – DNA copies itself
Prophase – Chromosomes pair up and nucleus breaks down
Metaphase – Chromosomes meet in the middle
Anaphase – Chromosomes are pulled apart
Telophase – Two new nuclei form
Cytokinesis – Cell completely splits
What are cancer cells?
Arise due to mutations in genes that control mitosis. Leads to uncontrolled cell division and tumours.
What are the two types of tumours?
Benign and malignant
What are benign tumours?
Unable to spread to other parts of the body and are non-cancerous tumours
What are malignant tumours?
Can invade neighbouring tissues and spread to different parts of the body in the blood where they form secondary tumours.
What is diffusion?
The movement of particles in a gas or a liquid from an area of high concentration to an area of low concentration
What is a partially permeable membrane?
Lets small soluble substances through but not others
What factors affect the rate of diffusion?
distance
surface area
concentration gradient / difference
temperature
What increases the rate of diffusion?
decreased distance
increased surface area
increased concentration gradient
increased temperature
What is osmosis?
Diffusion of water molecules from a low concentration to a more concentrated solution through a partially permeable membrane down a concentration gradient
What does a partially permeable membrane do?
Allows small water molecules to pass through but not large solute molecules
What happens when a red blood cell is placed in pure water?
Water moves into cells by osmosis and bursts
What happens when a cell is placed in a liquid the same concentration?
water doesn’t move in or out (via osmosis)
What happens when a red blood cell is placed in a concentrated solution?
Water moves out of the cell and shrivels
What does turgid mean?
When water has moved into the cell by osmosis and cell contents is pushed outwards against the wall
What does flaccid mean?
When a plant cell is flaccid, it means it has lost water and is soft or limp. The cell doesn’t have enough water to push against the cell wall, so the plant looks wilted.
This happens when a plant is in a weak solution, where water moves out of the cells.
what is plasmolysis?
Plasmolysis is what happens when a plant cell loses so much water that the cell membrane pulls away from the cell wall. This happens in a strong solution (like salty water), where water moves out of the cell.
simply, plasmolysis is when the cell shrinks and the membrane lifts off the cell wall.
What does a dilute solution of sugar contain?
A high concentration of water (solvent) and a low concentration of sugar (solute)
solvent vs solution
Solvent = liquid that dissolves.
(Example: Water is a common solvent that dissolves sugar or salt.)
Solution = mixture of solvent + solute.
(Example: When sugar dissolves in water, the result is a sugar solution.)
What does a concentrated solution of sugar contain?
A low concentration of water and a high concentration of sugar
What is active transport?
Active transport uses energy to move substances from low to high concentration. It’s needed when cells take in things like minerals or ions, even when there’s little of them outside the cell. (uses energy)
How does active transport go against the concentration gradient?
It uses energy from respiration and a carrier protein
What can be reabsorbed by active transport?
moves glucose from the kidney tubules back into the blood. (kidney is a filter)
Why do plants rely on active transport?
To obtain mineral ions through root hair cells
What do cells involved in active transport have?
Lots of mitochondria because aerobic respiration takes place here and releases energy needed for active transport
What happens to Surface Area to volume ratio when the size of an object increases?
SA Decreases
What happens to Surface Area to volume ratio when the size of an object decreases?
SA Increases
Why do multicellular organisms need a transport system?
As size increases SA/V ratio decreases
surface area is no longer big enough to supply needs of the body - needs to be sped up to move materials in and out of the organism
How many micrometres are in a millimetre?
1000
What is a concentration gradient?
The difference in concentration of two solutions.
What is a prokaryotic cell?
bacterial cell
no nucleus
genetic material is a single loop of DNA
Examples of some cells that divide by mitosis
hair and nail cells
skin cells
red and white blood cells
Is a bacterium a prokaryotic or eukaryotic cell?
Prokaryotic
Which cells are smaller? Plant cells or bacterial cells?
Bacterial cells
What substance is the cell wall made of?
Cellulose
