B.2.3 HL Flashcards
What are adaptation that cells have to increase SA : V ratio?
Cells which require rapid change of materials with their environment often need new adaptations. These help maximize the large surface area to volume ratio meaning they increase the membrane space. Two ways of increasing the surface area are the - formation of invaginations or microvilli which are infolds or outfolds. Invaginations happen when a substance folds inward to create a cavity. Microvilli are small finger like projections of the cell membrane of a cell. Some examples are:
- Red blood cells, biconcave and for gas exchange
- Forming long, thin extensions; significantly expand the cells surface area while adding small amounts of volume
- Phagocytic cell of the immune system
- Thin branches of a cell of a chordate nervous system,
- Epidermis cell forming a root hair in a plant
- Having a thin, flat shape; maximises the amount of surface are exposed to relative to the volume it occupies
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- Type 1 pneumocyte cells in the lung alveoli reduces distance for diffusion of gases
- Epithelial cells form the tube of a capillary vessel for maximizing gas and nutrient exchange
State the types of muscles and their characteristics.
The three main types of muscles are skeletal, cardiac and smooth.
Skeletal muscle:
- Striated: filaments of actin and myosin that power the contraction. Are organized into repeating sarcomeres that have a striped appearance under a microscope.
- Attach to bones to cause movements; antagonistic pair
- Voluntary and or involuntary (as pain reflex)
- Atypical cell structure fuses together to form large multinucleate structures
- Internal and external intercostal muscles
Cardiac muscle:
- Striated: filaments of actin and myosin that power the contraction. Are organized into repeating sarcomeres that have a striped appearance under a microscope.
- Responsible for pumping blood throughout the body
- Involuntary only
- More typical cell structure with one nucleus per cell
- Found only in the heart
Smooth muscle:
- Non striated: lack of visible stripes
- Responsible got contractions and movements within organs
- Involuntary only
- More typical cell structure with one nucleus per cell
- Found in the walls of internal organs such as the small intestine
What are some adaptations to muscle cells and striated muscle fibres?
All muscle tissues are contractile meaning they can shorten in length. Muscle fibres form bundles that run the entire length of the muscle. Microfibrils are long cylindrical contractile structures that are parallel to each other. They are composed of repeating units called sarcomeres containing actin and myosin. They slide past each other to generate a muscle contraction. Protein titan which uncoils the muscle by uncoiling actin and myosin. Levels of bundles of proteins and muscle fibre are the cells:
1. Myofibril
2. Muscle fibre
3. Fascicle
4. Muscle
There are debates whether muscle fibres should be classified as a cell because they actually result from the fusion of many precursor cells. They are a single plasma membrane with many nuclei and satellite cells keep the muscles with enough nutrition.
What are some adaptations to sperm and egg cells?
Gametes are cells formed in meiosis that contain a haploid nucleus that is used to pass on genetic information from parents to offspring. Sperm are adapted to reduce resistance as the cell moves towards the egg:
- Head: tightly packed haploid nucleus and small volume of cytoplasm
- Mostly the nucleus and the acrosome
- Acrosome: a sac of digestive enzymes
- Receptor proteins: recognize the egg
- Midpiece: multiple mitochondria producing ATP to power the tail movement
- Tail: long flagella, with microtubules that generate the force needed to propel the sperm
Egg cells are surrounded by structures that protect the egg prior to and after fertilization:
- Zona pellucida: layer of glycoproteins which are digested by the sperm
- Corona radiata: layer of protection as it awaits fertilization (crown)
- Cortical granules: vesicles full of enzymes along the inner edge of the cell
- Binding proteins: proteins on the plasma membrane of the egg cell that bind to the proteins of sperm cell
- Cytoplasm: full of nutrients
- Nucleus: at ovulation of the egg the nucleus is paused
- Mitochondria: produce the ATP to fuel cell division
- Yoke: volume of cytoplasm
